Developmental regulation and expression of the zebrafish connexin43 gene

We cloned and sequenced the zebrafish (Danio rerio) connexin43 (Cx43 alpha 1) gone. The predicted protein sequence shows a high degree of sequence conservation. Transcript analyses revealed multiple transcription start sites and a potential alternative transcript encoding a N-terminally truncated Cx43 alpha 1 protein. Maternal Cx43a1 transcripts were detected, with zygotic expression initiated before gastrulation. In situ hybridization revealed many Cx43 alpha 1 expression domains, including the notochord and brain, heart and vasculature, many resembling patterns seen in mammalian embryos. Of interest, a reporter construct under control of the mouse Cx43 alpha 1 promoter was observed to drive green fluorescent protein expression in zebrafish embryos in domains mimicking the native Cx43 alpha 1 expression pattern in fish and mice. Sequence comparison between the mouse and zebrafish Cx43 alpha 1 promoter sequences, showed the conservation of several transcription factor motifs, which otherwise shared little overall sequence homology. The conservation of protein sequence and developmental gene regulation would suggest that Cx43 alpha 1 gap junctions are likely to have conserved roles in vertebrate embryonic development. (c) 2005 Wiley-Liss, Inc.