SUMMARY Spermatogenesis has been intensely studied in rodents but remains poorly understood in humans. Here, we used single-cell RNA sequencing to analyze human testes. Clustering analysis of neonatal testes reveals several cell subsets, including cell populations with characteristics of primordial germ cells (PGCs) and spermatogonial stem cells (SSCs). In adult testes, we identify four undifferentiated spermatogonia (SPG) clusters, each of which expresses specific marker genes. We identify protein markers for the most primitive SPG state, allowing us to purify this likely SSC-enriched cell subset. We map the timeline of male germ cell development from PGCs through fetal germ cells to differentiating adult SPG stages. We also define somatic cell subsets in both neonatal and adult testes and trace their developmental trajectories. Our data provide a blueprint of the developing human male germline and supporting somatic cells. The PGC-like and SSC markers are candidates to be used for SSC therapy to treat infertility.

The cell type-specific and developmentally regulated expression pattern of the RHOX transcription factors suggests that they perform regulatory functions during human fetal germ cell development, spermatogenesis and oogenesis. Our results also raise the possibility that modulation of RHOX gene levels could correct some cases of human infertility and that their encoded proteins are candidate targets for contraceptive drug design.

SUMMARYIn humans, recent studies have correlated anogenital distance (AGD) in adult men to intrinsic testicular function. Although rodent studies suggest that AGD is determined in utero and remains constant in adult life, it is not certain if AGD remains constant across a man's adult life. We sought to determine if adult male AGD varies based on age. A cross-sectional study of men being evaluated at a men's health clinic. Anogenital distance (the distance from the posterior aspect of the scrotum to the anal verge) and penile length (PL) were measured using digital callipers. ANOVA and linear regression were used to determine correlations between AGD, fatherhood status and age. In all, 473 men were included in the analysis with a mean age of 43 ± 13 years. The mean AGD for the group was 39 ± 13 mm. Anogenital distance did not vary between age categories for the entire group, for fathers, and for childless men. Moreover, penile length also remained constant across age categories. On adjusted analyses stratified by fatherhood status, there was no relationship between AGDp and age. The current cross-sectional study demonstrates that anogenital distance, defined as the distance from the posterior scrotum to the anal verge, is similar for men of different ages. As such, AGD may provide a measure for genital development and function throughout adult life. However, confirmation with longitudinal studies is needed.

No abstract

M.K.S. has nothing to disclose. J.F.S. has nothing to disclose. K.C.L. is a past president of Society for the Study of Male Reproduction and is on the board of directors. J.M.H. owns equity in the following start-up companies unrelated to the submitted work: Stream Dx, Nanonc, and Andro360. S.L. has nothing to disclose. E.D.G. has nothing to disclose. J.C.T. has nothing to disclose. T.J.W. has nothing to disclose. P.N.K. has nothing to disclose. V.D.W.C. has nothing to disclose. A.S.Z. is a shareholder of YAD Tech Neutraceuticals. A.S. has received personal fees from Endo Pharmaceuticals, MD Concepts, and Tims Medical outside the submitted work. M.A.F. has nothing to disclose. T.D. has nothing to disclose. S.I.Z. has nothing to disclose. E.F.F. has nothing to disclose. J.C.H. has nothing to disclose. J.I.S. has nothing to disclose. R.E.B. has nothing to disclose. J.M.D. has received grants from Blue Cross Blue Shield of Michigan outside the submitted work. M.G. has nothing to disclose. E.Y.K. has nothing to disclose. T.-C.M.H. has nothing to disclose. J.M.B. has nothing to disclose. D.S. is on the board of directors of the Society for the Study of Male Reproduction. A.K.N. has nothing to disclose. K.A.J. has nothing to disclose.