Fig. 6

Conserved syntenies provide evidence that aldh1a3 was secondarily lost in medaka.

(A) Comparative syntenic analysis of ALDH1A3 genomic neighborhoods in human, stickleback, and medaka. These results show that aldh1a3 was lost in the medaka lineage. ALDH1A3 orthologs are highlighted in red, and ALDH1A3 nearest neighbors are labeled in purple. The presence of one LTR-flanked retrotransposon including an ORF2 reverse transcriptase (in brown) in the putative locus of the lost aldh1a3 gene suggests the hypothesis that the insertion of the retrotransposon was related to the aldh1a3 loss. (B) Comparative analysis by in situ hybridization of the expression of aldh1a gene family members in the developing eye of zebrafish and medaka reveals that the medaka aldh1a2 gene recapitulates both the dorsal expression of aldh1a2 and the ventral expression of aldh1a3 in zebrafish. This result suggests that in medaka, aldh1a2 provides a ventral RA source after the loss of aldh1a3.