A gene expression study of ornamental fin shape in Neolamprologus brichardi, an African cichlid species.

The diversity of fin morphology within and across fish taxa offers great, but still largely unexplored, opportunities to investigate the proximate mechanisms underlying fin shape variation. Relying on available genetic knowledge brought forth mainly by the comprehensive study of the zebrafish caudal fin, we explored candidate molecular mechanisms for the maintenance and formation of the conspicuously elongated filaments adorning the unpaired fins of the East African "princess cichlid" Neolamprologus brichardi. Via qPCR assays, we detected expression differences of candidate genes between elongated and short regions of intact and regenerating fins. The identified genes include skeletogenic and growth factors (igf2b, fgf3, bmp2 and bmp4), components of the WNT pathway (lef1, wnt5b and wnt10) and a regulatory network determining fin ray segment size and junction (cx43, esco2 and sema3d), as well as other genes with different roles (mmp9, msxb and pea3). Interestingly, some of these genes showed fin specific expression differences which are often neglected in studies of model fish that focus on the caudal fin. Moreover, while the observed expression patterns were generally consistent with zebrafish results, we also detected deviating expression correlations and gene functions.