Identification of Na‐driven anion exchanger (NDAE) splice variants from Malpighian (renal) tubules of the adult yellow‐fever mosquito

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To date, only one member of the bicarbonate transporter (SLC4) superfamily has been cloned from an insect—i.e., the Na‐driven anion exchanger (NDAE) of Drosophila (Romero et al., 2000, J Biol Chem 275: 24552). The goal of this study was to identify cDNAs encoding NDAE in Malpighian tubules of the yellow‐fever mosquito, Aedes aegypti. Using the recently completed Aedes genome, we designed gene‐specific primers to highly conserved regions of NDAE for conducting 5′ and 3′ RACE on Malpighian tubule cDNA. The 3′ RACE indicated that splicing does not occur at the end of the open‐reading frame (ORF) or in the 3′ ‐untranslated region (UTR). However, the 5′ RACE demonstrated extensive splicing in the 5′ ‐UTR immediately before the predicted start codon, resulting in transcripts with unique 5′ UTRs that we designate as NDAE‐A, NDAE‐B, and NDAE‐C. The putative functions of these unique 5′ UTRs are not known, but it is possible that they play a role in the translational efficiency or stability of a particular transcript within the Malpighian tubule. One splice variant (NDAE‐A’ ) contained a deletion of 162 nucleotides within the ORF, which would encode an NDAE with a cytosolic N‐terminal domain missing 54 amino acids. In conclusion, Aedes Malpighian tubules express a diversity of NDAE transcripts. Functional properties remain to be elucidated. Supported by NSF Grant IOB‐0542797 to KWB.