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1.
Genet Med ; 2019 Nov 08.
Artigo em Inglês | MEDLINE | ID: mdl-31700164

RESUMO

PURPOSE: Most classical aniridia is caused by PAX6 haploinsufficiency. PAX6 missense variants can be hypomorphic or mimic haploinsufficiency. We hypothesized that missense variants also cause previously undescribed disease by altering the affinity and/or specificity of PAX6 genomic interactions. METHODS: We screened PAX6 in 372 individuals with bilateral microphthalmia, anophthalmia, or coloboma (MAC) from the Medical Research Council Human Genetics Unit eye malformation cohort (HGUeye) and reviewed data from the Deciphering Developmental Disorders study. We performed cluster analysis on PAX6-associated ocular phenotypes by variant type and molecular modeling of the structural impact of 86 different PAX6 causative missense variants. RESULTS: Eight different PAX6 missense variants were identified in 17 individuals (15 families) with MAC, accounting for 4% (15/372) of our cohort. Seven altered the paired domain (p.[Arg26Gln]x1, p.[Gly36Val]x1, p.[Arg38Trp]x2, p.[Arg38Gln]x1, p.[Gly51Arg]x2, p.[Ser54Arg]x2, p.[Asn124Lys]x5) and one the homeodomain (p.[Asn260Tyr]x1). p.Ser54Arg and p.Asn124Lys were exclusively associated with severe bilateral microphthalmia. MAC-associated variants were predicted to alter but not ablate DNA interaction, consistent with the electrophoretic mobility shifts observed using mutant paired domains with well-characterized PAX6-binding sites. We found no strong evidence for novel PAX6-associated extraocular disease. CONCLUSION: Altering the affinity and specificity of PAX6-binding genome-wide provides a plausible mechanism for the worse-than-null effects of MAC-associated missense variants.

2.
Invest Ophthalmol Vis Sci ; 60(13): 4249-4256, 2019 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-31618761

RESUMO

Purpose: To investigate the role of two deep-intronic ABCA4 variants, that showed a mild splice defect in vitro and can occur on the same allele as the low penetrant c.5603A>T, in Stargardt disease (STGD1). Methods: Ophthalmic data were assessed of 18 STGD1 patients who harbored c.769-784C>T or c.4253+43G>A in combination with a severe ABCA4 variant. Subjects carrying c.[769-784C>T; 5603A>T] were clinically compared with a STGD1 cohort previously published carrying c.5603A>T noncomplex. We calculated the penetrances of the intronic variants using ABCA4 allele frequency data of the general population and investigated the effect of c.769-784C>T on splicing in photoreceptor progenitor cells (PPCs). Results: Mostly, late-onset, foveal-sparing STGD1 was observed among subjects harboring c.769-784C>T or c.4253+43G>A (median age of onset, 54.5 and 52.0 years, respectively). However, ages of onset, phenotypes in fundo, and visual acuity courses varied widely. No significant clinical differences were observed between the c.[769-784C>T; 5603A>T] cohort and the c.4253+43G>A or the c.5603A>T cohort. The penetrances of c.769-784C>T (20.5%-39.6%) and c.4253+43G>A (35.8%-43.1%) were reduced, when not considering the effect of yet unidentified or known factors in cis, such as c.5603A>T (identified in 7/7 probands with c.769-784C>T; 1/8 probands with c.4253+43G>A). Variant c.769-784C>T resulted in a pseudo-exon insertion in 15% of the total mRNA (i.e., ∼30% of the c.769-784C>T allele alone). Conclusions: Two mild intronic ABCA4 variants could further explain missing heritability in late-onset STGD1, distinguishing it from AMD. The observed clinical variability and calculated reduced penetrance urge research into modifiers within and outside of the ABCA4 gene.

3.
Genet Med ; 2019 Oct 24.
Artigo em Inglês | MEDLINE | ID: mdl-31649276

RESUMO

PURPOSE: Treacher Collins syndrome (TCS) is a rare autosomal dominant mandibulofacial dysostosis, with a prevalence of 0.2-1/10,000. Features include bilateral and symmetrical malar and mandibular hypoplasia and facial abnormalities due to abnormal neural crest cell (NCC) migration and differentiation. To date, three genes have been identified: TCOF1, POLR1C, and POLR1D. Despite a large number of patients with a molecular diagnosis, some remain without a known genetic anomaly. METHODS: We performed exome sequencing for four individuals with TCS but who were negative for pathogenic variants in the known causative genes. The effect of the pathogenic variants was investigated in zebrafish. RESULTS: We identified three novel pathogenic variants in POLR1B. Knockdown of polr1b in zebrafish induced an abnormal craniofacial phenotype mimicking TCS that was associated with altered ribosomal gene expression, massive p53-associated cellular apoptosis in the neuroepithelium, and reduced number of NCC derivatives. CONCLUSION: Pathogenic variants in the RNA polymerase I subunit POLR1B might induce massive p53-dependent apoptosis in a restricted neuroepithelium area, altering NCC migration and causing cranioskeletal malformations. We identify POLR1B as a new causative gene responsible for a novel TCS syndrome (TCS4) and establish a novel experimental model in zebrafish to study POLR1B-related TCS.

4.
Genet Med ; 21(8): 1751-1760, 2019 08.
Artigo em Inglês | MEDLINE | ID: mdl-30643219

RESUMO

PURPOSE: Using exome sequencing, the underlying variants in many persons with autosomal recessive diseases remain undetected. We explored autosomal recessive Stargardt disease (STGD1) as a model to identify the missing heritability. METHODS: Sequencing of ABCA4 was performed in 8 STGD1 cases with one variant and p.Asn1868Ile in trans, 25 cases with one variant, and 3 cases with no ABCA4 variant. The effect of intronic variants was analyzed using in vitro splice assays in HEK293T cells and patient-derived fibroblasts. Antisense oligonucleotides were used to correct splice defects. RESULTS: In 24 of the probands (67%), one known and five novel deep-intronic variants were found. The five novel variants resulted in messenger RNA pseudoexon inclusions, due to strengthening of cryptic splice sites or by disrupting a splicing silencer motif. Variant c.769-784C>T showed partial insertion of a pseudoexon and was found in cis with c.5603A>T (p.Asn1868Ile), so its causal role could not be fully established. Variant c.4253+43G>A resulted in partial skipping of exon 28. Remarkably, antisense oligonucleotides targeting the aberrant splice processes resulted in (partial) correction of all splicing defects. CONCLUSION: Our data demonstrate the importance of assessing noncoding variants in genetic diseases, and show the great potential of splice modulation therapy for deep-intronic variants.

5.
Invest Ophthalmol Vis Sci ; 59(8): 3220-3231, 2018 Jul 02.
Artigo em Inglês | MEDLINE | ID: mdl-29971439

RESUMO

Purpose: To assess the occurrence and the disease expression of the common p.Asn1868Ile variant in patients with Stargardt disease (STGD1) harboring known, monoallelic causal ABCA4 variants. Methods: The coding and noncoding regions of ABCA4 were sequenced in 67 and 63 STGD1 probands respectively, harboring monoallelic ABCA4 variants. In case p.Asn1868Ile was detected, segregation analysis was performed whenever possible. Probands and affected siblings harboring p.Asn1868Ile without additional variants in cis were clinically evaluated retrospectively. Two asymptomatic siblings carrying the same ABCA4 variants as their probands were clinically examined. The penetrance of p.Asn1868Ile was calculated using allele frequency data of ABCA4 variants in non-Finnish European individuals. Results: The p.Asn1868Ile variant was found in cis with known variants in 14/67 probands. In 27/67 probands, we identified p.Asn1868Ile without additional variants in cis, in combination with known, mainly severe ABCA4 variants. In 23/27 probands, the trans configuration was established. Among 27 probands and 6/7 STGD1 siblings carrying p.Asn1868Ile, 42% manifested late-onset disease (>44 years). We additionally identified four asymptomatic relatives carrying a combination of a severe variant and p.Asn1868Ile; ophthalmologic examination in two persons did not reveal STGD1. Based on ABCA4 allele frequency data, we conservatively estimated the penetrance of p.Asn1868Ile, when present in trans with a severe variant, to be below 5%. Conclusions: A significant fraction of genetically unexplained STGD1 cases carries p.Asn1868Ile as a second variant. Our findings suggest exceptional differences in disease expression or even nonpenetrance of this ABCA4 variant, pointing toward an important role for genetic or environmental modifiers in STGD1.

6.
Gastroenterology ; 155(1): 130-143.e15, 2018 07.
Artigo em Inglês | MEDLINE | ID: mdl-29604290

RESUMO

BACKGROUND & AIMS: Congenital diarrheal disorders are rare inherited intestinal disorders characterized by intractable, sometimes life-threatening, diarrhea and nutrient malabsorption; some have been associated with mutations in diacylglycerol-acyltransferase 1 (DGAT1), which catalyzes formation of triacylglycerol from diacylglycerol and acyl-CoA. We investigated the mechanisms by which DGAT1 deficiency contributes to intestinal failure using patient-derived organoids. METHODS: We collected blood samples from 10 patients, from 6 unrelated pedigrees, who presented with early-onset severe diarrhea and/or vomiting, hypoalbuminemia, and/or (fatal) protein-losing enteropathy with intestinal failure; we performed next-generation sequencing analysis of DNA from 8 patients. Organoids were generated from duodenal biopsies from 3 patients and 3 healthy individuals (controls). Caco-2 cells and patient-derived dermal fibroblasts were transfected or transduced with vectors that express full-length or mutant forms of DGAT1 or full-length DGAT2. We performed CRISPR/Cas9-guided disruption of DGAT1 in control intestinal organoids. Cells and organoids were analyzed by immunoblot, immunofluorescence, flow cytometry, chromatography, quantitative real-time polymerase chain reaction, and for the activity of caspases 3 and 7. RESULTS: In the 10 patients, we identified 5 bi-allelic loss-of-function mutations in DGAT1. In patient-derived fibroblasts and organoids, the mutations reduced expression of DGAT1 protein and altered triacylglycerol metabolism, resulting in decreased lipid droplet formation after oleic acid addition. Expression of full-length DGAT2 in patient-derived fibroblasts restored formation of lipid droplets. Organoids derived from patients with DGAT1 mutations were more susceptible to lipid-induced cell death than control organoids. CONCLUSIONS: We identified a large cohort of patients with congenital diarrheal disorders with mutations in DGAT1 that reduced expression of its product; dermal fibroblasts and intestinal organoids derived from these patients had altered lipid metabolism and were susceptible to lipid-induced cell death. Expression of full-length wildtype DGAT1 or DGAT2 restored normal lipid metabolism in these cells. These findings indicate the importance of DGAT1 in fat metabolism and lipotoxicity in the intestinal epithelium. A fat-free diet might serve as the first line of therapy for patients with reduced DGAT1 expression. It is important to identify genetic variants associated with congenital diarrheal disorders for proper diagnosis and selection of treatment strategies.


Assuntos
Diacilglicerol O-Aciltransferase/genética , Duodeno/metabolismo , Fibroblastos/metabolismo , Hipoalbuminemia/genética , Transtornos do Metabolismo dos Lipídeos/genética , Organoides/metabolismo , Enteropatias Perdedoras de Proteínas/genética , Células CACO-2 , Estudos de Casos e Controles , Caspase 3/metabolismo , Caspase 7/metabolismo , Criança , Pré-Escolar , Consanguinidade , Derme/citologia , Diacilglicerol O-Aciltransferase/deficiência , Feminino , Sequenciamento de Nucleotídeos em Larga Escala , Humanos , Masculino , Países Baixos , Forbóis , Reação em Cadeia da Polimerase em Tempo Real , Análise de Sequência de DNA , Turquia
7.
Genome Biol ; 18(1): 48, 2017 03 08.
Artigo em Inglês | MEDLINE | ID: mdl-28274275

RESUMO

BACKGROUND: Hirschsprung disease (HSCR), which is congenital obstruction of the bowel, results from a failure of enteric nervous system (ENS) progenitors to migrate, proliferate, differentiate, or survive within the distal intestine. Previous studies that have searched for genes underlying HSCR have focused on ENS-related pathways and genes not fitting the current knowledge have thus often been ignored. We identify and validate novel HSCR genes using whole exome sequencing (WES), burden tests, in silico prediction, unbiased in vivo analyses of the mutated genes in zebrafish, and expression analyses in zebrafish, mouse, and human. RESULTS: We performed de novo mutation (DNM) screening on 24 HSCR trios. We identify 28 DNMs in 21 different genes. Eight of the DNMs we identified occur in RET, the main HSCR gene, and the remaining 20 DNMs reside in genes not reported in the ENS. Knockdown of all 12 genes with missense or loss-of-function DNMs showed that the orthologs of four genes (DENND3, NCLN, NUP98, and TBATA) are indispensable for ENS development in zebrafish, and these results were confirmed by CRISPR knockout. These genes are also expressed in human and mouse gut and/or ENS progenitors. Importantly, the encoded proteins are linked to neuronal processes shared by the central nervous system and the ENS. CONCLUSIONS: Our data open new fields of investigation into HSCR pathology and provide novel insights into the development of the ENS. Moreover, the study demonstrates that functional analyses of genes carrying DNMs are warranted to delineate the full genetic architecture of rare complex diseases.


Assuntos
Exoma , Predisposição Genética para Doença , Estudo de Associação Genômica Ampla , Sequenciamento de Nucleotídeos em Larga Escala , Doença de Hirschsprung/genética , Alelos , Animais , Estudos de Casos e Controles , Biologia Computacional/métodos , Análise Mutacional de DNA , Modelos Animais de Doenças , Técnicas de Inativação de Genes , Genótipo , Humanos , Mutação , Fenótipo , Peixe-Zebra
8.
Proc Natl Acad Sci U S A ; 114(13): E2739-E2747, 2017 03 28.
Artigo em Inglês | MEDLINE | ID: mdl-28292896

RESUMO

Megacystis microcolon intestinal hypoperistalsis syndrome (MMIHS) is a congenital visceral myopathy characterized by severe dilation of the urinary bladder and defective intestinal motility. The genetic basis of MMIHS has been ascribed to spontaneous and autosomal dominant mutations in actin gamma 2 (ACTG2), a smooth muscle contractile gene. However, evidence suggesting a recessive origin of the disease also exists. Using combined homozygosity mapping and whole exome sequencing, a genetically isolated family was found to carry a premature termination codon in Leiomodin1 (LMOD1), a gene preferentially expressed in vascular and visceral smooth muscle cells. Parents heterozygous for the mutation exhibited no abnormalities, but a child homozygous for the premature termination codon displayed symptoms consistent with MMIHS. We used CRISPR-Cas9 (CRISPR-associated protein) genome editing of Lmod1 to generate a similar premature termination codon. Mice homozygous for the mutation showed loss of LMOD1 protein and pathology consistent with MMIHS, including late gestation expansion of the bladder, hydronephrosis, and rapid demise after parturition. Loss of LMOD1 resulted in a reduction of filamentous actin, elongated cytoskeletal dense bodies, and impaired intestinal smooth muscle contractility. These results define LMOD1 as a disease gene for MMIHS and suggest its role in establishing normal smooth muscle cytoskeletal-contractile coupling.


Assuntos
Anormalidades Múltiplas/genética , Autoantígenos/fisiologia , Colo/anormalidades , Proteínas do Citoesqueleto/fisiologia , Pseudo-Obstrução Intestinal/genética , Proteínas Musculares/fisiologia , Bexiga Urinária/anormalidades , Animais , Autoantígenos/genética , Autoantígenos/metabolismo , Códon sem Sentido , Proteínas do Citoesqueleto/genética , Proteínas do Citoesqueleto/metabolismo , Feminino , Humanos , Recém-Nascido , Camundongos , Contração Muscular/genética , Proteínas Musculares/genética , Proteínas Musculares/metabolismo , Músculo Liso/fisiologia
9.
Hum Mol Genet ; 25(23): 5265-5275, 2016 12 01.
Artigo em Inglês | MEDLINE | ID: mdl-27702942

RESUMO

Hirschsprung disease (HSCR) is the most common cause of neonatal intestinal obstruction. It is characterized by the absence of ganglia in the nerve plexuses of the lower gastrointestinal tract. So far, three common disease-susceptibility variants at the RET, SEMA3 and NRG1 loci have been detected through genome-wide association studies (GWAS) in Europeans and Asians to understand its genetic etiologies. Here we present a trans-ethnic meta-analysis of 507 HSCR cases and 1191 controls, combining all published GWAS results on HSCR to fine-map these loci and narrow down the putatively causal variants to 99% credible sets. We also demonstrate that the effects of RET and NRG1 are universal across European and Asian ancestries. In contrast, we detected a European-specific association of a low-frequency variant, rs80227144, in SEMA3 [odds ratio (OR) = 5.2, P = 4.7 × 10-10]. Conditional analyses on the lead SNPs revealed a secondary association signal, corresponding to an Asian-specific, low-frequency missense variant encoding RET p.Asp489Asn (rs9282834, conditional OR = 20.3, conditional P = 4.1 × 10-14). When in trans with the RET intron 1 enhancer risk allele, rs9282834 increases the risk of HSCR from 1.1 to 26.7. Overall, our study provides further insights into the genetic architecture of HSCR and has profound implications for future study designs.


Assuntos
Predisposição Genética para Doença , Doença de Hirschsprung/genética , Neuregulina-1/genética , Proteínas Proto-Oncogênicas c-ret/genética , Semaforina-3A/genética , Alelos , Grupo com Ancestrais do Continente Asiático/genética , Grupos Étnicos/genética , Grupo com Ancestrais do Continente Europeu/genética , Feminino , Estudo de Associação Genômica Ampla , Genótipo , Doença de Hirschsprung/patologia , Humanos , Íntrons/genética , Masculino , Polimorfismo de Nucleotídeo Único
10.
Sci Rep ; 6: 28253, 2016 06 24.
Artigo em Inglês | MEDLINE | ID: mdl-27339364

RESUMO

X-linked cone dysfunction disorders such as Blue Cone Monochromacy and X-linked Cone Dystrophy are characterized by complete loss (of) or reduced L- and M- cone function due to defects in the OPN1LW/OPN1MW gene cluster. Here we investigated 24 affected males from 16 families with either a structurally intact gene cluster or at least one intact single (hybrid) gene but harbouring rare combinations of common SNPs in exon 3 in single or multiple OPN1LW and OPN1MW gene copies. We assessed twelve different OPN1LW/MW exon 3 haplotypes by semi-quantitative minigene splicing assay. Nine haplotypes resulted in aberrant splicing of ≥20% of transcripts including the known pathogenic haplotypes (i.e. 'LIAVA', 'LVAVA') with absent or minute amounts of correctly spliced transcripts, respectively. De novo formation of the 'LIAVA' haplotype derived from an ancestral less deleterious 'LIAVS' haplotype was observed in one family with strikingly different phenotypes among affected family members. We could establish intrachromosomal gene conversion in the male germline as underlying mechanism. Gene conversion in the OPN1LW/OPN1MW genes has been postulated, however, we are first to demonstrate a de novo gene conversion within the lineage of a pedigree.


Assuntos
Defeitos da Visão Cromática/genética , Conversão Gênica , Doenças Genéticas Ligadas ao Cromossomo X/genética , Mutação em Linhagem Germinativa , Opsinas de Bastonetes/genética , Defeitos da Visão Cromática/diagnóstico por imagem , Defeitos da Visão Cromática/fisiopatologia , Eletrorretinografia , Éxons , Feminino , Genes Ligados ao Cromossomo X , Haplótipos , Humanos , Masculino , Família Multigênica , Linhagem , Polimorfismo de Nucleotídeo Único
11.
Eur J Hum Genet ; 24(4): 542-9, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-26173970

RESUMO

Variants in CIB2 can underlie either Usher syndrome type I (USH1J) or nonsyndromic hearing impairment (NSHI) (DFNB48). Here, a novel homozygous missense variant c.196C>T and compound heterozygous variants, c.[97C>T];[196C>T], were found, respectively, in two unrelated families of Dutch origin. Besides, the previously reported c.272 T>C functional missense variant in CIB2 was identified in two families of Pakistani origin. The missense variants are demonstrated not to affect subcellular localization of CIB2 in vestibular hair cells in ex vivo expression experiments. Furthermore, these variants do not affect the ATP-induced calcium responses in COS-7 cells. However, based on the residues affected, the variants are suggested to alter αIIß integrin binding. HI was nonsyndromic in all four families. However, deafness segregating with the c.272T>C variant in one Pakistani family is remarkably less severe than that in all other families with this mutation. Our results contribute to the insight in genotype-phenotype correlations of CIB2 mutations.


Assuntos
Proteínas de Ligação ao Cálcio/genética , Cálcio/metabolismo , Surdez/genética , Células Ciliadas Auditivas/metabolismo , Adolescente , Adulto , Animais , Células COS , Proteínas de Ligação ao Cálcio/metabolismo , Cercopithecus aethiops , Criança , Surdez/metabolismo , Feminino , Humanos , Integrina alfa2beta1/metabolismo , Masculino , Mutação de Sentido Incorreto , Linhagem , Ligação Proteica
12.
Hum Mol Genet ; 25(3): 571-83, 2016 Feb 01.
Artigo em Inglês | MEDLINE | ID: mdl-26647307

RESUMO

Megacystis Microcolon Intestinal Hypoperistalsis Syndrome (MMIHS) is a rare congenital disorder, in which heterozygous missense variants in the Enteric Smooth Muscle actin γ-2 (ACTG2) gene have been recently identified. To investigate the mechanism by which ACTG2 variants lead to MMIHS, we screened a cohort of eleven MMIHS patients, eight sporadic and three familial cases, and performed immunohistochemistry, molecular modeling and molecular dynamics (MD) simulations, and in vitro assays. In all sporadic cases, a heterozygous missense variant in ACTG2 was identified. ACTG2 expression was detected in all intestinal layers where smooth muscle cells are present in different stages of human development. No histopathological abnormalities were found in the patients. Using molecular modeling and MD simulations, we predicted that ACTG2 variants lead to significant changes to the protein function. This was confirmed by in vitro studies, which showed that the identified variants not only impair ACTG2 polymerization, but also contribute to reduced cell contractility. Taken together, our results confirm the involvement of ACTG2 in sporadic MMIHS, and bring new insights to MMIHS pathogenesis.


Assuntos
Anormalidades Múltiplas/genética , Actinas/genética , Colo/anormalidades , Mucosa Intestinal/metabolismo , Pseudo-Obstrução Intestinal/genética , Contração Muscular/genética , Músculo Liso/metabolismo , Mutação de Sentido Incorreto , Bexiga Urinária/anormalidades , Anormalidades Múltiplas/metabolismo , Anormalidades Múltiplas/patologia , Actinas/química , Actinas/metabolismo , Colo/metabolismo , Colo/patologia , Evolução Fatal , Feminino , Expressão Gênica , Heterozigoto , Humanos , Recém-Nascido , Pseudo-Obstrução Intestinal/metabolismo , Pseudo-Obstrução Intestinal/patologia , Intestinos/patologia , Masculino , Simulação de Dinâmica Molecular , Músculo Liso/patologia , Linhagem , Multimerização Proteica , Bexiga Urinária/metabolismo , Bexiga Urinária/patologia , Adulto Jovem
13.
Am J Hum Genet ; 97(3): 475-82, 2015 Sep 03.
Artigo em Inglês | MEDLINE | ID: mdl-26299364

RESUMO

Adams-Oliver syndrome (AOS) is a rare developmental disorder characterized by the presence of aplasia cutis congenita (ACC) of the scalp vertex and terminal limb-reduction defects. Cardiovascular anomalies are also frequently observed. Mutations in five genes have been identified as a cause for AOS prior to this report. Mutations in EOGT and DOCK6 cause autosomal-recessive AOS, whereas mutations in ARHGAP31, RBPJ, and NOTCH1 lead to autosomal-dominant AOS. Because RBPJ, NOTCH1, and EOGT are involved in NOTCH signaling, we hypothesized that mutations in other genes involved in this pathway might also be implicated in AOS pathogenesis. Using a candidate-gene-based approach, we prioritized DLL4, a critical NOTCH ligand, due to its essential role in vascular development in the context of cardiovascular features in AOS-affected individuals. Targeted resequencing of the DLL4 gene with a custom enrichment panel in 89 independent families resulted in the identification of seven mutations. A defect in DLL4 was also detected in two families via whole-exome or genome sequencing. In total, nine heterozygous mutations in DLL4 were identified, including two nonsense and seven missense variants, the latter encompassing four mutations that replace or create cysteine residues, which are most likely critical for maintaining structural integrity of the protein. Affected individuals with DLL4 mutations present with variable clinical expression with no emerging genotype-phenotype correlations. Our findings demonstrate that DLL4 mutations are an additional cause of autosomal-dominant AOS or isolated ACC and provide further evidence for a key role of NOTCH signaling in the etiology of this disorder.


Assuntos
Displasia Ectodérmica/genética , Displasia Ectodérmica/patologia , Peptídeos e Proteínas de Sinalização Intercelular/genética , Deformidades Congênitas dos Membros/genética , Deformidades Congênitas dos Membros/patologia , Mutação/genética , Dermatoses do Couro Cabeludo/congênito , Transdução de Sinais/genética , Sequência de Aminoácidos , Sequência de Bases , Heterozigoto , Humanos , Dados de Sequência Molecular , Linhagem , Receptores Notch/genética , Dermatoses do Couro Cabeludo/genética , Dermatoses do Couro Cabeludo/patologia , Análise de Sequência de DNA
14.
Biochim Biophys Acta ; 1852(11): 2352-61, 2015 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-26282049

RESUMO

Congenital Short Bowel Syndrome (CSBS) is a rare gastrointestinal disorder in which the mean length of the small intestine is substantially reduced when compared to its normal counterpart. Families with several affected members have been described and CSBS has been suggested to have a genetic basis. Recently, our group found mutations in CLMP as the cause of the recessive form of CSBS, and mutations in FLNA as the cause of the X-linked form of the disease. These findings have improved the quality of genetic counselling for CSBS patients and made prenatal diagnostics possible. Moreover, they provided a reliable starting point to further investigate the pathogenesis of CSBS, and to better understand the development of the small intestine. In this review, we present our current knowledge on CSBS and discuss hypotheses on how the recent genetic findings can help understand the cause of CSBS.

15.
Am J Hum Genet ; 96(4): 581-96, 2015 Apr 02.
Artigo em Inglês | MEDLINE | ID: mdl-25839327

RESUMO

Innervation of the gut is segmentally lost in Hirschsprung disease (HSCR), a consequence of cell-autonomous and non-autonomous defects in enteric neuronal cell differentiation, proliferation, migration, or survival. Rare, high-penetrance coding variants and common, low-penetrance non-coding variants in 13 genes are known to underlie HSCR risk, with the most frequent variants in the ret proto-oncogene (RET). We used a genome-wide association (220 trios) and replication (429 trios) study to reveal a second non-coding variant distal to RET and a non-coding allele on chromosome 7 within the class 3 Semaphorin gene cluster. Analysis in Ret wild-type and Ret-null mice demonstrates specific expression of Sema3a, Sema3c, and Sema3d in the enteric nervous system (ENS). In zebrafish embryos, sema3 knockdowns show reduction of migratory ENS precursors with complete ablation under conjoint ret loss of function. Seven candidate receptors of Sema3 proteins are also expressed within the mouse ENS and their expression is also lost in the ENS of Ret-null embryos. Sequencing of SEMA3A, SEMA3C, and SEMA3D in 254 HSCR-affected subjects followed by in silico protein structure modeling and functional analyses identified five disease-associated alleles with loss-of-function defects in semaphorin dimerization and binding to their cognate neuropilin and plexin receptors. Thus, semaphorin 3C/3D signaling is an evolutionarily conserved regulator of ENS development whose dys-regulation is a cause of enteric aganglionosis.


Assuntos
Epistasia Genética/genética , Predisposição Genética para Doença/genética , Variação Genética , Doença de Hirschsprung/genética , Proteínas Proto-Oncogênicas c-ret/genética , Semaforinas/genética , Animais , Sequência de Bases , Estudo de Associação Genômica Ampla , Camundongos , Dados de Sequência Molecular , Semaforinas/deficiência , Semaforinas/metabolismo , Análise de Sequência de DNA
16.
Eur J Med Genet ; 58(5): 279-92, 2015 May.
Artigo em Inglês | MEDLINE | ID: mdl-25792522

RESUMO

Tricho-rhino-phalangeal syndrome (TRPS) is characterized by craniofacial and skeletal abnormalities, and subdivided in TRPS I, caused by mutations in TRPS1, and TRPS II, caused by a contiguous gene deletion affecting (amongst others) TRPS1 and EXT1. We performed a collaborative international study to delineate phenotype, natural history, variability, and genotype-phenotype correlations in more detail. We gathered information on 103 cytogenetically or molecularly confirmed affected individuals. TRPS I was present in 85 individuals (22 missense mutations, 62 other mutations), TRPS II in 14, and in 5 it remained uncertain whether TRPS1 was partially or completely deleted. Main features defining the facial phenotype include fine and sparse hair, thick and broad eyebrows, especially the medial portion, a broad nasal ridge and tip, underdeveloped nasal alae, and a broad columella. The facial manifestations in patients with TRPS I and TRPS II do not show a significant difference. In the limbs the main findings are short hands and feet, hypermobility, and a tendency for isolated metacarpals and metatarsals to be shortened. Nails of fingers and toes are typically thin and dystrophic. The radiological hallmark are the cone-shaped epiphyses and in TRPS II multiple exostoses. Osteopenia is common in both, as is reduced linear growth, both prenatally and postnatally. Variability for all findings, also within a single family, can be marked. Morbidity mostly concerns joint problems, manifesting in increased or decreased mobility, pain and in a minority an increased fracture rate. The hips can be markedly affected at a (very) young age. Intellectual disability is uncommon in TRPS I and, if present, usually mild. In TRPS II intellectual disability is present in most but not all, and again typically mild to moderate in severity. Missense mutations are located exclusively in exon 6 and 7 of TRPS1. Other mutations are located anywhere in exons 4-7. Whole gene deletions are common but have variable breakpoints. Most of the phenotype in patients with TRPS II is explained by the deletion of TRPS1 and EXT1, but haploinsufficiency of RAD21 is also likely to contribute. Genotype-phenotype studies showed that mutations located in exon 6 may have somewhat more pronounced facial characteristics and more marked shortening of hands and feet compared to mutations located elsewhere in TRPS1, but numbers are too small to allow firm conclusions.


Assuntos
Anormalidades Múltiplas/genética , Proteínas de Ligação a DNA/genética , Síndrome de Langer-Giedion/genética , Fatores de Transcrição/genética , Anormalidades Múltiplas/patologia , Adolescente , Adulto , Idoso , Criança , Pré-Escolar , Feminino , Estudos de Associação Genética , Humanos , Lactente , Síndrome de Langer-Giedion/patologia , Masculino , Pessoa de Meia-Idade , Mutação de Sentido Incorreto , Adulto Jovem
17.
Acta Ophthalmol ; 92(3): 276-81, 2014 May.
Artigo em Inglês | MEDLINE | ID: mdl-23742260

RESUMO

PURPOSE: We present a genetic and clinical analysis of two sisters, 3 and 4 years of age, with nanophthalmos and macular folds. METHODS: Ophthalmological examination, general paediatric examination and molecular genetic analysis of the MFRP gene were performed in both affected siblings. RESULTS: Clinical analysis showed high hyperopia (+11 D and +12 D), short axial lengths (15 mm) and the presence of macular folds and optic nerve head drusen. Autofluorescence of the retina was generally normal with subtle macular abnormalities. Sequence analysis showed compound heterozygosity for severe MFRP mutations in both sisters: a previously reported p.Asn167fs (c.498dupC) and a novel stop codon mutation p.Gln91X (c.271C>T). CONCLUSION: These are the youngest nanophthalmos patients in the literature identified with severe loss of MFRP function, showing already the known structural abnormalities for this disease. Adult patients affected by homozygous or compound heterozygous MFRP mutations generally show signs of retinal dystrophy, with ERG disturbances and RPE abnormalities on autofluorescence imaging. ERG examination could not be performed in these children, but extensive RPE abnormalities were not seen at this young age.


Assuntos
DNA/genética , Oftalmopatias Hereditárias/fisiopatologia , Glicoproteínas/genética , Hiperopia/fisiopatologia , Microftalmia/genética , Mutação , Drusas do Disco Óptico/etiologia , Pré-Escolar , Oftalmopatias Hereditárias/etiologia , Oftalmopatias Hereditárias/genética , Feminino , Glicoproteínas/metabolismo , Heterozigoto , Humanos , Hiperopia/etiologia , Hiperopia/genética , Peptídeos e Proteínas de Sinalização Intracelular , Microftalmia/complicações , Microftalmia/metabolismo , Microscopia Acústica , Disco Óptico/patologia , Drusas do Disco Óptico/diagnóstico , Drusas do Disco Óptico/genética , Linhagem , Reação em Cadeia da Polimerase , Tomografia de Coerência Óptica
18.
Genet Med ; 15(4): 310-3, 2013 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-23037936

RESUMO

PURPOSE: Autosomal recessive congenital short bowel syndrome is caused by mutations in CLMP. No mutations were found in the affected males of a family with presumed X-linked congenital short bowel syndrome or in an isolated male patient. Our aim was to identify the disease-causing mutation in these patients. METHODS: We performed mutation analysis of the second exon of FLNA in the two surviving affected males of the presumed X-linked family and in the isolated patient. RESULTS: We identified a novel 2-base-pair deletion in the second exon of FLNA in all these male patients. The deletion is located between two nearby methionines at the N-terminus of filamin A. Previous studies showed that translation of FLNA occurs from both methionines, resulting in two isoforms of the protein. We hypothesized that the longer isoform is no longer translated due to the mutation and that this mutation is therefore not lethal for males in utero. CONCLUSION: Our findings emphasize that congenital short bowel syndrome can be the presenting symptom in male patients with mutations in FLNA.


Assuntos
Filaminas/genética , Mutação , Síndrome do Intestino Curto/diagnóstico , Síndrome do Intestino Curto/genética , Adolescente , Adulto , Sequência de Bases , Éxons , Doenças Genéticas Ligadas ao Cromossomo X/diagnóstico , Doenças Genéticas Ligadas ao Cromossomo X/genética , Humanos , Masculino , Linhagem , Fenótipo , Deleção de Sequência , Adulto Jovem
19.
Genet Med ; 15(3): 195-202, 2013 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-22995989

RESUMO

PURPOSE: Radial ray deficiencies are characterized by unilateral or bilateral absence of varying portions of the radius and thumb. Both isolated and syndromic forms have been described, and although for some of the syndromes the causal gene has been identified, many patients remain without a genetic diagnosis. METHODS: In this study, a cohort of 54 patients with radial ray deficiencies was screened for genomic aberrations by molecular karyotyping. RESULTS: In 8 of 54 cases, an aberration was detected. Two unrelated patients inherited a 1q21.1 microduplication from a healthy parent, whereas in a third patient, a 16p13.11 microduplication was identified. Two other interesting microdeletions were detected: a 10q24.3 deletion at the split hand-foot malformation (SHFM3) locus and a 7p22.1 deletion including the RAC1 gene. CONCLUSION: The finding of these microduplications may just be coincidental or, alternatively, they may illustrate the broad phenotypic spectrum of these microduplications. Duplications in the 10q24.3 region result in split hand-foot malformations, and our observation indicates that deletions may cause radial ray defects. Finally, a candidate gene for radial ray deficiencies was detected in the 7p22.1 deletion. RAC1 plays an important role in the canonical Wnt pathway and conditional RAC1 knockout mice exhibit truncated-limb defects.


Assuntos
Deformidades Congênitas das Extremidades Superiores/genética , Duplicação Cromossômica , Cromossomos Humanos Par 10 , Cromossomos Humanos Par 7 , Hibridização Genômica Comparativa , Proteínas F-Box/genética , Feminino , Humanos , Masculino , Radiografia , Deformidades Congênitas das Extremidades Superiores/diagnóstico , Deformidades Congênitas das Extremidades Superiores/diagnóstico por imagem , Proteínas rac1 de Ligação ao GTP/genética
20.
Eur J Hum Genet ; 20(9): 917-20, 2012 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-22395866

RESUMO

Hirschsprung disease (HSCR, aganglionic megacolon) is a complex and heterogeneous disease with an incidence of 1 in 5000 live births. Despite the multifactorial determination of HSCR in the vast majority of cases, there is a monogenic subgroup for which private rare RET coding sequence mutations with high penetrance are found (45% of HSCR familial cases). An asymmetrical parental origin is observed for RET coding sequence mutations with a higher maternal inheritance. A parent-of-origin effect is usually assumed. Here we show that a differential reproductive rate for males and females also leads to an asymmetrical parental origin, which was never considered as a possible explanation till now. In the case of HSCR, we show a positive association between penetrance of the mutation and parental transmission asymmetry: no parental transmission asymmetry is observed in sporadic RET CDS mutation carrier cases for which penetrance of the mutation is low, whereas a parental transmission asymmetry is observed in affected sib-pairs for which penetrance of the mutation is higher. This allows us to conclude that the explanation for this parental asymmetry is that more severe mutations have resulted in a differential reproductive rate between male and female carriers.


Assuntos
Doença de Hirschsprung/genética , Padrões de Herança , Proteínas Proto-Oncogênicas c-ret/genética , Reprodução/genética , Alelos , Feminino , Frequência do Gene , Humanos , Masculino , Taxa de Mutação , Fases de Leitura Aberta , Linhagem , Penetrância , Fatores Sexuais , Irmãos
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