Analysis of horse and donkey gonadotrophin genes using Southern blotting and DNA hybridization techniques

The number of genes encoding the common alpha-subunit and hormone-specific beta-subunits of the equine gonadotrophins (FSH, LH and CG) were investigated in the horse (Equus caballus), donkey (E. asinus) and 2 horse x donkey hybrids (the mule and hinny). The Southern technique, involving restriction enzyme digestion, blotting and DNA hybridization to 32P-labelled DNA probes was used to estimate the copy number for each gene and to assess the extent to which equids resemble primates, the only other animals that secrete a CG during pregnancy. These methods indicated that, in common with mammals, there was a single copy of the equine gonadotrophin alpha-and FSH beta-subunit genes. Also in common with other mammals, our results are consistent with there being a single LH beta-subunit gene but, unlike primates, no evidence of multiple LH/CG beta-subunit genes was obtained. There was no restriction fragment length polymorphism (RFLP) within species using the 4 enzymes chosen for this study, but the RFLP pattern for the beta-subunit genes differed between species, giving rise to species-specific 'fingerprints'. The mule and hinny Southern blots showed a combination of the horse and donkey fingerprints, consistent with the presence of both genomes in these hybrids and consistent with the expression of both horse and donkey CG by hybrid conceptuses. In man and baboons, multiple genes code for the beta-subunit as a consequence of LH beta-subunit gene duplication.(ABSTRACT TRUNCATED AT 250 WORDS)