TEX264 drives selective autophagy of DNA lesions to promote DNA repair and cell survival.

DNA repair and autophagy are distinct biological processes vital for cell survival. Although autophagy helps maintain genome stability, there is no evidence of its direct role in the repair of DNA lesions. We discovered that lysosomes process topoisomerase 1 cleavage complexes (TOP1cc) DNA lesions in vertebrates. Selective degradation of TOP1cc by autophagy directs DNA damage repair and cell survival at clinically relevant doses of topoisomerase 1 inhibitors. TOP1cc are exported from the nucleus to lysosomes through a transient alteration of the nuclear envelope and independent of the proteasome. Mechanistically, the autophagy receptor TEX264 acts as a TOP1cc sensor at DNA replication forks, triggering TOP1cc processing by the p97 ATPase and mediating the delivery of TOP1cc to lysosomes in an MRE11-nuclease- and ATR-kinase-dependent manner. We found an evolutionarily conserved role for selective autophagy in DNA repair that enables cell survival, protects genome stability, and is clinically relevant for colorectal cancer patients.

Mouse oocytes develop in cysts with the help of nurse cells.

Mouse germline cysts, on average, develop into six oocytes supported by 24 nurse cells that transfer cytoplasm and organelles to generate a Balbiani body. We showed that between E14.5 and P5, cysts periodically activate some nurse cells to begin cytoplasmic transfer, which causes them to shrink and turnover within 2 days. Nurse cells die by a programmed cell death (PCD) pathway involving acidification, similar to Drosophila nurse cells, and only infrequently by apoptosis. Prior to initiating transfer, nurse cells co-cluster by scRNA-seq with their pro-oocyte sisters, but during their final 2 days, they cluster separately. The genes promoting oocyte development and nurse cell PCD are upregulated, whereas the genes that repress transfer, such as Tex14, and oocyte factors, such as Nobox and Lhx8, are under-expressed. The transferred nurse cell centrosomes build a cytocentrum that establishes a large microtubule aster in the primordial oocyte that organizes the Balbiani body, defining the earliest oocyte polarity.

Stat5 opposes the transcription factor Tox and rewires exhausted CD8+ T cells toward durable effector-like states during chronic antigen exposure.

Rewiring exhausted CD8+ T (Tex) cells toward functional states remains a therapeutic challenge. Tex cells are epigenetically programmed by the transcription factor Tox. However, epigenetic remodeling occurs as Tex cells transition from progenitor (Texprog) to intermediate (Texint) and terminal (Texterm) subsets, suggesting development flexibility. We examined epigenetic transitions between Tex cell subsets and revealed a reciprocally antagonistic circuit between Stat5a and Tox. Stat5 directed Texint cell formation and re-instigated partial effector biology during this Texprog-to-Texint cell transition. Constitutive Stat5a activity antagonized Tox and rewired CD8+ T cells from exhaustion to a durable effector and/or natural killer (NK)-like state with superior anti-tumor potential. Temporal induction of Stat5 activity in Tex cells using an orthogonal IL-2:IL2Rß-pair fostered Texint cell accumulation, particularly upon PD-L1 blockade. Re-engaging Stat5 also partially reprogrammed the epigenetic landscape of exhaustion and restored polyfunctionality. These data highlight therapeutic opportunities of manipulating the IL-2-Stat5 axis to rewire Tex cells toward more durably protective states.

Non-terminally exhausted tumor-resident memory HBV-specific T cell responses correlate with relapse-free survival in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) often develops following chronic hepatitis B virus (HBV) infection and responds poorly to immune checkpoint blockade. Here, we examined the antigen specificities of HCC-infiltrating T cells and their relevance to tumor control. Using highly multiplexed peptide-MHC tetramer staining of unexpanded cells from blood, liver, and tumor tissues from 46 HCC patients, we detected 91 different antigen-specific CD8+ T cell populations targeting HBV, neoantigen, tumor-associated, and disease-unrelated antigens. Parallel high-dimensional analysis delineated five distinct antigen-specific tissue-resident memory T (Trm) cell populations. Intratumoral and intrahepatic HBV-specific T cells were enriched for two Trm cell subsets that were PD-1loTOXlo, despite being clonally expanded. High frequencies of intratumoral terminally exhausted T cells were uncommon. Patients with tumor-infiltrating HBV-specific CD8+ Trm cells exhibited longer-term relapse-free survival. Thus, non-terminally exhausted HBV-specific CD8+ Trm cells show hallmarks of active involvement and effective antitumor response, implying that these cells could be harnessed for therapeutic purposes.

TEX15 associates with MILI and silences transposable elements in male germ cells.

DNA methylation is a major silencing mechanism of transposable elements (TEs). Here we report that TEX15, a testis-specific protein, is required for TE silencing. TEX15 is expressed in embryonic germ cells and functions during genome-wide epigenetic reprogramming. The Tex15 mutant exhibits DNA hypomethylation in TEs at a level similar to Mili and Dnmt3c but not Miwi2 mutants. TEX15 is associated with MILI in testis. As loss of Tex15 causes TE desilencing with intact piRNA production, our results identify TEX15 as a new essential epigenetic regulator that may function as a nuclear effector of MILI to silence TEs by DNA methylation.

TEX264 Is an Endoplasmic Reticulum-Resident ATG8-Interacting Protein Critical for ER Remodeling during Nutrient Stress.

Cells respond to nutrient stress by trafficking cytosolic contents to lysosomes for degradation via macroautophagy. The endoplasmic reticulum (ER) serves as an initiation site for autophagosomes and is also remodeled in response to nutrient stress through ER-phagy, a form of selective autophagy. Quantitative proteome analysis during nutrient stress identified an unstudied single-pass transmembrane ER protein, TEX264, as an ER-phagy receptor. TEX264 uses an LC3-interacting region (LIR) to traffic into ATG8-positive puncta that often initiate from three-way ER tubule junctions and subsequently fuse with lysosomes. Interaction and proximity biotinylation proteomics identified a cohort of autophagy regulatory proteins and cargo adaptors located near TEX264 in an LIR-dependent manner. Global proteomics and ER-phagy flux analysis revealed the stabilization of a cohort of ER proteins in TEX264-/- cells during nutrient stress. This work reveals TEX264 as an unrecognized ER-phagy receptor that acts independently of other candidate ER-phagy receptors to remodel the ER during nutrient stress.

TEX13B is essential for metabolic reprogramming during germ cell differentiation.

STUDY QUESTION: What is the functional significance of Tex13b in male germ cell development and differentiation? SUMMARY ANSWER: Tex13b regulates male germ cell differentiation by metabolic reprogramming during spermatogenesis. WHAT IS KNOWN ALREADY: Studies in mice and humans suggest that TEX13B is a transcription factor and is exclusively expressed in germ cells. STUDY DESIGN, SIZE, DURATION: We sequenced the coding regions of TEX13B in 628 infertile men and 427 ethnically matched fertile control men. Further, to identify the molecular function of Tex13b, we created a Tex13b knockout and conditional overexpression system in GC-1spg (hereafter, GC-1) cells. PARTICIPANTS/MATERIALS, SETTING, METHODS: Our recent exome sequencing study identified novel candidate genes for male infertility. TEX13B was found to be one of the potential candidates, hence we explored the role of TEX13B in male infertility within a large infertile case-control cohort. We performed functional analyses of Tex13b in a GC-1 cell line using CRISPR-Cas9. We differentially labelled the cell proteins by stable isotope labelling of amino acids in cell culture (SILAC) and performed mass spectrometry-based whole-cell proteomics to identify the differential protein regulation in knockout cells compared to wild-type cells. We found that Tex13b knockout leads to downregulation of the OXPHOS complexes and upregulation of glycolysis genes, which was further validated by western blotting. These results were further confirmed by respirometry analysis in Tex13b knockout cells. Further, we also performed a conditional overexpression of TEX13B in GC-1 cells and studied the expression of OXPHOS complex proteins by western blotting. MAIN RESULTS AND THE ROLE OF CHANCE: We identified a rare variant, rs775429506 (p.Gly237Glu), exclusively in two non-obstructive-azoospermia (NOA) men, that may genetically predispose these men for infertility. Further, we demonstrated that Tex13b functions in the transcription regulation of OXPHOS complexes. LARGE SCALE DATA: N/A. LIMITATIONS, REASONS FOR CAUTION: We examined the function of Tex13b in GC-1 in vitro by knocking out and conditional overexpression, for understanding the function of Tex13b in germ cells. Unfortunately, this could not be replicated in either an animal model or in patient-derived tissue due to the non-availability of an animal model or patient's testis biopsies. WIDER IMPLICATIONS OF THE FINDINGS: This study identified that Tex13b plays an important role in male germ cell development and differentiation. The findings of this study would be useful for screening infertile males with spermatogenic failure and counselling them before the implementation of assisted reproduction technique(s). STUDY FUNDING/COMPETING INTEREST(S): Funding was provided by the Council of Scientific and Industrial Research (CSIR) under the network project (BSC0101 and MLP0113) and SERB, the Department of Science and Technology, Government of India (J C Bose Fellowship: JCB/2019/000027). The authors do not have any competing interest.

TEX19 increases the levels of CDK4 and promotes breast cancer by disrupting SKP2-mediated CDK4 ubiquitination.

BACKGROUND: Globally, breast cancer in women is the fifth leading cause of cancer death. There is an urgent need to explore the molecular mechanism of breast cancer proliferation and metastasis. METHOD: TCGA database analysis was used to analyze genes expression in breast cancer and normal samples and the association between gene expression and prognosis. Immunohistochemical staining, qPCR and western blotting was sued to detected gene expression. The cell function tests were conducted to investigate the effects of TEX19 and CDK4 with abnormal expression on cell proliferation, migration, apoptosis, cell cycle, and colony formation. Bioinformatics analysis methods combined with CHX tracking experiment and Co-IP experiment were performed to screen and verify the downstream molecule and regulatory mechanism of TEX19. Besides, subcutaneous tumorigenesis model in nude mice was constructed. RESULTS: TEX19 was significantly upregulated in breast cancer, and the TEX19 level was related to tumor invasion and prognosis. TEX19 knockdown inhibited the proliferation and migration of breast cancer cells, increased cell apoptosis, and blocked the cell cycle in the G2 phase. Besides, TEX19 suppressed the growth of tumors in the body. Mechanically, TEX19 upregulated the level of CDK4 protein, which depended on the E3 ubiquitin ligase SKP2. Specifically, TEX19 knockdown and SKP2 protein overexpression destroyed the stability of CDK4 protein and enhanced the ubiquitination of CDK4 protein. Additionally, CDK4 knockdown inhibited the proliferation, migration, and colony formation of breast cancer cells, and alleviated the promotion of TEX19 overexpression on the proliferation and migration of breast cancer cell. CONCLUSION: TEX19 and CDK4 were upregulated in breast cancer, and TEX19 increased the level of CDK4 protein by influencing SKP2-mediated ubiquitination of CDK4, thereby promoting the progression of breast cancer.

Picky Eating at the ER-phagy Buffet.

The degradation of the endoplasmic reticulum (ER) by autophagy (ER-phagy) regulates proteostasis. Two studies (An et al., Mol. Cell, 2019; Chino et al., Mol. Cell, 2019) have uncovered a new ER-phagy molecule, TEX264, yielding insight into how ER is packaged for degradation, and have illuminated the extent of redundancy between different ER-phagy 'pathways' in remodelling the ER proteome.

Immune capture and protein profiling of small extracellular vesicles from human plasma.

Extracellular vesicles (EVs), the key players in inter-cellular communication, are produced by all cell types and are present in all body fluids. Analysis of the proteome content is an important approach in structural and functional studies of these vesicles. EVs circulating in human plasma are heterogeneous in size, cellular origin, and functions. This heterogeneity and the potential presence of contamination with plasma components such as lipoprotein particles and soluble plasma proteins represent a challenge in profiling the proteome of EV subsets by mass spectrometry. An immunocapture strategy prior to mass spectrometry may be used to isolate a homogeneous subpopulation of small EVs (sEV) with a specific endocytic origin from plasma or other biofluids. Immunocapture selectively separates EV subpopulations in biofluids based on the presence of a unique protein carried on the vesicle surface. The advantages and disadvantages of EV immune capture as a preparative step for mass spectrometry are discussed.

Tex10 interacts with STAT3 to regulate hepatocellular carcinoma growth and metastasis.

Testis expression 10 (Tex10) is reported to be associated with tumorigenesis in several types of cancer types, but its role in hepatocellular carcinoma (HCC) metastasis has not been investigated. In this study, the expression of Tex10 in the HCC cell line and tissue microarray was determined by Western blot and immunohistochemistry (IHC), respectively. RNA sequencing-based transcriptome analysis was performed to identify the Tex10-mediated biological process. Cell Counting Kit-8, colony formation, transwell assays, xenograft tumor growth, and lung metastasis experiments in nude mice were applied to assess the effects of Tex10 on cell proliferation, migration, invasion, and metastasis. The underlying mechanisms were further investigated using dual-luciferase reporter, co-immunoprecipitation, immunofluorescence, and chromatin immunoprecipitation assays. We found that Tex10 was upregulated in HCC tumor tissues compared to adjacent normal tissues, with its expression correlated with a poor prognosis. Gene ontology function enrichment analysis revealed alterations in several biological processes in response to Tex10 knockdown, especially cell motility and cell migration. Functional studies demonstrated that Tex10 promotes HCC cell proliferation, migration, invasion, and metastasis in vitro and in vivo. Moreover, Tex10 was shown to regulate invasion and epithelial-mesenchymal transition via signal transducer and activator of transcription 3 (STAT3) signaling. Mechanistically, Tex10 was found to interact with STAT3 and promote its transcriptional activity. In addition, we found that Tex10 promotes p300-mediated STAT3 acetylation, while p300 silencing abolishes Tex10-enhanced STAT3 transcriptional activity. Together, these findings indicate that Tex10 functions as an oncogene by upregulating STAT3 activity, thus suggesting that Tex10 may serve as a prognostic biomarker and/or therapeutic target for HCC patients.

A novel surgical approach for fixation of a posterior chamber intraocular lens of Rayner 620 H with Gore-Tex suture.

PURPOSE: To report a novel surgical approach for the scleral fixation of the Rayner 620 H intraocular lens (IOL) with Gore-Tex suture and its outcomes at 6 months postoperatively. METHODS: 19 consecutive patients who underwent novel surgical approach for the scleral fixation of Rayner 620 H IOL with Gore-Tex suture at Peking Union Medical College Hospital between June 2020 and June 2021 were included. Data on best-corrected visual acuity (BCVA), spherical equivalent, total astigmatism/axis, short-term and long-term complications, and corresponding management with a follow-up of 6 months were collected. RESULTS: Nineteen patients (11 men and 8 women) with a mean age of 62.7 ± 10.6 years were included. The median BCVA improved significantly from 0.90 ± 0.90 (Snellen 20/160) preoperatively to 0.20 ± 0.30 (Snellen 20/32) at postoperative 6 months follow-up (P < 0.001). The stratification of the accuracy of refractive outcomes was 53% of patients within ± 0.5 D and 84% of patients within ± 1.0 D of the refractive target. Corneal edema (n = 3, 16%) and increased intraocular pressure (IOP) (n = 4, 11%) were short-term complications. Long-term complications included increased IOP (n = 1, 5%), and macular edema (n = 1, 5%). CONCLUSION: The novel surgical approach for scleral fixation of the Rayner 620 H IOL with Gore-Tex suture is a reasonable option for patients who need secondary IOL placement without adequate capsular support.

The enigma of Oligocene climate and global surface temperature evolution.

Falling atmospheric CO2 levels led to cooling through the Eocene and the expansion of Antarctic ice sheets close to their modern size near the beginning of the Oligocene, a period of poorly documented climate. Here, we present a record of climate evolution across the entire Oligocene (33.9 to 23.0 Ma) based on TEX86 sea surface temperature (SST) estimates from southwestern Atlantic Deep Sea Drilling Project Site 516 (paleolatitude ∼36°S) and western equatorial Atlantic Ocean Drilling Project Site 929 (paleolatitude ∼0°), combined with a compilation of existing SST records and climate modeling. In this relatively low CO2 Oligocene world (∼300 to 700 ppm), warm climates similar to those of the late Eocene continued with only brief interruptions, while the Antarctic ice sheet waxed and waned. SSTs are spatially heterogenous, but generally support late Oligocene warming coincident with declining atmospheric CO2 This Oligocene warmth, especially at high latitudes, belies a simple relationship between climate and atmospheric CO2 and/or ocean gateways, and is only partially explained by current climate models. Although the dominant climate drivers of this enigmatic Oligocene world remain unclear, our results help fill a gap in understanding past Cenozoic climates and the way long-term climate sensitivity responded to varying background climate states.

Diaphragmatic hernia repair porcine model to compare the performance of biodegradable membranes against Gore-Tex®.

BACKGROUND: Patch repair of congenital diaphragmatic hernia (CDH) using Gore-Tex® is associated with infection, adhesions, hernia recurrence, long-term musculoskeletal sequels and poor tissue regeneration. To overcome these limitations, the performance of two novel biodegradable membranes was tested to repair CDH in a growing pig model. METHODS: Twelve male pigs were randomly assigned to 3 different groups of 4 animals each, determined by the type of patch used during thoracoscopic diaphragmatic hernia repair (Gore-Tex®, polycaprolactone electrospun membrane-PCLem, and decellularized human chorion membrane-dHCM). After 7 weeks, all animals were euthanized, followed by necropsy for diaphragmatic evaluation and histological analysis. RESULTS: Thoracoscopic defect creation and diaphragmatic repair were performed without any technical difficulty in all groups. However, hernia recurrence rate was 0% in Gore-Tex®, 50% in PCLem and 100% in dHCM groups. At euthanasia, Gore-Tex® patches appeared virtually unchanged and covered with a fibrotic capsule, while PCLem and dHCM patches were replaced by either floppy connective tissue or vascularized and floppy regenerated membranous tissue, respectively. CONCLUSION: Gore-Tex® was associated with a higher survival rate and lower recurrence. Nevertheless, the proposed biodegradable membranes were associated with better tissue integration when compared with Gore-Tex®.

LINC00624/TEX10/NF-κB axis promotes proliferation and migration of human prostate cancer cells.

Prostate cancer (PCa) is a malignant epithelial tumor with a high rate of biochemical or local recurrence. Studies have suggested that LINC00624 plays an important oncogenic role in liver cancer. However, whether it exerts similar effects in PCa progression remains unknown. In this study, we explored the effects of LINC00624 on the malignant progression of PCa and sought to identify the relevant signaling pathways. The results showed that LINC00624 was highly expressed in PCa tissues and cells and was associated with poor prognosis in PCa patients. In vitro and in vivo assays further showed that LINC00624 knockdown could decrease the proliferative and migratory ability of PCa cells. Mechanistically, we found that LINC00624 and TEX10 formed a co-regulatory axis that stimulated NF-κB activity. Our data suggest that LINC00624 acts as an oncogene in PCa progression and has potential as a novel biomarker for PCa.

Outcomes of four-point suture fixated and two-point sutureless posterior chamber IOLs combined with pars plana vitrectomy.

BACKGROUND: While each scleral fixation method has its own advantages, there is a lack of strong evidence to suggest a superior technique. Advances in cataract surgery expand patient eligibility for successful cataract extraction, benefitting a growing population of pseudophakic patients. However, implantation of secondary intraocular lens (IOL) with compromised anterior or posterior capsule is a more challenging task. Each method of scleral fixation has its own advantages and none of them has strong evidence to be superior. This paper describes postsurgical outcomes of two scleral intraocular(IOL) fixation techniques combined with pars plana vitrectomy(PPV) from a single tertiary referral eye center. METHODS: Patients underwent PPV and IOL implantation with either four-point sutured scleral fixation (Akreos AO60(AK); n = 24) or two-point sutureless flanged intrascleral fixation (CT Lucia(CTL); n = 7). Reports include IOL and sclerotomy placement, fixation techniques, and IOL model. RESULTS: Thirty-one eyes of thirty patients were analyzed. Average change in vision from baseline measurement was LogMAR - 0.68 ± 0.66 and - 0.90 ± 0.63 for AK and CTL groups, respectively. Average postoperative refractive error was - 0.3 ± 1.03 D (AK) and 0.4 ± 0.60 D (CTL). No opacification cases of Akreos lens were found in this study with the longest follow up of 53 months. CONCLUSIONS: Both methods of implantation (sutured and sutureless) could provide good visual and refractive outcomes. Minimal complication rates were reported despite including patients with multiple comorbidities, making both techniques an attractive choice for secondary IOL implantation.

Exosome and mesenchymal stem cell cross-talk in the tumor microenvironment.

Mesenchymal stem cells (MSCs) are a major component of the tumor microenvironment (TME) and play a key role in promoting tumor progression. The tumor uses exosomes to co-opt MSCs and re-program their functional profile from normally trophic to pro-tumorigenic. These tumor-derived small vesicles called "TEX" carry and deliver a cargo rich in proteins and nucleic acids to MSCs. Upon interactions with surface receptors on MSCs and uptake of the exosome cargo by MSCs, molecular, transcriptional and translational changes occur that convert MSCs into producers of factors that are necessary for tumor growth and that also alter functions of non-tumor cells in the TME. The MSCs re-programmed by TEX become avid producers of their own exosomes that carry and deliver mRNA and miRNA species as well as molecular signals not only back to tumor cells, directly enhancing their growth, but also horizontally to fibroblasts, endothelial cells and immune cells in the TME, indirectly enhancing their pro-tumor functions. TEX-driven cross-talk of MSCs with immune cells blocks their anti-tumor activity and/or converts them into suppressor cells. MSCs re-programmed by TEX mediate pro-angiogenic activity and convert stromal cells into cancer-associated fibroblasts (CAFs). Although MSCs have a potential to exert anti-tumor activities, they largely provide service to the tumor using the multidirectional communication system established by exosomes in the TME. Future therapeutic options consider disruption of this complex vicious cycle by either molecular or gene-regulated silencing of pro-tumor effects mediated by MSCs in the TME.

Meiosis initiation: a story of two sexes in all creatures great and small.

Meiosis facilitates diversity across individuals and serves as a major driver of evolution. However, understanding how meiosis begins is complicated by fundamental differences that exist between sexes and species. Fundamental meiotic research is further hampered by a current lack of human meiotic cells lines. Consequently, much of what we know relies on data from model organisms. However, contextualising findings from yeast, worms, flies and mice can be challenging, due to marked differences in both nomenclature and the relative timing of meiosis. In this review, we set out to combine current knowledge of signalling and transcriptional pathways that control meiosis initiation across the sexes in a variety of organisms. Furthermore, we highlight the emerging links between meiosis initiation and oncogenesis, which might explain the frequent re-expression of normally silent meiotic genes in a variety of human cancers.

Outcomes of expanded polytetrafluoroethylene pericardial membrane implantation in left ventricular assist device explantation and heart transplantation.

OBJECTIVES: Redo sternotomy and explantation of left ventricular assist devices (LVAD) for heart transplantation (HT) involve prolonged dissection, potential injury to mediastinal structures and/or bleeding. Our study compared a complete expanded polytetrafluoroethylene (ePTFE) wrap versus minimal or no ePTFE during LVAD implantation, on outcomes of subsequent HT. METHODS: Between July 2005 and July 2018, 84 patients underwent a LVAD implant and later underwent HT. Thirty patients received a complete ePTFE wrap during LVAD implantation (Group 1), and 54 patients received either a sheet of ePTFE placed in the anterior mediastinum or no ePTFE (Group 2). RESULTS: Baseline characteristics were similar between Groups 1 and 2. Surgeons reported subjective improvements in speed, predictability, and safety of dissection with complete ePTFE compared with minimal or no ePTFE. Time from incision to initiation of cardiopulmonary bypass (CPB) were similar between groups (97 ± 38 vs. 89 ± 29 min, p = .3). Injury to mediastinal structures during the dissection was similar between groups (10% vs. 11%, p > .9). While surgeons reported less intraoperative bleeding in Group 1 (43% vs. 61%), this trend did not reach significance (p = .1). In-hospital mortality, intensive care unit length of stay and hospital length of stay were similar between both groups. CONCLUSIONS: In patients undergoing LVAD explant-HT, there was a trend toward reduced surgeon reported intraoperative bleeding with ePTFE placement. Despite qualitatively reported greater ease and speed of mediastinal dissection with ePTFE membrane placement, time to initiation of CPB did not differ, likely because surgeons remained cautious, allowing extra time for unanticipated difficulties.

Dynamic cytoplasmic projections connect mammalian spermatogonia in vivo.

Throughout the male reproductive lifespan, spermatogonial stem cells (SSCs) produce committed progenitors that proliferate and then remain physically connected in growing clones via short cylindrical intercellular bridges (ICBs). These ICBs, which enlarge in meiotic spermatocytes, have been demonstrated to provide a conduit for postmeiotic haploid spermatids to share sex chromosome-derived gene products. In addition to ICBs, spermatogonia exhibit multiple thin cytoplasmic projections. Here, we have explored the nature of these projections in mice and find that they are dynamic, span considerable distances from their cell body (≥25 µm), either terminate or physically connect multiple adjacent spermatogonia, and allow for sharing of macromolecules. Our results extend the current model that subsets of spermatogonia exist as isolated cells or clones, and support a model in which spermatogonia of similar developmental fates are functionally connected through a shared dynamic cytoplasm mediated by thin cytoplasmic projections.