Endorepellin和neurexin互作促进神经上皮细胞自噬并维持正常神经管发育

Heparan sulfate proteoglycan 2(HSPG2)gene encodes the matrix protein Perlecan,and genetic inactivation of this gene creates mice that are embryonic lethal with severe neural tube defects(NTDs).We discovered rare genetic variants of HSPG2 in 10%cases compared to only 4%in controls among a cohort of 369 NTDs.Endorepellin,a peptide cleaved from the domain V of Perlecan,is known to promote angiogenesis and autophagy in endothelial cells.The roles of enderepellin in neurodevelopment remain unclear so far.Our study revealed that endorepellin can migrate to the neuroepithelial cells and then be recognized and bind with the neuroepithelia receptor neurexin in vivo.Through the endocytic pathway,the interaction of endorepellin and neurexin physiologically triggers autophagy and appropriately modulates the differentiation of neural stem cells into neurons as a blocker,which is necessary for normal neural tube closure.We created knock-in(KI)mouse models with human-derived HSPG2 variants,using sperm-like stem cells that had been genetically edited by CRISPR/Cas9.We realized that any HSPG2 variants that affected the function of endorepellin were considered pathogenic causal variants for human NTDs given that the severe NTD phenotypes exhibited by these KI embryos occurred in a significantly higher response frequency compared to wildtype embryos.Our study provides a paradigm for effectively confirming pathogenic mutations in other genetic diseases.Furthermore,we demonstrated that using autophagy inhibitors at a cellular level can repress neuronal differentiation.Therefore,autophagy agonists may prevent NTDs resulting from failed autophagy maintenance and neuronal over-differentiation caused by deleterious endorepellin variants.

A mutation in TBXT causes congenital vertebral malformations in humans and mice

T-box transcription factor T(TBXT;T)is required for mesodermal formation and axial skeletal development.Although it has been extensively studied in various model organisms,human congenital vertebral malformations(CVMs)involving T are not well established.Here,we report a family with 15 CVM patients distributed across 4 generations.All affected individuals carry a heterozygous mutation,T c.596A>G(p.Q199R),which is not found in unaffected family members,indicating co-segregation of the genotype and phenotype.In vitro assays show that T p.Q199R increases the nucleocytoplasmic ratio and enhances its DNA-binding affinity,but reduces its transcriptional activity compared to the wild-type.To determine the pathogenicity of this mutation in vivo,we generated a Q199R knock-in mouse model that recapitulates the human CVM phenotype.Most heterozygous Q199R mice show subtle kinked or shortened tails,while homozygous mice exhibit tail filaments and severe vertebral deformities.Overall,we show that the Q199R mutation in T causes CVM in humans and mice,providing previously unreported evidence supporting the function of T in the genetic etiology of human CVM.

基因组结构变异研究的前瞻性及临床应用

The challenges and breakthroughs in human genetics can largely depend on the depth of exploring the missing heritability[1]and understanding of genetic variants,which enabled scientists to better elucidate the underlying causes of diseases and apply this knowledge in clinical settings.Human genomes differ from one individual to another in the form of single nucleotide variants(SNVs),small insertions and deletions(indels)(<50 base pairs(bp)),and structural variants(SVs)[2].

DVL mutations identified from human neural tube defects and Dandy-Walker malformation obstruct the Wnt signaling pathway

Wnt signaling pathways,including the canonical Wnt/β-catenin pathway,planar cell polarity pathway,and Wnt/Ca2+signaling pathway,play important roles in neural development during embryonic stages.The DVL genes encode the hub proteins for Wnt signaling pathways.The mutations in DVL2 and DVL3 were identified from patients with neural tube defects(NTDs),but their functions in the pathogenesis of human neural diseases remain elusive.Here,we sequenced the coding regions of three DVL genes in 176 stillborn or miscarried fetuses with NTDs or Dandy-Walker malformation(DWM)and 480 adult controls from a Han Chinese population.Four rare mutations were identified:DVL1 p.R558 H,DVL1 p.R606 C,DVL2 p.R633 W,and DVL3 p.R222 Q.To assess the effect of these mutations on NTDs and DWM,various functional analyses such as luciferase reporter assay,stress fiber formation,and in vivo teratogenic assay were performed.The results showed that the DVL2 p.R633 W mutation destabilized DVL2 protein and upregulated activities for all three Wnt signalings(Wnt/β-catenin signaling,Wnt/planar cell polarity signaling,and Wnt/Ca2+signaling)in mammalian cells.In contrast,DVL1 mutants(DVL1 p.R558 H and DVL1 p.R606 C)decreased canonical Wnt/β-catenin signaling but increased the activity of Wnt/Ca2+signaling,and DVL3 p.R222 Q only decreased the activity of Wnt/Ca2+signaling.We also found that only the DVL2 p.R633 W mutant displayed more severe teratogenicity in zebrafish embryos than wild-type DVL2.Our study demonstrates that these four rare DVL mutations,especially DVL2 p.R633 W,may contribute to human neural diseases such as NTDs and DWM by obstructing Wnt signaling pathways.

Homozygous Mutation in the MTHFS Gene May Contribute to the Development of Cerebral Folate Deficiency Syndrome

Objective:The purpose of this study was to examine the role of rare variants in the one-carbon metabolic pathway in the etiology of the cerebral folate deficiency(CFD)syndrome.The CFD syndrome is a neurometabolic syndrome identified by low concentrations of 5-methyltetrahydrofolate(5-MTHF)in the cerebrospinal fluid(CSF)in spite of near-normal peripheral folate levels resulting in neurodevelopmental disorders.Methods:The localized folate metabolism impairments in CFD are thought to be either the result of mutations in genes responsible for folate transport or folate turnover through degradation.Genes that have been previously implicated in the etiology of CFD include folate receptor alpha-1(FOLR1),dihydrofolate reductase,proton-coupled folate transporter,and capicua.We performed whole-exome sequencing(WES)analysis of a CFD patient that revealed 99 novel missense mutations,of which 21 were classified as damaging mutations through the Poly-Phen2 prediction algorithm.In vitro functional studies were conducted by transient transfection of wild-type and mutant MTHFS into HEK293T cells to determine the impact of the variants on enzyme activity.Results:Of the damaging variants identified in the WES studies,we focused on the gene coding for the enzyme 5,10-methenyl-tetrahydrofolate synthetase(MTHFS).This enzyme catalyzes the production of methenyl THF which is subsequently converted to 5-MTHF.The CFD patient described within was found to carry a homozygous mutation,c.101G>T(p.R34L,rs200058464)in MTHFS,while the parents of the proband are heterozygotes for the MTHFS gene,and the healthy sibling is not a carrier.Conclusion:The mutant allele displayed a 50%reduction in luciferase activity(P<0.05),suggesting that homozygous loss of the MTHFS gene may play a significant role in the development of CFD.