UCHL1 expression and localization on testicular development and spermatogenesis of Chinese giant salamanders

Ubiquitin carboxyl-terminal hydrolase L1 (UCHL1), which is extensively expressed in vertebrates, is a deubiquitinating enzymes that inhibits the degradation of proteins by reversing ubiquitination modification. Herein, a 1087-bp sequence encoding UCHL1 was identified from the Chinese giant salamander (CGS; Andrias davidianus). The coding sequences (CDS) of UCHL1 encoded a putative poly peptide of 222 amino acids. The CGS UCHL1 isoforms were more related to their human and mouse counterparts. The phylogenic tree of vertebrate UCHL1 indicated that CGS UCHL1 has the closest relationship with human UCHL1 (up to 73.99 %). Before the gonads of male CGSs matured, the peak level of UCHL1 expression in testes appeared in 3-year-old CGSs according to RT-qPCR and western blot. In adult testes, the level of UCHL1 protein was lower in the breeding period than in the post-breeding period, whereas the level of UCHL1 protein in interstitial fluid of adult CGS testes was higher during the breeding period than during the post-breeding period. In testicular seminiferous lobules in the developmental stage of CGSs, immunohistochemistry displayed three kinds of localizing patterns of UCHL1, including nuclear localization at half year old, cytoplasmic localization from one year to three years old, and extracellular localization in adult. In testicular seminiferous lobules of adult CGS, the different developmental germ cells were separated by cysts containing UCHL1 protein, but UCHL1 did not localize on the mature sperm. The results showed that extracellular UCHL1 loaded on exosomes, as a component of the homogeneous germ cell cysts, could regulate the synchronous development of sperm in testes of adult CGS.