Premature aging of skeletal stem/progenitor cells rather than osteoblasts causes bone loss with decreased mechanosensation

A distinct population of skeletal stem/progenitor cells(SSPCs)has been identified that is indispensable for the maintenance and remodeling of the adult skeleton.However,the cell types that are responsible for age-related bone loss and the characteristic changes in these cells during aging remain to be determined.Here,we established models of premature aging by conditional depletion of Zmpste24(Z24)in mice and found that Prx1-dependent Z24 deletion,but not Osx-dependent Z24 deletion,caused significant bone loss.However,Acan-associated Z24 depletion caused only trabecular bone loss.Single-cell RNA sequencing(sc RNA-seq)revealed that two populations of SSPCs,one that differentiates into trabecular bone cells and another that differentiates into cortical bone cells,were significantly decreased in Prx1-Cre;Z24^(f/f)mice.Both premature SSPC populations exhibited apoptotic signaling pathway activation and decreased mechanosensation.Physical exercise reversed the effects of Z24depletion on cellular apoptosis,extracellular matrix expression and bone mass.This study identified two populations of SSPCs that are responsible for premature aging-related bone loss.The impairment of mechanosensation in Z24-deficient SSPCs provides new insight into how physical exercise can be used to prevent bone aging.

TRIM72‑mediated degradation of the short form of p62/SQSTM1 rheostatically controls selective autophagy in human cells

Dear Editor,Autophagy is an evolutionarily conserved catabolic process that involves the sequestration and transport of organelles,macromolecules,or invading microorganisms to lysosomes for degradation[1].Sequestosome 1(p62/SQSTM1)was the first protein shown to bind target-associated ubiquitin(Ub)and LC3 conjugated to the phagophore membrane,thus,acting as an important autophagy receptor for ubiquitinated targets[2].

The interaction between KIF21A and KANK1 regulates dendritic morphology and synapse plasticity in neurons

Morphological alterations in dendritic spines have been linked to changes in functional communication between neurons that affect learning and memory.Kinesin-4 KIF21A helps organize the microtubule-actin network at the cell cortex by interacting with KANK1;however,whether KIF21A modulates dendritic structure and function in neurons remains unknown.In this study,we found that KIF21A was distributed in a subset of dendritic spines,and that these KIF21A-positive spines were larger and more structurally plastic than KIF21A-negative spines.Furthermore,the interaction between KIF21A and KANK1 was found to be critical for dendritic spine morphogenesis and synaptic plasticity.Knockdown of either KIF21A or KANK1 inhibited dendritic spine morphogenesis and dendritic branching,and these deficits were fully rescued by coexpressing full-length KIF21A or KANK1,but not by proteins with mutations disrupting direct binding between KIF21A and KANK1 or binding between KANK1 and talin1.Knocking down KIF21A in the hippocampus of rats inhibited the amplitudes of long-term potentiation induced by high-frequency stimulation and negatively impacted the animals’cognitive abilities.Taken together,our findings demonstrate the function of KIF21A in modulating spine morphology and provide insight into its role in synaptic function.

Cell signalling pathways underlying induced pluripotent stem cell reprogramming

Induced pluripotent stem(i PS) cells, somatic cells reprogrammed to the pluripotent state by forced expression of defined factors, represent a uniquely valuable resource for research and regenerative medicine. However, this methodology remains inefficient due to incomplete mechanistic understanding of the reprogramming process. In recent years, various groups have endeavoured to interrogate the cell signalling that governs the reprogramming process, including LIF/STAT3, BMP, PI3 K, FGF2, Wnt, TGFβ and MAPK pathways, with the aim of increasing our understanding and identifying new mechanisms of improving safety, reproducibility and efficiency. This has led to a unified model of reprogramming that consists of 3 stages: initiation, maturation and stabilisation. Initiation of reprogramming occurs in almost all cells that receive the reprogramming transgenes; most commonly Oct4, Sox2, Klf4 and c Myc, and involves a phenotypic mesenchymal-to-epithelial transition. The initiation stage is also characterised by increased proliferation and a metabolic switch from oxidative phosphorylation to glycolysis. The maturation stage is considered the major bottleneck within the process, resulting in very few "stabilisation competent" cells progressing to the final stabilisation phase. To reach this stage in both mouse and human cells, pre-i PS cells must activate endogenous expression of the core circuitry of pluripotency, comprising Oct4, Sox2, and Nanog, and thus reach a state of transgene independence. By the stabilisation stage, i PS cells generally use the same signalling networks that govern pluripotency in embryonic stem cells. These pathways differ between mouse and human cells although recent work has demonstrated that this is context dependent. As i PS cell generation technologies move forward, tools are being developed to interrogate the process in more detail, thus allowing a greater understanding of this intriguing biological phenomenon.

Reconstructing gene regulatory networks in single-cell transcriptomic data analysis

Gene regulatory networks play pivotal roles in our understanding of biological processes/mechanisms at the molecular level.Many studies have developed sample-specific or cell-type-specific gene regulatory networks from single-cell transcriptomic data based on a large amount of cell samples.Here,we review the state-of-the-art computational algorithms and describe various applications of gene regulatory networks in biological studies.

α-Pyrone Derivatives from a Streptomyces Strain Resensitize Tamoxifen Resistance in Breast Cancer Cells

Tamoxifen resistance(TamR)is the underlying cause of treatment failure in many breast cancer patients receiving tamoxifen.In order to look for noncytotoxic natural products with the ability to reverse TamR,an extract from strain Streptomyces sp.KIB-H0495 was detected to be active.Subsequent large scale fermentation and isolation led to the isolation of four a-pyrone derivatives including two new compounds,violapyrones J(2)and K(3),and two known analogues,violapyrones B(1)and I(4).Further bioactivity assays indicated that only 1 and 3 exerted potent resensitization effects on MCF-7/TamR cells at a concentration of 1 lM.Owing to the simple structures of 1 and 3,these two compounds might have potential for further investigation as novel tamoxifen resensitization agent in breast cancer chemotherapy.

Distinct Processing of lncRNAs Contributes to Non-conserved Functions in Stem Cells

Long noncoding RNAs(lncRNAs),which are longer than 200 nucleotides in length and lack protein coding potential,are pervasively transcribed in eukaryotic genomes.It is well established that lncRNAs play important roles in gene expression in diverse cellular and biological progress.

Generation of genetically modified mice using CRISPR/Cas9 and haploid embryonic stem cell systems

With the development of high-throughput sequencing technology in the post-genomic era, researchers have concentrated their efforts on elucidating the relationships between genes and their corresponding functions. Recently, important progress has been achieved in the generation of genetically modified mice based on CRISPR/Cas9 and haploid embryonic stem cell （haESC） approaches, which provide new platforms for gene function analysis, human disease modeling, and gene therapy. Here, we review the CRISPR/Cas9 and haESC technology for the generation of genetically modified mice and discuss the key challenges in the application of these approaches.

Advances in viral encephalitis:Viral transmission,host immunity,and experimental animal models

Viral infections have led to many public health crises and pandemics in the last few centuries.Neurotropic virus infection-induced viral encephalitis(VE),especially the symptomatic inflammation of the meninges and brain parenchyma,has attracted growing attention due to its high mortality and disability rates.Understanding the infectious routes of neurotropic viruses and the mechanism underlying the host immune response is critical to reduce viral spread and improve antiviral therapy outcomes.In this review,we summarize the common categories of neurotropic viruses,viral transmission routes in the body,host immune responses,and experimental animal models used for VE study to gain a deeper understanding of recent progress in the pathogenic and immunological mechanisms under neurotropic viral infection.This review should provide valuable resources and perspectives on how to cope with pandemic infections.

Primary cilia support cartilage regeneration after injury

In growing children,growth plate cartilage has limited self-repair ability upon fracture injury always leading to limb growth arrest.Interestingly,one type of fracture injuries within the growth plate achieve amazing self-healing,however,the mechanism is unclear.Using this type of fracture mouse model,we discovered the activation of Hedgehog(Hh)signaling in the injured growth plate,which could activate chondrocytes in growth plate and promote cartilage repair.

The ubiquitin codes in cellular stress responses

Ubiquitination/ubiquitylation,one of the most fundamental post-translational modifications,regulates almost every critical cellular process in eukaryotes.Emerging evidence has shown that essential components of numerous biological processes undergo ubiquitination in mammalian cells upon exposure to diverse stresses,from exogenous factors to cellular reactions,causing a dazzling variety of functional consequences.Various forms of ubiquitin sig-nals generated by ubiquitylation events in specific milieus,known as ubiquitin codes,constitute an intrinsic part of myriad cellular stress responses.These ubiquitination events,leading to proteolytic turnover of the substrates or just switch in functionality,initiate,regulate,or supervise multiple cellular stress-associated responses,supporting adaptation,homeostasis recovery,and survival of the stressed cells.In this review,we attempted to summarize the crucial roles of ubiquitination in response to different environmental and intracellular stresses,while discussing how stresses modulate the ubiquitin system.This review also updates the most recent advances in understanding ubiquitination machinery as well as different stress responses and discusses some important questions that may warrant future investigation.

Gene-knockout by iSTOP enables rapid reproductive disease modeling and phenotyping in germ cells of the founder generation

Cytosine base editing achieves C·G-to-T·A substitutions and can convert four codons(CAA/CAG/CGA/TGG)into STOP-codons(induction of STOP-codons,iSTOP)to knock out genes with reduced mosaicism.iSTOP enables direct phenotyping in founders’somatic cells,but it remains unknown whether this works in founders’germ cells so as to rapidly reveal novel genes for fertility.Here,we initially establish that iSTOP in mouse zygotes enables functional characterization of known genes in founders’germ cells:Cfap43-iSTOP male founders manifest expected sperm features resembling human“multiple morphological abnormalities of the flagella”syndrome(i.e.,MMAF-like features),while oocytes of Zp3-iSTOP female founders have no zona pellucida.We further illustrate iSTOP’s utility for dissecting the functions of unknown genes with Ccdc183,observing MMAF-like features and male infertility in Ccdc183-iSTOP founders,phenotypes concordant with those of Ccdc183-KO offspring.We ultimately establish that CCDC183 is essential for sperm morphogenesis through regulating the assembly of outer dynein arms and participating in the intra-flagellar transport.Our study demonstrates iSTOP as an efficient tool for direct reproductive disease modeling and phenotyping in germ cells of the founder generation,and rapidly reveals the essentiality of Ccdc183 in fertility,thus providing a time-saving approach for validating genetic defects(like nonsense mutations)for human infertility.

Establishment and transcriptome analysis of single blastomerederived cell lines from zebrafish

Maintaining chromosome euploidy in zebrafish embryonic cells is challenging because of the degradation of genomic integrity during cell passaging.In this study,we report the derivation of zebrafish cell lines from single blastomeres.These cell lines have a stable chromosome status attributed to BMP4 and exhibit continuous proliferation in vitro.Twenty zebrafish cell lines are successfully established from single blastomeres.Single-cell transcriptome sequencing analysis confirms the fidelity of gene expression profiles throughout long-term culturing of at least 45 passages.The long-term cultured cells are specialized into epithelial cells,exhibiting similar expression patterns validated by integrative transcriptomic analysis.Overall,this work provides a protocol for establishing zebrafish cell lines from single blastomeres,which can serve as valuable tools for in vitro investigations of epithelial cell dynamics in terms of lifeedeath balance and cell fate determination during normal homeostasis.

肝胆肿瘤中肿瘤特异性CircRNA衍生抗原肽的鉴定

基于肿瘤抗原的免疫治疗的应用受到验证免疫原性肽稀缺性的阻碍。本研究旨在研究环状RNA(circRNA)在肝胆肿瘤类器官中作为肿瘤抗原肽新来源的潜力。使用RNA测序(RNA-seq)和基于算法的评分工具,预测3950个翻译的肿瘤特异性环状RNA在27个类器官中产生18971个抗原肽。从抗原格局来看,11个氨基酸长度(mer)肽和人白细胞抗原(HLA)-A结合肽具有最高的免疫原性相关评分。在分析的3/5类器官中,有13个预测抗原肽通过质谱(MS)免疫肽组学被直接确认为HLA-A、HLA-B和HLA-C(HLA-ABC)结合肽。在流式细胞术和酶联免疫吸附试验(ELISA)中,由HLA-ABC分子呈递的circRNA衍生的肿瘤特异性肽刺激CD8(CD8)T细胞,显示CD107a干扰素γ(IFNγ)共表达和IFNγ分泌增加。免疫原性环状RNA衍生肽诱导的靶向类器官的细胞毒性T细胞活性在杀伤实验中得到验证。值得注意的是,来自circTBC1D15的抗原肽YGFNEILKK不仅被认为是类器官的HLA-ABC呈递肽,而且还显著降低了肿瘤类器官的存活率。本研究的发现强调了产生肿瘤抗原的一个关键亚群,这对靶向肿瘤特异性circRNA具有重要意义。

Defining two subpopulations of marginal zone B cells

Marginal zone(MZ)B cells,which are composed of heterogeneous subpopulations,are participate in the rapid response to antigens.Lee et al.showed that MZ B cells can be divided into two distinct subpopulations based on CD80 expression.These two subpopulations of MZ B cells exhibit differential autoreactivity,radiosensitivity,and functional capacities.

Pyruvate kinase M in germ cells is essential for sperm motility and male fertility but not spermatogenesis

Male germ cells employ specific metabolic pathways throughout their developmental stages.In a previous study,we discovered heightened expression of pyruvate kinase M(PKM),a pivotal glycolytic enzyme,in spermatogonia and spermatids.To gain deeper insights into PKM's roles in spermatogenesis,sperm function,and male fertility,we engineered a conditional-knockout mouse model(Pkm-vkO mice)to selectively disrupt the Pkm gene within germ cells.Despite maintaining regular testicular histology and sperm morphology,the male Pkm-vko mice were infertility,characterized by significant impairments in sperm motility and adenosine triphosphate(ATP)generation.In addition,Pkm-null spermatozoa exhibited similar deficits in protein tyrosine phosphorylation linked to capacitation,as well as compromised performance in in vitro fertilization experiments.To conclude,PKM's presence is not obligatory for the entirety of spermatogenesis in male germ cells;however,it emerges as a critical factor influencing sperm motility and overall male fertility.

T cell receptor signaling and cell immunotherapy

As the major sensor of adaptive immune system,T cell receptor(TCR)can recognize diverse antigens and initiate specific immune responses against invading pathogens and cancer cells.Understanding the mechanisms of TCR signaling has led to the development of engineered T cell therapies,which have extensive applications in the treatment of diseases such as cancer,infection and autoimmunity.Here,we review the current understanding of antigen-induced TCR signaling and discuss its applications in T cell therapies.

Smooth muscle cell-specific genetic targeting by Myh11-driven Cre(ER)knockin mice

Dear editor,Site specific recombinases have been widely used for genome engineering in cardiovascular research(Fu et al.,2024;Huang et al.,2023;Xue et al.,2022).In particular,Cre is the most broadly used recombinase for cell type-specific lineage tracing and gene manipulation in mammals.For smooth muscle cell(SMC)-specific targeting,several SMC promoters including Myh11(smooth muscle myosin heavy chain),Acta2(smooth muscle a-2 actin),and SM22a(Tagln)have been used to drive Cre or CreER.

Paracrine and endocrine actions of bone——the functions of secretory proteins from osteoblasts, osteocytes, and osteoclasts

The skeleton is a dynamic organ that is constantly remodeled. Proteins secreted from bone cells, namely osteoblasts, osteocytes,and osteoclasts exert regulation on osteoblastogenesis, osteclastogenesis, and angiogenesis in a paracrine manner. Osteoblasts secrete a range of different molecules including RANKL/OPG, M-CSF, SEMA3A, WNT5A, and WNT16 that regulate osteoclastogenesis. Osteoblasts also produce VEGFA that stimulates osteoblastogenesis and angiogenesis. Osteocytes produce sclerostin（SOST） that inhibits osteoblast differentiation and promotes osteoclast differentiation. Osteoclasts secrete factors including BMP6, CTHRC1, EFNB2, S1P, WNT10B, SEMA4D, and CT-1 that act on osteoblasts and osteocytes, and thereby influencea A osteogenesis. Osteoclast precursors produce the angiogenic factor PDGF-BB to promote the formation of Type H vessels, which then stimulate osteoblastogenesis. Besides, the evidences over the past decades show that at least three hormones or ＂osteokines＂from bone cells have endocrine functions. FGF23 is produced by osteoblasts and osteocytes and can regulate phosphate metabolism. Osteocalcin（OCN） secreted by osteoblasts regulates systemic glucose and energy metabolism, reproduction, and cognition. Lipocalin-2（LCN2） is secreted by osteoblasts and can influence energy metabolism by suppressing appetite in the brain.We review the recent progresses in the paracrine and endocrine functions of the secretory proteins of osteoblasts, osteocytes, and osteoclasts, revealing connections of the skeleton with other tissues and providing added insights into the pathogenesis of degenerative diseases affecting multiple organs and the drug discovery process.

Mechanical regulation of bone remodeling

Bone remodeling is a lifelong process that gives rise to a mature, dynamic bone structure via a balance between bone formation by osteoblasts and resorption by osteoclasts. These opposite processes allow the accommodation of bones to dynamic mechanical forces, altering bone mass in response to changing conditions. Mechanical forces are indispensable for bone homeostasis;skeletal formation, resorption, and adaptation are dependent on mechanical signals, and loss of mechanical stimulation can therefore significantly weaken the bone structure, causing disuse osteoporosis and increasing the risk of fracture. The exact mechanisms by which the body senses and transduces mechanical forces to regulate bone remodeling have long been an active area of study among researchers and clinicians. Such research will lead to a deeper understanding of bone disorders and identify new strategies for skeletal rejuvenation. Here, we will discuss the mechanical properties, mechanosensitive cell populations, and mechanotransducive signaling pathways of the skeletal system.