Novel GJA1/Cx43 Variant Associated With Oculo-Dento-Digital Dysplasia Syndrome: Clinical Phenotype and Cellular Mechanisms.
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ABSTRACT:
SUBMITTER: Sargiannidou I
PROVIDER: S-EPMC7873484 | biostudies-literature | 2020
REPOSITORIES: biostudies-literature
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Novel <i>GJA1/Cx43</i> Variant Associated With Oculo-Dento-Digital Dysplasia Syndrome: Clinical Phenotype and Cellular Mechanisms.
Sargiannidou Irene I Christophidou-Anastasiadou Violetta V Hadjisavvas Andreas A Tanteles George A GA Kleopa Kleopas A KA
Frontiers in genetics 20210127
Oculodentodigital dysplasia syndrome is associated with numerous pathogenic variants in <i>GJA1</i>, the gene encoding connexin43 gap junction protein. A novel in-frame deletion (p.Lys134del) was found in our clinic. The patient showed all the typical dysmorphic features of the syndrome. The functional consequences of this variant were also studied in an <i>in vitro</i> system. Cells expressed significantly less number of gap junction plaques with a great number of them retained intracellularly. ...[more]
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Project description:IntroductionOculo-dento-digital dysplasia (ODDD, OMIM# 164200) is a rare genetic disorder caused by mutation in Gap junction alpha gene that encodes connexin 43 (Cx43) protein. In this paper, the case of a 16-year-old boy is reported who presented with the complaint of toothache. Examination revealed unusual facial features, i.e., long narrow nose, hypertelorism, prominent epicanthal folds along with syndactyly and camptodactyly. We have also compiled available dental literature on ODDD that will help clinicians in early diagnosis and management of this condition.Materials and methodsA literature search was performed in PubMed NLM, EBSCO Dentistry & Oral Sciences Source, and EBSCO CINAHL Plus.ResultsA total of 309 articles were identified in the literature search. Only 17 articles were included based on the predetermined inclusion and exclusion criteria in the review synthesis. The included articles were case reports (n = 15), a case report and review (n = 1), and an original article (n = 1). Enamel hypoplasia, hypomineralization, microdontia, pulp stones, curved roots, and taurodontism were common dental findings in ODDD.ConclusionsAfter establishing definitive diagnosis, a multidisciplinary team should work in cohesion to improve the quality of life of patients. Immediate treatment should be focused on the correction of current oral condition and symptomatic treatment. In the long term, attention should be diverted to prevent tooth wear and maintaining the occlusal vertical dimension to establish adequate function.
| S-EPMC10060216 | biostudies-literature
Project description:Gap junctions are assemblies of intercellular channels that regulate a variety of physiologic and developmental processes through the exchange of small ions and signaling molecules. These channels consist of connexin family proteins that allow for diversity of channel composition and conductance properties. The human connexin 43 gene, or GJA1, is located at human chromosome 6q22-q23 within the candidate region for the oculodentodigital dysplasia locus. This autosomal dominant syndrome presents with craniofacial (ocular, nasal, and dental) and limb dysmorphisms, spastic paraplegia, and neurodegeneration. Syndactyly type III and conductive deafness can occur in some cases, and cardiac abnormalities are observed in rare instances. We found mutations in the GJA1 gene in all 17 families with oculodentodigital dysplasia that we screened. Sixteen different missense mutations and one codon duplication were detected. These mutations may cause misassembly of channels or alter channel conduction properties. Expression patterns and phenotypic features of gja1 animal mutants, reported elsewhere, are compatible with the pleiotropic clinical presentation of oculodentodigital dysplasia.
| S-EPMC379233 | biostudies-literature
Project description:Connexin 43 (Cx43, encoded by GJA1) is a cell-cell communication gap junction protein expressed in all organ systems. It was recently found that GJA1 mRNA undergoes alternative translation to generate N-terminal truncated isoforms, of which GJA1-20k is the most abundant. Here we report a surprising finding that, unlike full length GJA1-43k, GJA1-20k has a strong tropism for mitochondria. Exploring function, we found that GJA1-20k appears to be an organelle chaperone and that overexpression of GJA1-20k is sufficient to rescue mitochondrial localization to the cell periphery upon exposure to hydrogen peroxide, which effectively limits the network fragmentation that occurs with oxidative stress. By high-resolution fluorescent imaging and electron microscopy, we determined that GJA1-20k is enriched at the interface between mitochondria and microtubules, appearing to load organelles for transport. Mutagenesis experiments revealed that although the microtubule-binding domain (MTBD) in GJA1-20k is not necessary for protein localization to mitochondria, the MTBD is essential for GJA1-20k to facilitate mitochondrial transport and maintain mitochondrial localization at the periphery. These results reveal an unexpected role for the alternatively translated isoform of the Cx43 gap junction protein, GJA1-20k, which is to facilitate microtubule-based mitochondrial transport and to maintain mitochondrial network integrity during cellular stress.
| S-EPMC5682029 | biostudies-literature
Project description:BackgroundOculodentodigital dysplasia (ODDD) is a rare disorder with pleiotropic effects involving multiple body systems, caused by mutations in the gap junction protein alpha 1 (GJA1) gene. GJA1 gene encodes a polytopic connexin membrane protein, Cx43, that is a component of connexon membrane channels.MethodsWe describe two unrelated female probands referred for a genetic review in view of a dysmorphic clinical phenotype.ResultsTwo novel missense mutations in GJA1 that substitute conserved amino acids in the first and second transmembrane domains (NM_000165.5: c.77T>C p.Leu26Pro and NM_000165.5:c.287T>G p.Val96Gly) were detected through targeted sequencing of GJA1. These variants were detected in the heterozygous state in the two Maltese probands and segregated with the disease phenotype.ConclusionThis report further expands the mutational spectrum of ODDD.
| S-EPMC6732303 | biostudies-literature
Project description:RationaleDelivery of Cx43 (connexin 43) to the intercalated disc is a continuous and rapid process critical for intercellular coupling. By a pathway of targeted delivery involving microtubule highways, vesicles of Cx43 hemichannels are efficiently trafficked to adherens junctions at intercalated discs. It has also been identified that actin provides rest stops for Cx43 forward trafficking and that Cx43 has a 20 kDa internally translated small C terminus isoform, GJA1-20k (Gap Junction Protein Alpha 1- 20 kDa), which is required for full-length Cx43 trafficking, but by an unknown mechanism.ObjectiveWe explored the mechanism by which the GJA1-20k isoform is required for full-length Cx43 forward trafficking to intercalated discs.Methods and resultsUsing an in vivo Adeno-associated virus serotype 9-mediated gene transfer system, we confirmed in whole animal that GJA1-20k markedly increases endogenous myocardial Cx43 gap junction plaque size at the intercalated discs. In micropatterned cell pairing systems, we found that exogenous GJA1-20k expression stabilizes filamentous actin without affecting actin protein expression and that GJA1-20k complexes with both actin and tubulin. We also found that filamentous actin regulates microtubule organization as inhibition of actin polymerization with a low dose of latrunculin A disrupts the targeting of microtubules to cell-cell junctions. GJA1-20k protects actin filament from latrunculin A disruption, preserving microtubule trajectory to the cell-cell border. For therapeutic implications, we found that prior in vivo Adeno-associated virus serotype 9-mediated gene delivery of GJA1-20k to the heart protects Cx43 localization to the intercalated discs against acute ischemic injury.ConclusionsThe internally translated GJA1-20k isoform stabilizes actin filaments, which guides growth trajectories of the Cx43 microtubule trafficking machinery, increasing delivery of Cx43 hemichannels to cardiac intercalated discs. Exogenous GJA1-20k helps to maintain cell-cell coupling in instances of anticipated myocardial ischemia.
| S-EPMC5790189 | biostudies-literature
Project description:Connexin family proteins assemble into hexameric hemichannels in the cell membrane. The hemichannels dock together between two adjacent membranes to form gap junction intercellular channels (GJIChs). We report the cryo-electron microscopy structures of Cx43 GJICh, revealing the dynamic equilibrium state of various channel conformations in detergents and lipid nanodiscs. We identify three different N-terminal helix conformations of Cx43-gate-covering (GCN), pore-lining (PLN), and flexible intermediate (FIN)-that are randomly distributed in purified GJICh particles. The conformational equilibrium shifts to GCN by cholesteryl hemisuccinates and to PLN by C-terminal truncations and at varying pH. While GJIChs that mainly comprise GCN protomers are occluded by lipids, those containing conformationally heterogeneous protomers show markedly different pore sizes. We observe an α-to-π-helix transition in the first transmembrane helix, which creates a side opening to the membrane in the FIN and PLN conformations. This study provides basic structural information to understand the mechanisms of action and regulation of Cx43 GJICh.
| S-EPMC9938869 | biostudies-literature
Project description:Craniometaphyseal dysplasia (CMD) is a rare sclerosing skeletal disorder with progressive hyperostosis of craniofacial bones. CMD can be inherited in an autosomal dominant (AD) trait or occur after de novo mutations in the pyrophosphate transporter ANKH. Although the autosomal recessive (AR) form of CMD had been mapped to 6q21-22 the mutation has been elusive. In this study, we performed whole-exome sequencing for one subject with AR CMD and identified a novel missense mutation (c.716G>A, p.Arg239Gln) in the C-terminus of the gap junction protein alpha-1 (GJA1) coding for connexin 43 (Cx43). We confirmed this mutation in 6 individuals from 3 additional families. The homozygous mutation cosegregated only with affected family members. Connexin 43 is a major component of gap junctions in osteoblasts, osteocytes, osteoclasts and chondrocytes. Gap junctions are responsible for the diffusion of low molecular weight molecules between cells. Mutations in Cx43 cause several dominant and recessive disorders involving developmental abnormalities of bone such as dominant and recessive oculodentodigital dysplasia (ODDD; MIM #164200, 257850) and isolated syndactyly type III (MIM #186100), the characteristic digital anomaly in ODDD. However, characteristic ocular and dental features of ODDD as well as syndactyly are absent in patients with the recessive Arg239Gln Cx43 mutation. Bone remodeling mechanisms disrupted by this novel Cx43 mutation remain to be elucidated.
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Project description:Human skeletal progenitors were engineered to stably express R201C mutated, constitutively active Gs alpha using lentiviral vectors. Long-term transduced skeletal progenitors were characterized by an enhanced production of cAMP, indicating the transfer of the fundamental cellular phenotype caused by activating mutations of Gs alpha. Like skeletal progenitors isolated from natural fibrous dysplasia (FD) lesions, transduced cells could generate bone but not adipocytes or the hematopoietic microenvironment on in vivo transplantation. In vitro osteogenic differentiation was noted for the lack of mineral deposition, a blunted upregulation of osteocalcin, and enhanced upregulation of other osteogenic markers such as alkaline phosphatase (ALP) and bone sialoprotein (BSP) compared with controls. A very potent upregulation of RANKL expression was observed, which correlates with the pronounced osteoclastogenesis observed in FD lesions in vivo. Stable transduction resulted in a marked upregulation of selected phosphodiesterase (PDE) isoform mRNAs and a prominent increase in total PDE activity. This predicts an adaptive response in skeletal progenitors transduced with constitutively active, mutated Gs alpha. Indeed, like measurable cAMP levels, the differentiative responses of transduced skeletal progenitors were profoundly affected by inhibition of PDEs or lack thereof. Finally, using lentiviral vectors encoding short hairpin (sh) RNA interfering sequences, we demonstrated that selective silencing of the mutated allele is both feasible and effective in reverting the aberrant cAMP production brought about by the constitutively active Gs alpha and some of its effects on in vitro differentiation of skeletal progenitors.
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Project description:Progressive pseudorheumatoid dysplasia (PPRD) is a rare, autosomal-recessive condition characterized by mild spondyloepiphyseal dysplasia (SED) and severe, progressive, early-onset arthritis due to WISP3 mutations. SED, Stanescu type, is a vaguely delineated autosomal-dominant dysplasia of unknown genetic etiology. Here, we report three individuals from two unrelated families with radiological features similar to PPRD and SED, Stanescu type who share the same novel COL2A1 variant and were matched following discussion at an academic conference. In the first family, we performed whole-exome sequencing on three family members, two of whom have a PPRD-like phenotype, and identified a heterozygous variant (c.619G>A, p.Gly207Arg) in both affected individuals. Independently, targeted sequencing of the COL2A1 gene in an unrelated proband with a similar phenotype identified the same heterozygous variant. We suggest that the p.Gly207Arg variant causes a distinct type II collagenopathy with features of PPRD and SED, Stanescu type.
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Project description:BACKGROUND:Autosomal dominant anhidrotic ectodermal dysplasia with immune deficiency (AD EDA-ID) is caused by heterozygous point mutations at or close to serine 32 and serine 36 or N-terminal truncations in I?B? that impair its phosphorylation and degradation and thus activation of the canonical nuclear factor ? light chain enhancer of activated B cells (NF-?B) pathway. The outcome of hematopoietic stem cell transplantation is poor in patients with AD EDA-ID despite achievement of chimerism. Mice heterozygous for the serine 32I mutation in I?B? have impaired noncanonical NF-?B activity and defective lymphorganogenesis. OBJECTIVE:We sought to establish genotype-phenotype correlation in patients with AD EDA-ID. METHODS:A disease severity scoring system was devised. Stability of I?B? mutants was examined in transfected cells. Immunologic, biochemical, and gene expression analyses were performed to evaluate canonical and noncanonical NF-?B signaling in skin-derived fibroblasts. RESULTS:Disease severity was greater in patients with I?B? point mutations than in those with truncation mutations. I?B? point mutants were expressed at significantly higher levels in transfectants compared with truncation mutants. Canonical NF-?B-dependent IL-6 secretion and upregulation of the NF-?B subunit 2/p100 and RELB proto-oncogene, NF-?B subunit (RelB) components of the noncanonical NF-?B pathway were diminished significantly more in patients with point mutations compared with those with truncations. Noncanonical NF-?B-driven generation of the transcriptionally active p100 cleavage product p52 and upregulation of CCL20, intercellular adhesion molecule 1 (ICAM1), and vascular cell adhesion molecule 1 (VCAM1), which are important for lymphorganogenesis, were diminished significantly more in LPS plus ?-lymphotoxin ? receptor-stimulated fibroblasts from patients with point mutations compared with those with truncations. CONCLUSIONS:I?B? point mutants accumulate at higher levels compared with truncation mutants and are associated with more severe disease and greater impairment of canonical and noncanonical NF-?B activity in patients with AD EDA-ID.
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