Meiotic transcriptional reprogramming mediated by cell-cell communications in humans and mice revealed by scATACseq and scRNA-seq

Meiosis is a highly complex process significantly influenced by transcriptional regulation.However,studies on the mechanisms that govern transcriptomic changes during meiosis,especially in prophase I,are limited.Here,we performed single-cell ATAC-seq of human testis tissues and observed reprogramming during the transition from zygotene to pachytene spermatocytes.This event,conserved in mice,involved the deactivation of genes associated with meiosis after reprogramming and the activation of those related to spermatogenesis before their functional onset.Furthermore,we identified 282 transcriptional regulators(TRs)that underwent activation or deactivation subsequent to this process.Evidence suggested that physical contact signals from Sertoli cells may regulate these TRs in spermatocytes,while secreted ENHO signals may alter metabolic patterns in these cells.Our results further indicated that defective transcriptional reprogramming may be associated with non-obstructive azoospermia(NOA).This study revealed the importance of both physical contact and secreted signals between Sertoli cells and germ cells in meiotic progression.

Model animals and their applications

Looking back a decade ago when I decided to use ＂model animal＂ to name our newly established institute, my outrageous boldness can only be described by the old Chinese slang, ＂newborn calf could never sense the danger of tiger＂. Happily, my courageous belief, along with the hard work of my colleagues at Model Animal Research Center of Nanjing University, paid off eventually. We have witnessed the great progress in this research field in China in the past 10 years. This issue of Science China Life Sciences samplings some of these accomplishments.

Silencing the enhancer of zeste homologue 2,Ezh2,represses axon regeneration of dorsal root ganglion neurons

Recovery from injury to the peripheral nervous system is different from that of the central nervous system in that it can lead to gene reprogramming that can induce the expression of a series of regeneration-associated genes.This eventually leads to axonal regeneration of injured neurons.Although some regeneration-related genes have been identified,the regulatory network underlying axon regeneration remains largely unknown.To explore the regulator of axon regeneration,we performed RNA sequencing of lumbar L4 and L5 dorsal root ganglion(DRG)neurons at different time points(0,3,6,12 hours,1,3 and 7 days)after rat sciatic nerve crush.The isolation of neurons was carried out by laser capture microscopy combined with NeuN immunofluorescence staining.We found 1228 differentially expressed genes in the injured sciatic nerve tissue.The hub genes within these differentially expressed genes include Atf3,Jun,Myc,Ngf,Fgf2,Ezh2,Gfap and Il6.We verified that the expression of the enhancer of zeste homologue 2 gene(Ezh2)was up-regulated in DRG neurons after injury,and this up-regulation differed between large-and small-sized dorsal root ganglion neurons.To investigate whether the up-regulation of Ezh2 impacts axonal regeneration,we silenced Ezh2 with siRNA in cultured DRG neurons and found that the growth of the newborn axons was repressed.In our investigation into the regulatory network of Ezh2 by interpretive phenomenal analysis,we found some regulators of Ezh2(including Erk,Il6 and Hif1a)and targets(including Atf3,Cdkn1a and Smad1).Our findings suggest that Ezh2,as a nerve regeneration-related gene,participates in the repair of the injured DRG neurons,and knocking down the Ezh2 in vitro inhibits the axonal growth of DRG neurons.All the experimental procedures approved by the Administration Committee of Experimental Animals of Jiangsu Province of China(approval No.S20191201-201)on March 21,2019.

c-Fos enhances the survival of thymocytes during positive selection by upregulating Bcl-2

T cells are derived from progenitor thymocytes, of which only a minority receive the appropriate TCR signal, undergo positive selection and mature. Owing to the very short lifespan of thymocytes, the prerequisite for posi- tive selection is survival. TCR signal-induced Bcl-2 expression is believed to play a dominant role in the survival of positively selecting thymocytes, but how Bcl-2 is directly regulated is unknown. Here we report that the immediate early gene （IEG） c-Fos can stimulate the expression of Bcl-2, depending on a specific AP-l-binding site in the Bcl-2 promoter. In c-Fos transgenic （Fos-Tg） mice, c-Fos binds to this site and promotes the expression of Bcl-2. As a result, Fos-Tg thymocytes exhibited enhanced survival, and more mature single-positive （SP） thymocytes were generated, even on a unique TCR background. The TCR repertoire remained normal in Fos-Tg mice. Our results identified c-Fos as the mediator of the stimulatory effect of TCR signaling on Bcl-2 expression. Therefore, c-Fos, as an IEG, because of its early response ability, can quickly rescue the survival of short-lived thymocytes during positive selection. Our results provide novel insight into the mechanism regulating the survival of positively selecting thymocytes.

Microfilament-binding properties of N-terminal extension of the isoform of smooth muscle long myosin light chain kinase

Myosin light chain kinases （MLCK） phosphorylate the regulatory light chain of myosin II in thick filaments and bind to F-actin-containing thin filaments with high affinity. The ability of short myosin light chain kinase （S-MLCK） to bind F-actin is structurally attributed to the DFRXXL regions in its N-terminus. The long myosin light chain kinase （L-MLCK） has two additional DFRXXL motifs and six Ig-like modules in its N-terminal extension. The six Ig-like modules are capable of binding to stress fibers independently. Our results from the imaging analysis demonstrated that the first two intact Ig-like modules （2Ig） in N-terminal extension of L-MLCK is the minimal binding module required for microfilament binding. Binding assay confirmed that F-actin was able to bind 2Ig. Stoichiometries of 2Ig peptide were similar for myofilament or pure F-actin. The binding affinities were slightly lower than 5DFRXXL peptide as reported previously. Similar to DFRXXL peptides, the 2Ig peptide also caused efficient F-actin bundle formation in vitro. In the living cell, over-expression of 2Ig fragment increased ＂spike＂-like protrusion formation with over-bundled F-actin. Our results suggest that L-MLCK may act as a potent F-actin bundling protein via its DFRXXL region and the 2Ig region, implying that L-MLCK plays a role in cytoskeleton organization.

Transcriptional regulatory network during axonal regeneration of dorsal root ganglion neurons:laser-capture microdissection and deep sequencing

The key regulators and regeneration-associated genes involved in axonal regeneration of neurons after injury have not been clarified.In high-throughput sequencing,various factors influence the final sequencing results,including the number and size of cells,the depth of sequencing,and the method of cell separation.There is still a lack of research on the detailed molecular expression profile during the regeneration of dorsal root ganglion neuron axon.In this study,we performed lase r-capture microdissection coupled with RNA sequencing on dorsal root ganglion neurons at 0,3,6,and 12 hours and 1,3,and 7 days after sciatic nerve crush in rats.We identified three stages after dorsal root ganglion injury:early(3-12 hours),pre-regeneration(1 day),and regeneration(3-7 days).Gene expression patterns and related function enrichment res ults showed that one module of genes was highly related to axonal regeneration.We verified the up-regulation of activating transcription factor 3(Atf3),Kruppel like factor 6(Klf6),AT-rich inte raction domain 5A(Arid5α),CAMP responsive element modulator(Crem),and FOS like 1,AP-1 transcription factor Subunit(Fosl1) in dorsal root ganglion neurons after injury.Suppressing these transcription factors(Crem,Arid5o,Fosl1 and Klf6) reduced axonal regrowth in vitro.As the hub transcription factor,Atf3 showed higher expression and activity at the preregeneration and regeneration stages.G protein-coupled estrogen receptor 1(Gper1),inte rleukin 12a(Il12α),estrogen receptor 1(ESR1),and interleukin 6(IL6) may be upstream factors that trigger the activation of Atf3 during the repair of axon injury in the early stage.Our study presents the detailed molecular expression profile during axonal regeneration of dorsal root ganglion neurons after peripheral nerve injury.These findings may provide reference for the clinical screening of molecular targets for the treatment of peripheral nerve injury.

Potential application of let-7a antagomir in injured peripheral nerve regeneration

Neurotrophic factors,particularly nerve growth factor,enhance neuronal regeneration.However,the in vivo applications of nerve growth factor are largely limited by its intrinsic disadvantages,such as its short biological half-life,its contribution to pain response,and its inability to cross the blood-brain barrier.Considering that let-7(human miRNA)targets and regulates nerve growth factor,and that let-7 is a core regulator in peripheral nerve regeneration,we evaluated the possibilities of let-7 application in nerve repair.In this study,anti-let-7a was identified as the most suitable let-7 family molecule by analyses of endogenous expression and regulatory relationship,and functional screening.Let-7a antagomir demonstrated biosafety based on the results of in vivo safety assessments and it entered into the main cell types of the sciatic nerve,including Schwann cells,fibroblasts and macrophages.Use of hydrogel effectively achieved controlled,localized,and sustained delivery of let-7a antagomir.Finally,let-7a antagomir was integrated into chitosan conduit to construct a chitosan-hydrogel scaffold tissue-engineered nerve graft,which promoted nerve regeneration and functional recovery in a rat model of sciatic nerve transection.Our study provides an experimental basis for potential in vivo application of let-7a.

S6B-2 Matrine Inhibits Itching by Lowering the Activity of Calcium Channel

Sophorae Flavescentis Radix(SFR)is a medicinal herb with many functions that are involved in anti-inflammation,antinociception,and anticancer.SFR is also used to treat a variety of itching diseases.Matrine(MT)is one of the main constituents in SFR and also has the effect of relieving itching,but the antipruritic mechanism is still unclear.Here,we investigated the effect of MT on antipruritus.In acute and chronic itch models,MT significantly inhibited the scratching behavior not only in acute itching induced by histamine(His),chloroquine(CQ)and compound 48/80 with a dose-depended manner,but also in the chronic pruritus models of Atopic dermatitis(AD)and Acetone-ether-water(AEW)in mice.Furthermore,MT can be detected in the blood after intraperitoneal injection(i.p.)and subcutaneous injection(s.c.).Finally,electrophysiological and calcium image results show that MT inhibits the excitatory synaptic transmission from dorsal root ganglion(DRG)to the dorsal horn of the spinal cord by suppressing presynaptic N-type calcium channels.Taken together,we believe that MT is a novel drug candidate in treating pruritus diseases,especially for histamine-independent and chronic pruritus,which might be attributed to inhibition of presynaptic N-type calcium channels.

Generation of conditional knockout alleles for PRL-3

Phosphatase of regenerating liver-3 （PRL-3） is a member of the protein tyrosine phosphatase （PTP） superfamily and is highly expressed in cancer metastases. For better understanding of the role of PRL-3 in tumor metastasis, we applied a rapid and efficient method for generating PRL-3 floxed mice and investigated its phenotypes. A BAC retrieval strategy was applied to construct the PRL-3 conditional gene-targeting vector. Exon 4 was selected for deletion to generate a nonfunctional prematurely terminated short peptide as it will cause a frame-shift mutation. Conditional knockout PRL-3 mice were generated by using the Cre-loxP system and were validated by Southern blot and RT-PCR analysis. Further analysis revealed the phenotype characteristics of PRL-3 knockout mice and wildtype mice. In this study, we successfully constructed the PRL-3 conditional knockout mice, which will be helpful to clarify the roles of PRL-3 and the mechanisms in tumor metastasis.

Digital Barcode Development for Single Nuclotide Polymorphism (SNP) Identification of Suzhong Swine Individuals

Suzhong swine is a hybrid breed derived from Taihu sows and Landraee boars. To identify Suzhong swine individuals and trace the source of pork products, single nucleotide polymorphisms （SNPs） identification of Suzhong swine individuals was studied. A total of 29 pairs of primers were designed and sev- en pairs of primers were used for identification of Suzhong swine individuals. The products amplified by seven pairs of primers could be directly sequenced, with clean sequencing map background and no ambiguity in sequence read. Totally 52 SNPs loci were amplified by seven pairs of primers, and 41 SNPs loci were reserved for identification of Suzhong swine individuals through correlation analysis and heterezygosity filtration （ H ≥0.1 ）. Meantime, the digital barcodes for SNP identification of 96 individuals of Suzhong swine derived from seven boars and 12 sows were developed, which well distinguished 96 individuals of Suzhong swine. Theoretically, 41SNPs amplified by seven pairs of primers could be used for identification of 5.0 × 10^6 pig individuals. Therefore, digital barcode devel- opment method for SNP identification of Suzbong swine individuals can be used for individual identification of Suzhong swine in scale pig farm and meat product traceability.

Deficiency of transmembrane AMPA receptor regulatory protein γ-8 leads to attention-deficit hyperactivity disorder-like behavior in mice

Attention-deficit hyperactivity disorder(ADHD) is a neurodevelopmental disorder prevalent in schoolage children. At present, however, its etiologies and risk factors are unknown. Transmembrane α-amino-3-hydroxy-5-methyl-4-isoxazolepropionicacid(AMPA) receptor regulatory protein γ-8(TARP γ-8,also known as calcium voltage-gated channel auxiliary subunit gamma 8(CACNG8)) is an auxiliary AMPA receptor(AMPAR) subunit. Here, we report an association between TARP γ-8 and ADHD,whereby adolescent TARP γ-8 knockout(KO) mice exhibitedADHD-likebehaviors,including hyperactivity, impulsivity, anxiety, impaired cognition,and memory deficits. Human single-nucleotide polymorphism(SNP) analysis also revealed strong associations between intronic alleles in CACNG8genes and ADHD susceptibility. In addition,synaptosomal proteomic analysis revealed dysfunction of the AMPA glutamate receptor complex in the hippocampi of TARP γ-8 KO mice.Proteomic analysis also revealed dysregulation of dopaminergic and glutamatergic transmissions in the prefrontal cortices of TARP γ-8 KO mice.Methylphenidate(MPH), which is commonly used to treat ADHD, significantly rescued the major behavioral deficits and abnormal synaptosomal proteins in TARP γ-8 KO mice. Notably, MPH significantly reversed the up-regulation of Grik2 and Slc6a3 in the prefrontal cortex. MPH also significantly improved synaptic AMPAR complex function by up-regulating other AMPAR auxiliary proteins in hippocampal synaptosomes. Taken together, our results suggest that TARP γ-8 is involved in the development of ADHD in humans.This study provides a useful alternative animal model with ADHD-like phenotypes related to TARP γ-8deficiency, which has great potential for the development of new therapies.

Molecular mechanisms of dietary restriction in aging—insights from Caenorhabditis elegans research

Dietary restriction(DR) is one of the most robust environmental manipulations that not only extend life span but also delay the onset of age-related diseases in almost every species examined. Caenorhabditis elegans plays an important role in aging studies due to its simple life cycle, easy genetic manipulations and highly conserved genome. Recent studies have demonstrated that the beneficial effects of DR are mediated by the highly conserved transcription factors and signaling pathways in C. elegans. Here we review recent progress in the methodology and molecular mechanisms of DR using C. elegans as a model, as well as prospects for future research.

Rauwolfia vomitoria extract suppresses benign prostatic hyperplasia by reducing expression of androgen receptor and 5a-reductase in a rat model

Objective:Herbal medicine is an important therapeutic option for benign prostatic hyperplasia(BPH),a common disease in older men that can seriously affect their quality of life.Currently,it is crucial to develop agents with strong efficacy and few side effects.Herein we investigated the effects of the extract of Rauwolfia vomitoria,a shrub grown in West Africa,on BPH.Methods:Rats with testosterone-induced BPH were treated with R.vomitoria.Prostates were histologically analyzed by Hematoxylin and eosin staining.Proliferation index and the expression levels of androgen receptor and its associated proteins were quantified through immunohistochemistry and immunoblotting.Androgen receptor target genes were examined by quantitative real-time polymerase chain reaction.The sperm count and body weight of rats were also measured.Results:The oral administration of R.vomitoria extract significantly reduced the prostate weight and prostate weight index in BPH rats,supported by the decreased thickness of the prostate epithelial layer and increased lumen size.Similar effects were observed in the BPH rats treated with the reference drug,finasteride.R.vomitoria extract significantly reduced the testosterone-induced proliferation markers,including proliferating cell nuclear antigen and cyclin D1,in the prostate glands of BPH rats;it also reduced levels of androgen receptor,its associated protein steroid 5 a-reductase 1 and its downstream target genes(FK506-binding protein 5 and matrix metalloproteinase 2).Notably,compared with the finasteride group,R.vomitoria extract did not significantly reduce sperm count.Conclusion:R.vomitoria suppresses testosterone-induced BPH development.Due to its milder side effects,R.vomitoria could be a promising therapeutic agent for BPH.

Glucose metabolic abnormality is associated with defective mineral homeostasis in skeletal disorder mouse model

Bone was reported as a crucial organ for regulating glucose homeostasis. In this study, we found that Phex mutant mice(PUG), a model of human X-linked hypophosphatemic rickets(XLH), displayed metabolic abnormality in addition to abnormal phosphate homeostasis, skeletal deformity and growth retardation. Glucose tolerance was elevated with enhanced insulin sensitivity in PUG, though circulating insulin level decreased. Interestingly, bone mineral density defects and glucose metabolic abnormality were both rescued by adding phosphorus- and calcium-enriched supplements in daily diet. Serum insulin level, glucose tolerance and insulin sensitivity showed no differences between PUG and wild-type mice with rescued osteocalcin(OCN) following treatment. Our study suggested that OCN is a potential mediator between mineral homeostasis and glucose metabolism. This investigation brings a new perspective on glucose metabolism regulation through skeleton triggered mineral homeostasis and provides new clues in clinical therapeutics of potential metabolic disorders in XLH patients.

A bacterial artificial chromosome transgenic mouse model for visualization of neurite growth

Class Ⅲ β-tubulin （Tubb3） is a component of the microtubules in neurons and contributes to microtubule dynamics that are required for axon outgrowth and guidance during neuronal development. We here report a novel bacterial artificial chromosome （BAC） transgenic mouse line that expresses Class Ⅲ β-tubulin fused to mCherry, an improved monomeric red fluorescent protein, for the visualization of microtubules during neuronal development. A BAC containing Tubb3 gene was modified by insertion of mCherry complementary DNA downstream of Tubb3 coding sequence via homologous recombination, mCherry fusion protein was expressed in the nervous system and testis of the transgenic animal, and the fluorescent signal was observed in the neurons that located in the olfactory bulb, cerebral cortex, hippocampal formation, cerebellum, as well as the retina. Besides, Tubb3-mCherry fusion protein mainly distributed in neurites and colocalized with endogenous Class Ⅲ β-tubulin The fusion protein labels Purkinje cell dendrites during cerebellar circuit formation. Therefore, this transgenic line might be a novel tool for scientific community to study neuronal development both in vitro and in vivo.

TBC1D1 is an energy-responsive polarization regulator of macrophages via governing ROS production in obesity

Energy status is linked to the production of reactive oxygen species(ROS)in macrophages,which is elevated in obesity.However,it is unclear how ROS production is upregulated in macrophages in response to energy overload for mediating the development of obesity.Here,we show that the Rab-GTPase activating protein(Rab GAP)TBC1D1,a substrate of the energy sensor AMP-activated protein kinase(AMPK),is a critical regulator of macrophage ROS production and consequent adipose inflammation for obesity development.TBC1D1 deletion decreases,whereas an energy overload-mimetic non-phosphorylatable TBC1D1^(S231A)Amutation increases,ROS production and M1-like polarization in macrophages.Mechanistically,TBC1D1 and its downstream target Rab8a form an energy-responsive complex with NOX2 for ROS generation.Transplantation of TBC1D1^(S231A)bone marrow aggravates diet-induced obesity whereas treatment with an ultra-stable Tt SOD for removal of ROS selectively in macrophages alleviates both TBC1D1~(S231A)mutation-and diet-induced obesity.Our findings therefore have implications for drug discovery to combat obesity.

Knockdown of neuronal DAF-15/Raptor promotes healthy aging in C.elegans

The highly conserved target of rapamycin(TOR)pathway plays an important role in aging across species.Previous studies have established that inhibition of the TOR complex 1(TORC1)significantly extends lifespan in Caenorhabditis elegans.However,it has not been clear whether TORC1 perturbation affects aging in a spatiotemporal manner.Here,we apply the auxin-inducible degradation tool to knock down endogenous DAF-15,the C.elegans ortholog of regulatory associated protein of TOR(Raptor),to characterize its roles in aging.Global or tissue-specific inhibition of DAF-15 during development results in various growth defects,whereas neuron-specific knockdown of DAF-15 during adulthood significantly extends lifespan and healthspan.The neuronal DAF-15 deficiency-induced longevity requires the intestinal activities of DAF-16/FOXO and PHA-4/FOXA transcription factors,as well as the AAK-2/AMP-activated protein kinaseαcatalytic subunit.Transcriptome profiling reveals that the neuronal DAF-15 knockdown promotes the expression of genes involved in protection.These findings define the tissue-specific roles of TORC1 in healthy aging and highlight the importance of neuronal modulation of aging.

Depletion of Gsdma1/2/3 alleviates PMA-induced epidermal hyperplasia by inhibiting the EGFR–Stat3/Akt pathway

Homeostasis of the skin barrier is essential for maintaining normal skin function.Gasdermin A(GSDMA)is highly expressed in the skin and associated with many skin diseases,such as melanoma and psoriasis.In mice,GSDMA is encoded by three gene homologues,namely Gsdma1,Gsdma2,and Gsdma3.Although Gsdma3 gain-of-function mutations cause hair loss and skin inflammation,Gsdma3-deficient mice do not show any visible phenotypes in skin and hair structures.To explore the physiological function of GSDMA,we generated conventional Gsdma1/2/3 knockout(KO)mice.These mice showed significantly alleviated epidermal hyperplasia and inflammation induced by phorbol 12-myristate 13-acetate(PMA).Furthermore,the alleviation of epidermal hyperplasia depended on the expression of Gsdma1/2/3 specifically in keratinocytes.Mechanistically,Gsdma1/2/3 depletion downregulated epidermal growth factor receptor(EGFR)ligands,leading to the decreased EGFR–Stat3/Akt signalling.These results demonstrate that depletion of Gsdma1/2/3 alleviates PMA-induced epidermal hyperplasia partially by inhibiting the EGFR–Stat3/Akt pathway.

A human-specific cytotoxic neopeptide generated by the deafness gene Cingulin

Accumulation of mutant proteins in cells can induce proteinopathies and cause functional damage to organs.Recently,the Cingulin(CGN)protein has been shown to maintain the morphology of cuticular plates of inner ear hair cells and a frameshift mutation in CGN causes autosomal dominant non-syndromic hearing loss.Here,we find that the mutant CGN proteins form insoluble aggregates which accumulate intracellularly and lead to cell death.Expression of the mutant CGN in the inner ear results in severe hair cell death and hearing loss in mice,resembling the auditory phenotype in human patients.Interestingly,a human-specific residue(V1112)in the neopeptide generated by the frameshift mutation is critical for the aggregation and cytotoxicity of the mutant human CGN.Moreover,the expression of heat shock factor 1(HSF1)decreases the accumulation of insoluble mutant CGN aggregates and rescues cell death.In summary,these findings identify mutant-specific toxic polypeptides as a disease-causing mechanism of the deafness mutation in CGN,which can be targeted by the expression of the cell chaperone response regulator HSF1.