Association of Melatonin receptor 1A (MTNR1A) gene polymorphism with seasonal suppression of fertility in buffaloes

Abstract

The polymorphism in Melatonin receptor 1A (MTNR1A) gene and its association with reproductive cyclicity (cyclic, n=51; non-cyclic, n=50) during summer season and age at first calving (<3.5 years, n=38; >3.5 years, n=60) was investigated in buffaloes subjected to blood sampling. Polymerase chain reaction (PCR) of genomic DNA was carried out using three primers viz. 824 bp (primer pair 1), 856 bp (primer pair 2) and 268 bp (primer pair 3) corresponding to exon-II of MTNR1A gene. Restriction fragment length polymorphism was performed using PCR products of primer pair 1 and 2. The digestion of PCR product of primer pair 1 with restriction enzymes viz. MnII, RsaI or Eco3II generated total restriction sites respectively as 14, 4 and 5. Based upon differential restriction sites, six genotypes revealed in buffaloes using MnII were MM-1 to MM-6, four genotypes using RsaI were RR-1 to RR-4, and four genotypes using Eco3II were EE-1 to EE-4. The digestion of PCR product of primer pair 2 with MnII, RsaI or Eco3II generated restriction sites respectively as 13, 5 and 6. Based upon differential restriction sites, six genotypes revealed using MnII were mm-1 to mm-6, five genotypes using RsaI were rr-1to rr-5, and three genotypes using Eco3II were ee-1 to ee-3. For primer pair 3, single stranded conformational polymorphism analysis exhibited 5 genotypes viz. AA, BB, AB, CC and DD. The results revealed that the buffaloes during summer had polymorphic genotypes for MTNR1A gene as buffaloes showing reproductive cyclicity had MM-3, MM-4, RR-2, EE-3, mm-2, mm-4, rr-3, ee-3, CC and DD genotypes, whereas their non-cyclic counterparts had MM-2, MM-6, EE-4, mm-3, mm-6, AA, BB and AB genotypes. However, no such differences were recorded with respect to age at first calving. In conclusion, polymorphic genotypes of MTNR1A gene may be considered as genetic markers to identify buffaloes with better reproductive potential during summer season.