Decoding the spermatogonial stem cell niche under physiological and recovery conditions in adult mice and humans

The intricate interaction between spermatogonial stem cell (SSC) and testicular niche is essential for maintaining SSC homeostasis; however, this interaction remains largely uncharacterized. In this study, to characterize the underlying signaling pathways and related paracrine factors, we delineated the intercellular interactions between SSC and niche cell in both adult mice and humans under physiological conditions and dissected the niche-derived regulation of SSC maintenance under recovery conditions, thus uncovering the essential role of C-C motif chemokine ligand 24 and insulin-like growth factor binding protein 7 in SSC maintenance. We also established the clinical relevance of specific paracrine factors in human fertility. Collectively, our work on decoding the adult SSC niche serves as a valuable reference for future studies on the aetiology, diagnosis, and treatment of male infertility.</p

Gene Cdca2 knockout has no significant effect on spermatogenesis and fertility in mice

Objective To explore the physiological function of gene for cell devision cycle associated 2 (Cdca2), a highly expressed testis gene, in spermatogenesis and fertility in mice. Methods The expression of Cdca2 in different tissues of mice was detected by Q-PCR and Western blot; Using CRISPR/Cas9 gene editing technology and Cre-loxP mediated recombination system, a mouse strain with Cdca2 tissue specific knockout was constructed; By hematoxylin-eosin(HE) staining and morphological analysis, the effect of CDCA2 deletion on spermatogenic cell morphology at different stages of spermatogenesis was studied; The effects of CDCA2 deletion on sperm motility and motility parameters were detected by an automatic sperm detection and analysis system; The effect of CDCA2 deletion on the fertility of male mice was examined by fertility test. Results Cdca2 was a highly expressed gene in testis; Cdca2 germ cell specific knockout mice were successfully obtained by CRISPR/Cas9 technology and reproductive system; CDCA2 deletion in mice had no statistically significant effect on spermatogenic cells, sperm motility parameters and male fertility at all stages of spermatogenesis. Conclusions Cdca2 is probably not necessary for spermatogenesis and male fertility maintenance in mice

Assessment of the Impacts From the World's Largest Floating Macroalgae Blooms on the Water Clarity at the West Yellow Sea Using MODIS Data (2002-2016)

Water clarity (Secchi disk depth, SDD) is a very important factor for marine ecological environment. The world's largest "green tide" caused by the macroalgal blooms (MABs) of green macroalgae has occurred every summer in the Yellow Sea since 2008. In this study, we first present the effects of MABs on the water clarity in the west Yellow Sea. A regional empirical retrieval algorithm of SDD on the basis of moderate resolution imaging spectroradiometer (MODIS) remote sensing reflectance is evaluated with the field data and satellite reflectance data: the spectral simulation with the end-member reflectance of sea water and macroalgae, and the MODIS Level-2 standard products of the remote sensing reflectance. The results show that the mixture of sea water and macroalgae will lead to decreased water clarity when the SDD is larger than 1.2 m and increased chlorophyll-a, i.e., false values in the standard products for pure sea water which therefore should be used with caution for the regions with large scale of floating macroalgae blooms. The long-term SDD in June and July (2002-2016) over the Yellow Sea is investigated and analyzed with the presence of "green tide." The significant decrease in the SDD by 2.6 m and with 12 544 km(2) of sea surface in total in July while no pronouncing changes in June suggests that the water clarity in the west Yellow Sea has been strongly affected from the period of 2002-2007 (the pre-MAB phase) to the period of 2008-2016 (the MAB phase)

Effect of Pabpc6 knockout on spermatogenesis of male mice

Objective To investigate the role of cytoplasmic poly (A) binding protein-6 (PABPC6) in spermatogenesis of male mice. Methods The Pabpc6 in C57BL/6J mice was knocked out by CRISPR/Cas9 targeting, and the Pabpc6 was identified by PCR. Three types of mice with different genotypes of Pabpc6+/+, Pabpc6+/- and Pabpc6-/- were obtained by mating and breeding. Testis was weighed;Morphological observation and sperm counting were carried out. The mRNA and protein expression levels of Pabpc6 in different tissues were detected by real-time quantitative PCR and Western blot. Immunofluorescence and hematoxylin-eosin staining were used to observe the location of the gene and the morphological changes in the convoluted spermatic tubule of testis. Results The Pabpc6 knockout mice were successfully identified. Pabpc6 was highly expressed in testicular tissue(P＜0.001). Immunofluorescence showed that Pabpc6 was mainly expressed in spermatocyte at early sperm stage. Compared with wild-type mice, knockout mice showed no significant differences in testicular shape, sperm morphology, sperm count and the morphology of convoluted spermatic ducts. Conclusions Pabpc6 is found to be highly expressed in the testis tissue of mice. Pabpc6 has no obvious effect on spermatogenesis of male mice after knockout of Pabpc6. The results indicate that the protein encoded by Pabpc6 is not necessary for spermatogenesis of mice

Identification of quiescent FOXC2+ spermatogonial stem cells in adult mammals

In adult mammals, spermatogenesis embodies the complex developmental process from spermatogonial stem cells (SSCs) to spermatozoa. At the top of this developmental hierarchy lie a series of SSC subpopulations. Their individual identities as well as the relationships with each other, however, remain largely elusive. Using single-cell analysis and lineage tracing, we discovered both in mice and humans the quiescent adult SSC subpopulation marked specifically by forkhead box protein C2 (FOXC2). All spermatogenic progenies can be derived from FOXC2+ SSCs and the ablation of FOXC2+ SSCs led to the depletion of the undifferentiated spermatogonia pool. During germline regeneration, FOXC2+ SSCs were activated and able to completely restore the process. Germ cell-specific Foxc2 knockout resulted in an accelerated exhaustion of SSCs and eventually led to male infertility. Furthermore, FOXC2 prompts the expressions of negative regulators of cell cycle thereby ensures the SSCs reside in quiescence. Thus, this work proposes that the quiescent FOXC2+ SSCs are essential for maintaining the homeostasis and regeneration of spermatogenesis in adult mammals