Enrichment of spermatogonial stem cells and staging of the testis cycle in a dasyurid marsupial, the fat-tailed dunnart

Abstract

There is increasing interest in use of marsupial models in research, for use in next-generation conservation by improving fitness through genetic modification, and in de-extinction efforts. Specifically this includes dasyurid marsupials such as the Thylacine, Tasmanian devil, quolls and the small rodent-like dunnarts. Historically, the use of marsupials as experimental models has meant significant resource investment, such as with the well-researched tammar wallaby that requires large, dedicated facilities for housing and husbandry. Given the need to advance marsupial research by applying contemporary in-vivo genetic modification technology, the fat-tailed dunnart (Sminthopsis crassicaudata) is being established as a marsupial model. This species is small (60-90mm body size), polyovulatory (8-12 pups per birth), and can breed in standard rodent facilities when housed in a 12:12 light cycle. To develop the fat tailed dunnart as a model for marsupial next-generation conservation, this study aimed to enrich dunnart spermatogonial stem cells from whole testis digestions using a fluorescent dye technology and FACS. This approach is not dependent on antibodies or genetic reporter animals that are limiting factors when performing cell sorting on species separated from human and mouse by large evolutionary timescales. This study also assessed spermatogonial development and spermatogenesis in the fat-tailed dunnart, in vivo, by making the first definition of the cycle of the seminiferous epithelium in any dasyurid. Overall, this is the first detailed study to assess the cycle of dasyurid spermatogenesis and provides a valuable method to enrich marsupial spermatogonial stem cells for cellular, functional and molecular analysis.