Soma-germline communication drives sex maintenance in the Drosophila testis.

In adult gonads, disruption of somatic sexual identity leads to defective gametogenesis and infertility. However, the underlying mechanisms by which somatic signals regulate germline cells to achieve proper gametogenesis remain unclear. In our previous study, we introduced the chinmoSex Transformation (chinmoST ) mutant Drosophila testis phenotype as a valuable model for investigating the mechanisms underlying sex maintenance. In chinmoST testes, depletion of the Janus Kinase-Signal Transducer and Activator of Transcription downstream effector Chinmo from somatic cyst stem cells (CySCs) feminizes somatic cyst cells and arrests germline differentiation. Here, we use single-cell RNA sequencing to uncover chinmoST -specific cell populations and their transcriptomic changes during sex transformation. Comparative analysis of intercellular communication networks between wild-type and chinmoST testes revealed disruptions in several soma-germline signaling pathways in chinmoST testes. Notably, the insulin signaling pathway exhibited significant enhancement in germline stem cells (GSCs). Chinmo cleavage under targets and tagmentation (CUT&Tag) assay revealed that Chinmo directly regulates two male sex determination factors, doublesex (dsx) and fruitless (fru), as well as Ecdysone-inducible gene L2 (ImpL2), a negative regulator of the insulin signaling pathway. Further genetic manipulations confirmed that the impaired gametogenesis observed in chinmoST testes was partly contributed by dysregulation of the insulin signaling pathway. In summary, our study demonstrates that somatic sex maintenance promotes normal spermatogenesis through Chinmo-mediated conserved sex determination and the insulin signaling pathway. Our work offers new insights into the complex mechanisms of somatic stem cell sex maintenance and soma-germline communication at the single-cell level. Additionally, our discoveries highlight the potential significance of stem cell sex instability as a novel mechanism contributing to testicular tumorigenesis.

Functional dissection of PRC1 subunits RYBP and YAF2 during neural differentiation of embryonic stem cells.

Polycomb repressive complex 1 (PRC1) comprises two different complexes: CBX-containing canonical PRC1 (cPRC1) and RYBP/YAF2-containing variant PRC1 (vPRC1). RYBP-vPRC1 or YAF2-vPRC1 catalyzes H2AK119ub through a positive-feedback model; however, whether RYBP and YAF2 have different regulatory functions is still unclear. Here, we show that the expression of RYBP and YAF2 decreases and increases, respectively, during neural differentiation of embryonic stem cells (ESCs). Rybp knockout impairs neural differentiation by activating Wnt signaling and derepressing nonneuroectoderm-associated genes. However, Yaf2 knockout promotes neural differentiation and leads to redistribution of RYBP binding, increases enrichment of RYBP and H2AK119ub on the RYBP-YAF2 cotargeted genes, and prevents ectopic derepression of nonneuroectoderm-associated genes in neural-differentiated cells. Taken together, this study reveals that RYBP and YAF2 function differentially in regulating mESC neural differentiation.

A Droplet Method for Synthesis of Multiclass Ultrathin Metal Halides.

2D metal halides have attracted increasing research attention in recent years; however, it is still challenging to synthesize them via liquid-phase methods. Here it is demonstrated that a droplet method is simple and efficient for the synthesis of multiclass 2D metal halides, including trivalent (BiI3 , SbI3 ), divalent (SnI2 , GeI2 ), and monovalent (CuI) ones. In particular, 2D SbI3 is first experimentally achieved, of which the thinnest thickness is ≈6 nm. The nucleation and growth of these metal halide nanosheets are mainly determined by the supersaturation of precursor solutions that are dynamically varying during the solution evaporation. After solution drying, the nanosheets can fall on the surface of many different substrates, which further enables the feasible fabrication of related heterostructures and devices. With SbI3 /WSe2 being a good demonstration, the photoluminescence intensity and photo responsivity of WSe2 is obviously enhanced after interfacing with SbI3 . The work opens a new pathway for 2D metal halides toward widespread investigation and applications.

PRC1 uncomplexed.

Epigenetic enzymes are critically involved in gene regulation during lineage commitment. In this issue of Stem Cell Reports, Zhu et al. (2022) unravel extensive redundancy between subunits of the epigenetic regulatory Polycomb Repressive Complex 1 using a systematic knockout strategy in mouse embryonic stem cells.

R-loops coordinate with SOX2 in regulating reprogramming to pluripotency.

R-loops modulate genome stability and regulate gene expression, but the functions and the regulatory mechanisms of R-loops in stem cell biology are still unclear. Here, we profiled R-loops during somatic cell reprogramming and found that dynamic changes in R-loops are essential for reprogramming and occurred before changes in gene expression. Disrupting the homeostasis of R-loops by depleting RNaseH1 or catalytic inactivation of RNaseH1 at D209 (RNaseH1D209N) blocks reprogramming. Sox2, but not any other factor in the Yamanaka cocktail, overcomes the inhibitory effects of RNaseH1 activity loss on reprogramming. Sox2 interacts with the reprogramming barrier factor Ddx5 and inhibits the resolvase activity of Ddx5 on R-loops and thus facilitates reprogramming. Furthermore, reprogramming efficiency can be modulated by dCas9-mediated RNaseH1/RNaseH1D209N targeting the specific R-loop regions. Together, these results show that R-loops play important roles in reprogramming and shed light on the regulatory module of Sox2/Ddx5 on R-loops during reprogramming.

Generation of Rybp homozygous knockout murine ES cell line GIBHe001-A-1 by using CRISPR/Cas9 technology.

RYBP (Ring1 and YY1 Binding Protein) is critical for pluripotency and differentiation of embryonic stem cells (ESCs). RYBP depletion disturbs both neural and myocardial differentiation of ESCs. Moreover, low level of RYBP is correlated with diseases such as glioblastoma. To study the biological function of RYBP in neural differentiation of ESCs, here we generated Rybp homozygous knockout murine ESC line based on Sox1-GFP reporter using CRISPR/Cas9 genome editing technology. The last two exons of Rybp gene in which contain 115 amino acids have been replaced with PGK-Pruo by homologous recombination.