EXPRESSION OF SKIN COLOUR GENES IN THARPA- RKAR CATTLE DURING SUMMER AND WINTER SEASON

In order to observe the expression of the genes (MC1R and PMEL) and activity of the enzyme (tyrosinase) related to skin pigmentation, study was conducted on Tharparkar heifers. Blood samples were collected from Tharparkar heifers (2-3 years) during summer (Tmax, 36.4oC) and winter (Tmin, 4.1 oC) season at weekly interval. Just after blood collection, samples were transferred to the laboratory for lymphocytes separation and isolation of RNA. The RNA samples were further processed for cDNA preparation from which the relative mRNA expression of the genes was quantified using RT-PCR. The tyrosinase activity was determined in plasma samples using Bovine tyrosinase ELISA kit. The relative MC1R and PMEL mRNA expression in lymphocytes of Tharparkar heifers was found to be significantly (P<0.05) higher during winter season than summer season. Similarly, the activity of plasma tyrosinase enzyme was also found to be significantly (P<0.05) higher during winter season. The thyroidal hormones (Thyroxine and Triiodothyronine) was found to be significantly (P<0.05) higher during winter season than summer season. Thyroidal hormones showed the positive correlation with the skin colour related genes and tyrosinase enzyme activity. The results of the present study clearly showed the significant difference in the expression levels of skin colour related genes (MC1R and PMEL) and tyrosinase activity during the two different seasons. Therefore, it can be stated that these genes and tyrosinase enzyme activity is related to adaptability of Tharparkar cattle to different ambient conditions.