A general book on this area is N.L.First & F.P. Heseltine, eds., Transgenic Animals
(Butterworth-Heineman 1991), 358 pp., which is reviewed in Nature
349 (1991), 474. It is actually the proceedings of a 1988 conference, so is a mixture
of results some of which are dated.
A method for sex selection has been developed based on the binding of a fluorochrome benzimide dye with DNA, which will bind to DNA without killing sperm: NS (12 Jan 1991), 5. The X-chromosome has more DNA so it takes up more dye therefore having increased fluorescence which means that the sperm can be sorted in a cell sorter (a machine that can separate cells that have different labels). The US Government laboratories have used this sperm for artificial insemination, with good results on rabbits and pigs. A company Cytogram, which has also applied for a patent, uses the selected sperm to make antibodies to surface membrane "sex-associated" proteins, then these are inoculated into the female for use. This has also been tested on mammals. In animals the total sex difference in DNA mass between females and males is 3-4.5%, in humans it is about 2.9%, but it may still be applicable.
Another method for the selection of transformed embryonic stem cell lines (SG 125) has been reported, T.Yagi et al (1990) "Homologous recombination at c-fyn locus of mouse embryonic stem cells with the use of diptheria toxin A-fragment gene in negative selection" PNAS 87: 9918-22. It shortens the time required for selection of genetically altered ES cells, which is useful for the production of transgneic mice. Another useful development for ES cell research is the development of a murine retrovirus vector (M. Grez et al. (1990) "Embryonic stem cell virus, a recombinant murine retrovirus with expression in embryonic stem cells", PNAS 87: 9202-6). Currently gene transfer uses microinjection or electroporation, but with the development of this virus it will be able to be used as a vector to obtain higher gene transfer efficiency before cell selection.
Many researchers have developed methods to enhance the twinning of farm animals. However, an important question is whether this results in greater efficiency at the farm level, especially in cattle where the natural rate of twinning is very low. P.Guerra-Martinez et al (1990) "Embryo-transfer twinning and performance efficiency in beef production", J.Animal Science 68: 4039-50; have found that in a herd of 241 heifers and 84 cows the integrated herd costs per unit of age-constant output value would be about 24% lower using twin production than single production for selling at weaning or 400 days, despite the higher veternary costs for twins.
The use of animals to produce useful proteins in their milk is progressing in several species. One of the problems is the lack of high levels of gene expression. One paper reports levels of the protein -1 antitrypsin at 1mg/litre of rabbit plasma (not milk); M. Massoud et al (1990) "The production of human proteins in the blood of transgenic animals", Comptes Rendus de l'Academie des Sciences, Series 3, Sciences de la Vie 311: 275-80. Greater success is described in R.J.Wall et al (1991) "High-level synthesis of a heterologous milk protein in the mammary glands of transgenic swine", PNAS 88: 1696-1700. They produced a protein called whey acidic protein at a level of 1g/litre, about 3% of the milk protein.
A paper in farm breeding is K.J.McLaughlin et al. (1990) "In vitro embryo culture in the production of identical merino lambs by nuclear transplantation", Reprod. Fertil. Dev. 2: 619-22. They used the technique of fusing 8-16 day old blastomeres with enucleated oocytes, and measured the viability. Only 14 fetuses were produced from 86 of these embryos, with only one set of quads and four identical twins, much lower viability than using normal embryos, though these results are similar to other trials of nuclear transplants into enucleated oocytes. Another sheep experiment is S.K.Walker et al. (1990) "In vitro assessment of the viability of sheep zygotes after pronuclear microinjection", Reprod. Fertil. Dev. 2: 633-40. A general paper is C.A. Pinkert et al. (1990) "Characterization of transgenic livestock production", Domestic Animal Endocrinology 7: 1-18. The use of injection of the hormone epidermal growth factor to harvest wool is discussed in NS (23 March 1991), 20.
A review is D.W.Melton (1990) "The use of gene targeting to develop animal models for human genetic diseases", Biochemical Society Trans. 18: 1035-9. It covers ES cells, and principally the HPRT gene models. Some recent animal models include mice that are susceptable to poliovirus; PNAS 88 (1991), 951-5, made by inserting the gene for the poliovirus receptor into their genome; the disruption of the c-src gene leads to osteopetrosis in mice; Cell 64 (1991), 693-702; see also Nature 350 (1991), 243-6; Science 251 (1991), 1239-43. A technical paper is B.Eliceiri et al. (1991) "Stable integration and expression in mouse cells of yeast artificial chromosomes harboring human genes", PNAS 88: 2179-83.
The use of aquatic animals for genetic experiments are discussed in Biotechnology 9 (1991), 226, and for testing radiation-induced germ-cell mutagenesis in PNAS 88 (1991), 2545-9.
The efforts to produce a mouse model for multiple sclerosis appear to have been successful, A. M. Turnley et al., "Dysmyelination in transgenic mice resulting from expression of class I histocompatibility molecules in oligodendrocytes", Nature 353: 566-9, also see p. 503-5. For arthritis research see Y. Iwakura et al., "Induction of inflammatory arthropathy resembling rheumatoid arthritis in mice transgenic for HTLV-I", Science 253: 1026-8. For transgenic animals in Alzheimer's research see Science 253: 266-7; SA (Sept 1991), 20. On the use of Drosophila (fruitfly) for study of memory; Science 253: 1486-7.
Two mouse models for infertility have been produced, one modelling immotile sperm syndrome, Genes & Development 5: 1395-1406; PNAS 88: 8787-91; Nature 353: 306. Other transgenic mice models for experiments are described in Cell 66: 1051-66; Science 253: 555-7; PNAS 88: 8327-31. On the use of primates (rhesus monkeys) to model stress factors and alcohol abuse see PNAS 88: 7261-5.
On the culturing of germ cells, and embryonic stem cells see Nature 352: 807-9, 809-11; on chimeric mouse embryos made using ES cells see Nature 353: 348-51.
For reviews on transgenic animal disease models see J.M. Adams & S. Cory, "Transgenic models of tumor development", Science 1161-7; G.T. Merlino, "Transgenic animals in biomedical research", FASEB J. 5: 2996-3001. There is a new mouse model for Alzheimer's disease; S. Kawabata et al., "Amyloid plaques, neurofibrillary tangles and neuronal loss in brains of transgenic mice overexpressing a C-terminal fragment of human amyloid precursor protein",Nature 354: 476-8, see also 432-3. See also M.V. Sofroniew & K. Saley, "Transgenic modelling of neurodegenerative events gathers momentum", TINS 14: 513-4.
On chimeric mice , for a cancer model see Nature 353: 866-8, and for immunological research see PNAS 88: 10332-6; Nature 354: 235-8. On dominant male sterility in mice caused by gene insertion see PNAS 88: 10327-31. On the generation of IL-4 deficient mice, see Science 254: 707-10. On experiments to proliferate murine germ cells in vitro see Nature 353: 750-2.
The use of targetted mutations to the homeobox genes in mice, using ES cells is in Nature 355: 516-20; Nature 354 (1991), 522-5. On a predictive mouse model of arthritis see EMBO J 10: 4025-31; on sickle cell disease model see EMBO J 10: 3157-65. A general review is M.M. McGrane et al., "Metabolic control of gene expression: in vivo studies with transgenic mice", TIBS 17: 40-4. There were a large number of studies reported in 1991 using ES stem cells and homologous recombination; Science 254 (1991), 1709.
Some papers describing research using
transgenic animal models
include; R. Watanabe-Fukunaga et al., "Lympho-proliferation disorder in mice explained
by defects in Fas antigen that mediates apoptosis", Nature
356: 314-7; R.L. Tarleton et al., "Susceptability of ß2-microglobulin-deficient mice to Trypanosoma cruzi
356: 338-40; "Age-associated inclusions in normal and transgenic mouse brain", Science
255: 1443-5; U. Suter et al., "Trembler mouse carries a point mutation in a myelin
Two transgenic mouse strains reported to be models of Alzheimer's disease have been found not to be real models of the disease; Science 255: 1200-2; Nature 356: 103, though studies on Alzheimer's are still proceeding; Science 255: 688-9.
A review of embryonic stem cell technology was noted above, another news story is entitled "Scoring a technical knockout", Science 256: 1392-4. It is a discussion of the use of homologous recombination and gene targeting in mice, which can be used to make mice models of disease; but the title is rather distasteful, for the mice are often badly effected by such induced mutations. There is no discussion of the ethical issues, but purely a favourable comment on the diversity of genes that can be mutated. One such mouse, is a model for Gaucher's disease described in Nature 357: 407-10. Such mice die within 24 hours of birth. See also Nature 356: 577-82, 357: 161-4; Cell 69: 79-93, 251-64, 737-49; PNAS 89: 5020-4. A review on the subject is M.J. Justice et al., "Recombinant inbred mouse strains: models for disease study", TIBTECH 10: 120-6. It presents a list of diseases made in many mice strains by genetic engineering. On an animal model for AIDS dementia see JAMA 267: 2293.
The dramatic story in transgenic animal research was the news of experiments to change the sex of mice by the effect of a single gene; P.Koopman et al., "Male development of chromosomally female mice transgenic for Sry", Nature 351: 117-21, see also 96; Science 252: 782; NS (11 May), 22, (18 May), 9. SRY is short for sex-determining region of the Y-chromosome, and only it seems necessary for the development of male mice, though maybe several copies are required. Further studies of the new line of mice will be conducted, to test the involvement of other genes that may influence testis development.
Of more direct commercial use is the release of news about genetically engineered pigs that express human hemoglobin; Washington Post (17 June), A10. DNX of Princeton, NJ, said it has three pigs which produce up to 15% human hemoglobin, and are aiming for 20% human protein. The human protein can be separated from the porcine protein, and next year they will apply to the FDA to begin clinical trials, as a blood substitute.
Transgenic mice expressing a sialic acid-specific acetylesterase had developmental implications, and decreased the number of live born mice; Cell 65: 65-74. This is one enzyme involved in carbohydrate metabolism, and plays an apparently crucial role in the early embryo development. Another mutant mouse was via mutations in the cAMP response element binding protein, resulting in dwarfism; Nature 350: 622-4. Transgenic mice have also been used to uncover more of the functioning of the myc oncogene, including a new partner gene, max ; Cell 65: 715-6, 737-52, 753-63.
The targetted disruption of homeobox sequences in the Hox 1.5 gene of mice, which led to regionally restricted developmental defects is described in Nature 473-9, 458-9. The Hox genes appear to be important for control of development in all animals, and many further experiments are being conducted. Some of these experiments are done in a blind manner, so raise special ethical problems.
A review on the genetics of thoroughbred horses is in SA (May), 56-62. The authorities regulating horse-breeding for racing forbid the use of genetic manipulation to improve performance, but in the future (or even now) would such a ban be enforceable.
In France, a team at INRA, Jouy en Josas (National Institute of Agronomic Research) has obtained the birth of cloned rabbits using nuclear transplants from blastomeres of a 32 cell embryo into enucleated oocytes; IJB 2: 57. A report on the succesful use of IVF and embryo transfer in goats is in Biology of Reproduction 44: 1177-82.
The use of baculoviruses as insecticides is progressing, with the use of inserted toxin genes into the virus genome which speeds up the killing of the insects; M.D. Tomalski & L.K. Miller, "Insect paralysis by baculovirus-mediated expression of a mite neurotoxin gene",Nature 352: 82-5; L.M.D. Stewart et al., "Construction of an improved baculovirus insecticide containing an insect-specific toxin gene", Nature 352: 85-88, 16-17. Baculoviruses have a limited host range, but kill insects only slowly, taking 4-7 days, allowing the insect larvae to feed longer and cause more damage. The genes that were inserted were encoding a toxin from mite venom and an insect specific scorpion neurotoxin. The reduction in crop damage was about 50% in Brassica . The baculoviruses can be sprayed onto crops, but they have a protective polyhedrin coat so that they can survive in the environment. If they are not desired to survive, the gene for the coat can be deleted.
The US company DNAX has produced transgenic pigs that produce 10-15% human hemoglobin; Biotechnology 9: 696; Science 253: 32-4. It is hoped to raise the level of expression in these pigs to 50-60% of the total hemoglobin, after they obtained 70-80% expression of human protein in mice, without any noticeable undue effects. A competitor is using microbial derived human hemoglobin, the blood substitute market is worth US$5-10 billion annually. However, there are still problems in developing a safe and effective delivery system for hemoglobin.
A report on the cytogenetic analysis of a goat-sheep chimera is in J. Heredity 82: 244-5.
A review on the possibility of improving the rumen microorganisms of livestock to improve animal nutrition is D.A. Flores, "Biotechnology and the improvement of silage (tropical and temperate) rumen digestion: a mini-review", Appl. Microbiol. & Biotech 35: 277-82. The Dutch government has approved experiments with transgenic cows, with injected lactoferrin genes. The idea is that the gene may make the cows resistant to E. Coli , one of the bacteria that causes mastitis; NS (15 June 1991), 17.
Merck & Co. have applied for a patent for fast growing chickens, made via insertion
of bovine growth hormone in a retrovirus vector into fresh, fertile eggs; Science
A review of some of the transgenic fish that are being made is in Science 253: 512-3. The field trial of fast growing transgenic carp in Alabama occurred this summer. A series of papers on aquaculture are in J. Animal Science 69: 4176-227.
On the production of pharmaceutical proteins in milk of transgenic animals see Nature 353: 7; Science 254: 35-6; Biotechnology 9 (Sept. issue includes 3 papers). Proteins have been expressed in the milk of cows, goats and sheep. This work is attempting to increase the levels of proteins in milk, to those required for commercial production of erythropoietin, blood clotting factors, TPA and alpha-1-antitrypsin.
The possibilities of genetically modifying insect disease vectors is discussed in A.M. Fallon, "DNA-mediated gene transfer: applications to mosquitoes", Nature 352: 828-9.
As mentioned in EEIN
1: 73, there have been growing numbers of papers on transgenic animals making pharmaceutical
proteins. A discussion of these is in Biotechnology
9: 786-7, followed by several papers; G. Wright et al., "High level expression of
active human alpha-1-antitrypsin in the milk of transgenic sheep", p. 830-4; K.M.
Ebert et al., "Transgenic production of a variant of human tissue-type plasminogen
activator in goat milk: generation of transgenic goats and analysis of expression", p. 835-8;
J. Denman et al., "Transgenic expression of a variant of human tissue-type TPA in
goat milk: purification and characterization of the recombinant enzyme", p. 839-43.
These field is developing, and good levels of expression can be obtained.
The first reported transgenic dairy calf is in P. Krimpenfort et al., "Generation of transgenic dairy cattle using 'in vitro' embryo production", Biotechnology 9: 844-7. The numbers of embryos were very large, from 2470 oocytes, 1154 embryos were micro-injected with DNA, and 129 were transferred after cleavage, to give rise to 21 pregnancies and 2 transgenic individuals! The gene transferred was the human iron-binding protein, lactoferrin, with targeting information to take it to the mammary gland. Of course large quantities of milk are made in cows, but we can hope that a more efficient method of reproduction, can be used from these calves to make more progeny.
Intracellular immunization may be used to produce disease-resistant transgenic livestock, in chickens and mammals, see TIBTECH 9: 71-2. On the improvement of a recombinant Rinderpest vaccine for cattle, see GEN (Nov/Dec 1991), 44.
On the introduction of disease resistance genes into transgenic fish see GEN (Nov/Dec 1991), 1, 55. Aquaculture currently accounts for about 15% of the world's fish consumption, and the proportion should increase. It also discusses other topics of transgenic fish research in the USA. A letter correcting some errors in a recent description of transgenic carp, under field trials in Alabama, is in Science 254: 779.
On animal cell expression vectors based on the Semliki Forest virus replicon see Biotechnology 9: 1356-61.
As mentioned in EEIN 1: 73, there have been growing numbers of papers on transgenic animals making pharmaceutical proteins. See also; P. Ditullio et al., "Production of cystic fibrosis transmembrane conductance regulator in the milk of transgenic mice", Biotechnology 10:74-7. The availability of the CF transmembrane regulator could be useful for therapy, though gene therapy is also on the move (see later).
A discussion on the improvement of pork by biotechnology is in Science 255: 24. On making larger fish; S.J. Du et al., "Growth enhancement in transgenic Atlantic salmon by the use of an "all fish" chimeric growth hormone gene construct", Biotechnology 10:176-81. They used an antifreeze protein gene promoter linked to a chinook salmon growth hormone gene. In a one year old fish, the largest increase over a non-transgenic control was 13 times, with the average 2-6 times.
A general method of
is described in T.M. Klein et al., "Transformation of microbes, plants and animals
by particle bombardment", Biotechnology
10: 286-91. Genes can be directly inserted into the organs of living animals.
The production of human alpha-1-antitrypsin in the milk of sheep has been discussed (EEIN 2: 3). A commercial deal for 10 million between the research group and Bayer AG has been made, to develop a flock of high yield producing sheep; BMJ 304: 527.
A method using a rotating bioreactor has been developed by NASA which allows cultured human cells to take on the shape and intercellular connections characteristic of organs in vitro; SA (Feb 1992), 13. The tissues are still only several mm across, but many future applications could be imagined for larger tissues.
The advances in the use of transgenic animals to produce pharmaceuticals are discussed
from a commercial view point in Biotechnology
10: 498-9; Chemistry & Industry
(20 April), 283. A paper describing the production of recombinant hemoglobin is
M.E. Swanson et al., "Production of functional human hemoglobin in transgenic swine",
10: 557-60. It is potentially a very important result because it may allow the production
of long life and cheap hemoglobin for blood transfusions. A general review on the
production of red blood cell substitutes and recombinant hemoglobin is in TIBTECH
A review of embryonic stem cell technology for mouse genetic manipulation is in A. Bradley et al., "Modifying the mouse: design and desire", Biotechnology 10: 534-8. It is a technical review of the proceudres for growing ES cells and maintaining their totipotency, followed by choice of genes to manipulate.
Microsatellite gene markers found in cattle are being used to map the
and within a year are expected to cover the genome well enough for breeding of important
traits to begin using them; GEN
12(3; 1992), 32; 12(6), 14, 25. There is also about 80% homology between human and bovine
The production of useful molecules in animals has been reported in various species. A report using silkworm is U. Reis et al., "Antibody production in silkworm cells and silkworm larvae infected with a dual recombinant Bombyx mori nuclear polyhedrosis virus", Biotechnology 10: 910-2. A general review is J. Hodgson, "Whole animals for wholesale protein production", Biotechnology 10: 863-6. It also includes a comment on animal ethics involved, especially when some of the animal breeds are lethargic or disease- prone.
A review is I. Wilmut et al., "Impact of biotechnology on animal breeding", Animal Reproduction Science 28: 149-62. See also M. Thibier & M. Nibart, "Clinical aspects of embryo transfer in some domestic farm animals", Animal Reproduction Science 28: 139-48.
A pregnancy rate of 60% is reported for transfer of bovine embryos, in J. Reproduction & Fertility 95: 363-70. The general production of embryos is the topic of A. Trounson, "The production of ruminant embryos in vitro", Animal Reproduction Science 28: 125-37. The use of PCR to sex-type bovine embryos is reported in Biotechnology 10: 9805-10. The use of lasers for micromanipulation of mice embryos, opening of the zona pellucida without interrupting blastocyst formation, is reported in F&S 57: 1337-41. A gene directing the assembly and number of germ (reproductive) cells in Drosophila has been called 'oskar'; Nature 358: 387-92.
A change from former listing of papers will be that papers describing animal experiments using genetic engineering will be generally listed here, instead of in the later "animal rights "section.
Transgenic mice models reported include, the expression of intra-MHC transporter genes and class 1 antigens in Diabetes-susceptible NOD mice; Science 256: 1826-32. Studies on cancer include: M. Lakso et al., "Targeted oncogene activation by site-specific recombination in transgenic mice", PNAS 89: 6232-6. An investigation of heart disease and altering renin levels is C.C.J. Miller et al., "Targeted integration of the Ren-1D locus in mouse embryonic stem cells", PNAS 89: 5020-4. Studies on interleukin-6 overexpression in mice are in PNAS 89: 5068-72. The process of memory is being investigated, and some mice lacking kinase genes lack a process (long term potentiation) that is involved in remembering spatial information; Science 257: 162-3. It represents a class of studies called knockout studies (EEIN 2: 48), where gene functions are knocked out and effects observed. See a short review of animal models and human genetics in AJHG 51: 211-5. Studies on somatic genetic recombination in the central nervous system of mice are in Science 257: 404-10.
An autoregulatory element of Drosophila (fruitfly) homeo box gene complexes, called 'Deformed' has been reported to function in transgenic mice; Nature 358: 341-4. See also PNAS 89: 6280-4; 6861-5, 6906-10, 6943-7. Another homeobox experiment using targeted disruption in chick embryos is in Nature 358: 236-9.
A new model for AIDS research, which chimpanzees will be pleased about, is pigtail macaque monkeys; Science 256: 1630-1. However, a few weeks later this was in doubt, as 3 other groups could not repeat it; NS (8 Aug. 1992), 10. There is still not a good model, because chimpanzees don't appear to get AIDS, only to catch HIV. On the failed Alzheimer mice models see SA (June 1992), 10-11.
A method of biological control of house mice using a nematode, Capillaria hepatica may be used in Australia; NS (18 July), 8. Biological control of nematodes is reported in Can. J. Microbiol. 38: 359-64. Research to identify the mechanisms of genetic resistance to pesticides is described in Pest Control (July), 36-7.
Some US research on producing proteins in the milk of animals is reported in Science 257: 1213, including attempts to produce lactoferrin, alpha-1-antitrypsin, clotting factor C, and cystic fibrosis transmembrane receptor protein.
A paper describing genetic transformation of a predatory mite which is used in biological control is in J.K. Presnail & M.A. Hoy, "Stable genetic transformation of a beneficial arthropod, Metaseiulus occidentalis (Acari: Phytoseidae), by a microinjection technique", PNAS 89: 7732-6. They suggest that it may be useful to improve the use of this mite in biocontrol by genetic engineering. Addition of ice-nucleating bacteria to insects can decrease there cold tolerance, which could be useful in pest control, J.M. Strong-Gunderson et al., "Topical application of ice-nucleating-active bacteria decreases insect cold tolerance", AEM 58: 2711-6.
A review of the increasing number of mouse models of human diseases made by genetic engineering, usually using embryonic stem cell approaches, is in Nature 359: 86; Nature Genetics 2 (see also EEIN 2: 60); JAMA 268: 1507, 1511-2. A general review for popular reading is in Newsweek (26 Oct), 62. A system for long-term growth of germ cells has been developed for mouse embryonic germ cells , J.L. Resnick et al., "Long-term proliferation of mouse primordial germ cells in culture", Nature 359: 550-1, reviewed under the heading "The quest for immortality" in p. 482-3. Instead of calling these embryonic stem cells they are called embryonic germ cells, because they can give rise to complete mice, not just some tissues of mice. It is now more possible to imagine a human germ cell line that could be used for cloning, being made.
Of particular interest are several mouse models reported for cystic fibrosis ; Science 257: 1046-7, 1083-8, 1125-8; Nature 358: 708-9; 359: 211-5; Lancet 340: 680, 702-3; BMJ 305: 734; NS (19 Sept 1992), 6. The mice reportedly show similar symptoms to humans with the disease; though the two different strains show different symptoms; Nature 359: 195-6. Interestingly also, the researchers who developed the mouse described in Science , say that they intend to make the mice available to as many people as possible for breeding costs - unlike some researchers who license such mice to companies who charge expensive prices for them. A letter from one of the companies selling transgenic animal disease models that had been criticised, genPharm, is in Science 257: 1188. They say that there average price, of licensed transgenic mice is double the price of a non-transgenic mouse line from the Jackson Laboratory in Bar Habour, Maine, USA, a standard non-profit source of mice.
Mouse models using an allele, Rb - a tumour suppressor gene, linked to retinoblastoma are in E. Y.-H.P. Lee et al., "Mice deficient for Rb are nonviable and show defects in neurogenesis and haematopoiesis", Nature 359: 288-94; T. Jacks et al., "Effects of an Rb mutation in the mouse", Nature 359: 295-300; A.R. Clarke et al., "Requirement for a functional Rb-1 gene in murine development", Nature 359: 328-30. Homozygous mice die as embryos, but heterogeneous mice are not predisposed to retinoblastoma. If the normal allele is transferred into the mice, the developmental defects are corrected - so gene therapy may be effective. Sometimes mice do not have the same symptoms as humans when a gene is deleted, as in the case of a mouse made as a model of Waardenburg's syndrome type 1; Nature Genetics 2: 75-9. Models of interest to studies of Prader-Willi syndrome and Angelman syndromes are in Science 257: 1115-8, 1118-21. Developmental lessons from short mice are in Cell 70: 527-30. The Nov. 1992 issue of TINS 15: 411-465, contains numerous articles on modelling the nervous system, including computer and animal models. A transgenic fish model for cancer research is in J. Wittbrodt et al., "The Xmrk receptor tyrosine kinase is activated in Xiphophorus malignant melanoma", EMBO J. 11: 4239-46.
The production of chimeric rainbow trout by blastomere injection is described in PNAS 89: 9425-8. The objective is to make embryonic stem cell technology, which has been developed for mice, hamsters, and other mammals, applicable for fish. A technique for "rescuing" transgene expression by co-integration is reported in Biotechnology 10: 1450-4. The transfer and expression of the human multiple drug resistance gene in live mice is reportedly useful to prevent marrow toxicity induced by anticancer agents such as taxol, or as a selectable cell marker for gene therapy trials; PNAS 89: 9676-80.
A report from a symposium on the molecular genetics of mental disease stressing the use of animal models of disease is in GEN (1 Nov 1992), 1, 23. It includes discussion of a model for Gaucher's disease, and also looks at mice which can be selected to prefer alcohol or water. Among humans, a study of University of California male students found that of the 20% with the lowest sensitivity to alcohol, 50% develop into alcoholics later in life. The rodent models selected for their like of alcohol, fall into a hypnotic sleep soon after each drinking bout. They estimate there are seven genes involved, after many generations of selection.
A model for inflammatory disease made by disrupting mouse transforming growth factor-b1 gene is in Nature 359: 693-9. Mice that have 3-fold higher cholesterol levels and eventually die by deposits in their blood vessels were made by removing the apolipoprotein E gene function, by two groups of researchers; Science 258: 468-71; Cell 71: 343-53. Effects of mutations in the T cell receptor genes in mice are in Nature 360: 225-32; and on mutations in the myelin gene affecting neuron axons is in Cell 71: 565-76. A review on studies of intestinal stem cells in transgenic mice is in FASEB J. 6: 3039-50.
The use of molecular diagnostics for genetic disease in animals (cattle and horses) is reviewed in Nature 360: 108-9, following the identification of several animal disease genes. An article comparing different beef cattle agricultural systems is in Ambio 21: 451-9.
A review of therapeutic proteins made from transgenic animals is in BioScience 42 (1992), 815-6. Pigs that produced 1g/l of human protein C in milk are reported in PNAS 89 (1992), 12003-7.
A review of the use of quail-chicken chimeras to study development of the cerebellum is N.M. Le Douarin, "Embryonic neural chimeras in the study of brain development", TINS 16: 64-72. A method to freeze Drosophila embryos and thaw them as adults is reported and reviewed in Science 258 (1992), 1896-7, 1932. Genetic models of Drosophila with altered synaptic connections have been made which may be useful to study brain organisation, Nature 361: 299-300; and models of xeroderma pigmentosum and Cockayne's syndrome are in Cell 71 (1992), 925-37. A review of developmental gene studies of metamorphosis in insects and frogs is in Nature 361: 116-7. Fish models of melanoma to study cancer are reviewed in Science 259: 774-5.
A review of mouse models of human single gene disorders that are not transgenic is in BioEssays 14 (1992), 359-65. Examples of rodent (generally mice) models of disease made by genetic engineering include: rats with altered GABA receptors which are non-tolerant to alcohol, Nature 361: 302-3, 356-9; a paper with a review entitled "Mice with half a mind", which reports mice with altered Hox genes and altered development, Nature 360 (1992), 708, 737-41, Cell 71 (1992), 901-10; mice with mutations in tyrosine kinase genes were found to have altered spatial learning and memory, Science 258 (1992), 1903-10; mice expressing a human collagenase gene develop pulmonary emphysema, Cell 71 (1992), 955-61; a line with HTLV-1 Tax gene which develops fibroblastic tumours, Science 258 (1992), 1792-5; mice expressing HIV in the brain, Science 258 (1992), 1804-8; a line expressing the oncogene c-fos which have unusual bone and haematopoietic defects, Nature 360 (1992), 741-5; mouse models of muscular dystrophy expressing the dystropin protein, Nature 360 (1992), 588-91, 591-3; PNAS 89: 11642-4. A review of mouse embryonal carcinoma cells is BioEssays 14 (1992), 769-75.
The production of mice which express a human DNA repair gene which made them less likely to have tumours induced by a carcinogen is a model for carcinogenesis that actually benefits the mice!; Science 259: 219-22. Do we regard this differently to the previous disease models, which cause suffering?
The types of digestive enzymes that animals secrete can be genetically altered, as shown in a transgenic mice study; Biotechnology 11: 376-9. The goal is to engineer non-ruminant animals that can depolymerise cellulose in the small intestines - this is genetic engineering!
In Australia, researchers have inserted the gene for a sulphur-rich protein from sunflower into clover, increasing the level of sulphur-rich protein in clover one hundred times. Sulphur is the limiting factor for sheep and wool growth; NS (3 April), 19. Field trials are hoped for in about 18 months. In Scotland a herd of sheep that produce alpha-antitrypsin is being grown; Science 259: 1698.
Further rapid "advance" is genetic control of aging! A dramatic strain of mice has been bred that appears to grow without aging , until a genetically programmed death; Nature 362: 411. The gene comes from a protein isolated from carp, encoding a protein tithonin. A breeding moratorium has been suggested, and at least concern must be discussed before this gene is applied to domestic animals. If transferred, it may make tender meat.
A review of marine biotechnology, especially in the Pacific rim, is GEN (1 April), 10-4, 25.
The use of baculovirus -infected insect cells to produce enzymes by genetic engineering is reported in P. Vihko et al., "Rat acid phosphatase: Overexpression of active, secreted enzyme by recombinant baculovirus-infected insect cells, molecular properties, and crystallization", PNAS 90: 799-803.
A report on the long term consequences of somatotropin implants in pigs indicates that the pigs had the same growth rate but 15% more efficient feed conversion; J. Animal Science 71: 564-70. The animals had significantly less fat and appeared not to suffer any detrimental affect, compared to controls. The UK MAF is using genetic tests to check for a gene marker linked to leanness of meat; Nature 362: 688. A study on cloning cows using nuclear transplants is in Biology of Reproduction 48: 715-9.
A description of mouse mutations that affect colour of the coat is in Nature 362: 587-8; with abnormal kidneys, Nature 362: 65-7; with abnormal limbs, Nature 362: 546-9; that develop diabetes, Science 259: 1165-9; to develop osteopetrosis, J. Cell Biology 120: 1079-81; altering T-cell development, Science 259: 822-5; Cell 72: 337-48; altered interferon gene activity, Science 259: 1693-4, 1739-42, 1742-5; and altering immunoglobulin gene arrangement, Cell 72: 695-704. Traditional selection methods over 21 generations of mice resulted in good selection of litter size in mice; J. Animal Science 71: 751-8. An experiment investigating the effect of vasoactive intestinal peptide in vitro mouse embryos is in Nature 362: 155-8.
The use of an insect cell line (Spodoptera frugiperda ) to produce recombinant proteins is reported in Biotechnology & Bioengineering 42: 235-9. The Ministry of Agriculture in Japan has inserted the luminescence gene from glowworms into silkworms , as a marker. They are attempting to use silkworms as bioreactors to make interferon or growth hormone. A point mutation has been found to be a major cause of frutifly resistance to insecticides; Nature 363 (3 June 1993).
In Japan a 278 million Yen project to grow black tuna in culture is underway in Kagoshima prefecture; Yomiuri Shinbun (1 June 1993), 9. A review of research to improve animal feed by biotechnology is in Biotechnology 11: 552. Genetic analysis and mapping of farm animals is reported in Nature Genetics 3: 103-12; 206-10; Nature 363 (3 June). A photo of the sheep "bioreactors" in Edinburgh is NS (19 June), 12.
Mice can be born after the transplantation of early cell cycle stage embryonic nuclei (up to 8 cell embryoes tried) into enucleated oocytes, producing clones; Biology of Reproduction 48: 958-63. The period of the cell cycle influences the success greatly. A simplified method for producing ES cells is reported in S.A. Wood et al., "Simple and efficient production of embryonic stem cell-embryo chimeras by coculture", PNAS 90: 4582-5. A study on the affect of maternal aging on the heritability of transgenes in mice found that their was a strong age effect in females (older females are less likely to transmit the new gene), but no effect in males; Biology of Reproduction 48: 1104-12.
A computerized database called TBASE has been established for transgenic animals and targeted mutations; Nature 363: 375-6. New animal models include transgenic mice: expressing the CD4 receptor allowing entry of HIV-1 as a small mammal model for AIDS research, GEN (1 Jun), 34; Mol. & Cell. Genetics (May); the use of SCID-hu mice as a model for HIV infection is also suggested, Nature 363: 732-6; with microphthalmia; Transgenic Research 2: 14-20; a model of amyotrophic lateral sclerosis, Cell 73: 35-46; osteoarthritis, PNAS 90: 2870-4; osteogenesis imperfecta, PNAS 90: 1701-5; neurocristopathy, PNAS 90: 3192-3196; hypobetalipoproteinemia, PNAS 90: 2389-93; cross species mice for diabetic study, PNAS 90: 1877-81. Other transgenic mice with diseased characters for research include mutations of the transforming growth factor gene, Cell 73: 249-61; mutations of the retinoic acid receptor, Cell 73: 643-58; disrupted collagen fibrils by overexpression of collagen, PNAS 90: 3825-9; mice expressing the gene fos can be signalled to die within a few days, showing it can act as a signal for cell death in vivo, Nature 363: 166-9. It is claimed that most researchers overvalue the usefulness of transgenic mice are in Biotechnology 11: 663. Perhaps it is part of the general trend to promote genetics as the cure to all ills and problems.
Improving control of livestock diseases using new biotech is reviewed in BioScience 43: 475-83. A short review of the techniques for genetic engineering of pigs to attempt to make them organ donors for humans is in Newsweek (2 Aug), 53. The use of a YAC to transfer human immunoglobulin genes into mice is reported in Biotechnology 11: 911-4.
A book review on baculovirus expression is in Cell 74: 7-8; and a paper on the use of them to express glutathione-S-transferase fusion proteins is Biotechnology 11: 933-6.
The Jackson Laboratory in the USA is now a clearinghouse for transgenic mice, supported by various medical aid organizations; Nature 364: 755. New animal models include transgenic mice: model of atherosclerosis, Science 261: 469-72; altered myogenin genes and muscle disease, Nature 364: 485, 501-6, 532-5; studies of the GABA receptor genes, Nature 364: 448-50, for propagating prions, Cell 73: 979-88; immunodeficiency, Science 261: 358-61; resistance to systemic lupus erythematosus, Science 261: 91-3; on aging gene studies, Nature 364: 806-9. Gene mutations affecting behaviour of the nematode Caenorhabditis elegans are reported in Nature 364: 327-30. Mice expressing the tumour germ cell marker alkaline phosphatase have been made as a model for human cancer antigenes, PNAS 90: 5081-5. A rat experiment using a suicide gene therapy for treatment of liver cancer is reported in PNAS 90: 7024-8.
A general letter saying the use of transgenic animals for xenografting is unlikely to succeed soon is Biotechnology 11: 966. It says there have so far been 35 attempts at xenografting, and all have failed (though some had relatively long term survival for kidneys). A letter on the postulated immunorejection of a complement inactive pig organ (from a transgenic pig), because of other antibodies; Lancet 342 (11 Sept); Transplantation 55: 857-66; Lancet 342: 879-80; BMJ 307: 637-8. A more technical paper is U. Galili, "Interaction of the natural anti-Gal antibody with alpha-galactosyl epitopes: a major obstacle for xenotransplantation in humans", Immunology Today 14: 480-2. On the ethical issues of xenografts see J.L. Nelson, "Moral sensibilities and moral standing: Caplan on xenograft "donors"", Bioethics 7(4), 315-22.
A review of products available for producing embryonic stem (ES) cell chimeras is Nature 365: 87-9. Simple aggregation of ES cells with morulae-stage embryos can make chimeras as efficiently as injection of ES cells into blastocysts. Mouse models include: atherosclerosis models are reviewed in J.L. Breshow, "Transgenic mouse models of lipoprotein metabolism and atherosclerosis", PNAS 90: 8314-8, see also Nature 364: 73-5, 762-4; skeletal deformities due to altered collagen gene, Nature 365: 56-61; cancer genes, Nature 365: 179-81, Science 261: 1584-8; Alzheimer's (though no signs of the disease yet), Science 261: 1520; diabetes, Cell 74: 1089-100; motor neuron degeneration, Nature 365: 27-32.