As a critical guanine nucleotide exchange factor(GEF) regulating neurite outgrowth, Trio coordinates multiple processes of cytoskeletal dynamics through activating Rac1, Cdc42 and RhoA small GTPases by two GEF domains...As a critical guanine nucleotide exchange factor(GEF) regulating neurite outgrowth, Trio coordinates multiple processes of cytoskeletal dynamics through activating Rac1, Cdc42 and RhoA small GTPases by two GEF domains, but the in vivo roles of these GEF domains and corresponding downstream effectors have not been determined yet. We established multiple lines of knockout mice and assessed the respective roles of Trio GEF domains and Rac1 in axon outgrowth. Knockout of total Trio in cerebellar granule neurons(CGNs) led to an impaired F-actin rearrangement of growth cone and hence a retarded neurite outgrowth. Such a retardation was reproduced by inhibition of GEF1 domain or knockdown of Cdc42 and restored apparently by introduction of active Cdc42. As Rac1 deficiency did not affect the neurite outgrowth of CGNs, we suggested that Trio GEF1-mediated Cdc42 activation was required for neurite outgrowth. We established a GEF2-knockout line with deletion of all Trio isoforms except a cerebella-specific Trio8, a short isoform of Trio without GEF2 domain, and used this line as a GEF2-deficient animal model. The GEF2-deficient CGNs had a normal neurite outgrowth but abolished Netrin-1-promoted growth, without affecting Netrin-1 induced Rac1 activation. We thus suggested that Trio GEF1-mediated Cdc42 activation rather than Rac1 activation drives the F-actin dynamics necessary for neurite outgrowth, while GEF2 functions in Netrin-1-promoted neurite elongation. Our results delineated the distinct roles of Trio GEF domains in neurite outgrowth, which is instructive to understand the pathogenesis of clinical Trio-related neurodevelopmental disorders.展开更多
A Mendelsohn triple system on a set X is a pair(X, B), where B is a collection of cyclically ordered triples of distinct elements from X such that each ordered pair of distinct elements from X is covered by a unique t...A Mendelsohn triple system on a set X is a pair(X, B), where B is a collection of cyclically ordered triples of distinct elements from X such that each ordered pair of distinct elements from X is covered by a unique triple from B. (Here the cyclic triples (x, y, z ), (y, z, x ) and (z, x, y ) are considered equal, and cover the three pairs (x, y), (y, z)and (z, x). ) If |X|=v, this system is denoted by MTS(v). It is well known that an MTS(v)does exist if and only if v≡0, 1(mod 3), v≠6 (cf. [1]).展开更多
Importance:Pathogenic variants in theRBM20 gene are associated with aggressive dilated cardiomyopathy(DCM).Recently,RBM20 was found to be associated with left ventricular non-compaction cardiomyopathy(LVNC).Thus far,o...Importance:Pathogenic variants in theRBM20 gene are associated with aggressive dilated cardiomyopathy(DCM).Recently,RBM20 was found to be associated with left ventricular non-compaction cardiomyopathy(LVNC).Thus far,only five families with LVNC have been reported to carry variants inRBM20.It remains unknown whether the variants inRBM20 associated with DCM can also cause LVNC.Objective:To elucidate the causativeRBM20 variant in two unrelated patients with both LVNC and DCM,and to identify the clinical characteristics associated with variants inRBM20.Methods:Trio whole-exome sequencing(WES)was performed.Variants were filtered and classified in accordance with the guidelines of the American College of Medical Genetics and Genomics(ACMG).Results:We identified two distinctde novo variants inRBM20(one per patient)in these two patients with LVNC.Both variants have been reported in patients with DCM,without the LVNC phenotype.Patient 1 was an 11-year-old girl who had DCM,LVNC,and heart failure;the ratio of noncompacted-to-compacted myocardium was 2.7:1.Ade novo heterozygous variant c.1907G>A(p.Arg636His)in exon 9 was identified in this patient.Patient 2 was a 13-year-old boy who had clinical phenotypes identical to those of Patient 1;the ratio of noncompacted-to-compacted myocardium was 3.2:1 in this patient.WES revealed ade novo heterozygous variant c.1909A>G(p.Ser637Gly)in exon 9.Both variants were previously characterized as pathogenic,and our study classified them as pathogenic variants based on the ACMG guidelines.Interpretation:We found that two patients with LVNC had variants inRBM20.Our results extended the clinical spectrum of the twoRBM20 variants and illustrated that the same variant inRBM20 can cause DCM,with or without the LVNC phenotype.展开更多
The radial migration of cortical pyramidal neurons(PNs)during corticogenesis is necessary for establishing a multilayered cerebral cortex.Neuronal migration defects are considered a critical etiology of neurodevelopme...The radial migration of cortical pyramidal neurons(PNs)during corticogenesis is necessary for establishing a multilayered cerebral cortex.Neuronal migration defects are considered a critical etiology of neurodevelopmental disorders,including autism spectrum disorders(ASDs),schizophrenia,epilepsy,and intellectual disability(ID).TRIO is a high-risk candidate gene for ASDs and ID.However,its role in embryonic radial migration and the etiology of ASDs and ID are not fully understood.In this study,we found that the in vivo conditional knockout or in utero knockout of Trio in excitatory precursors in the neocortex caused aberrant polarity and halted the migration of late-born PNs.Further investigation of the underlying mechanism revealed that the interaction of the Trio N-terminal SH3 domain with Myosin X mediated the adherence of migrating neurons to radial glial fibers through regulating the membrane location of neuronal cadherin(N-cadherin).Also,independent or synergistic overexpression of RAC1 and RHOA showed different phenotypic recoveries of the abnormal neuronal migration by affecting the morphological transition and/or the glial fiber-dependent locomotion.Taken together,our findings clarify a novel mechanism of Trio in regulating N-cadherin cell surface expression via the interaction of Myosin X with its N-terminal SH3 domain.These results suggest the vital roles of the guanine nucleotide exchange factor 1(GEF1)and GEF2 domains in regulating radial migration by activating their Rho GTPase effectors in both distinct and cooperative manners,which might be associated with the abnormal phenotypes in neurodevelopmental disorders.展开更多
基金supported by grants from the National Natural Science Foundation of China (31272311 and 31330034) to M.S.Z.
文摘As a critical guanine nucleotide exchange factor(GEF) regulating neurite outgrowth, Trio coordinates multiple processes of cytoskeletal dynamics through activating Rac1, Cdc42 and RhoA small GTPases by two GEF domains, but the in vivo roles of these GEF domains and corresponding downstream effectors have not been determined yet. We established multiple lines of knockout mice and assessed the respective roles of Trio GEF domains and Rac1 in axon outgrowth. Knockout of total Trio in cerebellar granule neurons(CGNs) led to an impaired F-actin rearrangement of growth cone and hence a retarded neurite outgrowth. Such a retardation was reproduced by inhibition of GEF1 domain or knockdown of Cdc42 and restored apparently by introduction of active Cdc42. As Rac1 deficiency did not affect the neurite outgrowth of CGNs, we suggested that Trio GEF1-mediated Cdc42 activation was required for neurite outgrowth. We established a GEF2-knockout line with deletion of all Trio isoforms except a cerebella-specific Trio8, a short isoform of Trio without GEF2 domain, and used this line as a GEF2-deficient animal model. The GEF2-deficient CGNs had a normal neurite outgrowth but abolished Netrin-1-promoted growth, without affecting Netrin-1 induced Rac1 activation. We thus suggested that Trio GEF1-mediated Cdc42 activation rather than Rac1 activation drives the F-actin dynamics necessary for neurite outgrowth, while GEF2 functions in Netrin-1-promoted neurite elongation. Our results delineated the distinct roles of Trio GEF domains in neurite outgrowth, which is instructive to understand the pathogenesis of clinical Trio-related neurodevelopmental disorders.
文摘A Mendelsohn triple system on a set X is a pair(X, B), where B is a collection of cyclically ordered triples of distinct elements from X such that each ordered pair of distinct elements from X is covered by a unique triple from B. (Here the cyclic triples (x, y, z ), (y, z, x ) and (z, x, y ) are considered equal, and cover the three pairs (x, y), (y, z)and (z, x). ) If |X|=v, this system is denoted by MTS(v). It is well known that an MTS(v)does exist if and only if v≡0, 1(mod 3), v≠6 (cf. [1]).
文摘Importance:Pathogenic variants in theRBM20 gene are associated with aggressive dilated cardiomyopathy(DCM).Recently,RBM20 was found to be associated with left ventricular non-compaction cardiomyopathy(LVNC).Thus far,only five families with LVNC have been reported to carry variants inRBM20.It remains unknown whether the variants inRBM20 associated with DCM can also cause LVNC.Objective:To elucidate the causativeRBM20 variant in two unrelated patients with both LVNC and DCM,and to identify the clinical characteristics associated with variants inRBM20.Methods:Trio whole-exome sequencing(WES)was performed.Variants were filtered and classified in accordance with the guidelines of the American College of Medical Genetics and Genomics(ACMG).Results:We identified two distinctde novo variants inRBM20(one per patient)in these two patients with LVNC.Both variants have been reported in patients with DCM,without the LVNC phenotype.Patient 1 was an 11-year-old girl who had DCM,LVNC,and heart failure;the ratio of noncompacted-to-compacted myocardium was 2.7:1.Ade novo heterozygous variant c.1907G>A(p.Arg636His)in exon 9 was identified in this patient.Patient 2 was a 13-year-old boy who had clinical phenotypes identical to those of Patient 1;the ratio of noncompacted-to-compacted myocardium was 3.2:1 in this patient.WES revealed ade novo heterozygous variant c.1909A>G(p.Ser637Gly)in exon 9.Both variants were previously characterized as pathogenic,and our study classified them as pathogenic variants based on the ACMG guidelines.Interpretation:We found that two patients with LVNC had variants inRBM20.Our results extended the clinical spectrum of the twoRBM20 variants and illustrated that the same variant inRBM20 can cause DCM,with or without the LVNC phenotype.
基金the Key Realm R&D Program of Guangdong Province(2019B030335001)the National Key R&D Program of China(2016YFC1307000)+1 种基金the National Natural Science Foundation of China(81730037,81825009,81871077,81671363,and 82071541)the Beijing Major Science and Technology Projects(Z181100001518001).
文摘The radial migration of cortical pyramidal neurons(PNs)during corticogenesis is necessary for establishing a multilayered cerebral cortex.Neuronal migration defects are considered a critical etiology of neurodevelopmental disorders,including autism spectrum disorders(ASDs),schizophrenia,epilepsy,and intellectual disability(ID).TRIO is a high-risk candidate gene for ASDs and ID.However,its role in embryonic radial migration and the etiology of ASDs and ID are not fully understood.In this study,we found that the in vivo conditional knockout or in utero knockout of Trio in excitatory precursors in the neocortex caused aberrant polarity and halted the migration of late-born PNs.Further investigation of the underlying mechanism revealed that the interaction of the Trio N-terminal SH3 domain with Myosin X mediated the adherence of migrating neurons to radial glial fibers through regulating the membrane location of neuronal cadherin(N-cadherin).Also,independent or synergistic overexpression of RAC1 and RHOA showed different phenotypic recoveries of the abnormal neuronal migration by affecting the morphological transition and/or the glial fiber-dependent locomotion.Taken together,our findings clarify a novel mechanism of Trio in regulating N-cadherin cell surface expression via the interaction of Myosin X with its N-terminal SH3 domain.These results suggest the vital roles of the guanine nucleotide exchange factor 1(GEF1)and GEF2 domains in regulating radial migration by activating their Rho GTPase effectors in both distinct and cooperative manners,which might be associated with the abnormal phenotypes in neurodevelopmental disorders.
