Ovine Genomic Sequence and Polymorphisms Present in Leptin and Promoter Region

The objectives of this research were to sequence leptin and its promoter region in sheep and identify polymorphisms within these regions.  We hypothesized that genotypic variants previously identified within leptin in New Zealand sheep populations would also be present in U.S. populations of sheep.  Six contemporary groups of dual-purpose (n = 100) and meat breed (n = 220) rams from the annual University of Wyoming performance tests were used for DNA analysis.  Blood was collected from each ram and DNA extracted from white blood cells for sequencing and SNP detection.  Breeds analyzed in the current study included Rambouillet, Colombia, Targhee, Suffolk, and Hampshire for comparison with Romney, Merino, Coopworth, Corriedale, Poll Dorset, and Suffolk breeds in which leptin polymorphisms have been reported.  Primers were designed for leptin and its promoter to span introns using bovine sequences.  The leptin gene was successfully sequenced; however, only the anterior and posterior regions of its promoter could be sequenced.  Amplified PCR products were used for sequencing.  Four amplicons aligned to chromosome 4, two amplicons did not align, and one amplicon aligned to a zinc finger region on chromosome 11.  Despite successful sequencing within leptin, no polymorphisms that matched previous reports were detected.  Difficulty in sequencing the leptin promoter region may be attributed to gene structure differences between ovine and bovine, and further research is needed to elucidate those sequence variations.  Results suggested that polymorphisms previously identified in island pacific sheep are not applicable to U.S. populations of sheep.