Tbx4 and Tbx5 gene expression associated with appendage development and its relationship with the absence of a ventral fin in Pampus argenteus

Abstract

Background The Tbx family was first known through the study of their functions in the body and limbs, and its members Tbx4 and Tbx5 genes are important factors in determining the characteristics of the appendages. Pampus argenteus is an important fishery resource and an emerging target of aquaculture. It has a bizarre morphology, the lack of ventral fin. So, it is necessary to study the role of Tbx family genes in the deletion of pelvic fin in P. argenteus. Results Cloning Tbx4 and Tbx5 cDNA sequence of P. argenteus for the first time (GenBank: MH709128 and MH712458), which both contain highly conserved T-box region (DNA binding domain). In different developmental stages of P. argenteus, the expression of Tbx4 mRNA showed an overall "M" trend of increasing, then decreasing and then increasing again, with the highest peak at the age of 13 days old larvae; and a positive RNA hybridization signal was detected in the abdominal epithelium, while its protein expression was significantly inhibited. TBX4 protein expression was lowest in the abdominal epithelium and even inferior to its expression in the pectoral fin. At different developmental stages of P. argenteus, the expression of Tbx5 mRNA showed an overall trend of first increase and then decrease, and reached the highest at larvae 1 day (the appearance of pectoral fin primordium). Consistent with in situ hybridization, positive signals were concentrated in the heart and pectoral fins. The expression of TBX5 protein is basically consistent with the expression of mRNA, that is, when the expression of Tbx5 mRNA increases, its protein content also increases relatively, and after accumulation to a certain extent, the accumulation of pectoral fin cells begins to appear. Conclusions The translation of Tbx4 mRNA may be inhibited during the critical period of ventral fin development. Among different tissues, TBX4 protein levels were the lowest in the abdominal epithelium, and even lower than that in the pectoral fin, suggesting that the protein expression may be also inhibited in the abdominal epithelium of adult P. argenteus.