Bouvet A, Basrur PK
1 Department of Molecular Physiology, AFRC Institute of Animal Physiology and Genetics Research, Babraham, Cambridge, UK, CB2 4AT
2 Department of Biomedical Sciences, Ontario Veterinary College University of Guelph, Guelph, Ontario, Canada, NIG, 2W1
In humans, fragile sites, their association with clinical syndromes and their usefulness as markers for gene mapping is well established (1). In cattl e, an unstained gap on the long arm of the X chromosome has been reported(2,3). Baldy Calf Syndrome is an inherited condition involving parakeratosis, immunodepression, death at an early age of heifers (4) and embryo mortality in males (5), in certain lines of Canadian Holstein-Friesian heifers. The association of the Fragile X and this Syndrome was investigated in six clinical cases of Baldy Calf Syndrome compared to normal individuals including adult cows, heifers and bull calves, and mothers that have produced Baldy Calves. An unstained gap, or a break involving one or both chromatids was detected on the long arm of the X chromosome (Xq31) in 11.1 to 32.5 % of the metaphase spreads examined, from the affected heifers. In contrast, the fragile site was detected only in 0 to 4% of metaphase spreads from the other animals of the Holstein- Friesian breed. Therefore, a higher frequency of Fragile X chromosome seems to be ftrmly associated with Baldy Calf Syndrome. There was no biochemical deficiency in the blood of Baldy Calves that could have triggered breakage (6) and the experimental contunination of cultures with Mycoplasma arginini isolated from the skin of Baldy Calves did not produce an increase in Fragile X expression (7). Since the Fragile X seems to exist in Australia in Shorthorn farnilies in both normal males and females (2), the increase in frequency could be associated with the pleiotropic effect of the autosomal gene for Baldy Calf Syndrome.
Similarities with the Human Fragile X Syndrome include frequencies of normal and affected individuals, affected tissues of ectodermal origin, more severe impact on males(l) and autosomal control of high frequency (8), and would point towards an impairment at a critical step of DNA synthesis. Common features (chromosome breakage, parakeratosis, and immunodepression) with Bovine Inherited Zinc deficiency "Lethal trait A46" (9), despite normal zinc levels (6), would suggest a mutation at the level of one of the enzymes involved in zinc metabolism.
1 Opitz JM, Sutherland GR: Conference Report: International Workshop on the Fragile X and X-link ed Mental Retardation Am Med Genet 17: 5-94 (1984)
2 Halnan CRE: Proceedings of the 5th European Colloquium on Cytogenetics of Domestic Animals 93-102 24 Milano (1982)
3 Uchida IA, Freeeman VCP, Basrur PK: The Fragile X in Cattle Am j Med Genet 23: 557-562 (1986)
4 GLMAN JPW: Proceedings of the 92th Annual Meeting of the American Veterinary Medical Association 49-53 (1955)
5 Basrur PK: Genetics in Veterinary Medicine pp, 26-28, Guelph (1986)
6 BOUVET A: Fragile X chromosome in Baldy calf Syndrome Ph.D. Ontario, Veterinary College, University of Guelph, Canada (1988)
7 Bouvet A, Ruhnke L, Basrur PK: Procecdings of the III Satellite Symposium on Aberrant genes and Chromosomes in the Etiology of Reproductive Problems , Guelph, Ontario, Canada (1988)
8 Israel MH: Autosomal suppressor gene for Fragile X: An hypothesis Am J Med Genet 26: 19-31 (1987)
9 Weismann K, Flagstad T: Hereditary Zinc deficiency (Adema disease) in cattle. An animal parallel to Acrodermatitis Enteropatica Acta Derm-Venereol 6: 151-154 (1976)
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