Comparative transcriptomics unravels molecular players shaping the dorsal lip hypertrophy in the vacuum cleaner cichlid, Gnathochromis permaxillaris

Teleosts display a spectacular diversity of craniofacial adaptations that often mediate ecological specializations. A considerable amount of research has revealed molecular players underlying skeletal craniofacial morphologies, but less is known about soft craniofacial phenotypes. Here we focus on a bizarre example of lip hypertrophy in the Lake Tangnayika cichlid, Gnathochromis permaxillaris. In this study, we investigate the molecular and regulatory basis of lip development G. permaxillaris, using a comparative transcriptomic approach. We identified a gene regulatory network involved in tissue overgrowth and cellular hypertrophy, potentially associated with the formation of a locally restricted hypertrophic lip in a teleost fish species. Our results provide a genetic foundation for future studies of molecular players shaping soft and exaggerated, but locally restricted, craniofacial morphological changes in fish and perhaps across vertebrates.