Isolation and characterization of As60A, a transforming growth factor-β gene, from the malaria vector Anopheles stephensi

We have isolated the first mosquito member of the TGF-β superfamily, As60A. As60A is a single copy gene, ∼5 kb in length and encodes eight exons. Here we report the isolation and characterization of two of four transcripts produced from this gene. The transcripts As60A¹ and As60A² encode related 5'UTR/exon 1 sequences. As60A is most similar to the 60A genes from Drosophila and is thus a member of the Dpp/BMP subfamily of the TGF-β superfamily. The splice junction of intron 2 is conserved among As60A, BMP2, BMP4, Tc-Dpp, Bm-tgh-1, TGF-β1 and Dpp. Intron 2 also contains three putative binding sites for a Dorsal/Gambif1 transcription factor. The large number of introns and the conservation of intron 2 indicate that As60A is relatively ancient compared to the other arthropod TGF-β genes. We also propose that As60A plays a role in the mosquito immune response to Plasmodium infection.