ABSTRACT
Rab GTPases are important regulators of intracellular vesicular trafficking. RAB5C is a member of the Rab GTPase family that plays an important role in the endocytic pathway, membrane protein recycling and signaling. Here we report on 12 individuals with nine different heterozygous de novo variants in RAB5C. All but one patient with missense variants (n = 9) exhibited macrocephaly, combined with mild-to-moderate developmental delay. Patients with loss of function variants (n = 2) had an apparently more severe clinical phenotype with refractory epilepsy and intellectual disability but a normal head circumference. Four missense variants were investigated experimentally. In vitro biochemical studies revealed that all four variants were damaging, resulting in increased nucleotide exchange rate, attenuated responsivity to guanine exchange factors and heterogeneous effects on interactions with effector proteins. Studies in C. elegans confirmed that all four variants were damaging in vivo and showed defects in endocytic pathway function. The variant heterozygotes displayed phenotypes that were not observed in null heterozygotes, with two shown to be through a dominant negative mechanism. Expression of the human RAB5C variants in zebrafish embryos resulted in defective development, further underscoring the damaging effects of the RAB5C variants. Our combined bioinformatic, in vitro and in vivo experimental studies and clinical data support the association of RAB5C missense variants with a neurodevelopmental disorder characterized by macrocephaly and mild-to-moderate developmental delay through disruption of the endocytic pathway.
Subject(s)
Intellectual Disability , Megalencephaly , Neurodevelopmental Disorders , Animals , Humans , Child , Zebrafish/genetics , Zebrafish/metabolism , Caenorhabditis elegans/metabolism , Neurodevelopmental Disorders/genetics , Intellectual Disability/genetics , Phenotype , rab GTP-Binding Proteins/genetics , rab GTP-Binding Proteins/metabolism , Megalencephaly/genetics , Developmental Disabilities/genetics , Mutation, Missense/genetics , rab5 GTP-Binding Proteins/genetics , rab5 GTP-Binding Proteins/metabolismABSTRACT
SWI/SNF-related intellectual disability disorders (SSRIDDs) are rare neurodevelopmental disorders characterized by developmental disability, coarse facial features, and fifth digit/nail hypoplasia that are caused by pathogenic variants in genes that encode for members of the SWI/SNF (or BAF) family of chromatin remodeling complexes. We have identified 12 individuals with rare variants (10 loss-of-function, 2 missense) in the BICRA (BRD4 interacting chromatin remodeling complex-associated protein) gene, also known as GLTSCR1, which encodes a subunit of the non-canonical BAF (ncBAF) complex. These individuals exhibited neurodevelopmental phenotypes that include developmental delay, intellectual disability, autism spectrum disorder, and behavioral abnormalities as well as dysmorphic features. Notably, the majority of individuals lack the fifth digit/nail hypoplasia phenotype, a hallmark of most SSRIDDs. To confirm the role of BICRA in the development of these phenotypes, we performed functional characterization of the zebrafish and Drosophila orthologs of BICRA. In zebrafish, a mutation of bicra that mimics one of the loss-of-function variants leads to craniofacial defects possibly akin to the dysmorphic facial features seen in individuals harboring putatively pathogenic BICRA variants. We further show that Bicra physically binds to other non-canonical ncBAF complex members, including the BRD9/7 ortholog, CG7154, and is the defining member of the ncBAF complex in flies. Like other SWI/SNF complex members, loss of Bicra function in flies acts as a dominant enhancer of position effect variegation but in a more context-specific manner. We conclude that haploinsufficiency of BICRA leads to a unique SSRIDD in humans whose phenotypes overlap with those previously reported.
Subject(s)
Chromosomal Proteins, Non-Histone/genetics , Developmental Disabilities/genetics , Mutation, Missense , Phenotype , Tumor Suppressor Proteins/genetics , Adolescent , Animals , Child , Child, Preschool , Drosophila Proteins/genetics , Drosophila melanogaster , Female , Genes, Dominant , Genetic Variation , Haploinsufficiency , Humans , Infant , Male , Microscopy, Confocal , Neuroglia/metabolism , Neurons/metabolism , Protein Binding , Zebrafish , Zebrafish Proteins/geneticsABSTRACT
BACKGROUND: Laboratories utilizing next-generation sequencing align sequence data to a standardized human reference genome (HRG). Several updated versions, or builds, have been released since the original HRG in 2001, including the Genome Reference Consortium Human Build 38 (GRCh38) in 2013. However, most clinical laboratories still use GRCh37, which was released in 2009. We report our laboratory's clinical validation of GRCh38. METHODS: Migration to GRCh38 was validated by comparing the coordinates (lifting over) of 9443 internally curated variants from GRCh37 to GRCh38, globally comparing protein coding sequence variants aligned with GRCh37 vs GRCh38 from 917 exomes, assessing genes with known discrepancies, comparing coverage differences, and establishing the analytic sensitivity and specificity of variant detection using Genome in a Bottle data. RESULTS: Eight discrepancies, due to strand swap or reference base, were observed. Three clinically relevant variants had the GRCh37 alternate allele as the reference allele in GRCh38. A comparison of 88 295 calls between builds identified 8 disease-associated genes with sequence differences: ABO, BNC2, KIZ, NEFL, NR2E3, PTPRQ, SHANK2, and SRD5A2. Discrepancies in coding regions in GRCh37 were resolved in GRCh38. CONCLUSIONS: There were a small number of clinically significant changes between the 2 genome builds. GRCh38 provided improved detection of nucleotide changes due to the resolution of discrepancies present in GRCh37. Implementation of GRCh38 results in more accurate and consistent reporting.
Subject(s)
Genome, Human , Laboratories , 3-Oxo-5-alpha-Steroid 4-Dehydrogenase , Alleles , Cell Cycle Proteins , Exome , High-Throughput Nucleotide Sequencing/methods , Humans , Membrane Proteins , Receptor-Like Protein Tyrosine Phosphatases, Class 3ABSTRACT
Alveologenesis, the final step of lung development, is characterized by the formation of millions of alveolar septa that constitute the vast gas-exchange surface area. The genetic network driving alveologenesis is poorly understood compared with earlier steps in lung development. FGF signaling through receptors Fgfr3 and Fgfr4 is crucial for alveologenesis, but the mechanisms through which they mediate this process remain unclear. Here we show that in Fgfr3;Fgfr4 (Fgfr3;4) global mutant mice, alveolar simplification is first observed at the onset of alveologenesis at postnatal day 3. This is preceded by disorganization of elastin, indicating defects in the extracellular matrix (ECM). Although Fgfr3 and Fgfr4 are expressed in the mesenchyme and epithelium, inactivation in the mesenchyme, but not the epithelium, recapitulated the defects. Expression analysis of components of the elastogenesis machinery revealed that Mfap5 (also known as Magp2), which encodes an elastin-microfibril bridging factor, is upregulated in Fgfr3;4 mutants. Mfap5 mutation in the Fgfr3;4 mutant background partially attenuated the alveologenesis defects. These data demonstrate that, during normal lung maturation, FGF signaling restricts expression of the elastogenic machinery in the lung mesenchyme to control orderly formation of the elastin ECM, thereby driving alveolar septa formation to increase the gas-exchange surface.
Subject(s)
Contractile Proteins/biosynthesis , Extracellular Matrix Proteins/biosynthesis , Organogenesis/physiology , Pulmonary Alveoli/embryology , Receptor, Fibroblast Growth Factor, Type 3/metabolism , Receptor, Fibroblast Growth Factor, Type 4/metabolism , Animals , Contractile Proteins/genetics , Epithelium/metabolism , Extracellular Matrix/pathology , Extracellular Matrix Proteins/genetics , Mesoderm/metabolism , Mice , Mice, Knockout , Pulmonary Alveoli/cytology , RNA Splicing Factors , Receptor, Fibroblast Growth Factor, Type 3/genetics , Receptor, Fibroblast Growth Factor, Type 4/genetics , Signal Transduction/physiologyABSTRACT
Neuroblastoma (NB) in children older than 10 years is rare. We reviewed our archives for patients with NB aged 10 to 18 years and summarized their clinicopathologic/genetic records. Of 96 patients, 4 patients were identified in this age group. Four tumors were abdominal; 1 patient had 2 tumors at diagnosis, one of which was presacral. Tumor sizes ranged from 3 to 20 cm. All tumors were high risk at clinical stages 3 and 4, with metastasis to bone marrow and other areas. Four tumors were poorly differentiated with unfavorable histology and one patient with bilateral adrenal disease had an intermixed ganglioneuroblastoma on one side. Another tumor exhibited pheochromocytoma-like morphology. MYCN amplification was present in bone marrow metastasis in one case. Complex chromosomal gains and 19p deletions were common. Exome sequencing revealed ALK variants in 2 cases and previously unreported MAGI2, RUNX1, and MLL mutations. All patients received standard chemotherapy and 2 patients received ALK-targeted trial therapy. Three patients died of disease, ranging 18 to 23 months after diagnosis. One patient has active disease and is receiving trial therapy. In conclusion, NB in children older than 10 years may exhibit unusual clinicopathologic and genetic features with large tumors, bilateral adrenal disease, rare morphologic features, complex DNA microarray findings and novel mutations. Patients often have grim prognoses despite genomic profiling-guided targeted therapy.
Subject(s)
Antineoplastic Agents/administration & dosage , Neoplasm Proteins/genetics , Neuroblastoma , Adolescent , Child , Female , Humans , Male , Neoplasm Metastasis , Neoplasm Staging , Neuroblastoma/diagnosis , Neuroblastoma/drug therapy , Neuroblastoma/genetics , Neuroblastoma/pathology , PrognosisABSTRACT
The mammalian lung is an elaborate branching organ, and it forms following a highly stereotypical morphogenesis program. It is well established that precise control at the transcript level is a key genetic underpinning of lung branching. In comparison, little is known about how regulation at the protein level may play a role. Ring finger and WD domain 2 (RFWD2, also termed COP1) is an E3 ubiquitin ligase that modifies specific target proteins, priming their degradation via the ubiquitin proteasome system. RFWD2 is known to function in the adult in pathogenic processes such as tumorigenesis. Here, we show that prenatal inactivation of Rfwd2 gene in the lung epithelium led to a striking halt in branching morphogenesis shortly after secondary branch formation. This defect is accompanied by distalization of the lung epithelium while growth and cellular differentiation still occurred. In the mutant lung, two E26 transformation-specific (ETS) transcription factors essential for normal lung branching, ETS translocation variant 4 (ETV4) and ETV5, were up-regulated at the protein level, but not at the transcript level. Introduction of Etv loss-of-function alleles into the Rfwd2 mutant background attenuated the branching phenotype, suggesting that RFWD2 functions, at least in part, through degrading ETV proteins. Because a number of E3 ligases are known to target factors important for lung development, our findings provide a preview of protein-level regulatory network essential for lung branching morphogenesis.
Subject(s)
DNA-Binding Proteins/metabolism , Lung/embryology , Nuclear Proteins/metabolism , Transcription Factors/metabolism , Ubiquitin-Protein Ligases/metabolism , Animals , Female , Hedgehog Proteins/metabolism , Lung/enzymology , Mice , Morphogenesis , Nuclear Proteins/genetics , Pregnancy , Proto-Oncogene Proteins c-ets/metabolism , Respiratory Mucosa/enzymology , Ubiquitin-Protein Ligases/geneticsABSTRACT
BACKGROUND: Fras1 encodes an extracellular matrix protein that is critical for the establishment of the epidermal basement membrane during gestation. In humans, mutations in FRAS1 cause Fraser Syndrome (FS), a pleiotropic condition with many clinical presentations such as limb, eye, kidney, and craniofacial deformations. Many of these defects are mimicked by loss of Fras1 in mice, and are preceded by the formation of epidermal blisters in utero. RESULTS: In this study, we identified a novel ENU-derived rounded foot (rdf) mouse mutant with highly penetrant hindlimb soft-tissue syndactyly, among other structural defects. Mapping and sequencing revealed that rdf is a novel loss-of-function nonsense allele of Fras1 (Fras1(rdf)). Focusing on the limb, we found that the Fras1(rdf) syndactyly phenotype originates from loss of interdigital cell death (ICD). Despite normal expression of bone morphogenetic protein (BMP) ligands and their receptors, the BMP downstream target gene Msx2, which is also necessary and sufficient to promote ICD, was down-regulated in the interdigital regions of Fras1(rdf) hindlimb buds. CONCLUSIONS: The close correlation between limb bud epidermal blistering, decreased Msx2 expression, and reduced ICD in the Fras1(rdf) hindlimb buds suggests that epithelium detachment from the mesenchyme may create a physical gap that interrupts the transmission of BMP, among other signals, resulting in soft tissue syndactyly.
Subject(s)
Apoptosis , Extracellular Matrix Proteins/metabolism , Hindlimb/embryology , Mutation , Syndactyly/embryology , Animals , Bone Morphogenetic Proteins/genetics , Bone Morphogenetic Proteins/metabolism , Extracellular Matrix Proteins/genetics , Hindlimb/pathology , Homeodomain Proteins/genetics , Homeodomain Proteins/metabolism , Humans , Mice , Mice, Mutant Strains , Syndactyly/genetics , Syndactyly/pathologyABSTRACT
This investigation provides the first systematic determination of the cellular and molecular progression of vocal fold (VF) epithelium development in a murine model. We define five principal developmental events that constitute the progression from VF initiation in the embryonic anterior foregut tube to fully differentiated and functional adult tissue. These developmental events include (1) the initiation of the larynx and vocal folds with apposition of the lateral walls of the primitive laryngopharynx (embryonic (E) day 10.5); (2) the establishment of the epithelial lamina with fusion of the lateral walls of the primitive laryngopharynx (E11.5); (3) the epithelial lamina recanalization and separation of VFs (E13.5-18.5); (4) the stratification of the vocal folds (E13.5-18.5); and (5) the maturation of vocal fold epithelium (postnatal stages). The illustration of these morphogenetic events is substantiated by dynamic changes in cell proliferation and apoptosis, as well as the expression pattern of key transcription factors, FOXA2, SOX2 and NKX2-1 that specify and pattern the foregut endoderm. Furthermore, we documented the gradual conversion of VF epithelial cells from simple precursors expressing cytokeratins 8 and 18 in the embryo into mature stratified epithelial cells also expressing cytokeratins 5 and 14 in the adult. Interestingly, in the adult, cytokeratins 5 and 14 appear to be expressed in all cell layers in the VF, in contrast to their preferential localization to the basal cell layer in surrounding epithelium. To begin investigating the role of signaling molecules in vocal fold development, we characterized the expression pattern of SHH pathway genes, and how loss of Shh affects vocal fold development in the mutant. This study defines the cellular and molecular context and serves as the necessary foundation for future functional investigations of VF formation.
Subject(s)
Gene Expression Regulation, Developmental/physiology , Laryngeal Mucosa/embryology , Morphogenesis/physiology , Vocal Cords/embryology , Animals , Apoptosis/physiology , Cell Proliferation/physiology , Gene Expression Profiling , Gene Expression Regulation, Developmental/genetics , Hepatocyte Nuclear Factor 3-beta/metabolism , Immunohistochemistry , In Situ Hybridization , In Situ Nick-End Labeling , Mice , Nuclear Proteins/metabolism , SOXB1 Transcription Factors/metabolism , Thyroid Nuclear Factor 1 , Transcription Factors/metabolismABSTRACT
BACKGROUND: Mammalian lung development consists of a series of precisely choreographed events that drive the progression from simple lung buds to the elaborately branched organ that fulfills the vital function of gas exchange. Strict transcriptional control is essential for lung development. Among the large number of transcription factors encoded in the mouse genome, only a small portion of them are known to be expressed and function in the developing lung. Thus a systematic investigation of transcription factors expressed in the lung is warranted. RESULTS: To enrich for genes that may be responsible for regional growth and patterning, we performed a screen using RNA in situ hybridization to identify genes that show restricted expression patterns in the embryonic lung. We focused on the pseudoglandular stage during which the lung undergoes branching morphogenesis, a cardinal event of lung development. Using a genome-scale probe set that represents over 90% of the transcription factors encoded in the mouse genome, we identified 62 transcription factor genes with localized expression in the epithelium, mesenchyme, or both. Many of these genes have not been previously implicated in lung development. CONCLUSIONS: Our findings provide new starting points for the elucidation of the transcriptional circuitry that controls lung development.
Subject(s)
Gene Expression Regulation, Developmental , Lung/embryology , Lung/metabolism , Transcription Factors/genetics , Animals , Embryo, Mammalian , Gene Expression Profiling/methods , Genome/genetics , High-Throughput Screening Assays , In Situ Hybridization/methods , Mice , Morphogenesis/genetics , Respiratory Mucosa/cytology , Respiratory Mucosa/embryology , Respiratory Mucosa/metabolism , Transcription Factors/metabolismABSTRACT
Hypoglycemia is concerning for neurological complications in infants and children. Determining the cause of hypoglycemia is essential in providing appropriate treatment. Hyperinsulinism and growth hormone deficiency are known causes of hypoglycemia but are not commonly found together. We report a 4-month-old boy who presented with severe hypoglycemia and was found to have both hyperinsulinism and growth hormone deficiency. Treatment with both recombinant human growth hormone and diazoxide led to blood glucose normalization. Subsequently, he was found to have a genetic diagnosis of 20p11.22p11.21 deletion. 20p11 deletions have been associated with hypopituitarism, most commonly seen in growth hormone deficiency causing hypoglycemia. This case is one of a few to report hyperinsulinism as a manifestation of this deletion.
ABSTRACT
Though rare, pediatric high-grade gliomas (pHGG) are a leading cause of cancer-related mortality in children. We wanted to determine whether our currently available clinical laboratory methods could better define diagnosis for pHGG that had been archived at our institution for the past 20 years (1998 to 2017). We investigated 33 formalin-fixed paraffin-embedded pHGG using ThermoFisher Oncoscan SNP microarray with somatic mutation analysis, Sanger sequencing, and whole genome sequencing. These data were correlated with historical histopathological, chromosomal, clinical, and radiological data. Tumors were subsequently classified according to the 2021 WHO Classification of Paediatric CNS Tumours. All 33 tumors were found to have genetic aberrations that placed them within a 2021 WHO subtype and/or provided prognostic information; 6 tumors were upgraded from WHO CNS grade 3 to grade 4. New pHGG genetic features were found including two small cell glioblastomas with H3 G34 mutations not previously described; one tumor with STRN-NTRK2 fusion; and a congenital diffuse leptomeningeal glioneuronal tumor without a chromosomal 1p deletion but with KIAA1549-BRAF fusion. Overall, the combination of laboratory methods yielded key information for tumor classification. Thus, even small studies of these uncommon tumor types may yield new genetic features and possible new subtypes that warrant future investigations.
Subject(s)
Brain Neoplasms , Central Nervous System Neoplasms , Glioma , Child , Humans , Brain Neoplasms/genetics , Brain Neoplasms/pathology , Glioma/genetics , Glioma/pathology , Central Nervous System Neoplasms/genetics , Mutation/genetics , World Health OrganizationABSTRACT
The most recent build of the human reference genome, GRCh38, was released in 2013. However, many laboratories performing next-generation sequencing (NGS) continue to align to GRCh37. Our aim was to assess the number of clinical diagnostic laboratories that have migrated to GRCh38 and discern factors impeding migration for those still using GRCh37. A brief, five-question survey was electronically administered to 71 clinical laboratories offering constitutional NGS-based testing and analyzed categorically. Twenty-eight responses meeting inclusion criteria were collected from 24 academic and four commercial diagnostic laboratories. Most of these (14; 50%) reported volumes of <500 NGS-based tests in 2019. Only two respondents (7%) had already migrated entirely to GRCh38; most laboratories (15; 54%) had no plans to migrate. The two prevailing reasons for not yet migrating were as follows: laboratories did not feel the benefits outweighed the time and monetary costs (14; 50%); and laboratories had insufficient staff to facilitate the migration (12; 43%). These data, although limited, suggest most clinical molecular laboratories are reluctant to migrate to GRCh38, and there appear to be multiple obstacles to overcome before GRCh38 is widely adopted.
Subject(s)
Genome, Human , High-Throughput Nucleotide Sequencing/standards , Laboratories/standards , Molecular Sequence Annotation , Sequence Analysis, DNA/standards , Data Accuracy , High-Throughput Nucleotide Sequencing/methods , Humans , Reference Values , Sequence Analysis, DNA/methodsABSTRACT
BACKGROUND: There are only ten reported cases of interstitial deletions involving cytogenetic bands 10q21.3q22.2 in the literature. Of the ten patients with overlapping 10q21.3q22.2 interstitial deletions, only nine have been characterized by chromosomal microarray analysis. Here, we report a two-and-a-half-year-old patient with a de novo 10.2-Mb deletion that extends from 10q21.3 to 10q22.3 and contains 92 protein coding genes. CASE PRESENTATION: The patient is the product of a 37-week dizygotic twin pregnancy and presented with global developmental delay, hypotonia, feeding difficulties, short stature, poor weight gain, scaphocephaly, retrognathia, hypoplasia of the optic nerves/chiasms, a distinctive facial gestalt, as well as additional minor dysmorphic features. The deletion identified in our patient is the second largest reported interstitial deletion involving the 10q21.3q22.2 region. Our patient presents with the generalized features observed in 10q21.3q22.2 deletion patients and also presents with several novel findings including scaphocephaly, hypoplasia of the optic nerves and chiasms, and a very distinctive facial gestalt. CONCLUSIONS: Based on a literature review, we identify a commonly deleted region and suggest that KAT6B is a critical gene within the 10q21.3q22.2 region. However, a review of the reported overlapping deletions also suggests that there are additional critical genes contributing to the clinical presentation of these patients.
ABSTRACT
To date, 13 patients with interstitial microduplications involving Xq25q26.2 have been reported. Here, we report 6 additional patients from 2 families with duplications involving Xq25q26.2. Family I carries a 5.3-Mb duplication involving 26 genes. This duplication was identified in 3 patients and was associated with microcephaly, growth failure, developmental delay, and dysmorphic features. Family II carries an overlapping 791-kb duplication that involves 3 genes. This duplication was identified in 3 patients and was associated with learning disability and speech delay. The size and gene content of published overlapping Xq25q26.2 duplications vary, making it difficult to define a critical region or establish a genotype-phenotype correlation. However, patients with overlapping duplications have been found to share common clinical features including microcephaly, growth failure, intellectual disability, learning difficulties, and dysmorphic features. The 2 families presented here provide additional insight into the phenotypic spectrum and clinical significance of duplications in this region.
Subject(s)
Abnormalities, Multiple/genetics , Chromosome Duplication , Chromosomes, Human, X , Developmental Disabilities/genetics , Intellectual Disability/genetics , Microcephaly/genetics , Phenotype , Child , Child, Preschool , Female , Humans , Language Development Disorders/genetics , Male , PedigreeABSTRACT
DICER1 encodes an RNase III endonuclease protein that regulates the production of small non-coding RNAs. Germline mutations in DICER1 are associated with an autosomal dominant hereditary cancer predisposition syndrome that confers an increased risk for the development of several rare childhood and adult-onset tumors, the most frequent of which include pleuropulmonary blastoma, ovarian sex cord-stromal tumors, cystic nephroma, and thyroid gland neoplasia. The majority of reported germline DICER1 mutations are truncating sequence-level alterations, suggesting that a loss-of-function type mechanism drives tumor formation in DICER1 syndrome. However, reports of patients with germline DICER1 whole gene deletions are limited, and thus far, only two have reported an association with tumor development. Here we report the clinical findings of three patients from two unrelated families with 14q32 deletions that encompass the DICER1 locus. The deletion identified in Family I is 1.4â¯Mb and was initially identified in a 6-year-old male referred for developmental delay, hypotonia, macrocephaly, obesity, and behavioral problems. Subsequent testing revealed that this deletion was inherited from his mother, who had a clinical history that included bilateral multinodular goiter and papillary thyroid carcinoma. The second deletion is 5.0â¯Mb and was identified in a 15-year-old female who presented with autism, coarse facial features, Sertoli-Leydig cell tumor, and Wilms' tumor. These findings provide additional supportive evidence that germline deletion of DICER1 confers an increased risk for DICER1-related tumor development, and provide new insight into the clinical significance of deletions involving the 14q32 region.
Subject(s)
Chromosome Deletion , Chromosome Disorders/genetics , Chromosomes, Human, Pair 14/genetics , DEAD-box RNA Helicases/genetics , Developmental Disabilities/genetics , Neoplasms/genetics , Ribonuclease III/genetics , Adolescent , Adult , Child , Chromosome Disorders/pathology , Developmental Disabilities/pathology , Female , Humans , Male , Neoplasms/pathology , Pedigree , SyndromeABSTRACT
We report an 8-year-old female with autism spectrum disorder (ASD), intellectual disability and speech delay who was found to carry a de novo 82 kb deletion of chromosome Xq11.1-11.2 involving the ARHGEF9 gene on chromosomal microarray. So far, 11 patients with point mutations, disruptions due to chromosomal rearrangements and deletions involving ARHGEF9 have been reported in the literature. ARHGEF9-related disorders comprise a wide phenotypic spectrum, including behavior disorders, autism spectrum disorder, intellectual disability, hyperekplexia and infantile epileptic encephalopathy. ARHGEF9 encodes for collybistin which plays an important role in post synaptic clustering of glycine and inhibitory gamma-aminobutyric acid receptors along with its scaffolding partner, gephyrin. The reduction of inhibitory receptor clusters in brain has been proposed as a plausible underlying pathophysiological mechanism. With this report, we provide further evidence for the role of ARHGEF9 in neurocognitive function, its implication in ASD, and review the clinical features of previously published individuals with ARHGEF9-related intellectual disability.
Subject(s)
Autism Spectrum Disorder/genetics , Chromosomes, Human, X , Rho Guanine Nucleotide Exchange Factors/genetics , Child , Chromosome Deletion , Female , Humans , Infant, Newborn , PregnancyABSTRACT
The mammalian lung forms its elaborate tree-like structure following a largely stereotypical branching sequence. While a number of genes have been identified to play essential roles in lung branching, what coordinates the choice between branch growth and new branch formation has not been elucidated. Here we show that loss of FGF-activated transcription factor genes, Etv4 and Etv5 (collectively Etv), led to prolonged branch tip growth and delayed new branch formation. Unexpectedly, this phenotype is more similar to mutants with increased rather than decreased FGF activity. Indeed, an increased Fgf10 expression is observed, and reducing Fgf10 dosage can attenuate the Etv mutant phenotype. Further evidence indicates that ETV inhibits Fgf10 via directly promoting Shh expression. SHH in turn inhibits local Fgf10 expression and redirects growth, thereby initiating new branches. Together, our findings establish ETV as a key node in the FGF-ETV-SHH inhibitory feedback loop that dictates branching periodicity.
Subject(s)
Gene Expression Regulation, Developmental/genetics , Lung/metabolism , Proto-Oncogene Proteins c-ets/metabolism , Transcription Factors/metabolism , Animals , Body Patterning/genetics , Fibroblast Growth Factor 10/metabolism , Hedgehog Proteins/metabolism , Mice , Mice, Transgenic , Morphogenesis/genetics , Signal Transduction/geneticsABSTRACT
BACKGROUND: G protein-coupled receptors (GPCRs) play central roles in mediating cellular responses to environmental signals leading to changes in cell physiology and behaviors, including cell migration. Numerous clinical pathologies including metastasis, an invasive form of cell migration, have been linked to abnormal GPCR signaling. While the structures of some GPCRs have been defined, the in vivo roles of conserved amino acid residues and their relationships to receptor function are not fully understood. Trapped in endoderm 1 (Tre1) is an orphan receptor of the rhodopsin class that is necessary for primordial germ cell migration in Drosophila melanogaster embryos. In this study, we employ molecular genetic approaches to identify residues in Tre1 that are critical to its functions in germ cell migration. METHODOLOGY/PRINCIPAL FINDINGS: First, we show that the previously reported scattershot mutation is an allele of tre1. The scattershot allele results in an in-frame deletion of 8 amino acids at the junction of the third transmembrane domain and the second intracellular loop of Tre1 that dramatically impairs the function of this GPCR in germ cell migration. To further refine the molecular basis for this phenotype, we assayed the effects of single amino acid substitutions in transgenic animals and determined that the arginine within the evolutionarily conserved E/N/DRY motif is critical for receptor function in mediating germ cell migration within an intact developing embryo. CONCLUSIONS/SIGNIFICANCE: These structure-function studies of GPCR signaling in native contexts will inform future studies into the basic biology of this large and clinically important family of receptors.