Molecular cloning, expression pattern, and chemical analysis of heat shock protein 70 (HSP70) in the mudskipper Boleophthalmus pectinirostris: Evidence for its role in regulating spermatogenesis

• We identified Boleophthalmus pectinirostris HSP70 complete cDNA sequence.
• Tissue expression of HSP70 mRNA was analyzed by RT-PCR.
• Distribution pattern of HSP70 in testes was investigated by immunohistochemistry.
• Heat-shocked injury in testes and response of HSP70 mRNA were observed.
• HSP70 plays an important role in spermatogenesis and tissue protection.

Heat shock protein 70 (HSP70) is molecular chaperone that is important for reproductive biological processes. In this study, a full length HSP70 from the mudskipper (Boleophthalmus pectinirostris) was characterized. It was found to contain: a 108 bp 5′-untranslated region, a 208 bp 3′-untranslated region, and a 1953 bp open reading frame, which encodes a protein of 650 amino acids with a theoretical molecular weight of 71.1 kDa and an isoelectric point of 5.17. RT-PCR analysis revealed that HSP70 was ubiquitously expressed in all major tissues with differential expression levels. This suggests that HSP70 has vital and conserved biological functions. HSP70 was localized mainly in the cytoplasm of germinal cells, indicating an important role of this protein during spermatogenesis. In response to heat stress, the testes presented abnormal morphology in connective tissues, in which HSP70 immunoreactivity was not observed. HSP70 mRNA expression in the gill, liver, and testes was significantly increased, which suggests that HSP70 plays an important role in protection against heat stress.