Nucleotide sequencing and DNA polymorphism studies on IGFBP-3 gene in sheep and its comparison with cattle and buffalo

The insulin-like growth factor binding protein-3 (IGFBP-3) gene is a structural gene associated with the growth and development of the animals. The present investigation was carried out to study nucleotide sequencing and DNA polymorphism by PCR-RFLP of IGFBP-3 gene in sheep and its comparison with cattle and buffalo. Genomic DNA was isolated from a total of 152 animals from different livestock farms of India belonging to five Indian breeds of sheep namely Marwari, Mandya, Madras Red, Muzaffarnagari and Banur. A fragment of IGFBP-3 gene, comprising of a part of exon 2, complete intron 2, exon 3, and a part of intron 3, was amplified. The amplified fragment was found to be 654 bp in sheep as compared to our earlier reports of 651 bp in cattle and 655 bp in buffalo. On digestion of 654 bp with HaeIII restriction enzyme yielded single restriction pattern of eight fragments of sizes 201, 201, 87, 67, 56, 19, 16 and 7 bp in all the animals studied revealing absence of polymorphism in sheep. On comparison, this fragment was reported to be polymorphic in cattle and monomorphic in buffalo. Nucleotide sequencing of the amplified fragment of IGFBP-3 gene of Banur sheep was done and submitted to the NCBI GenBank (accession no. AY306012). The nucleotide sequence analysis indicated that the percent similarity of IGFBP-3 gene fragment of sheep with cattle and buffalo was nearly 90%. There was approximately 93% similarity in the amino acid sequence of sheep with cattle and buffalo.