Yaqing Wang

Atg7 is required for acrosome biogenesis during spermatogenesis in mice

The acrosome is a specialized organelle that covers the anterior part of the sperm nucleus and plays an essential role in the process of fertilization. The molecular mechanism underlying the biogenesis of this lysosome-related organelle (LRO) is still largely unknown. Here, we show that germ cell-specific Atg7-knockout mice were infertile due to a defect in acrosome biogenesis and displayed a phenotype similar to human globozoospermia; this reproductive defect was successfully rescued by intracytoplasmic sperm injections. Furthermore, the depletion of Atg7 in germ cells did not affect the early stages of development of germ cells, but at later stages of spermatogenesis, the proacrosomal vesicles failed to fuse into a single acrosomal vesicle during the Golgi phase, which finally resulted in irregular or nearly round-headed spermatozoa. Autophagic flux was disrupted in Atg7-depleted germ cells, finally leading to the failure of LC3 conjugation to Golgi apparatus-derived vesicles. In addition, Atg7 partially regulated another globozoospermia-related protein, Golgi-associated PDZ- and coiled-coil motif-containing protein (GOPC), during acrosome biogenesis. Finally, the injection of either autophagy or lysosome inhibitors into testis resulted in a similar phenotype to that of germ cell-specific Atg7-knockout mice. Altogether, our results uncover a new role for Atg7 in the biogenesis of the acrosome, and we provide evidence to support the autolysosome origination hypothesis for the acrosome.

Microcephaly-Associated Protein WDR62 Regulates Neurogenesis through JNK1 in the Developing Neocortex

Mutations of WD40-repeat protein 62 (WDR62) have been identified recently to cause human MCPH (autosomal-recessive primary microcephaly), a neurodevelopmental disorder characterized by decreased brain size. However, the underlying mechanism is unclear. Here, we investigate the function of WDR62 in brain development and the pathological role of WDR62 mutations. We find that WDR62 knockdown leads to premature differentiation of neural progenitor cells (NPCs). The defect can be rescued by wild-type human WDR62, but not by the five MCPH-associated WDR62 mutants. We demonstrate that WDR62 acts upstream of JNK signaling in the control of neurogenesis. Depletion of JNK1 and WDR62 incurs very similar defects including abnormal spindle formation and mitotic division of NPCs as well as premature NPC differentiation during cortical development. Thus, our findings indicate that WDR62 is required for proper neurogenesis via JNK1 and provide an insight into the molecular mechanisms underlying MCPH pathogenesis.

Reprogramming of Sertoli cells to fetal-like Leydig cells by Wt1 ablation

Significance Genetic control of the differentiation between Sertoli cells and granulosa cells has been reported previously. However, the relationship between Sertoli cells and Leydig cells in the testis has not yet been definitively determined. In the present study, we demonstrate for the first time, to our knowledge, that these two cell types can be mutually reprogrammed and that Wilms’ Tumor Gene 1 (Wt1) plays a critical role in this process. This study provides a novel concept for cell fate determination in testis development that will improve our understanding of the regulatory mechanisms of gonad development. Sertoli and Leydig cells, the two major somatic cell types in the testis, have different morphologies and functions. Both are essential for gonad development and spermatogenesis. However, whether these cells are derived from the same progenitor cells and the mechanism regulating the differentiation between these two cell types during gonad development remains unclear. A previous study showed that overactivation of Ctnnb1 (cadherin-associated protein, beta 1) in Sertoli cells resulted in Sertoli cell tumors. Surprisingly, in the present study, we found that simultaneous deletion of Wilms’ Tumor Gene 1 (Wt1) and overactivation of Ctnnb1 in Sertoli cells led to Leydig cell-like tumor development. Lineage tracing experiments revealed that the Leydig-like tumor cells were derived from Sertoli cells. Further studies confirmed that Wt1 is required for the maintenance of the Sertoli cell lineage and that deletion of Wt1 resulted in the reprogramming of Sertoli cells to Leydig cells. Consistent with this interpretation, overexpression of Wt1 in Leydig cells led to the up-regulation of Sertoli cell-specific gene expression and the down-regulation of steroidogenic gene expression. These results demonstrate that the distinction between Sertoli cells and Leydig cells is regulated by Wt1, implying that these two cell types most likely originate from the same progenitor cells. This study thus provides a novel concept for somatic cell fate determination in testis development that may also represent an etiology of male infertility in human patients.

Zika virus directly infects peripheral neurons and induces cell death

Zika virus (ZIKV) infection is associated with neurological disorders of both the CNS and peripheral nervous systems (PNS), yet few studies have directly examined PNS infection. Here we show that intraperitoneally or intraventricularly injected ZIKV in the mouse can infect and impact peripheral neurons in vivo. Moreover, ZIKV productively infects stem-cell-derived human neural crest cells and peripheral neurons in vitro, leading to increased cell death, transcriptional dysregulation and cell-type-specific molecular pathology.

Brain-specific Crmp2 deletion leads to neuronal development deficits and behavioural impairments in mice

Several genome- and proteome-wide studies have associated transcription and translation changes of CRMP2 (collapsing response mediator protein 2) with psychiatric disorders, yet little is known about its function in the developing or adult mammalian brain in vivo. Here we show that brain-specific Crmp2 knockout (cKO) mice display molecular, cellular, structural and behavioural deficits, many of which are reminiscent of neural features and symptoms associated with schizophrenia. cKO mice exhibit enlarged ventricles and impaired social behaviour, locomotor activity, and learning and memory. Loss of Crmp2 in the hippocampus leads to reduced long-term potentiation, abnormal NMDA receptor composition, aberrant dendrite development and defective synapse formation in CA1 neurons. Furthermore, knockdown of crmp2 specifically in newborn neurons results in stage-dependent defects in their development during adult hippocampal neurogenesis. Our findings reveal a critical role for CRMP2 in neuronal plasticity, neural function and behavioural modulation in mice.

Equatorin is not essential for acrosome biogenesis but is required for the acrosome reaction.

The acrosome is a specialized organelle that covers the anterior part of the sperm nucleus and plays an essential role in mammalian fertilization. However, the regulatory mechanisms controlling acrosome biogenesis and acrosome exocytosis during fertilization are largely unknown. Equatorin (Eqtn) is a membrane protein that is specifically localized to the acrosomal membrane. In the present study, the physiological functions of Eqtn were investigated using a gene knockout mouse model. We found that Eqtn(-/-) males were subfertile. Only approximately 50% of plugged females were pregnant after mating with Eqtn(-/-) males, whereas more than 90% of plugged females were pregnant after mating with control males. Sperm and acrosomes from Eqtn(-/-) mice presented normal motility and morphology. However, the fertilization and induced acrosome exocytosis rates of Eqtn-deficient sperm were dramatically reduced. Further studies revealed that the Eqtn protein might interact with Syntaxin1a and SNAP25, but loss of Eqtn did not affect the protein levels of these genes. Therefore, our study demonstrates that Eqtn is not essential for acrosome biogenesis but is required for the acrosome reaction. Eqtn is involved in the fusion of the outer acrosomal membrane and the sperm plasma membrane during the acrosome reaction, most likely via an interaction with the SNARE complex.

Wt1 directs the lineage specification of sertoli and granulosa cells by repressing Sf1 expression.

Supporting cells (Sertoli and granulosa) and steroidogenic cells (Leydig and theca-interstitium) are two major somatic cell types in mammalian gonads, but the mechanisms that control their differentiation during gonad development remain elusive. In this study, we found that deletion of Wt1 in the ovary after sex determination caused ectopic development of steroidogenic cells at the embryonic stage. Furthermore, differentiation of both Sertoli and granulosa cells was blocked when Wt1 was deleted before sex determination and most genital ridge somatic cells differentiated into steroidogenic cells in both male and female gonads. Further studies revealed that WT1 repressed Sf1 expression by directly binding to the Sf1 promoter region, and the repressive function was completely abolished when WT1 binding sites were mutated. This study demonstrates that Wt1 is required for the lineage specification of both Sertoli and granulosa cells by repressing Sf1 expression. Without Wt1, the expression of Sf1 was upregulated and the somatic cells differentiated into steroidogenic cells instead of supporting cells. Our study uncovers a novel mechanism of somatic cell differentiation during gonad development. Highlighted article: Genital ridge somatic cells have the potential to differentiate into supporting cells or steroidogenic cells depending on Wt1 gene expression.

Intranasal infection and contact transmission of Zika virus in guinea pigs

Zika virus (ZIKV) is primarily transmitted to humans through mosquito bites or sexual contact. The excretion and persistence of contagious ZIKV in various body fluids have been well documented in ZIKV patients; however, the risk of direct contact exposure remains unclear. Here, we show that guinea pigs are susceptible to ZIKV infection via subcutaneous inoculation route; infected guinea pigs exhibit seroconversion and significant viral secretion in sera, saliva, and tears. Notably, ZIKV is efficiently transmitted from infected guinea pigs to naïve co-caged animals. In particular, intranasal inoculation of ZIKV is fully capable of establishing infection in guinea pigs, and viral antigens are detected in multiple tissues including brain and parotid glands. Cynomolgus macaques also efficiently acquire ZIKV infection via intranasal and intragastric inoculation routes. These collective results from animal models highlight the risk of exposure to ZIKV contaminants and raise the possibility of close contact transmission of ZIKV in humans.Human case studies suggest that Zika virus can be transmitted independently of mosquitoes and sexual contact. Here, the authors show intranasal Zika infection in different animal models and show that contact transmission of Zika virus occurs in guinea pigs.

Globozoospermia and lack of acrosome formation in GM130-deficient mice

Globozoospermia is a common reproductive disorder that causes male infertility in humans, and the malformation or loss of acrosomes is the prominent feature of this disease. Although the acrosome is thought to be derived from the Golgi apparatus, the detailed molecular mechanisms remain unclear. GM130 is a cis-side localized Golgi matrix protein,whereas the physiological functions of this protein remain elusive. Here we showed that inactivation of GM130-caused male infertility in mouse model. The primary defects were the absence of acrosomes, round sperm heads, and aberrant assembly of the mitochondrial sheath, which comprise the characteristic features of human globozoospermia. Further investigation indicated that loss of GM130 did not affect the secretion of pro-acrosomic vesicles, whereas the vesicles failed to fuse into a single large acrosome vesicle. Co-localization of the adaptor protein complex AP1 and trans-Golgi network (TGN) protein TGN46 was disrupted, suggesting that the malformation of acrosomes is most likely due to the defect in the sorting and coating of Golgi-derived pro-acrosomic vesicles. Thus, the GM130-deficient mouse provides a valuable model for investigating the etiology of human globozoospermia.

cTAGE5 deletion in pancreatic β cells impairs proinsulin trafficking and insulin biogenesis in mice

Proinsulin is synthesized in the endoplasmic reticulum (ER) in pancreatic &bgr; cells and transported to the Golgi apparatus for proper processing and secretion into plasma. Defects in insulin biogenesis may cause diabetes. However, the underlying mechanisms for proinsulin transport are still not fully understood. We show that &bgr; cell–specific deletion of cTAGE5, also known as Mea6, leads to increased ER stress, reduced insulin biogenesis in the pancreas, and severe glucose intolerance in mice. We reveal that cTAGE5/MEA6 interacts with vesicle membrane soluble N-ethyl-maleimide sensitive factor attachment protein receptor Sec22b. Sec22b and its interaction with cTAGE5/MEA6 are essential for proinsulin processing. cTAGE5/MEA6 may coordinate with Sec22b to control the release of COPII vesicles from the ER, and thereby the ER-to-Golgi trafficking of proinsulin. Importantly, transgenic expression of human cTAGE5/MEA6 in &bgr; cells can rescue not only the defect in islet structure, but also dysfunctional insulin biogenesis and glucose intolerance on cTAGE5/Mea6 conditional knockout background. Together our data provide more insight into the underlying mechanism of the proinsulin trafficking pathway.