If the great god Pan wore horns as a sign of male sexual pride, he might have been curious to know that all polled, or hornless, goats carry a gene for hermaphroditism. Now, it appears that a rare human disorder causing excess eyelid growth and premature ovarian failure is genetically related to the goat Polled Intersex Syndrome (PIS). In the March issue of Genome Research, Daniel Vaiman and colleagues (Institut National de la Recherche Agronomique) locate the gene region responsible for PIS and show that it is analogous to the human region responsible for Blepharophimosis Ptosis Epicanthus inversus syndrome (BPES).
Long ago scientists recognized that a single goat gene or gene region (PIS) causes both hornlessness and the growth of male genitals on female animals. To pinpoint this region, Vaiman and colleagues identified and located 16 genetic markers, or unique sequences, spaced out over the chromosome area harboring PIS. For each marker, they also identified several variations, or alleles. They then examined hundreds of goats to see whether particular alleles were strongly associated with hornlessness, thus identifying the genetic markers nearest PIS. According to their work, PIS is near two known genes (RBP1 and COP), as is the human disorder BPES. The eyelid deformities seen in BPES patients may thus be the human equivalent of hornlessness in goats. In addition, deciphering the obscure relationship between BPES-related ovarian failure and PIS-related hermaphroditism may help to explain how sex is determined in mammalian species.