title: Transcriptional and translational heterogeneity among neonatal mouse spermatogonia.
abstract: Spermatogonial stem cells (SSCs) are a subset of undifferentiated spermatogonia responsible for ongoing spermatogenesis in mammalian testes. Spermatogonial stem cells arise from morphologically homogeneous prospermatogonia, but growing evidence suggests that only a subset of prospermatogonia develops into the foundational SSC pool. This predicts that subtypes of undifferentiated spermatogonia with discrete mRNA and protein signatures should be distinguishable in neonatal testes. We used single-cell quantitative RT-PCR to examine mRNA levels of 172 genes in individual spermatogonia from 6-day postnatal (P6) mouse testes. Cells enriched from P6 testes using the StaPut or THY1(+) magnetic cell sorting methods exhibited considerable heterogeneity in the abundance of specific germ cell and stem cell mRNAs, segregating into one somatic and three distinct spermatogonial clusters. However, P6 Id4-eGFP(+) transgenic spermatogonia, which are known to be enriched for SSCs, were more homogeneous in their mRNA levels, exhibiting uniform levels for the majority of genes examined (122 of 172). Interestingly, these cells displayed nonuniform (50 of 172) expression of a smaller cohort of these genes, suggesting there is substantial heterogeneity even within the Id4-eGFP(+) population. Further, although immunofluorescence staining largely demonstrated conformity between mRNA and protein levels, some proteins were observed in patterns that were disparate from those detected for the corresponding mRNAs in Id4-eGFP(+) spermatogonia (e.g., Kit, Sohlh2, Stra8), suggesting additional heterogeneity is introduced at the posttranscriptional level. Taken together, these data demonstrate the existence of multiple spermatogonial subtypes in P6 mouse testes and raise the intriguing possibility that these subpopulations may correlate with the development of functionally distinct spermatogenic cell types.
authors.affiliation: Department of Biology, The University of Texas at San Antonio, San Antonio, Texas brian.hermann@utsa.edu.
authors.forename: Brian P
authors.initials: BP
authors.lastname: Hermann
authors.affiliation: Department of Biology, The University of Texas at San Antonio, San Antonio, Texas.
authors.forename: Kazadi N
authors.initials: KN
authors.lastname: Mutoji
authors.affiliation: Department of Anatomy and Cell Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina.
authors.forename: Ellen K
authors.initials: EK
authors.lastname: Velte
authors.affiliation: Department of Management Science and Statistics, The University of Texas at San Antonio, San Antonio, Texas.
authors.forename: Daijin
authors.initials: D
authors.lastname: Ko
authors.affiliation: Center for Reproductive Biology, School of Molecular Biosciences, Washington State University, Pullman, Washington.
authors.forename: Jon M
authors.initials: JM
authors.lastname: Oatley
authors.affiliation: Department of Anatomy and Cell Biology, Brody School of Medicine, East Carolina University, Greenville, North Carolina East Carolina Diabetes and Obesity Institute, East Carolina University, Greenville, North Carolina.
authors.forename: Christopher B
authors.initials: CB
authors.lastname: Geyer
authors.affiliation: Department of Biology, The University of Texas at San Antonio, San Antonio, Texas.
authors.forename: John R
authors.initials: JR
authors.lastname: McCarrey
mesh_terms: D000818:Animals; D018507:Gene Expression Regulation, Developmental; D008297:Male; D051379:Mice; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013091:Spermatogenesis / Q000235:genetics*; D013093:Spermatogonia / Q000378:metabolism*; D013737:Testis / Q000166:cytology / Q000378:metabolism*
chemical_list: D012333:RNA, Messenger
keywords: first wave spermatogenesis; germline development; prospermatogonia; single-cell gene expression; spermatogonial stem cells