Polymorphism of melatonin receptor (MTNR1A) gene and its association with seasonal reproduction in water buffalo (Bubalus bubalis).

The water buffalo have a seasonal pattern of reproduction with decreased sexual activity during the longer photoperiod. The present study was designed to identify a single nucleotide polymorphism (SNP) in the MTNR1 A gene and its association with seasonal reproduction and reproductive characteristics in Murrah buffalo cows. The 812 bp fragment encompassing exon II of the MTNR1 A gene was amplified from genomic DNA of 190 pluriparous Murrah buffalo cows. Amplified PCR products from 12 samples were subjected to custom sequencing of both ends (5' and 3' ends). A synonymous mutation was identified at position 72 in exon II of MTNR1 A gene. Digestion of PCR products with HpaI enzyme indicated there was one polymorphic site caused by the presence of nucleotide C at position 72 in place of T that resulted in three genotypes: T/T (812bp), C/T (812, 743 and 69 bp) and C/C (743 and 69 bp). There was an association (P < 0.05) between the MTNR1 A genotype and reproductive activity in Murrah buffalo cows such that buffalo cows with T/T genotype had less seasonal reproductive activity as compared with those with the C/C genotype. The period of greatest mating activity of buffalo cows with the C/C genotype was from November to December whereas buffalo cows with the T/T genotype mated mainly between May and July. Thus, the polymorphism of the MTNR1 A gene might be considered as a genetic marker to identify Murrah buffalo, which are able to reproduce during periods that are not a part of the typical breeding season for these buffalo.