Allelic polymorphism of exon 2 in BMP15 gene in F1 crossbred sheep from crossing Romanov rams with Kermani ewes

This study was carried out to investigate the polymorphisms of bone morphogenetic protein 15 (BMP15) exon 2 in purebred Kermani and crossbred Romanov × Kermani sheep and functional analysis of the underlying mutations. A number of 50 purebred Kermani and 115 F1 Romanov (ram) × Kermani (ewe) crossbred sheep were sampled and a 153 bp fragment from exon 2 of the ovine BMP15 gene was successfully amplified from the genomic DNA of each animal using designed primers. The polymerase chain reaction-single-strand conformation polymorphism (PCR-SSCP) technique was used to investigate the polymorphism of BMP15 gene (exon 2(. Twenty samples of different SSCP patterns were randomly selected for DNA sequencing and detecting the BMP15 mutations and subsequent functional analyses. The polymorphic fragments amplified by designed primers were sequenced. There were eight SSCP patterns (AA, AB, BB, AC, AD, AE, AF and AG) with frequencies of 0.24, 0.17, 0.24, 0.08, 0.05, 0.10, 0.03 and 0.09, respectively. The frequency of A allele was obviously higher than those of other alleles. The sequencing results revealed two single nucleotide mutations; the first mutation at position 32bp which did not cause any change in the amino acid sequence but the second mutation led to a change in 40th amino acid (a Lysine amino acid replaced by an Asparagine amino acid). The result of this experiment indicates that the genetic diversity level of BMP15 exon 2 gene was high in the Romanov × Kermani crossbreds indicating that BMP15 exon 2 can played a vital function in the development of ovary and follicles, especially in the improvement of fertility trait and could be used as a potential advantageous molecular marker for reproduction traits in this genetic group. Our finding provides exciting new opportunities for understanding the role of the BMP15 on ovarian follicular growth and development in crossbreed ewes in breeding programs.  However, further investigation using a large population of Romanov × Kermani crossbred sheep is required to confirm the link between the identified mutation and the observed increased prolificacy in this population.