Molecular cloning of an avian anti-Müllerian hormone homologue

Anti-Müllerian hormone (AMH) is responsible for regression of the Müllerian ducts in males during embryonic development. This peptide hormone of the transforming growth factor-beta family is also believed to play a broader role in sex determination, affecting differentiation and morphogenesis of the testes. Accordingly, in mammals, AMH is produced at much higher levels in male fetuses than in female fetuses. In contrast, in birds, both male and female embryonic gonads produce AMH at high levels, although in males it is still responsible for regression of the Müllerian ducts. Its persistent expression by the embryonic ovaries and its role in female sex determination in birds is not understood. We have cloned an avian homologue to AMH. Avian AMH cDNA encodes a 644 amino acid protein that is 42% identical to human AMH overall with increased identity at the carboxyl terminus. Similarities to human AMH include motifs of sequence identity, a conserved putative plasmin cleavage site and cysteine alignments, and similar genomic intron/exon structure. Antibodies to recombinant avian AMH cross-react with recombinant human AMH and were used to show that avian AMH is glycosylated as has been shown for the human form. The avian AMH gene is transcribed in both male and female gonads but not in liver, heart, kidney or muscle.