Spermatogenesis is characterized by sequential transitions of multiple processes: self-renewal of spermatogonial stem cells, mitotic growth of differentiating spermatogonia, and meiosis leading to the production of sperm. Molecular dissection of these complex processes and transitions could be facilitated by cell culture approaches. We have developed techniques to recapitulate the entire spermatogenesis process, from stem cell propagation to differentiation of functional sperm, solely in culture. In addition, we have already isolated several ENU-induced zebrafish mutants that have a defect in spermatogenesis. We are working on the molecular mechanisms to regulate spermatogenesis of vertebrates both in vivo and in vitro.
Propagation and differentiation of spermatogonial stem cells (SSCs) in culture. SSCs that express green fluorescent protein grow in propagation culture (left and middle panels), while they differentiate into sperm in differentiation culture (the right panel).
Kawasaki, T., Maeno, A., Shiroishi, T., and Sakai, N. (2017). Development and growth of organs in living whole embryo and larval grafts in zebrafish. Sci Rep 7, 16508.
Kawasaki, T., Siegfried, K.R., and Sakai, N. (2016). Differentiation of zebrafish spermatogonial stem cells to functional sperm in culture. Development 143, 566-574.
Saito, K., Sakai, C., Kawasaki, T., and Sakai, N. (2014). Telomere distribution pattern and synapsis initiation during spermatogenesis in zebrafish. Dev Dyn 243, 1448-1456.