Single-cell RNA-sequencing reveals the dynamic process and novel markers in porcine spermatogenesis

Background:Spermatogenesis is the process by which male gametes are formed from spermatogonial stem cells and it is essential for the reliable transmission of genetic information between generations.To date,the dynamic transcriptional changes of defined populations of male germ cells in pigs have not been reported.Results:To characterize the atlas of porcine spermatogenesis,we profiled the transcriptomes of~16,966 testicular cells from a 150-day-old pig testis through single-cell RNA-sequencing(scRNA-seq).The scRNA-seq analysis identified spermatogonia,spermatocytes,spermatids and three somatic cell types in porcine testes.The functional enrichment analysis demonstrated that these cell types played diverse roles in porcine spermatogenesis.The accuracy of the defined porcine germ cell types was further validated by comparing the data from scRNA-seq with those from bulk RNA-seq.Since we delineated four distinct spermatogonial subsets,we further identified CD99 and PODXL2 as novel cell surface markers for undifferentiated and differentiating spermatogonia,respectively.Conclusions:The present study has for the first time analyzed the transcriptome of male germ cells and somatic cells in porcine testes through scRNA-seq.Four subsets of spermatogonia were identified and two novel cell surface markers were discovered,which would be helpful for studies on spermatogonial differentiation in pigs.The datasets offer valuable information on porcine spermatogenesis,and pave the way for identification of key molecular markers involved in development of male germ cells.