Model Fish Genomics Resource Laboratory / Sakai Group

Molecular dissection of spermatogenesis could be facilitated by cell culture approaches that allow easy access for experimental manipulation and live imaging of specific molecules; however, technical limitations have thus far prevented the complete reconstruction of spermatogenic events in cell culture. Here, we established cell culture systems for production of functional sperm from self-renewing spermatogonial stem cells (SSCs), using zebrafish testicular hyperplasias that accumulate SSCs. By serially transplanting into immuno-deficient mutant zebrafish, we succeeded in long-term and efficient production of hyperplasias. Through improvements of culture conditions, we achieved efficient propagation of the SSCs and differentiation to sperm that gave rise to offspring. Oxygen at the concentration of air proved to be detrimental for sperm differentiation from SSCs. These results indicate that the whole spermatogenic process can be represented in cell culture, facilitating analyses of molecular mechanisms of spermatogenesis in vertebrates. This work was supported by JSPS KAKENHI (23013023, 25251034, 25114003).

Propagation and differentiation of SSCs in culture. SSCs that express green fluorescent protein grow in propagation culture (left and middle panels), while they differentiated into sperm in differentiation culture (the right panel).