Expression profile and association of ghrelin gene polymorphism with growth and litter traits in Indian goat breeds

Ghrelin (GHRL) is a 28 amino acid bioactive peptide influencing growth hormone secretion, regulation of energy homeostasis and appetite stimulation. The present investigation was undertaken to study the expression profile of the caprine ghrelin gene and to identify single nucleotide variations in caprine ghrelin gene to evaluate its association with production traits. Tissue samples of abomasum, lung, liver, spleen, fallopian tube and ovary were collected from six Malabari and Attappady Black adult goats to study the ghrelin gene expression pattern. Quantitative Real-Time PCR was used to find out the relative expression of ghrelin in various tissues. It was observed that there was a higher expression of ghrelin in the abomasal (3.67) tissues and the least expression in the liver (0.19) tissues. Significantly higher level of expression was noticed in Attappady Black than Malabari goats. Highly significant (p < 0.01) 4.07 fold upregulation was noticed in the ovary compared to the lung (3.85) and abomasum (3.80). A total of 176 Malabari and Attappady Black adult goats were screened for polymorphism using PCR-SSCP. Representative samples from different band patterns were sequenced. Two SNPs at the 9th position (C & RARR;A transversion) and at the 38th position (G & RARR;T transversion) in exon 4 and two SNPs at the 45th position (C & RARR;T transition) and 89th position (C & RARR;T transition) in intron 4 were identified. A significant associ-ation was observed between body measurement traits and the identified single nucleotide polymorphisms. The AB genotype demonstrated superior values over the AA genotype in body length and height for exon 4, while for intron 4 AA genotype was superior to the AB genotype. The AB genotype demonstrated higher values over the AA genotype for chest girth, CCI and TI. However, no association was found between body weight and litter size. The ghrelin gene may be used in marker-assisted selection for improving conformation traits in goats.