title: The evolution of cichlid fish egg-spots is linked with a cis-regulatory change.
abstract: The origin of novel phenotypic characters is a key component in organismal diversification; yet, the mechanisms underlying the emergence of such evolutionary novelties are largely unknown. Here we examine the origin of egg-spots, an evolutionary innovation of the most species-rich group of cichlids, the haplochromines, where these conspicuous male fin colour markings are involved in mating. Applying a combination of RNAseq, comparative genomics and functional experiments, we identify two novel pigmentation genes, fhl2a and fhl2b, and show that especially the more rapidly evolving b-paralog is associated with egg-spot formation. We further find that egg-spot bearing haplochromines, but not other cichlids, feature a transposable element in the cis-regulatory region of fhl2b. Using transgenic zebrafish, we finally demonstrate that this region shows specific enhancer activities in iridophores, a type of pigment cells found in egg-spots, suggesting that a cis-regulatory change is causally linked to the gain of expression in egg-spot bearing haplochromines.
authors.affiliation: Zoological Institute, University of Basel, Basel 4051, Switzerland.
authors.forename: M Emília
authors.initials: ME
authors.lastname: Santos
authors.affiliation: Institute of Neuroscience, University of Oregon, Eugene, Oregon 97403-1254, USA.
authors.forename: Ingo
authors.initials: I
authors.lastname: Braasch
authors.affiliation: Zoological Institute, University of Basel, Basel 4051, Switzerland.
authors.forename: Nicolas
authors.initials: N
authors.lastname: Boileau
authors.affiliation: Zoological Institute, University of Basel, Basel 4051, Switzerland.
authors.forename: Britta S
authors.initials: BS
authors.lastname: Meyer
authors.affiliation: Biozentrum, University of Basel, Basel 4056, Switzerland.
authors.forename: Loïc
authors.initials: L
authors.lastname: Sauteur
authors.affiliation: Zoological Institute, University of Basel, Basel 4051, Switzerland.
authors.forename: Astrid
authors.initials: A
authors.lastname: Böhne
authors.affiliation: Biozentrum, University of Basel, Basel 4056, Switzerland.
authors.forename: Heinz-Georg
authors.initials: HG
authors.lastname: Belting
authors.affiliation: Biozentrum, University of Basel, Basel 4056, Switzerland.
authors.forename: Markus
authors.initials: M
authors.lastname: Affolter
authors.affiliation: Zoological Institute, University of Basel, Basel 4051, Switzerland.
authors.forename: Walter
authors.initials: W
authors.lastname: Salzburger
mesh_terms: D000818:Animals; D001483:Base Sequence; D023681:Cichlids; D019143:Evolution, Molecular; D005786:Gene Expression Regulation; D060588:LIM Domain Proteins / Q000235:genetics*; D008969:Molecular Sequence Data; D010063:Ovum / Q000378:metabolism*; D010858:Pigmentation / Q000235:genetics*; D015027:Zebrafish
chemical_list: D060588:LIM Domain Proteins