her8a encodes a Hes6-like E(spl) protein closely related to, but not directly orthologous to, mammalian Hes6. A. Phylogenetic tree depicting protein relationship within the Hes6 subfamily, based on the bHLH and Orange domain sequences. Note the absence of Hes6.2 proteins in marsupials and eutherian mammals. In zebrafish, the closest relative to Her8a is Her8.2, and the closest relative to Her13 is Hes6. B. Genomic organization of Hes6-like genes through evolution, confirming that the generation of the two Hes6.1 and Hes6.2 genes is ancestral and that Hes6.2 was secondarily lost within the mammalian taxa subsequent to the divergence of marsupials and eutherian mammals from monotremes. "?" indicates cases where genomic linkage cannot be resolved at present, in the absence of a genome sequence for the corresponding species. C. Genomic organization of the areas surrounding Hes6-like genes in teleost species compared to mouse. With the exception of zebrafish, for all of the teleosts studied, synteny analyses suggest a secondary loss of the hes6.2 duplicate (missing from locus 2) after the duplication of locus 1. In zebrafish, this gene (her8a) has been relocated to a third locus on a distinct chromosome. 1-3: genomic loci.