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Recent advances have enabled the direct induction of human tissue-specific stem and progenitor cells from differentiated somatic cells. However, it is not known whether human hepatic progenitor cells (hHepPCs) can be generated from other cell types by direct lineage reprogramming with defined transcription factors. Here, we show that a set of three transcription factors, FOXA3, HNF1A, and HNF6, can induce human umbilical vein endothelial cells to directly acquire the properties of hHepPCs. These induced hHepPCs (hiHepPCs) propagate in long-term monolayer culture and differentiate into functional hepatocytes and cholangiocytes by forming cell aggregates and cystic epithelial spheroids, respectively, under three-dimensional culture conditions. After transplantation, hiHepPC-derived hepatocytes and cholangiocytes reconstitute damaged liver tissues and support hepatic function. The defined transcription factors also induce hiHepPCs from endothelial cells circulating in adult human peripheral blood. These expandable and bipotential hiHepPCs may be useful in the study and treatment of human liver diseases.

Intestinal organoids are useful models for studying the characteristics of intestinal diseases and their treatment. However, a major limiting factor in their usability is the need for donor tissue fragments or pluripotent stem cells to generate the organoids. Here, we describe an approach to generate intestinal organoids from fibroblasts, a new source. We used direct reprogramming technology to generate cells with the properties of fetal intestine-derived progenitor cells (FIPCs) from mouse embryonic fibroblasts (MEFs). These induced FIPCs (iFIPCs) can give rise to cells resembling intestinal stem cells (ISCs), henceforth referred to as induced ISCs (iISCs). These iFIPCs and iISCs form spherical and budding organoids, respectively, similar to FIPCs and ISCs. These induced intestinal organoids could be used for studies on intestinal diseases and regenerative therapy.

Placental development is a key event in mammalian reproduction and embryogenesis. However, the molecular basis underlying placental development is not fully understood. Here, we conduct a forward genetic screen to identify regulators for extraembryonic development and identify Zfp281 as a key factor. Zfp281 overexpression in mouse embryonic stem cells facilitates the induction of trophoblast stem-like cells. Zfp281 is preferentially expressed in the undifferentiated trophoblast stem cell population in an FGF-dependent manner, and disruption of Zfp281 in mice causes severe defects in early placental development. Consistently, Zfp281-depleted trophoblast stem cells exhibit defects in maintaining the transcriptome and differentiation capacity. Mechanistically, Zfp281 interacts with MLL or COMPASS subunits and occupies the promoters of its target genes. Importantly, ZNF281, the human ortholog of this factor, is required to stabilize the undifferentiated status of human trophoblast stem cells. Thus, we identify Zfp281 as a conserved factor for the maintenance of trophoblast stem cell plasticity., (Copyright © 2019 The Authors. Published by Elsevier Inc. All rights reserved.)

The intestine has fundamental functions for the maintenance of homeostasis, including food digestion and nutrient/water absorption. Although the lumen of the intestine is always exposed to pathogens, intestinal epithelial cells form monolayer sheets that act as an epithelial barrier to prevent the invasion of pathogens. Thus, disruption of the intestinal epithelial barrier causes inflammatory bowel diseases. To investigate the details of these intractable intestinal diseases, it is necessary to analyze the characteristics of intestinal epithelial cells in vitro. However, it is difficult to maintain and propagate intestinal epithelial cells in culture. Recently, intestinal organoid culture systems have been established, in which differentiated intestinal epithelial lineage cells can be continuously produced from intestinal stem cells and form epithelial organoids with crypt-like structures in long-term culture. Moreover, intestinal epithelial organoids can be generated not only from intestinal tissue-derived cells, embryonic stem cells, and induced pluripotent stem cells, but also by inducing direct conversion of nonintestinal somatic cells into intestinal epithelial cells. These intestinal organoids can be used in basic studies for understanding the mechanisms underlying intestinal development and diseases and will be applied in future transplantation therapy and drug discovery to treat intestinal diseases., (© 2018 Japanese Society of Developmental Biologists.)

Intestinal organoids hold great promise as a valuable tool for studying and treating intestinal diseases. The currently available sources of human intestinal organoids, tissue fragments or pluripotent stem cells, involve invasive procedures or complex differentiation protocols, respectively. Here, we show that a set of four transcription factors, Hnf4α, Foxa3, Gata6, and Cdx2, can directly reprogram mouse fibroblasts to acquire the identity of fetal intestine-derived progenitor cells (FIPCs). These induced FIPCs (iFIPCs) form spherical organoids that develop into adult-type budding organoids containing cells with intestinal stem cell properties. The resulting stem cells produce all intestinal epithelial cell lineages and undergo self-renewing cell divisions. After transplantation, the induced spherical and budding organoids can reconstitute colonic and intestinal epithelia, respectively. The same combination of four defined transcription factors can also induce human iFIPCs. This alternative approach for producing intestinal organoids may well facilitate application for disease analysis and therapy development., (Copyright © 2017 Elsevier Inc. All rights reserved.)

P bodies (PBs) and stress granules (SGs) are conserved cytoplasmic aggregates of cellular messenger ribonucleoprotein complexes (mRNPs) that are implicated in mRNA metabolism and play crucial roles in adult stem cell homeostasis and stress responses. However, the mechanisms underlying the dynamics of mRNP granules are poorly understood. Here, we report NEDD4, an E3 ubiquitin ligase, as a key regulator of mRNP dynamics that controls the size of the spermatogonial progenitor cell (SPC) pool. We find that NEDD4 targets an RNA-binding protein, NANOS2, in spermatogonia to destabilize it, leading to cell differentiation. In addition, NEDD4 is required for SG clearance. NEDD4 targets SGs and facilitates their rapid clearance through the endosomal-lysosomal pathway during the recovery period. Therefore, NEDD4 controls the turnover of mRNP components and inhibits pathological SG accumulation. Accordingly, we propose that a NEDD4-mediated mechanism regulates mRNP dynamics, and facilitates SPC homeostasis and viability under normal and stress conditions.

Hepatic progenitor cells (HPCs) appear in response to several types of chronic injury in the human and rodent liver that often develop into liver fibrosis, cirrhosis, and primary liver cancers. However, the contribution of HPCs to the pathogenesis and progression of such liver diseases remains controversial. HPCs are generally defined as cells that can differentiate into hepatocytes and cholangiocytes. In this study, however, we found that HPCs isolated from the chronically injured liver can also give rise to myofibroblasts as a third type of descendant. While myofibroblast differentiation from HPCs is not significant in culture, during tumor development, HPCs can contribute to the formation of the tumor microenvironment by producing abundant myofibroblasts that might form a niche for tumor growth and survival. Thus, HPCs can be redefined as cells with a potential for differentiation into myofibroblasts that is specifically activated during tumor formation., (Copyright © 2016 The Authors. Published by Elsevier Inc. All rights reserved.)

Unlabelled: In liver development, hepatoblasts that act as hepatic stem/progenitor cells proliferate and differentiate into both hepatocytes and cholangiocytes to form liver tissues. Although numerous factors contribute to this event, little is known about the roles of microRNAs in hepatoblast proliferation and differentiation. In this study, we focused on the lineage-28 (Lin28) family proteins, which are required for microRNA regulation in pluripotent stem cells and cancer cells, and investigated their roles as regulatory factors for the properties of hepatoblasts., Conclusion: Lin28b was specifically expressed in hepatoblasts, and its suppression induced growth arrest and cholangiocyte differentiation of hepatoblasts; mechanistically, Lin28b positively regulates the expression of Lin28b itself and cell cycle-related proteins in hepatoblasts by suppressing the maturation of target microRNAs, lethal-7b and miR-125a/b, enabling maintenance of the stem cell properties of hepatoblasts, such as their capabilities for proliferation and bi-lineage differentiation, during liver development. (Hepatology 2016;64:245-260)., (© 2016 by the American Association for the Study of Liver Diseases.)

T-box transcription factors containing the common DNA-binding domain T-box contribute to the organization of multiple tissues in vertebrates and invertebrates. In mammals, 17 T-box genes are divided into five subfamilies depending on their amino acid homology. The proper distribution and expression of individual T-box transcription factors in different tissues enable regulation of the proliferation and differentiation of tissue-specific stem cells and progenitor cells in a suitable time schedule for tissue organization. Consequently, uncontrollable expressions of T-box genes induce abnormal tissue organization, and eventually cause various diseases with malformation and malfunction of tissues and organs. Furthermore, some T-box transcription factors are essential for maintaining embryonic stem cell pluripotency, improving the quality of induced pluripotent stem cells, and inducing cell-lineage conversion of differentiated cells. These lines of evidence indicate fundamental roles of T-box transcription factors in tissue organization and stem cell properties, and suggest that these transcription factors will be useful for developing therapeutic approaches in regenerative medicine.

The homeostatic renewal of the intestinal epithelium depends on regulation of proliferation and differentiation of stem/progenitor cells residing in a specific site, called the 'stem cell niche.' Thus, the reconstitution of the microenvironment of the stem cell niche may allow us to maintain intestinal stem/progenitor cells in culture for a longer period. Although epidermal growth factor (EGF) is conventionally used as a supplement of intestinal epithelial cell culture, little has been known regarding a role of EGF signaling in a stem/progenitor cell population. In this study, we attempted to clarify the role of EGF signaling in intestinal stem/progenitor cells, and to establish a culture system in which these cells could be maintained with normal differentiation potential. We first examined the expression pattern of EGF and its receptor, EGFR, and inhibited EGF signaling in mouse intestines. Next, we cultured intestinal cells isolated from mouse and human intestines in the presence of EGF and analyzed the function of EGF signaling in cultured cells. In both embryonic and adult mouse intestines, EGFR and EGF were expressed in immature epithelial cells and adjacent fibroblasts, respectively, and EGF signaling was essential to activate proliferation and inhibit apoptosis of intestinal stem/progenitor cells. Activation of EGF signaling also stimulated proliferation and suppressed apoptosis, both of which are necessary to maintain mouse and human intestinal epithelial cells in culture. Moreover, in these cultured epithelial cells, putative intestinal stem/progenitor cells persisted longer, and gave rise to different types of differentiated intestinal epithelial cells. We conclude that EGF signaling is indispensable for activation of proliferation and inhibition of unexpected cell death, not only in the intestinal stem cell niche, but also in culture of primitive intestinal epithelial cells.

Stem cells give rise to differentiated cell types but also preserve their undifferentiated state through cell self-renewal. With the use of transgenic mice, we found that the RNA-binding protein NANOS2 is essential for maintaining spermatogonial stem cells. Lineage-tracing analyses revealed that undifferentiated spermatogonia expressing Nanos2 self-renew and generate the entire spermatogenic cell lineage. Conditional disruption of postnatal Nanos2 depleted spermatogonial stem cell reserves, whereas mouse testes in which Nanos2 had been overexpressed accumulated spermatogonia with undifferentiated, stem cell-like properties. Thus, NANOS2 is a key stem cell regulator that is expressed in self-renewing spermatogonial stem cells and maintains the stem cell state during murine spermatogenesis.

Unlabelled: The adult liver progenitor cells appear in response to several types of pathological liver injury, especially when hepatocyte replication is blocked. These cells are histologically identified as cells that express cholangiocyte markers and proliferate in the portal area of the hepatic lobule. Although these cells play an important role in liver regeneration, the precise characterization that determines these cells as self-renewing bipotent primitive hepatic cells remains to be shown. Here we attempted to isolate cells that express a cholangiocyte marker from the adult mouse liver and perform single cell-based analysis to examine precisely bilineage differentiation potential and self-renewing capability of these cells. Based on the results of microarray analysis and immunohistochemistry, we used an antibody against CD133 and isolate CD133(+) cells via flow cytometry. We then cultured and propagated isolated cells in a single cell culture condition and examined their potential for proliferation and differentiation in vitro and in vivo. Isolated cells that could form large colonies (LCs) in culture gave rise to both hepatocytes and cholangiocytes as descendants, while maintaining undifferentiated cells by self-renewing cell divisions. The clonogenic progeny of an LC-forming cell is capable of reconstituting hepatic tissues in vivo by differentiating into fully functional hepatocytes. Moreover, the deletion of p53 in isolated LC-forming cells resulted in the formation of tumors with some characteristics of hepatocellular carcinoma and cholangiocarcinoma upon subcutaneous injection into immunodeficient mutant mice. These data provide evidence for the stem cell-like capacity of isolated and clonally cultured CD133(+) LC-forming cells., Conclusion: Our method for prospectively isolating hepatic progenitor cells from the adult mouse liver will facilitate study of their roles in liver regeneration and carcinogenesis.

Background & Aims: Islet transplantation has become available across the globe since a novel protocol was reported. However, because donors are in short supply, only a minority of patients benefit from this procedure. Pancreatic progenitor cells are a promising resource for regeneration of new islets, but whether progenitor cells reside in ductal epithelium is not clear., Methods: Mouse pancreas was examined by immunohistochemistry with cell surface markers specific for ductal cells. We developed an isolation method for ductal cells by flow cytometric cell sorting using a newly identified specific marker for ductal cells. By using an in vitro colony assay, we characterized their proliferative and multipotent capacity., Results: CD133 is expressed specifically in ductal epithelium. Flow cytometric analysis revealed that purified ductal cells are highly enriched in the CD133(+)CD34(-)CD45(-)Ter119(-) fraction. An analysis of clonal epithelial colonies formed by individual cells revealed that progenitor cells with multilineage differentiation capacity are present in neonatal ductal epithelium. Moreover, these progenitor cells express c-Met. In adult mice, progenitor cells that show a high proliferative capacity but appear committed to a ductal lineage are co-purified with CD133(+)CD34(-)CD45(-)Ter119(-) cells., Conclusions: We established a system for isolating and culturing mouse pancreatic ductal cells that relies on flow cytometric cell sorting. Clonal analysis revealed that a population of progenitor cells is present among CD133(+) ductal cells. Isolation of these cells will facilitate future studies into the roles of pancreatic progenitor cells in regeneration and carcinogenesis.

ES cells represent a valuable model for investigating early embryo development and hold promise for future regenerative medicine strategies. The self-renewal of pluripotent mouse ES cells has been shown to require extrinsic stimulation by the bone morphogenetic protein (BMP) and leukemia inhibitory factor signaling pathways and the expression of the transcription factors Oct4 and Nanog. However, the network of interactions among extrinsic and intrinsic determinants of ES cell pluripotency is currently poorly understood. Here, we show that Nanog expression is up-regulated in mouse ES cells by the binding of T (Brachyury) and STAT3 to an enhancer element in the mouse Nanog gene. We further show that Nanog blocks BMP-induced mesoderm differentiation of ES cells by physically interacting with Smad1 and interfering with the recruitment of coactivators to the active Smad transcriptional complexes. Taken together, our findings illustrate the existence of ES cell-specific regulatory networks that underlie the maintenance of ES cell pluripotency and provide mechanistic insights into the role of Nanog in this process.

During pancreatic development, neogenesis, and regeneration, stem cells might act as a central player to generate endocrine, acinar, and duct cells. Although these cells are well known as pancreatic stem cells (PSCs), indisputable proof of their existence has not been reported. Identification of phenotypic markers for PSCs leads to their prospective isolation and precise characterization to clear whether stem cells exist in the pancreas. By combining flow cytometry and clonal analysis, we show here that a possible pancreatic stem or progenitor cell candidate that resides in the developing and adult mouse pancreas expresses the receptor for the hepatocyte growth factor (HGF) c-Met, but does not express hematopoietic and vascular endothelial antigens such as CD45, TER119, c-Kit, and Flk-1. These cells formed clonal colonies in vitro and differentiated into multiple pancreatic lineage cells from single cells. Some of them could largely expand with self-renewing cell divisions in culture, and, following cell transplantation, they differentiated into pancreatic endocrine and acinar cells in vivo. Furthermore, they produced cells expressing multiple markers of nonpancreatic organs including liver, stomach, and intestine in vitro. Our data strongly suggest that c-Met/HGF signaling plays an important role in stem/progenitor cell function in both developing and adult pancreas. By using this antigen, PSCs could be isolated prospectively, enabling a detailed investigation of stem cell markers and application toward regenerative therapies for diabetes.

Background/aims: Self-renewing stem cells responsible for tissue or organ development and regeneration have been recently described. To isolate such cells using flow cytometry, it should be required to find molecules expressing on their cell surfaces. We have previously reported that, on cells fulfilling the criteria for hepatic stem cells, the hepatocyte growth factor receptor c-Met is expressed specifically in the developing mouse liver. In this study, to determine whether c-Met is an essential marker for hepatic stem cells in other animal strains, we examined the potential for in vivo liver-repopulation in sorted fetal rat-derived c-Met+ cells using the retrorsine model., Methodology: Using flow cytometry and monoclonal antibodies for c-Met and leukocyte common antigen CD45, fetal rat liver cells were fractionated according to the expression of these molecules. Then, cells in each cell subpopulation were sorted and transplanted into the retrorsine-treated adult rats with two-third hepatectomy. At 9 months post transplant, frequency of liver-repopulation was examined by qualitative and quantitative analyses., Results: When we transplanted c-Met+ CD45- sorted cells, many donor-derived cells formed colonies that included mature hepatocytes expressing albumin and containing abundant glycogen in their cytoplasm. In contrast, c-Met- cells and CD45+ cells could not repopulate damaged recipient livers., Conclusions: High enrichment of liver-repopulating cells was conducted by sorting of c-Met+ cells from the developing rat liver. This result suggests that c-Met/HGF interaction plays a crucial role for stem cell growth, differentiation, and self-renewal in rat liver organogenesis. Since the c-Met is also expressed in the fetal mouse-derived hepatic stem cells, this molecule could be expected to be an essential marker for such cell population in the various animal strains, including human.

In liver development, a number of growth factors (GFs) and components of the extracellular matrix (ECMs) lead to differentiation of liver parenchymal cells. As the liver contains many cell types, specifically investigating their functional effects on hepatic stem cell populations is difficult. Prospective isolation and clonal assays for hepatic stem cells enable the examination of direct effects of GFs and ECMs on this rare cell fraction. Using previously purified cells that fulfill the criteria for hepatic stem cells, we examined how GFs and ECMs regulate differentiation in the developing liver. We show here that hepatocyte growth factor (HGF) induced early transition of albumin (ALB)-negative stem cells to ALB-positive hepatic precursors resembling hepatoblasts and then oncostatin M (OSM) promoted their differentiation to tryptophan-2, 3-dioxygenase (TO)-positive mature hepatocytes. During this transition, ECMs were necessary for the differentiation of stem cells and precursors, but their effects were only supportive. In the first step of stem cell differentiation induced by HGF, the expression of CCAAT/enhancer binding protein (C/EBP), a basic leucine zipper transcription factor, changed dramatically. When C/EBP function was inhibited in stem cells, they stopped differentiating to hepatocyte-lineage cells and proliferated actively. These are the first findings to illustrate the mechanism of hepatic stem cell differentiation in liver development.

Hepatocyte transplantation and artificial organ hepatic support require a number of functionally mature hepatocytes. However, their growth activity and functional behaviors are much smaller in culture after isolation from the liver. We examined whether continuously differentiating hepatocytes from multipotent hepatic stem cells that were isolated by using flow cytometry and propagated clonally in culture could be a source of clinical application. They actually gave rise to cells that were functionally equal to mature hepatocytes found in the adult liver, which secreted albumin into culture medium and metabolized harmful ammonium into urea. These data suggest that stem cell-derived hepatocytes are a useful cell source for developing therapeutic strategies, such as cell transplantation, gene therapy, and artificial liver organ to treat various liver disorders.

Although the liver has been known for its enormous regenerative capacity, little is known about the mechanisms responsible for such regeneration.To provide evidence for the existence of liver stem cell, using FACS and single cell-based assays, cells with multi-lineage differentiation potential and self-renewal capability have been prospectively identified. These cells could be clonally propagated in culture where they continuously produced hepatocytes and cholangiocytes as descendants while maintaining primitive stem cells. When the cells clonally expanded in vitro were transplanted into mouse, they morphologically and functionally differentiated into hepatocytes and cholangiocytes. Furthermore, these cells differentiated into pancreatic acinar cells or intestinal epithelial cells upon transplantation into pancreas or duodenal wall. Manipulation of self-renewing liver stem cells may provide new insight into therapies for diseases of the digestive system.

Using flow cytometry and single cell-based assays, we prospectively identified hepatic stem cells with multilineage differentiation potential and self-renewing capability. These cells could be clonally propagated in culture where they continuously produced hepatocytes and cholangiocytes as descendants while maintaining primitive stem cells. When cells that expanded in vitro were transplanted into recipient animals, they morphologically and functionally differentiated into hepatocytes and cholangiocytes with reconstitution of hepatocyte and bile duct structures. Furthermore, these cells differentiated into pancreatic ductal and acinar cells or intestinal epithelial cells when transplanted into pancreas or duodenal wall. These data indicate that self-renewing pluripotent stem cells persist in the developing mouse liver and that such cells can be induced to become cells of other organs of endodermal origin under appropriate microenvironment. Manipulation of hepatic stem cells may provide new insight into therapies for diseases of the digestive system.

Pluripotent stem cells found in a number of organs are usually in small cell populations. However, under adaptive stimulation, they enter the stage of growth and differentiation to compensate for the loss of differentiated cells. To analyze stem cell potential precisely, the exclusion of other differentiated cells and a clonal assay system are strongly required. In this study, we established a colony-forming assay system for pancreatic stem/progenitor cells in vitro. In this culture condition, they received signals for growth and differentiation, and formed clonal colonies including pancreatic endocrine-lineage cells, such as alpha and beta cells. By combining this culture system with flow cytometric cell sorting, pancreatic stem/progenitor cells will be enriched, and their potential can be analyzed precisely in single cell-based experiments.

We confirmed hepatocyte differentiation from embryonic stem (ES) cells in vitro. RT-PCR analysis revealed that a broad range of hepatic gene expression was observed in ES cells differentiated through formation of embryoid bodies (EBs) and its attachment culture. Quantitative PCR analysis revealed that hepatic gene expression related to early and late-stage liver development were enhanced through in vitro differentiation of ES cells. The presence of albumin-producing cells in the peripheral region of attached EBs was confirmed by immunocytochemical analysis. Future experiments will reveal the molecules that induce hepatocyte differentiation from ES cells in vitro. This research will provide systems for the investigation of mechanisms in liver development and establish a method of ES cell-based therapy for liver diseases.

E3 ubiquitin ligase complexes of the SCF type consist of ring-box 1 (Rbx1), cullin 1 (Cul1), S-phase kinase-associated protein 1 (Skp1), and a member of the F-box family of proteins. The identity of the F-box protein determines the substrate specificity of the complex. The F-box family member F-box- and WD repeat domain-containing 7 (Fbxw7; also known as Fbw7, SEL-10, hCdc4, and hAgo) targets for degradation proteins with wide-ranging functions, and uncovering its in vivo role has been difficult, because Fbxw7-/- embryos die in utero. Using two different Cre-loxP systems (Mx1-Cre and Alb-Cre), we generated mice with liver-specific null mutations of Fbxw7. Hepatic ablation of Fbxw7 resulted in hepatomegaly and steatohepatitis, with massive deposition of triglyceride, a phenotype similar to that observed in humans with nonalcoholic steatohepatitis. Both cell proliferation and the abundance of Fbxw7 substrates were increased in the Fbxw7-deficient liver. Long-term Fbxw7 deficiency resulted in marked proliferation of the biliary system and the development of hamartomas. Fbxw7 deficiency also skewed the differentiation of liver stem cells toward the cholangiocyte lineage rather than the hepatocyte lineage in vitro. This bias was corrected by additional loss of the Notch cofactor RBP-J, suggesting that Notch accumulation triggered the abnormal proliferation of the biliary system. Together, our results suggest that Fbxw7 plays key roles, regulating lipogenesis and cell proliferation and differentiation in the liver. [ABSTRACT FROM AUTHOR]

Abstract Dead end is a vertebrate-specific RNA-binding protein implicated in germ cell development. We have previously shown that mouse Dead end1 (DND1) is expressed in male embryonic germ cells and directly interacts with NANOS2 to cooperatively promote sexual differentiation of fetal germ cells. In addition, we have also reported that NANOS2 is expressed in self-renewing spermatogonial stem cells and is required for the maintenance of the stem cell state. However, it remains to be determined whether DND1 works with NANOS2 in the spermatogonia. Here, we show that DND1 is expressed in a subpopulation of differentiating spermatogonia and undifferentiated spermatogonia, including NANOS2-positive spermatogonia. Conditional disruption of DND1 depleted both differentiating and undifferentiated spermatogonia; however, the numbers of A single and A paired spermatogonia were preferentially decreased as compared with those of A aligned spermatogonia. Finally, we found that postnatal DND1 associates with NANOS2 in vivo , independently of RNA, and interacts with some of NANOS2-target mRNAs. These data not only suggest that DND1 is a partner of NANOS2 in undifferentiated spermatogonia as well as in male embryonic germ cells, but also show that DND1 plays an essential role in the survival of differentiating spermatogonia. Highlights • Dead end1 is expressed in almost all the PLZF-positive spermatogonia. • Deletion of Dead end1 causes apoptotic cell death of differentiating spermatogonia. • Deletion of Dead end1 also causes preferential reduction of A s and A pr spermatogonia. • Dead end1 interacts with NANOS2 in undifferentiated spermatogonia. [ABSTRACT FROM AUTHOR]