Genetic and molecular evidence of an X-chromosome deletion spanning the tabby (Ta) and testicular feminization (Tfm) loci in the mouse

Abstract

A new radiation-induced mutation in the mouse, tabby-25H (Ta^25H), has proved to be a deletion which spans both the tabby and testicular feminization (Tfm) loci on the X chromosome. The Ta phenotype closely resembles that of the original Ta^Famutation in both the heterozygous and hemizygous conditions but Ta^25H/Y animals additionally show the Tfm/Y phenotype, being externally female but possessing abdominally located testes. There is a shortage of both Ta^25Hl+ and Ta^25H/Y classes relative to their normal sibs among the progeny of Ta^25H/+ females at weaning age and this was indicated to be due to prenatal or neonatal losses. Exencephaly was observed in some members of both classes prior to birth. Both Ta^25Hclasses tend to be runted at weaning but, remarkably, Ta^25H/+ females often show a range of abnormalities not evident in Ta^25HIY animals. When probes for the Zfx, Ccg-1, Phk, and DXPas19 loci, which lie close to Ta, were hybridised to DNAs from Ta^25Hhemizygotes, the profiles of the X-linked bands were similar to those of control DNAs, suggesting these loci lie outside the deletion. However, a clear absence of an X-linked band was found with human androgen receptor probes, indicating that the Tfm locus is indeed missing. The deletion, therefore, extends a minimum of 1.5 cM and, with its proximal and distal boundaries partially defined, it could be as large as 4 cM. As Ta^25H/+ females show the striped X-inactivation coat pattern, the putative X-inactivation centre, Xce, which lies close to Ta, cannot be located within the region deleted. The greasy (Gs) locus similarly appears to lie outside the deletion.