Cloning, tissue distribution of desert hedgehog (dhh) gene and expression profiling during different developmental stages of Pseudopleuronectes yokohamae

As a crucial member of the Hedgehog (Hh) protein family, desert hedgehog (dhh) plays a vital role in multiple developmental processes, cell differentiation and tissue homeostasis. However, it is unclear how it regulates development in fish. In this study, we cloned and characterized the dhh gene from Pseudopleuronectes yokohamae. The full-length cDNA of Pydhh comprises 3194 bp, with a 1386 bp open reading frame (ORF) that encodes a polypeptide of 461 amino acids with a typical HH-signal domain, Hint-N and Hint-C domains. Multiple sequence alignment revealed that the putative PyDHH protein sequence was highly conserved across species, especially in the typical domains. Phylogenetic analysis showed that the PyDHH clustered within the Pleuronectiformes. Real-time quantitative PCR showed that Pydhh was detected in fourteen different tissues in adult-female and adult-male marbled flounder, and nine different tissues in juvenile fish. During early embryonic development stages, the expression of Pydhh was revealed high levels at hatching stage of embryo development. Moreover, the relative expression of Pydhh was significantly higher in the juvenile liver than adults’, and higher in the female skin than the male skin. To further investigate its location, the in situ hybridization (ISH) assay was performed, the results showed that the hybridization signal was obviously expressed in the immune organs of Pseudopleuronectes yokohamae, with weak signal expression in the other tissues. Our results suggested that Pydhh is highly conserved among species and plays a vital role in embryonic development and formation of immune related organs.