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1.
Eur J Hum Genet ; 2019 Nov 06.
Artigo em Inglês | MEDLINE | ID: mdl-31695177

RESUMO

Neonatal progeroid syndrome, also known as Wiedemann-Rautenstrauch syndrome, is a rare condition characterized by severe growth retardation, apparent macrocephaly with prominent scalp veins, and lipodystrophy. It is caused by biallelic variants in POLR3A, a gene encoding for a subunit of the RNA polymerase III. All variants reported in the literature lead to at least a partial loss-of-function (when considering both alleles together). Here, we describe an individual with several clinical features of neonatal progeroid syndrome in whom exome sequencing revealed a homozygous nonsense variant in POLR3GL (NM_032305.2:c.358C>T; p.(Arg120Ter)). POLR3GL also encodes a subunit of RNA polymerase III and has recently been associated with endosteal hyperostosis and oligodontia in three patients with a phenotype distinct from the patient described here. Given the important role of POLR3GL in the same complex as the protein implicated in neonatal progeroid syndrome, the nature of the variant identified, our RNA studies suggesting nonsense-mediated decay, and the clinical overlap, we propose POLR3GL as a gene causing a variant of neonatal progeroid syndrome and therefore expand the phenotype associated with POLR3GL variants.

2.
Eur J Med Genet ; : 103784, 2019 Oct 09.
Artigo em Inglês | MEDLINE | ID: mdl-31605817

RESUMO

Multiple epiphyseal dysplasia (MED) is a genetically and clinically heterogeneous disease with both dominant and recessive inheritance. Eight different genes are known to cause the disease but in 15% of cases of MED, no mutation is found. Fibroblast growth factor receptor 1 (FGFR1) is a crucial regulator of bone formation and when mutated, can cause diseases with skeletal manifestations; nevertheless, MED has not been described in individuals with FGFR1 mutations. In this report, we describe a proband with MED and congenital normosmic hypogonadotropic hypogonadism (HH). DNA analysis showed a de novo frameshift variant in FGFR1 likely explaining the HH (p.Arg852Thrfs*165). No other mutation was found after a large gene sequencing panel, exome sequencing and an array CGH, except for a variant of unknown significance in FBN1 (rs755375255), but there were no features of a disease associated with FBN1 mutations and this variant is found a few times in population databases. We thus discuss the possibility that MED might be a new skeletal feature associated with FGFR1 mutations.

3.
Bone ; : 115047, 2019 Aug 28.
Artigo em Inglês | MEDLINE | ID: mdl-31472299

RESUMO

Bruck syndrome (BRKS) is the rare disorder that features congenital joint contractures often with pterygia and subsequent fractures, early on called osteogenesis imperfecta (OI) type XI (OMIM # 610968). Its two forms, BRKS1 (OMIM # 259450) and BRKS2 (OMIM # 609220), reflect autosomal recessive (AR) inheritance of FKBP10 and PLOD2 loss-of-function mutations, respectively. A 10-year-old girl was referred with blue sclera, osteopenia, poorly-healing fragility fractures, Wormian skull bones, cleft soft palate, congenital fusion of cervical vertebrae, progressive scoliosis, bell-shaped thorax, restrictive and reactive pulmonary disease, protrusio acetabuli, short stature, and additional dysmorphic features without joint contractures. Iliac crest biopsy after alendronate treatment that improved her bone density revealed low trabecular connectivity, abundant patchy osteoid, and active bone formation with widely-spaced tetracycline labels. Chromosome 22q11 deletion analysis for velocardiofacial syndrome, COL1A1 and COL1A2 sequencing for prevalent types of OI, and Sanger sequencing of LRP5, PPIB, FKBP10, and IFITM5 for rare pediatric osteoporoses were negative. Copy number microarray excluded a contiguous gene syndrome. Instead, exome sequencing revealed two missense variants in PLOD2 which encodes procollagen-lysine, 2-oxoglutarate 5-dioxygenase 2 (lysyl hydroxylase 2, LH2); exon 8, c.797G>T, p.Gly266Val (paternal), and exon 12, c.1280A>G, p.Asn427Ser (maternal). In the Exome Aggregation Consortium (ExAC) database, low frequency (Gly266Val, 0.0000419) and absence (Asn427Ser) implicated both variants as mutations of PLOD2. The father, mother, and sister (who carried the exon 12 defect) were reportedly well with normal parental DXA findings. BRKS2, characterized by under-hydroxylation of type I collagen telopeptides compromising their crosslinking, has been reported in at least 16 probands/families. Most PLOD2 mutations involve exons 17-19 (of 20 total) encoding the C-terminal domain with LH activity. However, truncating defects (nonsense, frameshift, splice site mutations) are also found throughout PLOD2. In three reports, AR PLOD2 mutations are not associated with congenital contractures. Our patient's missense defects lie within the central domain of unknown function of PLOD2. In our patient, compound heterozygosity with PLOD2 mutations is associated with a clinical phenotype distinctive from classic BRKS2 indicating that when COL1A1 and COL1A2 mutation testing is negative for OI without congenital contractures or pterygia, atypical BRKS should be considered.

4.
Genet Med ; 2019 Aug 07.
Artigo em Inglês | MEDLINE | ID: mdl-31388190

RESUMO

PURPOSE: Sifrim-Hitz-Weiss syndrome (SIHIWES) is a recently described multisystemic neurodevelopmental disorder caused by de novo variants in CHD4. In this study, we investigated the clinical spectrum of the disorder, genotype-phenotype correlations, and the effect of different missense variants on CHD4 function. METHODS: We collected clinical and molecular data from 32 individuals with mostly de novo variants in CHD4, identified through next-generation sequencing. We performed adenosine triphosphate (ATP) hydrolysis and nucleosome remodeling assays on variants from five different CHD4 domains. RESULTS: The majority of participants had global developmental delay, mild to moderate intellectual disability, brain anomalies, congenital heart defects, and dysmorphic features. Macrocephaly was a frequent but not universal finding. Additional common abnormalities included hypogonadism in males, skeletal and limb anomalies, hearing impairment, and ophthalmic abnormalities. The majority of variants were nontruncating and affected the SNF2-like region of the protein. We did not identify genotype-phenotype correlations based on the type or location of variants. Alterations in ATP hydrolysis and chromatin remodeling activities were observed in variants from different domains. CONCLUSION: The CHD4-related syndrome is a multisystemic neurodevelopmental disorder. Missense substitutions in different protein domains alter CHD4 function in a variant-specific manner, but result in a similar phenotype in humans.

5.
Am J Hum Genet ; 105(3): 534-548, 2019 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-31422819

RESUMO

Early-infantile encephalopathies with epilepsy are devastating conditions mandating an accurate diagnosis to guide proper management. Whole-exome sequencing was used to investigate the disease etiology in four children from independent families with intellectual disability and epilepsy, revealing bi-allelic GOT2 mutations. In-depth metabolic studies in individual 1 showed low plasma serine, hypercitrullinemia, hyperlactatemia, and hyperammonemia. The epilepsy was serine and pyridoxine responsive. Functional consequences of observed mutations were tested by measuring enzyme activity and by cell and animal models. Zebrafish and mouse models were used to validate brain developmental and functional defects and to test therapeutic strategies. GOT2 encodes the mitochondrial glutamate oxaloacetate transaminase. GOT2 enzyme activity was deficient in fibroblasts with bi-allelic mutations. GOT2, a member of the malate-aspartate shuttle, plays an essential role in the intracellular NAD(H) redox balance. De novo serine biosynthesis was impaired in fibroblasts with GOT2 mutations and GOT2-knockout HEK293 cells. Correcting the highly oxidized cytosolic NAD-redox state by pyruvate supplementation restored serine biosynthesis in GOT2-deficient cells. Knockdown of got2a in zebrafish resulted in a brain developmental defect associated with seizure-like electroencephalography spikes, which could be rescued by supplying pyridoxine in embryo water. Both pyridoxine and serine synergistically rescued embryonic developmental defects in zebrafish got2a morphants. The two treated individuals reacted favorably to their treatment. Our data provide a mechanistic basis for the biochemical abnormalities in GOT2 deficiency that may also hold for other MAS defects.

6.
Am J Hum Genet ; 105(3): 625-630, 2019 Sep 05.
Artigo em Inglês | MEDLINE | ID: mdl-31303264

RESUMO

Rothmund-Thomson syndrome (RTS) is an autosomal-recessive disorder characterized by poikiloderma, sparse hair, short stature, and skeletal anomalies. Type 2 RTS, which is defined by the presence of bi-allelic mutations in RECQL4, is characterized by increased cancer susceptibility and skeletal anomalies, whereas the genetic basis of RTS type 1, which is associated with juvenile cataracts, is unknown. We studied ten individuals, from seven families, who had RTS type 1 and identified a deep intronic splicing mutation of the ANAPC1 gene, a component of the anaphase-promoting complex/cyclosome (APC/C), in all affected individuals, either in the homozygous state or in trans with another mutation. Fibroblast studies showed that the intronic mutation causes the activation of a 95 bp pseudoexon, leading to mRNAs with premature termination codons and nonsense-mediated decay, decreased ANAPC1 protein levels, and prolongation of interphase. Interestingly, mice that were heterozygous for a knockout mutation have an increased incidence of cataracts. Our results demonstrate that deficiency in the APC/C is a cause of RTS type 1 and suggest a possible link between the APC/C and RECQL4 helicase because both proteins are involved in DNA repair and replication.

7.
Am J Hum Genet ; 105(2): 384-394, 2019 Aug 01.
Artigo em Inglês | MEDLINE | ID: mdl-31256876

RESUMO

Proteins anchored to the cell surface via glycosylphosphatidylinositol (GPI) play various key roles in the human body, particularly in development and neurogenesis. As such, many developmental disorders are caused by mutations in genes involved in the GPI biosynthesis and remodeling pathway. We describe ten unrelated families with bi-allelic mutations in PIGB, a gene that encodes phosphatidylinositol glycan class B, which transfers the third mannose to the GPI. Ten different PIGB variants were found in these individuals. Flow cytometric analysis of blood cells and fibroblasts from the affected individuals showed decreased cell surface presence of GPI-anchored proteins. Most of the affected individuals have global developmental and/or intellectual delay, all had seizures, two had polymicrogyria, and four had a peripheral neuropathy. Eight children passed away before four years old. Two of them had a clinical diagnosis of DOORS syndrome (deafness, onychodystrophy, osteodystrophy, mental retardation, and seizures), a condition that includes sensorineural deafness, shortened terminal phalanges with small finger and toenails, intellectual disability, and seizures; this condition overlaps with the severe phenotypes associated with inherited GPI deficiency. Most individuals tested showed elevated alkaline phosphatase, which is a characteristic of the inherited GPI deficiency but not DOORS syndrome. It is notable that two severely affected individuals showed 2-oxoglutaric aciduria, which can be seen in DOORS syndrome, suggesting that severe cases of inherited GPI deficiency and DOORS syndrome might share some molecular pathway disruptions.

8.
Am J Hum Genet ; 104(6): 1139-1157, 2019 Jun 06.
Artigo em Inglês | MEDLINE | ID: mdl-31155282

RESUMO

Zimmermann-Laband syndrome (ZLS) is characterized by coarse facial features with gingival enlargement, intellectual disability (ID), hypertrichosis, and hypoplasia or aplasia of nails and terminal phalanges. De novo missense mutations in KCNH1 and KCNK4, encoding K+ channels, have been identified in subjects with ZLS and ZLS-like phenotype, respectively. We report de novo missense variants in KCNN3 in three individuals with typical clinical features of ZLS. KCNN3 (SK3/KCa2.3) constitutes one of three members of the small-conductance Ca2+-activated K+ (SK) channels that are part of a multiprotein complex consisting of the pore-forming channel subunits, the constitutively bound Ca2+ sensor calmodulin, protein kinase CK2, and protein phosphatase 2A. CK2 modulates Ca2+ sensitivity of the channels by phosphorylating SK-bound calmodulin. Patch-clamp whole-cell recordings of KCNN3 channel-expressing CHO cells demonstrated that disease-associated mutations result in gain of function of the mutant channels, characterized by increased Ca2+ sensitivity leading to faster and more complete activation of KCNN3 mutant channels. Pretreatment of cells with the CK2 inhibitor 4,5,6,7-tetrabromobenzotriazole revealed basal inhibition of wild-type and mutant KCNN3 channels by CK2. Analogous experiments with the KCNN3 p.Val450Leu mutant previously identified in a family with portal hypertension indicated basal constitutive channel activity and thus a different gain-of-function mechanism compared to the ZLS-associated mutant channels. With the report on de novo KCNK4 mutations in subjects with facial dysmorphism, hypertrichosis, epilepsy, ID, and gingival overgrowth, we propose to combine the phenotypes caused by mutations in KCNH1, KCNK4, and KCNN3 in a group of neurological potassium channelopathies caused by an increase in K+ conductance.

9.
Genet Med ; 21(11): 2521-2531, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31092906

RESUMO

PURPOSE: Skeletal muscle growth and regeneration rely on muscle stem cells, called satellite cells. Specific transcription factors, particularly PAX7, are key regulators of the function of these cells. Knockout of this factor in mice leads to poor postnatal survival; however, the consequences of a lack of PAX7 in humans have not been established. METHODS: Here, we study five individuals with myopathy of variable severity from four unrelated consanguineous couples. Exome sequencing identified pathogenic variants in the PAX7 gene. Clinical examination, laboratory tests, and muscle biopsies were performed to characterize the disease. RESULTS: The disease was characterized by hypotonia, ptosis, muscular atrophy, scoliosis, and mildly dysmorphic facial features. The disease spectrum ranged from mild to severe and appears to be progressive. Muscle biopsies showed the presence of atrophic fibers and fibroadipose tissue replacement, with the absence of myofiber necrosis. A lack of PAX7 expression was associated with satellite cell pool exhaustion; however, the presence of residual myoblasts together with regenerating myofibers suggest that a population of PAX7-independent myogenic cells partially contributes to muscle regeneration. CONCLUSION: These findings show that biallelic variants in the master transcription factor PAX7 cause a new type of myopathy that specifically affects satellite cell survival.

10.
Mol Genet Genomic Med ; 7(7): e00743, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31127708

RESUMO

BACKGROUND: Glycophosphatidylinositol-anchored proteins (GPI-APs) mediate several physiological processes such as embryogenesis and neurogenesis. Germline variants in genes involved in their synthesis can disrupt normal development and result in a variety of clinical phenotypes. With the advent of new sequencing technologies, more cases are identified, leading to a rapidly growing number of reported genetic variants. With this number expected to rise with increased accessibility to molecular tests, an accurate and up-to-date database is needed to keep track of the information and help interpret results. METHODS: We therefore developed an online resource (www.gpibiosynthesis.org) which compiles all published pathogenic variants in GPI biosynthesis genes which are deposited in the LOVD database. It contains 276 individuals and 192 unique public variants; 92% of which are predicted as damaging by bioinformatics tools. RESULTS: A significant proportion of recorded variants was substitution variants (81%) and resulted mainly in missense and frameshift alterations. Interestingly, five patients (2%) had deleterious mutations in untranslated regions. CADD score analysis placed 97% of variants in the top 1% of deleterious variants in the human genome. In genome aggregation database, the gene with the highest frequency of reported pathogenic variants is PIGL, with a carrier rate of 1/937. CONCLUSION: We thus present the GPI biosynthesis database and review the molecular genetics of published variants in GPI-anchor biosynthesis genes.

11.
Am J Hum Genet ; 104(4): 596-610, 2019 Apr 04.
Artigo em Inglês | MEDLINE | ID: mdl-30879640

RESUMO

Mutations in several genes encoding components of the SWI/SNF chromatin remodeling complex cause neurodevelopmental disorders (NDDs). Here, we report on five individuals with mutations in SMARCD1; the individuals present with developmental delay, intellectual disability, hypotonia, feeding difficulties, and small hands and feet. Trio exome sequencing proved the mutations to be de novo in four of the five individuals. Mutations in other SWI/SNF components cause Coffin-Siris syndrome, Nicolaides-Baraitser syndrome, or other syndromic and non-syndromic NDDs. Although the individuals presented here have dysmorphisms and some clinical overlap with these syndromes, they lack their typical facial dysmorphisms. To gain insight into the function of SMARCD1 in neurons, we investigated the Drosophila ortholog Bap60 in postmitotic memory-forming neurons of the adult Drosophila mushroom body (MB). Targeted knockdown of Bap60 in the MB of adult flies causes defects in long-term memory. Mushroom-body-specific transcriptome analysis revealed that Bap60 is required for context-dependent expression of genes involved in neuron function and development in juvenile flies when synaptic connections are actively being formed in response to experience. Taken together, we identify an NDD caused by SMARCD1 mutations and establish a role for the SMARCD1 ortholog Bap60 in the regulation of neurodevelopmental genes during a critical time window of juvenile adult brain development when neuronal circuits that are required for learning and memory are formed.

14.
Bone ; 121: 163-171, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30599297

RESUMO

Heterozygous pathogenic variants in the FN1 gene, encoding fibronectin (FN), have recently been shown to be associated with a skeletal disorder in some individuals affected by spondylometaphyseal dysplasia with "corner fractures" (SMD-CF). The most striking feature characterizing SMD-CF is irregularly shaped metaphyses giving the appearance of "corner fractures". An array of secondary features, including developmental coxa vara, ovoid vertebral bodies and severe scoliosis, may also be present. FN is an important extracellular matrix component for bone and cartilage development. Here we report five patients affected by this subtype of SMD-CF caused by five novel FN1 missense mutations: p.Cys123Tyr, p.Cys169Tyr, p.Cys213Tyr, p.Cys231Trp and p.Cys258Tyr. All individuals shared a substitution of a cysteine residue, disrupting disulfide bonds in the FN type-I assembly domains located in the N-terminal assembly region. The abnormal metaphyseal ossification and "corner fracture" appearances were the most remarkable clinical feature in these patients. In addition, generalized skeletal fragility with low-trauma bilateral femoral fractures was identified in one patient. Interestingly, the distal femoral changes in this patient healed with skeletal maturation. Our report expands the phenotypic and genetic spectrum of the FN1-related SMD-CF and emphasizes the importance of FN in bone formation and possibly also in the maintenance of bone strength.

15.
Eur J Hum Genet ; 27(5): 671-680, 2019 May.
Artigo em Inglês | MEDLINE | ID: mdl-30664715

RESUMO

We review genetic diseases with identified molecular bases that include abnormal, reduced (hypoplasia), or absent (aplasia) patellae as a significant aspect of the phenotype. The known causal genes can be broadly organized according to three major developmental and cellular processes, although some genes may act in more than one of these: limb specification and pattern formation; DNA replication and chromatin structure; bone development and differentiation. There are also several genes whose phenotypes in mice indicate relevance to patellar development, for which human equivalent syndromes have not been reported. Developmental studies in mouse and chick embryos, as well as patellar involvement in human diseases with decreased mobility, document the additional importance of local environmental factors in patellar ontogenesis. Patellar anomalies found in humans can be an important clue to a clinical genetic diagnosis, and a better knowledge of the genetics of patellar anomalies will improve our understanding of limb development.

16.
Am J Hum Genet ; 104(1): 164-178, 2019 01 03.
Artigo em Inglês | MEDLINE | ID: mdl-30580808

RESUMO

SMARCC2 (BAF170) is one of the invariable core subunits of the ATP-dependent chromatin remodeling BAF (BRG1-associated factor) complex and plays a crucial role in embryogenesis and corticogenesis. Pathogenic variants in genes encoding other components of the BAF complex have been associated with intellectual disability syndromes. Despite its significant biological role, variants in SMARCC2 have not been directly associated with human disease previously. Using whole-exome sequencing and a web-based gene-matching program, we identified 15 individuals with variable degrees of neurodevelopmental delay and growth retardation harboring one of 13 heterozygous variants in SMARCC2, most of them novel and proven de novo. The clinical presentation overlaps with intellectual disability syndromes associated with other BAF subunits, such as Coffin-Siris and Nicolaides-Baraitser syndromes and includes prominent speech impairment, hypotonia, feeding difficulties, behavioral abnormalities, and dysmorphic features such as hypertrichosis, thick eyebrows, thin upper lip vermilion, and upturned nose. Nine out of the fifteen individuals harbor variants in the highly conserved SMARCC2 DNA-interacting domains (SANT and SWIRM) and present with a more severe phenotype. Two of these individuals present cardiac abnormalities. Transcriptomic analysis of fibroblasts from affected individuals highlights a group of differentially expressed genes with possible roles in regulation of neuronal development and function, namely H19, SCRG1, RELN, and CACNB4. Our findings suggest a novel SMARCC2-related syndrome that overlaps with neurodevelopmental disorders associated with variants in BAF-complex subunits.


Assuntos
Deficiências do Desenvolvimento/complicações , Deficiências do Desenvolvimento/genética , Deficiência Intelectual/complicações , Deficiência Intelectual/genética , Mutação , Fatores de Transcrição/genética , Anormalidades Múltiplas/genética , Adolescente , Criança , Pré-Escolar , Face/anormalidades , Feminino , Deformidades Congênitas da Mão/genética , Humanos , Masculino , Micrognatismo/genética , Pescoço/anormalidades , Síndrome
17.
18.
Nat Commun ; 9(1): 4885, 2018 Nov 20.
Artigo em Inglês | MEDLINE | ID: mdl-30459321

RESUMO

Coffin-Siris and Nicolaides-Baraitser syndromes (CSS and NCBRS) are Mendelian disorders caused by mutations in subunits of the BAF chromatin remodeling complex. We report overlapping peripheral blood DNA methylation epi-signatures in individuals with various subtypes of CSS (ARID1B, SMARCB1, and SMARCA4) and NCBRS (SMARCA2). We demonstrate that the degree of similarity in the epi-signatures of some CSS subtypes and NCBRS can be greater than that within CSS, indicating a link in the functional basis of the two syndromes. We show that chromosome 6q25 microdeletion syndrome, harboring ARID1B deletions, exhibits a similar CSS/NCBRS methylation profile. Specificity of this epi-signature was confirmed across a wide range of neurodevelopmental conditions including other chromatin remodeling and epigenetic machinery disorders. We demonstrate that a machine-learning model trained on this DNA methylation profile can resolve ambiguous clinical cases, reclassify those with variants of unknown significance, and identify previously undiagnosed subjects through targeted population screening.

19.
Hum Genet ; 137(11-12): 905-909, 2018 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-30368667

RESUMO

Lowry-Wood syndrome (LWS) is a skeletal dysplasia characterized by multiple epiphyseal dysplasia associated with microcephaly, developmental delay and intellectual disability, and eye involvement. Pathogenic variants in RNU4ATAC, an RNA of the minor spliceosome important for the excision of U12-dependent introns, have been recently associated with LWS. This gene had previously also been associated with microcephalic osteodysplastic primordial dwarfism (MOPD) and Roifman syndrome (RS), two distinct conditions which share with LWS some skeletal and neurological anomalies. We performed exome sequencing in two individuals with Lowry-Wood syndrome. We report RNU4ATAC pathogenic variants in two further patients. Moreover, an analysis of all RNU4ATAC variants reported so far showed that FitCons scores for nucleotides mutated in the more severe MOPD are higher than RS or LWS and that they were more frequently located in the 5' Stem-Loop of the RNA critical for the formation of the U4/U6.U5 tri-snRNP complex, whereas the variants are more dispersed in the other conditions. We are thus confirming that RNU4ATAC is the gene responsible for LWS and provide a genotype-phenotype correlation analysis.

20.
Hum Mol Genet ; 2018 Oct 17.
Artigo em Inglês | MEDLINE | ID: mdl-30335140

RESUMO

Mutations in the Tre2/Bub2/Cdc16 (TBC)1 domain family member 24 (TBC1D24) gene are associated with a range of inherited neurological disorders, from drug-refractory lethal epileptic encephalopathy and DOORS syndrome (Deafness, Onychodystrophy, Osteodystrophy, mental Retardation, Seizures) to non-syndromic hearing loss. TBC1D24 has been implicated in neuronal transmission and maturation, although the molecular function of the gene and the cause of the apparently complex disease spectrum remain unclear. Importantly, heterozygous TBC1D24 mutation carriers have also been reported with seizures, suggesting that haploinsufficiency for TBC1D24 is significant clinically. Here we have systematically investigated an allelic series of disease-associated mutations in neurons alongside a new mouse model to investigate the consequences of TBC1D24 haploinsufficiency to mammalian neurodevelopment and synaptic physiology. The cellular studies reveal that disease-causing mutations that disrupt either of the conserved protein domains in TBC1D24 are implicated in neuronal development and survival and are likely acting as loss-of-function alleles. We then further investigated TBC1D24 haploinsufficiency in vivo and demonstrate that TBC1D24 is also critical for normal presynaptic function: genetic disruption of Tbc1d24 expression in the mouse leads to an impairment of endocytosis and an enlarged endosomal compartment in neurons with a decrease in spontaneous neurotransmission. These data reveal the essential role for TBC1D24 at the mammalian synapse and help to define common synaptic mechanisms that could underlie the varied effects of TBC1D24 mutations in neurological disease.

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