A gene expression study of dorso-ventrally restricted pigment pattern in adult fins ofNeolamprologus meeli, an African cichlid species

Abstract

Fish color patterns are among the most diverse phenotypic traits found in the animal kingdom. Understanding the molecular and cellular mechanisms that control in chromatophore distribution and pigmentation underlying this diversity is a major goal in developmental and evolutionary biology, which has predominantly been pursued in the zebrafish model system. Here, we apply results from zebrafish work to study a naturally occurring color pattern phenotype in the fins of an African cichlid species from Lake Tanganyika. The cichlid fishNeolamprologus meelidisplays a distinct dorsal color pattern, with black and white stripes along the edges of the dorsal fin and of the dorsal half of the caudal fin, corresponding with differences in melanophore density. To elucidate the molecular mechanisms controlling the differences in dorsal and ventral color patterning in the fins, we quantitatively assessed the expression of 15 candidate target genes involved in adult zebrafish pigmentation and stripe formation. For reference gene validation, we screened the expression stability of seven widely expressed genes across the investigated tissue samples and identifiedtbpas appropriate reference. Relative expression levels of the candidate target genes were compared between the dorsal, striped fin regions and the corresponding uniform, grey-colored regions in the anal and ventral caudal fin. Dorso-ventral expression differences, with elevated levels in both white and black stripes, were observed in two genes, the melanosome protein coding genepmeland inigsf11, which affects melanophore adhesion, migration and survival. Next, we predicted potential shared upstream regulators ofpmelandigsf11. Testing the expression patterns of six predicted transcriptions factors revealed dorso-ventral expression difference ofirf1and significant, negative expression correlation ofirf1with bothpmelandigsf11. Based on these results, we proposepmel,igsf11andirf1as likely components of the genetic mechanism controlling distinct dorso-ventral color patterns inN. meelifins.