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1.
Nat Commun ; 11(1): 2813, 2020 06 04.
Artigo em Inglês | MEDLINE | ID: mdl-32499479

RESUMO

5'-aminolevulinate synthase (ALAS) catalyzes the first step in heme biosynthesis, generating 5'-aminolevulinate from glycine and succinyl-CoA. Inherited frameshift indel mutations of human erythroid-specific isozyme ALAS2, within a C-terminal (Ct) extension of its catalytic core that is only present in higher eukaryotes, lead to gain-of-function X-linked protoporphyria (XLP). Here, we report the human ALAS2 crystal structure, revealing that its Ct-extension folds onto the catalytic core, sits atop the active site, and precludes binding of substrate succinyl-CoA. The Ct-extension is therefore an autoinhibitory element that must re-orient during catalysis, as supported by molecular dynamics simulations. Our data explain how Ct deletions in XLP alleviate autoinhibition and increase enzyme activity. Crystallography-based fragment screening reveals a binding hotspot around the Ct-extension, where fragments interfere with the Ct conformational dynamics and inhibit ALAS2 activity. These fragments represent a starting point to develop ALAS2 inhibitors as substrate reduction therapy for porphyria disorders that accumulate toxic heme intermediates.


Assuntos
5-Aminolevulinato Sintetase/química , Regulação Enzimológica da Expressão Gênica , 5-Aminolevulinato Sintetase/deficiência , 5-Aminolevulinato Sintetase/genética , Acil Coenzima A/química , Catálise , Domínio Catalítico , Cristalografia por Raios X , Doenças Genéticas Ligadas ao Cromossomo X/genética , Heme/química , Humanos , Cinética , Simulação de Dinâmica Molecular , Ligação Proteica , Conformação Proteica , Domínios Proteicos , Protoporfiria Eritropoética/genética , Especificidade por Substrato
2.
Eur J Endocrinol ; 183(2): R29-R40, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32580146

RESUMO

For an endocrinologist, nephrogenic diabetes insipidus (NDI) is an end-organ disease, that is the antidiuretic hormone, arginine-vasopressin (AVP) is normally produced but not recognized by the kidney with an inability to concentrate urine despite elevated plasma concentrations of AVP. Polyuria with hyposthenuria and polydipsia are the cardinal clinical manifestations of the disease. For a geneticist, hereditary NDI is a rare disease with a prevalence of five per million males secondary to loss of function of the vasopressin V2 receptor, an X-linked gene, or loss of function of the water channel AQP2. These are small genes, easily sequenced, with a number of both recurrent and private mutations described as disease causing. Other inherited disorders with mild, moderate or severe inability to concentrate urine include Bartter's syndrome and cystinosis. MAGED2 mutations are responsible for a transient form of Bartter's syndrome with severe polyhydramnios. The purpose of this review is to describe classical phenotype findings that will help physicians to identify early, before dehydration episodes with hypernatremia, patients with familial NDI. A number of patients are still diagnosed late with repeated dehydration episodes and large dilations of the urinary tract leading to a flow obstructive nephropathy with progressive deterioration of glomerular function. Families with ancestral X-linked AVPR2 mutations could be reconstructed and all female heterozygote patients identified with subsequent perinatal genetic testing to recognize affected males within 2 weeks of birth. Prevention of dehydration episodes is of critical importance in early life and beyond and decreasing solute intake will diminish total urine output.


Assuntos
Diabetes Insípido Nefrogênico/genética , Diabetes Insípido Nefrogênico/fisiopatologia , Desidratação/prevenção & controle , Diabetes Insípido Nefrogênico/terapia , Feminino , Triagem de Portadores Genéticos , Doenças Genéticas Ligadas ao Cromossomo X/genética , Testes Genéticos , Humanos , Hipernatremia , Recém-Nascido , Glomérulos Renais/fisiopatologia , Masculino , Mutação , Neurofisinas/sangue , Neurofisinas/fisiologia , Concentração Osmolar , Gravidez , Diagnóstico Pré-Natal , Precursores de Proteínas/sangue , Precursores de Proteínas/fisiologia , Receptores de Vasopressinas/genética , Receptores de Vasopressinas/fisiologia , Vasopressinas/sangue , Vasopressinas/fisiologia
5.
Invest Ophthalmol Vis Sci ; 61(5): 41, 2020 05 11.
Artigo em Inglês | MEDLINE | ID: mdl-32446246

RESUMO

Purpose: To identify the pathogenic gene of infantile nystagmus syndrome (INS) in three Chinese families and explore the potential pathogenic mechanism of FERM domain-containing 7 (FRMD7) mutations. Methods: Genetic testing was performed via Sanger sequencing. Western blotting was used to analyze protein expression of FRMD7. Glutathione S-transferase pull-down and immunoprecipitation were conducted to investigate the proteins interacting with FRMD7. Rescue assays were performed in Caenorhabditis elegans to explore the potential role of FRMD7 in vivo. Results: We recruited three Chinese families with X-linked INS and identified a duplication and two missense mutations in FRMD7: c.998dupA/p.His333Glnfs*2, c.580G>A/p.Ala194Thr, and c.973A>G/p.Arg325Gly (one in each family). Expression levels of three mutants were similar to that of wild-type FRMD7 in vitro. Interestingly, the mutant p.His333Glnfs*2 exhibited a predominantly nuclear location, whereas wild-type FRMD7 localized to the cytoplasm. In addition, we found FRMD7 to directly interact with the loop between transmembrane domains 3 and 4 of GABRA2, a type A gamma-aminobutyric acid (GABA) receptor (GABAARs) subunit critical for receptor transport and localization, whereas the mutants p.Ala194Thr and p.Arg325Gly exhibited decreased binding to GABRA2. In frm-3 (a nematode homologue of FRMD7) null C. elegans, we found that FRMD7 mutants exhibited a poor rescue effect on the defects of locomotion and fluorescence recovery after photobleaching of GABAARs. Conclusions: Our findings identified three FRMD7 mutants in three Chinese families with X-linked INS and confirmed GABRA2 as a novel binding partner of FRMD7. These findings suggest that FRMD7 plays an important role by targeting GABAARs.


Assuntos
Proteínas do Citoesqueleto/genética , Doenças Genéticas Ligadas ao Cromossomo X/genética , Proteínas de Membrana/genética , Mutação , Nistagmo Congênito/genética , Domínios e Motivos de Interação entre Proteínas/genética , Receptores de GABA-A/metabolismo , Animais , Grupo com Ancestrais do Continente Asiático/genética , Western Blotting , Células COS , Caenorhabditis elegans/genética , Proteínas de Caenorhabditis elegans/genética , Células Cultivadas , China/epidemiologia , Chlorocebus aethiops , Proteínas do Citoesqueleto/metabolismo , Análise Mutacional de DNA , Feminino , Doenças Genéticas Ligadas ao Cromossomo X/metabolismo , Testes Genéticos , Humanos , Imunoprecipitação , Masculino , Proteínas de Membrana/metabolismo , Nistagmo Congênito/metabolismo , Linhagem , Plasmídeos/genética
6.
Am J Hum Genet ; 106(6): 859-871, 2020 06 04.
Artigo em Inglês | MEDLINE | ID: mdl-32470375

RESUMO

Congenital cone-rod synaptic disorder (CRSD), also known as incomplete congenital stationary night blindness (iCSNB), is a non-progressive inherited retinal disease (IRD) characterized by night blindness, photophobia, and nystagmus, and distinctive electroretinographic features. Here, we report bi-allelic RIMS2 variants in seven CRSD-affected individuals from four unrelated families. Apart from CRSD, neurodevelopmental disease was observed in all affected individuals, and abnormal glucose homeostasis was observed in the eldest affected individual. RIMS2 regulates synaptic membrane exocytosis. Data mining of human adult bulk and single-cell retinal transcriptional datasets revealed predominant expression in rod photoreceptors, and immunostaining demonstrated RIMS2 localization in the human retinal outer plexiform layer, Purkinje cells, and pancreatic islets. Additionally, nonsense variants were shown to result in truncated RIMS2 and decreased insulin secretion in mammalian cells. The identification of a syndromic stationary congenital IRD has a major impact on the differential diagnosis of syndromic congenital IRD, which has previously been exclusively linked with degenerative IRD.


Assuntos
Oftalmopatias Hereditárias/genética , Proteínas de Ligação ao GTP/genética , Doenças Genéticas Ligadas ao Cromossomo X/genética , Mutação com Perda de Função , Miopia/genética , Proteínas do Tecido Nervoso/genética , Cegueira Noturna/genética , Adulto , Alelos , Processamento Alternativo , Encéfalo/metabolismo , Linhagem Celular , Criança , Pré-Escolar , Diagnóstico Diferencial , Saúde da Família , Feminino , França , Proteínas de Ligação ao GTP/química , Proteínas de Ligação ao GTP/metabolismo , Glucose/metabolismo , Humanos , Secreção de Insulina , Masculino , Proteínas do Tecido Nervoso/química , Proteínas do Tecido Nervoso/metabolismo , Pâncreas/metabolismo , Linhagem , Retina/metabolismo , Arábia Saudita , Senegal
7.
Hum Genet ; 139(8): 1057-1064, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32248360

RESUMO

Congenital motor nystagmus (CMN) is characterized by early-onset bilateral ocular oscillations without other ocular deficits. To date, mutations in only one gene have been identified to be responsible for CMN, i.e., FRMD7 for X-linked CMN. Four loci for autosomal dominant CMN, including NYS7 (OMIM 614826), have been mapped but the causative genes have yet to be identified. NYS7 was mapped to 1q32.1 based on independent genome-wide linkage scan on two large families with CMN. In this study, mutations in all known protein-coding genes, both intronic sequence with predicted effect and coding sequence, in the linkage interval were excluded by whole-genome sequencing. Then, long-read genome sequencing based on the Nanopore platform was performed with a sample from each of the two families. Two deletions with an overlapping region of 775,699 bp, located in a region without any known protein-coding genes, were identified in the two families in the linkage region. The two deletions as well as their breakpoints were confirmed by Sanger sequencing and co-segregated with CMN in the two families. The 775,699 bp deleted region contains uncharacterized non-protein-coding expressed sequences and pseudogenes but no protein-coding genes. However, Hi-C data predicted that the deletions span two topologically associated domains and probably lead to a change in the 3D genomic architecture. These results provide novel evidence of a strong association between structural variations in non-coding genomic regions and human hereditary diseases like CMN with a potential mechanism involving changes in 3D genome architecture, which provides clues regarding the molecular pathogenicity of CMN.


Assuntos
Doenças Genéticas Ligadas ao Cromossomo X/genética , Variação Estrutural do Genoma/genética , Nistagmo Congênito/genética , Mapeamento Cromossômico , Proteínas do Citoesqueleto/genética , Feminino , Deleção de Genes , Ligação Genética , Humanos , Masculino , Proteínas de Membrana/genética , Mutação , Linhagem , Sequenciamento Completo do Genoma
8.
Invest Ophthalmol Vis Sci ; 61(3): 11, 2020 03 09.
Artigo em Inglês | MEDLINE | ID: mdl-32176262

RESUMO

Purpose: To define remodeling of photoreceptor synaptic terminals and second-order retinal neurons in canine X-linked progressive retinal atrophy 1 caused by a five-nucleotide deletion in the RPGR exon ORF15. Methods: Retinas of normal and mutant dogs were used for gene expression, Western blot, and immunohistochemistry. Cell-specific markers were used to examine disease-dependent retinal remodeling. Results: In mutant retinas, a number of rod axon terminals retract into the outer nuclear layer. This neuritic atrophy preceded significant loss of rods and was evident early in disease. Rod bipolar and horizontal cell processes were found to extend into the outer nuclear layer, where they seemed to form contacts with the spherules of rod photoreceptors. No ectopic rewiring was observed. Because cytoskeletal reorganization was previously shown to underlie photoreceptor axon retraction, we examined normal and mutant retinas for expression of axon guidance receptors ROBO1 and ROBO2, which are known to regulate actin cytoskeleton dynamics. We found that the overall expression of both ROBO1 and ROBO2 is retained at the same level in premature and fully developed normal retinas. However, analysis of predisease and early disease retinas identified markedly decreased levels of ROBO1 in rod spherules compared with controls. In contrast, no differences in ROBO1 signals were noted in cone pedicles in normal and mutant retinas, where ROBO1 levels remained similarly low. Conclusions: Depletion of ROBO1 in rod synaptic terminals correlates with the remodeling of axonal and dendritic processes in the outer retina of dogs with X-linked progressive retinal atrophy 1 and may play a role in the retraction of rod axons.


Assuntos
Doenças do Cão/metabolismo , Doenças Genéticas Ligadas ao Cromossomo X/metabolismo , Proteínas do Tecido Nervoso/metabolismo , Terminações Pré-Sinápticas/metabolismo , Receptores Imunológicos/metabolismo , Degeneração Retiniana/metabolismo , Animais , Orientação de Axônios/fisiologia , Axônios/patologia , Doenças do Cão/genética , Doenças do Cão/patologia , Cães , Proteínas do Olho/genética , Proteínas do Olho/metabolismo , Doenças Genéticas Ligadas ao Cromossomo X/genética , Doenças Genéticas Ligadas ao Cromossomo X/patologia , Doenças Genéticas Ligadas ao Cromossomo X/veterinária , Microscopia Confocal , Proteínas do Tecido Nervoso/deficiência , Plasticidade Neuronal/fisiologia , Terminações Pré-Sinápticas/patologia , Receptores Imunológicos/deficiência , Retina/metabolismo , Degeneração Retiniana/genética , Degeneração Retiniana/patologia , Degeneração Retiniana/veterinária , Neurônios Retinianos/metabolismo , Neurônios Retinianos/patologia , Células Fotorreceptoras Retinianas Bastonetes/metabolismo , Células Fotorreceptoras Retinianas Bastonetes/patologia
10.
BMC Med Genet ; 21(1): 38, 2020 02 21.
Artigo em Inglês | MEDLINE | ID: mdl-32085749

RESUMO

BACKGROUND: Prune belly syndrome (PBS) is a rare, multi-system congenital myopathy primarily affecting males that is poorly described genetically. Phenotypically, its morbidity spans from mild to lethal, however, all isolated PBS cases manifest three cardinal pathological features: 1) wrinkled flaccid ventral abdominal wall with skeletal muscle deficiency, 2) urinary tract dilation with poorly contractile smooth muscle, and 3) intra-abdominal undescended testes. Despite evidence for a genetic basis, previously reported PBS autosomal candidate genes only account for one consanguineous family and single cases. METHODS: We performed whole exome sequencing (WES) of two maternal adult half-brothers with syndromic PBS (PBS + Otopalatodigital spectrum disorder [OPDSD]) and two unrelated sporadic individuals with isolated PBS and further functionally validated the identified mutations. RESULTS: We identified three unreported hemizygous missense point mutations in the X-chromosome gene Filamin A (FLNA) (c.4952 C > T (p.A1448V), c.6727C > T (p.C2160R), c.5966 G > A (p.G2236E)) in two related cases and two unrelated sporadic individuals. Two of the three PBS mutations map to the highly regulatory, stretch-sensing Ig19-21 region of FLNA and enhance binding to intracellular tails of the transmembrane receptor ß-integrin 1 (ITGß1). CONCLUSIONS: FLNA is a regulatory actin-crosslinking protein that functions in smooth muscle cells as a mechanosensing molecular scaffold, transmitting force signals from the actin-myosin motor units and cytoskeleton via binding partners to the extracellular matrix. This is the first evidence for an X-linked cause of PBS in multiple unrelated individuals and expands the phenotypic spectrum associated with FLNA in males surviving even into adulthood.


Assuntos
Filaminas/genética , Genes Ligados ao Cromossomo X/genética , Doenças Genéticas Ligadas ao Cromossomo X/genética , Síndrome do Abdome em Ameixa Seca/genética , Adulto , Doenças Genéticas Ligadas ao Cromossomo X/fisiopatologia , Predisposição Genética para Doença , Genótipo , Hemizigoto , Humanos , Masculino , Pessoa de Meia-Idade , Mutação de Sentido Incorreto/genética , Linhagem , Fenótipo , Síndrome do Abdome em Ameixa Seca/fisiopatologia , Sequenciamento Completo do Exoma
12.
Proc Natl Acad Sci U S A ; 117(8): 4262-4272, 2020 02 25.
Artigo em Inglês | MEDLINE | ID: mdl-32041873

RESUMO

Long thought to be dispensable after establishing X chromosome inactivation (XCI), Xist RNA is now known to also maintain the inactive X (Xi). To what extent somatic X reactivation causes physiological abnormalities is an active area of inquiry. Here, we use multiple mouse models to investigate in vivo consequences. First, when Xist is deleted systemically in post-XCI embryonic cells using the Meox2-Cre driver, female pups exhibit no morbidity or mortality despite partial X reactivation. Second, when Xist is conditionally deleted in epithelial cells using Keratin14-Cre or in B cells using CD19-Cre, female mice have a normal life span without obvious illness. Third, when Xist is deleted in gut using Villin-Cre, female mice remain healthy despite significant X-autosome dosage imbalance. Finally, when the gut is acutely stressed by azoxymethane/dextran sulfate (AOM/DSS) exposure, both Xist-deleted and wild-type mice develop gastrointestinal tumors. Intriguingly, however, under prolonged stress, mutant mice develop larger tumors and have a higher tumor burden. The effect is female specific. Altogether, these observations reveal a surprising systemic tolerance to Xist loss but importantly reveal that Xist and XCI are protective to females during chronic stress.


Assuntos
Neoplasias Gastrointestinais/fisiopatologia , Doenças Genéticas Ligadas ao Cromossomo X/genética , Doenças Genéticas Ligadas ao Cromossomo X/microbiologia , RNA Longo não Codificante/genética , Cromossomo X/genética , Animais , Feminino , Neoplasias Gastrointestinais/etiologia , Neoplasias Gastrointestinais/genética , Neoplasias Gastrointestinais/metabolismo , Trato Gastrointestinal/metabolismo , Doenças Genéticas Ligadas ao Cromossomo X/complicações , Doenças Genéticas Ligadas ao Cromossomo X/metabolismo , Humanos , Masculino , Camundongos , RNA Longo não Codificante/metabolismo , Estresse Fisiológico , Carga Tumoral , Inativação do Cromossomo X
13.
Nat Med ; 26(3): 354-359, 2020 03.
Artigo em Inglês | MEDLINE | ID: mdl-32094925

RESUMO

Retinal gene therapy has shown great promise in treating retinitis pigmentosa (RP), a primary photoreceptor degeneration that leads to severe sight loss in young people. In the present study, we report the first-in-human phase 1/2, dose-escalation clinical trial for X-linked RP caused by mutations in the RP GTPase regulator (RPGR) gene in 18 patients over up to 6 months of follow-up (https://clinicaltrials.gov/: NCT03116113). The primary outcome of the study was safety, and secondary outcomes included visual acuity, microperimetry and central retinal thickness. Apart from steroid-responsive subretinal inflammation in patients at the higher doses, there were no notable safety concerns after subretinal delivery of an adeno-associated viral vector encoding codon-optimized human RPGR (AAV8-coRPGR), meeting the pre-specified primary endpoint. Visual field improvements beginning at 1 month and maintained to the last point of follow-up were observed in six patients.


Assuntos
Proteínas do Olho/genética , Proteínas do Olho/uso terapêutico , Doenças Genéticas Ligadas ao Cromossomo X/genética , Doenças Genéticas Ligadas ao Cromossomo X/terapia , Terapia Genética , Mutação/genética , Retinite Pigmentosa/genética , Retinite Pigmentosa/terapia , Adulto , Humanos , Pessoa de Meia-Idade , Retina/patologia , Retina/fisiopatologia , Retinite Pigmentosa/fisiopatologia , Adulto Jovem
14.
Eur J Endocrinol ; 182(3): K15-K24, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31917682

RESUMO

Objective: CYP11A1 mutations cause P450 side-chain cleavage (scc) deficiency, a rare form of congenital adrenal hyperplasia with a wide clinical spectrum. We detail the phenotype and evolution in a male sibship identified by HaloPlex targeted capture array. Family study: The youngest of three brothers from a non-consanguineous Scottish family presented with hyperpigmentation at 3.7 years. Investigation showed grossly impaired glucocorticoid function with ACTH elevation, moderately impaired mineralocorticoid function, and normal external genitalia. The older brothers were found to be pigmented also, with glucocorticoid impairment but normal electrolytes. Linkage studies in 2002 showed that all three brothers had inherited the same critical regions of the maternal X chromosome suggesting an X-linked disorder, but analysis of NR0B1 (DAX-1, adrenal hypoplasia) and ABCD1 (adrenoleukodystrophy) were negative. In 2016, next-generation sequencing revealed compound heterozygosity for the rs6161 variant in CYP11A1 (c.940G>A, p.Glu314Lys), together with a severely disruptive frameshift mutation (c.790_802del, K264Lfs*5). The brothers were stable on hydrocortisone and fludrocortisone replacement, testicular volumes (15-20 mL), and serum testosterone levels (24.7, 33.3, and 27.2 nmol/L) were normal, but FSH (41.2 µ/L) was elevated in the proband. The latter had undergone left orchidectomy for suspected malignancy at the age of 25 years and was attending a fertility clinic for oligospermia. Initial histology was reported as showing nodular Leydig cell hyperplasia. However, histological review using CD56 staining confirmed testicular adrenal rest cell tumour (TART). Conclusion: This kinship with partial P450scc deficiency demonstrates the importance of precise diagnosis in primary adrenal insufficiency to ensure appropriate counselling and management, particularly of TART.


Assuntos
Hiperplasia Suprarrenal Congênita/diagnóstico , Hiperplasia Suprarrenal Congênita/genética , Enzima de Clivagem da Cadeia Lateral do Colesterol/deficiência , Enzima de Clivagem da Cadeia Lateral do Colesterol/genética , Tumor de Resto Suprarrenal/genética , Tumor de Resto Suprarrenal/patologia , Tumor de Resto Suprarrenal/cirurgia , Adulto , Pré-Escolar , Progressão da Doença , Diagnóstico Precoce , Família , Mutação da Fase de Leitura , Doenças Genéticas Ligadas ao Cromossomo X/genética , Glucocorticoides/metabolismo , Terapia de Reposição Hormonal , Humanos , Hiperpigmentação/etiologia , Hiperpigmentação/genética , Masculino , Linhagem , Fenótipo , Neoplasias Testiculares/genética , Neoplasias Testiculares/patologia , Neoplasias Testiculares/cirurgia , Resultado do Tratamento
15.
Zhonghua Yi Xue Yi Chuan Xue Za Zhi ; 37(1): 25-27, 2020 Jan 10.
Artigo em Chinês | MEDLINE | ID: mdl-31922590

RESUMO

OBJECTIVE: To explore the genetic etiology of a pedigree affected with Norrie disease. METHODS: Four individuals from the core family of the proband were subjected to whole exome sequencing in order to identify the pathological variant. Sanger sequencing was used to verify the finding among 7 additional members from the pedigree. RESULTS: The proband and other 3 male patients have all carried a hemizygote c.361C>T (p.Arg121Trp) missense variant of the NDP gene, for which his mother, grandmother and two younger female cousins were heterozygous carriers. The same variant was not detected among unaffected males. Above results conformed to a X-linked recessive pattern of inheritance. CONCLUSION: The missense variant c.361C>T of the NDP gene probably underlies the Norrie disease in this pedigree.


Assuntos
Cegueira/congênito , Proteínas do Olho , Doenças Genéticas Ligadas ao Cromossomo X , Proteínas do Tecido Nervoso , Doenças do Sistema Nervoso , Degeneração Retiniana , Espasmos Infantis , Cegueira/genética , Proteínas do Olho/genética , Feminino , Doenças Genéticas Ligadas ao Cromossomo X/genética , Humanos , Masculino , Proteínas do Tecido Nervoso/genética , Doenças do Sistema Nervoso/genética , Linhagem , Degeneração Retiniana/genética , Espasmos Infantis/genética
16.
Eur J Endocrinol ; 182(1): K1-K6, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31658436

RESUMO

Objective: X-linked hypophosphatemic rickets (XLHR) is the most common form of inherited rickets caused by pathogenic variants of PHEX gene with an X-linked dominant inheritance pattern. Precise molecular diagnosis of pathogenic variant will benefit the genetic counseling and prenatal diagnosis for the family with XLHR. Here, we presented an 'isolated' germline mosaicism in the phenotypically normal father of a girl with XLHR. Methods and results: For the initial molecular screen of PHEX gene, DNA samples of the proband and her parents were extracted from their peripheral blood samples respectively. Sanger sequencing found a 'de novo' novel heterozygous variant, c.1666C>T(p.Q556X), at the PHEX gene in the proband, but not in her phenotypically healthy parents. Due to an occasional abnormality of his serum phosphate previously, further examinations for the father were taken to exclude the possibility of paternal mosaicism. Eight samples from different tissues were analyzed for PHEX gene by Sanger sequencing. Surprisingly, one 'isolated' germline mosaicism was detected only in his sperm with an estimated frequency of 26.67%. The mosaic allele was identical to the c.1666C>T(p.Q556X) variant in the proband. Conclusions: This is the first case of 'isolated' germline mosaicism with pathogenic PHEX variant. Our study provides accurate diagnosis and valuable counseling for this family. This report also alerts clinicians and geneticists to exclude the possibility of the isolated germline mosaicism and prevent intrafamilial recurrences of inherited diseases.


Assuntos
Raquitismo Hipofosfatêmico Familiar/genética , Doenças Genéticas Ligadas ao Cromossomo X/genética , Mutação/genética , Criança , Feminino , Mutação em Linhagem Germinativa/genética , Humanos , Mosaicismo , Linhagem , Fenótipo
17.
Doc Ophthalmol ; 140(2): 147-157, 2020 04.
Artigo em Inglês | MEDLINE | ID: mdl-31583501

RESUMO

PURPOSE: A single variant (p.G38D) in the GNAT1 gene, encoding the rod-specific transducin α-subunit in phototransduction, has been reported only in one French family with Nougaret-type autosomal dominant congenital stationary night blindness (CSNB). We identified a Japanese family with Nougaret-type CSNB and cone-rod dystrophy (CORD). METHODS: Five patients with CSNB and two patients with childhood-onset CORD were recruited. We performed a comprehensive ophthalmic examination including electroretinography (ERG). Disease-causing variants were identified by whole exome sequencing, with candidates confirmed by Sanger sequencing in nine family members. RESULTS: The GNAT1 variant (p.G38D) was identified in all four CSNB patients, whereas the two CORD patients carried biallelic truncated known ABCA4 variants as well as the GNAT1 variant. Clinically, no remarkable findings were observed in fuduscopy, fundus autofluorescence, or optical coherence tomography images from the CSNB patients. No response was detectable by rod ERG. The a-waves of standard and bright flash ERG were delayed and broadened rather than biphasic, and b/a-wave amplitude ratio was negative. Cone and 30-Hz flicker responses were normal, and overall, the ERG findings were compatible with previous descriptions of Nougaret-type CSNB. ERG of the CORD patients with macular atrophy showed non-recordable rod response and severely decreased standard flash, cone and 30-Hz flicker responses. CONCLUSIONS: This is the second report of a Nougaret-type CSNB family with the GNAT1 variant. Our novel findings suggest that coexistence of the GNAT1 and biallelic ABCA4 variants is associated with an overlapping phenotype with both Nougaret-type CSNB and CORD.


Assuntos
Transportadores de Cassetes de Ligação de ATP/genética , Distrofias de Cones e Bastonetes/genética , Oftalmopatias Hereditárias/genética , Doenças Genéticas Ligadas ao Cromossomo X/genética , Miopia/genética , Cegueira Noturna/genética , Polimorfismo de Nucleotídeo Único , Transducina/genética , Adolescente , Adulto , Idoso , Criança , Pré-Escolar , Distrofias de Cones e Bastonetes/fisiopatologia , Eletrorretinografia , Oftalmopatias Hereditárias/fisiopatologia , Feminino , Doenças Genéticas Ligadas ao Cromossomo X/fisiopatologia , Humanos , Masculino , Pessoa de Meia-Idade , Miopia/fisiopatologia , Cegueira Noturna/fisiopatologia , Linhagem , Fenótipo , Estimulação Luminosa , Retina/fisiologia , Células Fotorreceptoras Retinianas Cones/fisiologia , Tomografia de Coerência Óptica , Acuidade Visual/fisiologia , Sequenciamento Completo do Exoma
20.
J Biol Chem ; 295(6): 1464-1473, 2020 02 07.
Artigo em Inglês | MEDLINE | ID: mdl-31852738

RESUMO

Dent disease 1 (DD1) is caused by mutations in the CLCN5 gene encoding a voltage-gated electrogenic nCl-/H+ exchanger ClC-5. Using ion-selective microelectrodes and Xenopus oocytes, here we studied Cl-/H+ coupling properties of WT ClC-5 and four DD1-associated variants (S244L, R345W, Q629*, and T657S), along with trafficking and localization of ClC-5. WT ClC-5 had a 2Cl-/H+ exchange ratio at a Vh of +40 mV with a [Cl-]out of 104 mm, but the transport direction did not reverse with a [Cl-]out of 5 mm, indicating that ClC-5-mediated exchange of two Cl- out for one H+ in is not permissible. We hypothesized that ClC-5 and H+-ATPase are functionally coupled during H+-ATPase-mediated endosomal acidification, crucial for ClC-5 activation by depolarizing endosomes. ClC-5 transport that provides three net negative charges appeared self-inhibitory because of ClC-5's voltage-gated properties, but shunt conductance facilitated further H+-ATPase-mediated endosomal acidification. Thus, an on-and-off "burst" of ClC-5 activity was crucial for preventing Cl- exit from endosomes. The subcellular distribution of the ClC-5:S244L variant was comparable with that of WT ClC-5, but the variant had a much slower Cl- and H+ transport and displayed an altered stoichiometry of 1.6:1. The ClC-5:R345W variant exhibited slightly higher Cl-/H+ transport than ClC-5:S244L, but co-localized with early endosomes, suggesting decreased ClC-5:R345W membrane trafficking is perhaps in a fully functional form. The truncated ClC-5:Q629* variant displayed the lowest Cl-/H+ exchange and was retained in the endoplasmic reticulum and cis-Golgi, but not in early endosomes, suggesting the nonsense mutation affects ClC-5 maturation and trafficking.


Assuntos
Canais de Cloreto/genética , Doenças Genéticas Ligadas ao Cromossomo X/genética , Nefrolitíase/genética , Mutação Puntual , Animais , Linhagem Celular , Canais de Cloreto/análise , Canais de Cloreto/metabolismo , Cloretos/metabolismo , Endossomos/genética , Endossomos/metabolismo , Doenças Genéticas Ligadas ao Cromossomo X/metabolismo , Humanos , Hidrogênio/metabolismo , Transporte de Íons , Nefrolitíase/metabolismo , Transporte Proteico , Xenopus
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