Differential expression pattern of hox genes between larval development and metamorphosis of Senegalese sole (Solea senegalensis, Kaup 1858)

Abstract

The Senegalese sole (Solea senegalensis, Kaup 1858) is a highly valued marine flatfish species in the fishery market. Its aquaculture faces several farming bottlenecks, such as skeletal malformations, which increase production costs. Hox genes are a family of homeotic genes encoding transcription factors that control development in metazoans, primarily the organization of the anteroposterior axis. While some studies have focused on the expression pattern of specific hox genes during embryonic development, this work represents the first holistic expression analysis of all hox genes during larval and metamorphic development. This study will allow, in a first place, having a general knowledge about the behavior of hox genes during these life stages of the Senegalese sole and, secondly, to gain new possible candidate genes involved in the skeletal malformations observed in this fish species during metamorphosis. A RNA-seq approach was employed, and expression data for all hox genes were extracted from samples collected on eight different days after hatching, covering the main phases and stages of larval and metamorphic development. Up to five distinct expression profiles were detected, revealing a marked difference between larval and metamorphic stages. Central hox genes are preferentially expressed in the early larval phases, while posterior hox genes are expressed during metamorphosis. This trend could play a key role in the development of the central-anterior pharyngeal arches and pectoral and caudal fins. These results provide a valuable starting point for further studies to address the high incidence of skeletal abnormalities observed in both larval and metamorphic stages.