Comparative genomic analysis of eutherian connexin genes.

The eutherian connexins were characterized as protein constituents of gap junctions implicated in cell-cell communications between adjoining cells in multiple cell types, regulation of major physiological processes and disease pathogeneses. However, conventional connexin gene and protein classifications could be regarded as unsuitable in descriptions of comprehensive eutherian connexin gene data sets, due to ambiguities and inconsistencies in connexin gene and protein nomenclatures. Using eutherian comparative genomic analysis protocol and 35 public eutherian reference genomic sequence data sets, the present analysis attempted to update and revise comprehensive eutherian connexin gene data sets, and address and resolve major discrepancies in their descriptions. Among 631 potential coding sequences, the tests of reliability of eutherian public genomic sequences annotated, in aggregate, 349 connexin complete coding sequences. The most comprehensive curated eutherian connexin gene data set described 21 major gene clusters, 4 of which included evidence of differential gene expansions. For example, the present gene annotations initially described human CXNK1 gene and annotated 22 human connexin genes. Phylogenetic tree calculations and calculations of pairwise nucleotide sequence identity patterns proposed revised and updated phylogenetic classification of eutherian connexin genes. Therefore, the present study integrating gene annotations, phylogenetic analysis and protein molecular evolution analysis proposed new nomenclature of eutherian connexin genes and proteins.