Association between PCR-RFLP of Melatonin Receptor 1a Gene and High Prolificacy in Small Tail Han Sheep

Abstract

Melatonin regulates circadian rhythms and reproduction changes in seasonally reproductive mammals through binding to high-affinity, G-protein-coupled receptors. Small Tail Han sheep that has significant characteristics of high prolificacy and non- seasonal ovulatory activity is an excellent local sheep breed in P. R. China. The exon 2 of the ovine melatonin receptor 1a (MTNR1A) gene was amplified and a uniform fragment of 824 bp was obtained in 150 ewes of Small Tail Han sheep. The 824 bp PCR product was digested with restriction endonucleases Mnl and Ⅰ Rsa , and genetic polymorphism was detected by PCR Ⅰ -RFLP. Polymorphic Mnl site was detected at base position 605 of the exon 2 of Ⅰ the MTNR1A gene. There were two kinds of genotypes in Small Tail Han sheep, AB (303 bp, 236 bp/67 bp) and BB (236 bp/67 bp, 236 bp/67 bp). The results indicated that genotype AA (303 bp, 303 bp) at MnlⅠ-RFLP site did not exist in non-seasonal estrous Small Tail Han sheep, which suggested that there was an association between genotype AA (303 bp, 303 bp) and reproductive seasonality in sheep. Polymorphic Rsa site was detected at base position 604 of the Ⅰ exon 2 of the MTNR1A gene. Three kinds of genotypes were found in Small Tail Han sheep, AA (290 bp, 290 bp), AB (290 bp, 267 bp/23 bp) and BB (267 bp/23 bp, 267 bp/23 bp). Least squares means of litter size in the first parity and the second parity for genotype AA (290 bp, 290 bp) at RsaⅠ-RFLP site were 0.43 and 1.06 more than those for genotype AB (290 bp, 267 bp/23 bp) in Small Tail Han sheep. (Asian-Aust. J. Anim. Sci. 2003. Vol 16, No. 12 :1701-1704)