Genetic variation of a disintegrin gene found in the American copperhead snake (Agkistrodon contortrix)

Disintegrins are small, non-enzymatic proteins produced in snake venom. PCR and DNA sequencing analysis of genomic DNA for all subspecies of the copperhead snake (Agkistrodon contortrix) were analyzed for the presence of a disintegrin gene. Four samples each of the subspecies: A. c. contortrix, A. c. laticinctus, A. c. mokasen, A. c. phaeogaster, and A. c. pictigaster were collected from different locations across their geographic range and analyzed. A single PCR fragment from each sample was obtained, containing exon and intron sequences. The disintegrins identified in this study shared the highest amino acid identity to contortrostatin and acostatin b chain. Neighbor joining analysis of the disintegrin haplotypes and bootstrap tests of significance grouped the A. contortrix subspecies into two clades. The A. c. mokasen samples collected in Kentucky were grouped in one clade, while the A. c. contortrix, A. c. laticinctus, A. c. phaeogaster, and A. c. pictigaster samples collected in Texas, Louisiana, and Missouri were grouped in a different clade. Analysis of molecular variance (AMOVA) and ΦST pairwise comparisons showed significant genetic variation between subspecies. Nucleotide substitution analysis suggests the rapid evolution of disintegrin genes in A. contortrix subspecies.