Cytogenetics of Saanen goats showing abnormal development of the reproductive tract associated with the dominant gene for polledness

Abstract

Genetic studies have shown that the dominant gene for polledness found in the Saanen breed will, when homozygous, lead to pseudohermaphrodism, testicular hypoplasia or epididymal sperm granuloma and to an abnormal sex ratio (excess of males). An analysis of chromosomal constitution and nuclear appendages in peripheral leucocytes and tissue cultures of 17 pseudohermaphrodites, 10 males with epididymal sperm granuloma and 3 males with testicular hypoplasia was carried out. Sex chromatin could not be unequivocally distinguished in buccal or urinary bladder smears owing to the presence of other large chromatin masses. In no case was any trace of ovarian tissue found. One pseudohermaphrodite was a blood chimaera (XX/XY). This animal, a typical freemartin, was indistinguishable in anatomy or histology from the other pseudohermaphrodites. The chromosomal constitution and nuclear appendages of the remaining 16 pseudohermaphrodites and of the males with testicular hypoplasia were those of a genetic female. It is concluded that the pseudohermaphroditic effect of the polled gene is limited to genetic females and that males with testicular hypoplasia are actually genetic females showing an extreme pseudohermaphroditic effect. The abnormal sex ratio characteristic of the Saanen breed is thus shown to be a trivial consequence of classifying extreme pseudohermaphrodites as males. The chromosomal constitution and nuclear appendages of the males with epididymal sperm granuloma were those of a normal male. Hence the genetic factor for polledness, when homozygous in genetic males, can lead to the development of epididymal sperm granuloma.

Fertile XO males and females in the varying lemming, Dicrostonyx torquatus pall. (1779)

“…Although it can be assumed that the translocated part of the Y is too small to be detectable, another possibility to be taken into consideration is the complete loss of the Y chromosome. The development of a male phenotype was observed in some XX specimens of the mouse (Cattanach et al, 1971), the goat (Soller et al, 1969) and the human (Wachtel et al, 1976). This condition, often called sex reversal, is inherited as an autosomal trait, dominant (mouse) or recessive (goat).…”

Fine Mapping Suggests that the Goat Polled Intersex Syndrome and the Human Blepharophimosis Ptosis Epicanthus Syndrome Map to a 100-kb Homologous Region

“…One peculiarity of this syndrome is the full association between absence of horns and intersexuality (Asdell 1944). No recombinant has ever been observed between the two phenotypes (Ricordeau and Lauvergne 1967;Soller et al 1969), suggesting that they are either under the control of a single pleiotropic gene or two very closely linked genes. Whereas intersexuality appears as autosomal recessive, polledness is autosomal dominant, which has been helpful in building resource families (Vaiman et al 1996a).…”

Unilateral Testicular Hypoplasia in a Goat

“…The more common occurs in genetically female goats which are homozygous for the gene for polledness [ 5 ] . The karyotype of the goats is normal female [6], but the phenotype varies from pseudohermaphrodites which appear externally female to an extreme male phenotype which includes small descended testes that are bilaterally symmetric [5,61. These testes are half normal size and contain cysts three to five mm in diameter near the head of the epididymis.…”

“…These testes are half normal size and contain cysts three to five mm in diameter near the head of the epididymis. No sperm are present in the epididymis or testis, but cells resembling spermatogonia are present in small, rudimentary seminiferous tubules [6]. The genetically male goats homozygous for the gene for polledness usually develop sperm granulomas in the heads of the epididymides [6].…”