RESUMEN
De novo variants are a leading cause of neurodevelopmental disorders (NDDs), but because every monogenic NDD is different and usually extremely rare, it remains a major challenge to understand the complete phenotype and genotype spectrum of any morbid gene. According to OMIM, heterozygous variants in KDM6B cause "neurodevelopmental disorder with coarse facies and mild distal skeletal abnormalities." Here, by examining the molecular and clinical spectrum of 85 reported individuals with mostly de novo (likely) pathogenic KDM6B variants, we demonstrate that this description is inaccurate and potentially misleading. Cognitive deficits are seen consistently in all individuals, but the overall phenotype is highly variable. Notably, coarse facies and distal skeletal anomalies, as defined by OMIM, are rare in this expanded cohort while other features are unexpectedly common (e.g., hypotonia, psychosis, etc.). Using 3D protein structure analysis and an innovative dual Drosophila gain-of-function assay, we demonstrated a disruptive effect of 11 missense/in-frame indels located in or near the enzymatic JmJC or Zn-containing domain of KDM6B. Consistent with the role of KDM6B in human cognition, we demonstrated a role for the Drosophila KDM6B ortholog in memory and behavior. Taken together, we accurately define the broad clinical spectrum of the KDM6B-related NDD, introduce an innovative functional testing paradigm for the assessment of KDM6B variants, and demonstrate a conserved role for KDM6B in cognition and behavior. Our study demonstrates the critical importance of international collaboration, sharing of clinical data, and rigorous functional analysis of genetic variants to ensure correct disease diagnosis for rare disorders.
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Discapacidad Intelectual , Trastornos del Neurodesarrollo , Humanos , Animales , Facies , Trastornos del Neurodesarrollo/genética , Trastornos del Neurodesarrollo/patología , Fenotipo , Drosophila , Discapacidad Intelectual/patología , Histona Demetilasas con Dominio de Jumonji/genéticaRESUMEN
Autosomal dominant polycystic kidney disease (ADPKD) resulting from pathogenic variants in PKD1 and PKD2 is the most common form of PKD, but other genetic causes tied to primary cilia function have been identified. Biallelic pathogenic variants in the serine/threonine kinase NEK8 cause a syndromic ciliopathy with extra-kidney manifestations. Here we identify NEK8 as a disease gene for ADPKD in 12 families. Clinical evaluation was combined with functional studies using fibroblasts and tubuloids from affected individuals. Nek8 knockout mouse kidney epithelial (IMCD3) cells transfected with wild type or variant NEK8 were further used to study ciliogenesis, ciliary trafficking, kinase function, and DNA damage responses. Twenty-one affected monoallelic individuals uniformly exhibited cystic kidney disease (mostly neonatal) without consistent extra-kidney manifestations. Recurrent de novo mutations of the NEK8 missense variant p.Arg45Trp, including mosaicism, were seen in ten families. Missense variants elsewhere within the kinase domain (p.Ile150Met and p.Lys157Gln) were also identified. Functional studies demonstrated normal localization of the NEK8 protein to the proximal cilium and no consistent cilia formation defects in patient-derived cells. NEK8-wild type protein and all variant forms of the protein expressed in Nek8 knockout IMCD3 cells were localized to cilia and supported ciliogenesis. However, Nek8 knockout IMCD3 cells expressing NEK8-p.Arg45Trp and NEK8-p.Lys157Gln showed significantly decreased polycystin-2 but normal ANKS6 localization in cilia. Moreover, p.Arg45Trp NEK8 exhibited reduced kinase activity in vitro. In patient derived tubuloids and IMCD3 cells expressing NEK8-p.Arg45Trp, DNA damage signaling was increased compared to healthy passage-matched controls. Thus, we propose a dominant-negative effect for specific heterozygous missense variants in the NEK8 kinase domain as a new cause of PKD.
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Enfermedades Renales Poliquísticas , Riñón Poliquístico Autosómico Dominante , Animales , Humanos , Recién Nacido , Ratones , Proteínas Portadoras/metabolismo , Cilios/patología , Riñón/metabolismo , Mutación , Quinasas Relacionadas con NIMA/genética , Quinasas Relacionadas con NIMA/metabolismo , Enfermedades Renales Poliquísticas/genética , Riñón Poliquístico Autosómico Dominante/patología , Proteínas Serina-Treonina Quinasas/genética , Proteínas Serina-Treonina Quinasas/metabolismo , Serina/genética , Serina/metabolismo , Canales Catiónicos TRPP/genética , Canales Catiónicos TRPP/metabolismoRESUMEN
Developmental dysplasia of the hip (DDH) is a common condition involving instability of the hip with multifactorial etiology. Early diagnosis and treatment are critical as undetected DDH is an important cause of long-term hip complications. Better diagnostics may be achieved through genetic methods, especially for patients with positive family history. Several candidate genes have been reported but the exact molecular etiology of the disease is yet unknown. In the present study, we performed whole exome sequencing of DDH patients from 28 families with at least two affected first-degree relatives. Four genes previously not associated with DDH (METTL21B, DIS3L2, PPP6R2, and TM4SF19) were identified with the same variants shared among affected family members, in more than two families. Among known association genes, we found damaging variants in DACH1, MYH10, NOTCH2, TBX4, EVC2, OTOG, and SHC3. Mutational burden analysis across the families identified 322 candidate genes, and enriched pathways include the extracellular matrix, cytoskeleton, ion-binding, and detection of mechanical stimulus. Taken altogether, our data suggest a polygenic mode of inheritance for DDH, and we propose that an impaired transduction of the mechanical stimulus is involved in the etiopathological mechanism. Our findings refine our current understanding of candidate causal genes in DDH, and provide a foundation for downstream functional studies.
Asunto(s)
Displasia del Desarrollo de la Cadera , Luxación Congénita de la Cadera , Humanos , Secuenciación del Exoma , Luxación Congénita de la Cadera/genética , Luxación Congénita de la Cadera/diagnóstico , Luxación Congénita de la Cadera/patología , Linaje , DinamarcaRESUMEN
BACKGROUND: Autosomal recessive polycystic kidney disease is a cystic kidney disease with early onset and clinically characterized by enlarged echogenic kidneys, hypertension, varying degrees of kidney dysfunction, and liver fibrosis. It is most frequently caused by sequence variants in the PKHD1 gene, encoding fibrocystin. In more rare cases, sequence variants in DZIP1L are seen, encoding the basal body protein DAZ interacting protein 1-like protein (DZIP1L). So far, only four different DZIP1L variants have been reported. METHODS: Four children from three consanguineous families presenting with polycystic kidney disease were selected for targeted or untargeted exome sequencing. RESULTS: We identified two different, previously not reported homozygous DZIP1L sequence variants: c.193 T > C; p.(Cys65Arg), and c.216C > G; p.(Cys72Trp). Functional analyses of the c.216C > G; p.(Cys72Trp) variant indicated mislocalization of mutant DZIP1L. CONCLUSIONS: In line with published data, our results suggest a critical role of the N-terminal domain for proper protein function. Although patients with PKHD1-associated autosomal recessive polycystic kidney disease often have liver abnormalities, none of the present four patients showed any clinically relevant liver involvement. Our data demonstrate the power and efficiency of next-generation sequencing-based approaches. While DZIP1L-related polycystic kidney disease certainly represents a rare form of the disease, our results emphasize the importance of including DZIP1L in multigene panels and in the data analysis of whole-exome sequencing for cystic kidney diseases. A higher resolution version of the Graphical abstract is available as Supplementary information.
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Proteínas Adaptadoras Transductoras de Señales , Riñón Poliquístico Autosómico Recesivo , Proteínas Adaptadoras Transductoras de Señales/análisis , Proteínas Adaptadoras Transductoras de Señales/genética , Niño , Consanguinidad , Pruebas Genéticas/métodos , Humanos , Mutación , Riñón Poliquístico Autosómico Recesivo/diagnóstico , Riñón Poliquístico Autosómico Recesivo/genética , Receptores de Superficie Celular/genética , Secuenciación del ExomaRESUMEN
BACKGROUND: Primary familial brain calcification is a rare autosomal dominant or recessive neurodegenerative disease, characterized by bilateral brain calcifications in different areas of the brain. It is a clinically heterogeneous disease and patients are reported to exhibit a wide spectrum of neurological and psychiatric symptoms. Mutations in five genes have been identified so far including SLC20A2, PDGFRB, PDGFB, XPR1, and MYORG. PDGFRB encodes the platelet-derived growth factor receptor-beta, and is expressed in neurons, vascular smooth muscle cells and pericytes. Patients with a PDGFRB mutation seem to exhibit a milder phenotype and milder brain calcification on brain imaging than patients with SLC20A2 and PDGFB mutations. However, this is based on a few observations so far. CASE PRESENTATION: We present a Danish family with bilateral brain calcifications and mild clinical symptoms of primary familial brain calcification, segregating with a novel PDGFRB sequence variant: c.1834G > A; p.(Gly612Arg), detected by whole exome sequencing. The variant results in physiochemical changes at the amino acid level, and affects a highly conserved nucleotide as well as amino acid. It is located in the tyrosine kinase domain of PDGFRß. Segregation analysis and in silico analyses predicted the missense variant to be disease causing. CONCLUSION: Our study confirms that PDGFRB mutation carriers in general have a mild clinical phenotype, and basal ganglia calcifications can be detected by a CT scan, also in asymptomatic mutation carriers.
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Encefalopatías/genética , Calcinosis/genética , Receptor beta de Factor de Crecimiento Derivado de Plaquetas/genética , Encefalopatías/patología , Calcinosis/patología , Dinamarca , Femenino , Heterocigoto , Humanos , Masculino , Persona de Mediana Edad , Mutación , Enfermedades Neurodegenerativas/genética , Enfermedades Neurodegenerativas/patología , Linaje , Tomografía Computarizada por Rayos X , Receptor de Retrovirus Xenotrópico y PolitrópicoRESUMEN
OBJECTIVES: The overall distribution of disease courses in multiple sclerosis (MS) is well established, but little is known about the distribution among familial MS cases. We examine the frequency of the different MS courses among familial and sporadic MS cases and determine whether MS cases within the same family had the same age at diagnosis and have experienced the same disease course. MATERIALS AND METHODS: This is a nationwide register study, based on data from the Danish MS Registry, the Danish Civil Registration System, and the Danish National Patient Registry. The main variables are MS diagnosis, MS course, and first-degree relatives with MS The statistical analyses were carried out using logistic regression analysis, Kappa coefficient, and intraclass correlations coefficient. RESULTS: In total, 7402 MS cases were included in the study, of which 531 have an affected first-degree relatives, and 6871 are sporadic. We found that relapsing-remitting MS including secondary progressive MS was more common among familial MS cases than among sporadic MS cases (Odds ratio = 1.64, 95% CI: 1.20-2.24, P = 0.002). We subsequently analyzed data on 133 MS families and found that MS courses correlate between the first and the second MS case diagnosed, while age at diagnosis does not. CONCLUSION: Familial MS cases are more likely to have relapsing-remitting MS than a progressive course compared to sporadic MS cases. Secondly, we find that within MS families, first-degree relatives are likely to have the same MS course, but we do not find that they are diagnosed at the same age.
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Esclerosis Múltiple/epidemiología , Adulto , Dinamarca/epidemiología , Progresión de la Enfermedad , Femenino , Predisposición Genética a la Enfermedad , Humanos , Masculino , Persona de Mediana Edad , Esclerosis Múltiple/genética , Esclerosis Múltiple/fisiopatología , Sistema de RegistrosRESUMEN
Mutations in ALDH18A1 can cause autosomal recessive and dominant hereditary spastic paraplegia and autosomal recessive and dominant cutis laxa. ALDH18A1 encodes delta-1-pyrroline-5-carboxylate synthetase (P5CS), which consists of two domains, the glutamate 5-kinase (G5K) and the gamma-glutamyl phosphate reductase (GR5P) domain. The location of the mutations in the gene has influence on whether the amino acid levels are affected. Mutations affecting the G5K domain have previously been found to cause reduced plasma levels of proline, citrulline and arginine, whereas such effect is not seen with mutations affecting the GR5P domain. We present a 19-year old male patient with autosomal recessive spastic paraplegia and compound heterozygosity for two ALDH18A1 mutations, one in each of the P5CS domains. This young man has spastic paraplegia with onset in childhood and temporal lobe epilepsy, but normal levels of proline, ornithine and arginine. To our knowledge, this is the first case with compound heterozygous mutations affecting both P5CS domains, where levels of plasma amino acids have been reported.
Asunto(s)
Aldehído Deshidrogenasa/genética , Aminoácidos/sangre , Mutación , Paraplejía Espástica Hereditaria/sangre , Paraplejía Espástica Hereditaria/genética , Aldehído Deshidrogenasa/química , Aldehído Deshidrogenasa/metabolismo , Aminoácidos/metabolismo , Pruebas Genéticas , Heterocigoto , Humanos , Masculino , Linaje , Dominios Proteicos/genética , Paraplejía Espástica Hereditaria/metabolismo , Adulto JovenRESUMEN
Dihydropyrimidine dehydrogenase (DPD) is the initial and rate-limiting enzyme in the catabolism of 5-fluorouracil (5FU). Genetic variations in DPD have emerged as predictive risk factors for severe fluoropyrimidine toxicity. Here, we report novel and rare genetic variants underlying DPD deficiency in 9 cancer patients presenting with severe fluoropyrimidine-associated toxicity. All patients possessed a strongly reduced DPD activity, ranging from 9 to 53% of controls. Analysis of the DPD gene (DPYD) showed the presence of 21 variable sites including 4 novel and 4 very rare aberrations: 3 missense mutations, 2 splice-site mutations, 1 intronic mutation, a deletion of 21 nucleotides and a genomic amplification of exons 9-12. Two novel/rare variants (c.2843T>C, c.321+1G>A) were present in multiple, unrelated patients. Functional analysis of recombinantly-expressed DPD mutants carrying the p.I948T and p.G284V mutation showed residual DPD activities of 30% and 0.5%, respectively. Analysis of a DPD homology model indicated that the p.I948T and p.G284V mutations may affect electron transfer and the binding of FAD, respectively. cDNA analysis showed that the c.321+1G>A mutation in DPYD leads to skipping of exon 4 immediately upstream of the mutated splice-donor site in the process of DPD pre-mRNA splicing. A lethal toxicity in two DPD patients suggests that fluoropyrimidines combined with other therapies such as radiotherapy might be particularly toxic for DPD deficient patients. Our study advocates a more comprehensive genotyping approach combined with phenotyping strategies for upfront screening for DPD deficiency to ensure the safe administration of fluoropyrimidines.
Asunto(s)
Antimetabolitos Antineoplásicos/efectos adversos , Capecitabina/efectos adversos , Dihidrouracilo Deshidrogenasa (NADP)/genética , Fluorouracilo/efectos adversos , Mutación , Empalme del ARN , Anciano , Deficiencia de Dihidropirimidina Deshidrogenasa/complicaciones , Deficiencia de Dihidropirimidina Deshidrogenasa/genética , Femenino , Amplificación de Genes , Células HEK293 , Humanos , Masculino , Persona de Mediana Edad , Modelos Moleculares , Mutación Missense , Neoplasias/complicaciones , Neoplasias/tratamiento farmacológico , Neoplasias/genética , Variantes Farmacogenómicas , Eliminación de SecuenciaRESUMEN
Genome instability, epigenetic remodelling and structural chromosomal rearrangements are hallmarks of cancer. However, the coordinated epigenetic effects of constitutional chromosomal rearrangements that disrupt genes associated with congenital neurodevelopmental diseases are poorly understood. To understand the genetic-epigenetic interplay at breakpoints of chromosomal translocations disrupting CG-rich loci, we quantified epigenetic modifications at DLGAP4 (SAPAP4), a key post-synaptic density 95 (PSD95) associated gene, truncated by the chromosome translocation t(8;20)(p12;q11.23), co-segregating with cerebellar ataxia in a five-generation family. We report significant epigenetic remodelling of the DLGAP4 locus triggered by the t(8;20)(p12;q11.23) translocation and leading to dysregulation of DLGAP4 expression in affected carriers. Disruption of DLGAP4 results in monoallelic hypermethylation of the truncated DLGAP4 promoter CpG island. This induced hypermethylation is maintained in somatic cells of carriers across several generations in a t(8;20) dependent-manner however, is erased in the germ cells of the translocation carriers. Subsequently, chromatin remodelling of the locus-perturbed monoallelic expression of DLGAP4 mRNAs and non-coding RNAs in haploid cells having the translocation. Our results provide new mechanistic insight into the way a balanced chromosomal rearrangement associated with a neurodevelopmental disorder perturbs allele-specific epigenetic mechanisms at breakpoints leading to the deregulation of the truncated locus.
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Ataxia Cerebelosa/genética , Ensamble y Desensamble de Cromatina , Epigénesis Genética , Proteínas del Tejido Nervioso/genética , Cromosomas Humanos Par 8/genética , Islas de CpG , Metilación de ADN , Femenino , Histonas/genética , Histonas/metabolismo , Humanos , Masculino , Proteínas del Tejido Nervioso/metabolismo , ARN Largo no Codificante/genética , ARN Largo no Codificante/metabolismo , Proteínas Asociadas a SAP90-PSD95 , Translocación GenéticaRESUMEN
BACKGROUND: Odonto-onycho-dermal dysplasia (OODD) is a rare form of ectodermal dysplasia characterized by severe oligodontia, onychodysplasia, palmoplantar hyperkeratosis, dry skin, hypotrichosis, and hyperhidrosis of the palms and soles. The ectodermal dysplasias resulting from biallelic mutations in the WNT10A gene result in highly variable phenotypes, ranging from isolated tooth agenesis to OODD and Schöpf-Schulz-Passarge syndrome (SSPS). CASE PRESENTATION: We identified a female patient, with consanguineous parents, who was clinically diagnosed with OODD. Genetic testing showed that she was homozygous for a previously reported pathogenic mutation in the WNT10A gene, c.321C > A, p.Cys107*. The skin and nail abnormalities were for many years interpreted as psoriasis and treated accordingly. A thorough clinical examination revealed hypotrichosis and hyperhidrosis of the soles and dental examination revealed agenesis of permanent teeth except the two maxillary central incisors. Skin biopsies from the hyperkeratotic palms and soles showed the characteristic changes of eccrine syringofibroadenomatosis, which has been described in patients with ectodermal dysplasias. Together with a family history of tooth anomalies, this lead to the clinical suspicion of a hereditary ectodermal dysplasia. CONCLUSION: This case illustrates the challenges of diagnosing ectodermal dysplasia like OODD and highlights the relevance of interdisciplinary cooperation in the diagnosis of rare conditions.
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Codón sin Sentido , Displasia Ectodérmica/genética , Homocigoto , Odontodisplasia/genética , Proteínas Wnt/genética , Adulto , Femenino , HumanosRESUMEN
BACKGROUND: An autosomal dominant form of diffuse non-epidermolytic palmoplantar keratoderma, palmoplantar keratoderma of Bothnian type, is caused by mutations in the AQP5 gene encoding the cell-membrane water channel protein aquaporin 5 leading to defective epidermal-water-barrier function in the epidermis of the palms and soles. CASE PRESENTATION: We report the first Danish family diagnosed with diffuse non-epidermolytic palmoplantar keratoderma of Bothnian type in which fourteen individuals are potentially affected. The proband, a 36-year-old male had since childhood been affected by pronounced hyperhidrosis of the palms and soles along with palmoplantar keratoderma. He reported a very distinctive feature of the disorder, aquagenic wrinkling, as he developed pronounced maceration of the skin with translucent white papules and a spongy appearance following exposure to water. The patient presented recurrent fungal infections, a wellknown feature of the condition, but also periodic worsening with pitted keratolysis and malodour due to bacterial infections. CONCLUSIONS: Palmoplantar keratoderma of Bothnian type, which may be associated with hyperhidrosis, is frequently complicated by fungal infections and may be complicated by Corynebacterium infections.
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Acuaporina 5/genética , Infecciones por Corynebacterium/etiología , Hiperhidrosis/genética , Queratodermia Palmoplantar/genética , Mutación , Adulto , Niño , Dinamarca , Humanos , MasculinoAsunto(s)
Artrogriposis/genética , Enfermedad de la Neurona Motora/genética , Proteínas de Transporte Nucleocitoplasmático/genética , Artrogriposis/complicaciones , Artrogriposis/diagnóstico , Artrogriposis/patología , Predisposición Genética a la Enfermedad , Humanos , Recién Nacido , Enfermedad de la Neurona Motora/complicaciones , Enfermedad de la Neurona Motora/diagnóstico , Enfermedad de la Neurona Motora/patologíaRESUMEN
Ectodermal dysplasias form a complex, nosologic group of diseases with defects in at least 2 ectodermal structures. A retrospective study of patients with ectodermal dysplasia seen at our department over a period of 19 years (1994-2013) was performed. The study population consisted of 67 patients covering 17 different diagnoses. Forty-five families were identified of which 26 were sporadic cases with no affected family members. In 27 tested families a disease-causing mutation was identified in 23 families. Eleven mutations were novel mutations. To our knowledge, we present the first large ectodermal dysplasia cohort focusing on clinical manifestations in combination with mutational analysis. We recommend a nationwide study to estimate the prevalence of the ectodermal dysplasia and to ensure relevant molecular genetic testing which may form the basis of a national ectodermal dysplasia database.
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Displasia Ectodérmica/genética , Mutación , Adolescente , Adulto , Anciano , Anciano de 80 o más Años , Niño , Preescolar , Dinamarca , Ectodisplasinas/genética , Receptor Edar/genética , Femenino , Humanos , Masculino , Persona de Mediana Edad , Linaje , Estudios Retrospectivos , Adulto JovenRESUMEN
Alport post-transplant nephritis (APTN) is an aggressive form of anti-glomerular basement membrane disease that targets the allograft in transplanted patients with X-linked Alport syndrome. Alloantibodies develop against the NC1 domain of α5(IV) collagen, which occurs in normal kidneys, including renal allografts, forming distinct α345(IV) and α1256(IV) networks. Here, we studied the roles of these networks as antigens inciting alloimmunity and as targets of nephritogenic alloantibodies in APTN. We found that patients with APTN, but not those without nephritis, produce two kinds of alloantibodies against allogeneic collagen IV. Some alloantibodies targeted alloepitopes within α5NC1 monomers, shared by α345NC1 and α1256NC1 hexamers. Other alloantibodies specifically targeted alloepitopes that depended on the quaternary structure of α345NC1 hexamers. In Col4a5-null mice, immunization with native forms of allogeneic collagen IV exclusively elicited antibodies to quaternary α345NC1 alloepitopes, whereas alloimmunogens lacking native quaternary structure elicited antibodies to shared α5NC1 alloepitopes. These results imply that quaternary epitopes within α345NC1 hexamers may initiate alloimmune responses after transplant in X-linked Alport patients. Thus, α345NC1 hexamers are the culprit alloantigen and primary target of all alloantibodies mediating APTN, whereas α1256NC1 hexamers become secondary targets of anti-α5NC1 alloantibodies. Reliable detection of alloantibodies by immunoassays using α345NC1 hexamers may improve outcomes by facilitating early, accurate diagnosis.
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Enfermedad por Anticuerpos Antimembrana Basal Glomerular/inmunología , Autoantígenos/inmunología , Colágeno Tipo IV/inmunología , Mapeo Epitopo , Trasplante de Riñón/inmunología , Nefritis Hereditaria/inmunología , Nefritis Hereditaria/cirugía , Animales , Autoantígenos/química , Membrana Basal/inmunología , Bovinos , Colágeno Tipo IV/química , Haplorrinos , Humanos , Inmunoglobulina G/sangre , Inmunoglobulina G/inmunología , Isoanticuerpos/sangre , Isoanticuerpos/inmunología , Glomérulos Renales/inmunología , Ratones , Ratones Transgénicos , Complicaciones Posoperatorias/inmunología , Dominios y Motivos de Interacción de Proteínas/inmunología , Estructura Cuaternaria de Proteína , Trasplante HomólogoRESUMEN
BACKGROUND: We report a three-generation family with isolated Alport-like retinal abnormalities in the absence of lenticonus, hearing loss, kidney disease, and detectable molecular genetic defects in known Alport-related genes. METHODS: Clinical examination includes ocular biomicroscopy, fundus photography, optical coherence tomography, dipstick urinalysis, serum creatinine assessment, and molecular genetic analysis. RESULTS: The proband, her mother, and her maternal grandmother had normal best-corrected visual acuity and normal visual fields in both eyes. The macula presented a petaloid stair-case profile with scarce vessels in both eyes of the proband and a flat temporal macula lacking a foveal avascular zone in her mother and her grandmother. No family member had renal symptoms, unexplained subnormal hearing, or lenticonus. Sequencing and MLPA found no defect in COL4A3, COL4A4, and COL4A5. Common SNPs around the genes ± 1Mb showed no segregation. Furthermore, none of the variants shared between the affected individuals in genes from a gene panel of genes relevant for ophthalmopathy nor whole exome- and genome sequencing explained the phenotype. CONCLUSION: A new condition with two retinal Alport-like phenotypes was found. No abnormalities of the kidneys and lens were found, neither abnormalities of the type IV collagen genes related to Alport syndrome. Homology with retinal abnormalities seen in patients after surgical removal of the inner limiting membrane of the retina suggests that this is where the defect is located. We therefore suggest that the new retinal phenotypes and similar phenotypes can be described with the new definition "frail inner limiting membrane maculopathy."
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Nefritis Hereditaria , Linaje , Tomografía de Coherencia Óptica , Humanos , Femenino , Nefritis Hereditaria/genética , Nefritis Hereditaria/diagnóstico , Nefritis Hereditaria/patología , Adulto , Persona de Mediana Edad , Agudeza Visual/fisiología , Colágeno Tipo IV/genética , Enfermedades de la Retina/genética , Enfermedades de la Retina/diagnóstico , FenotipoRESUMEN
BACKGROUND: Imerslund-Gräsbeck Syndrome (IGS) is a rare genetic disorder characterised by juvenile megaloblastic anaemia. IGS is caused by mutations in either of the genes encoding the intestinal intrinsic factor-vitamin B12 receptor complex, cubam. The cubam receptor proteins cubilin and amnionless are both expressed in the small intestine as well as the proximal tubules of the kidney and exhibit an interdependent relationship for post-translational processing and trafficking. In the proximal tubules cubilin is involved in the reabsorption of several filtered plasma proteins including vitamin carriers and lipoproteins. Consistent with this, low-molecular-weight proteinuria has been observed in most patients with IGS. The aim of this study was to characterise novel disease-causing mutations and correlate novel and previously reported mutations with the presence of low-molecular-weight proteinuria. METHODS: Genetic screening was performed by direct sequencing of the CUBN and AMN genes and novel identified mutations were characterised by in silico and/or in vitro investigations. Urinary protein excretion was analysed by immunoblotting and high-resolution gel electrophoresis of collected urines from patients and healthy controls to determine renal phenotype. RESULTS: Genetic characterisation of nine IGS patients identified two novel AMN frameshift mutations alongside a frequently reported AMN splice site mutation and two CUBN missense mutations; one novel and one previously reported in Finnish patients. The novel AMN mutations were predicted to result in functionally null AMN alleles with no cell-surface expression of cubilin. Also, the novel CUBN missense mutation was predicted to affect structural integrity of the IF-B12 binding site of cubilin and hereby most likely cubilin cell-surface expression. Analysis of urinary protein excretion in the patients and 20 healthy controls revealed increased urinary excretion of cubilin ligands including apolipoprotein A-I, transferrin, vitamin D-binding protein, and albumin. This was, however, only observed in patients where plasma membrane expression of cubilin was predicted to be perturbed. CONCLUSIONS: In the present study, mutational characterisation of nine IGS patients coupled with analyses of urinary protein excretion provide additional evidence for a correlation between mutation type and presence of the characteristic low-molecular-weight proteinuria.
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Túbulos Renales Proximales/fisiopatología , Síndromes de Malabsorción/genética , Síndromes de Malabsorción/fisiopatología , Proteínas/genética , Proteinuria/genética , Proteinuria/fisiopatología , Receptores de Superficie Celular/genética , Deficiencia de Vitamina B 12/genética , Deficiencia de Vitamina B 12/fisiopatología , Albuminuria/diagnóstico , Anemia Megaloblástica , Animales , Apolipoproteína A-I/orina , Sitios de Unión , Células CHO , Estudios de Casos y Controles , Cricetulus , Femenino , Mutación del Sistema de Lectura , Humanos , Túbulos Renales Proximales/metabolismo , Masculino , Proteínas de la Membrana , Peso Molecular , Mutación Missense , Linaje , Conformación Proteica , Proteínas/metabolismo , Proteinuria/diagnóstico , Receptores de Superficie Celular/química , Receptores de Superficie Celular/metabolismo , Transferrina/orina , Proteína de Unión a Vitamina D/orinaRESUMEN
Angelman syndrome (AS) is a neurogenetic disorder caused by loss of expression of the maternal imprinted gene UBE3A on chromosome 15q11.2-q13. Clinical features of AS include severe intellectual disability, a happy disposition, ataxia, mandibular prognatism, and epilepsy. Our objectives were to examine the birth incidence of AS in Denmark and to characterize the size of the 15q11.2-q13 deletions with 1,000K array CGH. In addition, we analyzed genotype differences in regard to age at diagnosis and investigated the occurrence of deletions/duplications outside the 15q11.2-q13 regions. We identified 51 patients with genetically verified AS, which corresponded to a birth incidence of 1:24,580 (95%CI: 1:23,727-1:25,433). Thirty-six patients showed a deletion; 13 had a Class I deletion and 20 had a Class II deletion. There was bimodal distribution of the BP3 breakpoint. Three patients had larger and atypical deletions, with distal breakpoints telomeric to BP3. Five patients had paternal uniparental disomy (pUPD) of chromosome 15, and four had a verified UBE3A mutation. Additional deletions/duplications outside the 15q11.2-q13 areas were demonstrated in half the participants. Six harbored more than one CNV. Mean age at diagnosis was 21 months (95%CI: 17-23 months) for children with a deletion and 46 months (95%CI: 36-55 months) for children with pUPD or a UBE3A mutation (P < 0.01). The presence of a CNV outside 15q11.2-q13 did not have an impact on age at diagnosis.
Asunto(s)
Síndrome de Angelman/epidemiología , Adolescente , Síndrome de Angelman/diagnóstico , Síndrome de Angelman/genética , Niño , Preescolar , Deleción Cromosómica , Duplicación Cromosómica , Cromosomas Humanos Par 15 , Dinamarca/epidemiología , Femenino , Humanos , Incidencia , MasculinoRESUMEN
BACKGROUND: The reabsorption of filtered plasma proteins, hormones and vitamins by the renal proximal tubules is vital for body homeostasis. Studies of megalin-deficient mice suggest that the large multi-ligand endocytic receptor megalin plays an essential role in this process. In humans, dysfunctional megalin causes the extremely rare Donnai-Barrow/Facio-Oculo-Acustico-Renal (DB/FOAR) syndrome characterized by a characteristic and multifaceted phenotype including low-molecular-weight proteinuria. In this study, we examined the role of megalin for tubular protein reabsorption in humans through analysis of proximal tubular function in megalin-deficient patients. METHODS: Direct sequencing of the megalin-encoding gene (LRP2) was performed in a family in which three children presented with classical DB/FOAR manifestations. Renal consequences of megalin deficiency were investigated through immunohistochemical analyses of renal biopsy material and immunoblotting of urine samples. RESULTS: In the patients, a characteristic urinary protein profile with increased urinary excretion of vitamin D-binding protein, retinol-binding protein and albumin was associated with absence of, or reduced, proximal tubular endocytic uptake as shown by renal immunohistochemistry. In the absence of tubular uptake, urinary albumin excretion was in the micro-albuminuric range suggesting that limited amounts of albumin are filtered in human glomeruli. CONCLUSIONS: This study demonstrated that megalin plays an essential role for human proximal tubular protein reabsorption and suggests that only limited amounts of albumin is normally filtered in the human glomeruli. Finally, we propose that the characteristic urinary protein profile of DB/FOAR patients may be utilized as a diagnostic marker of megalin dysfunction.
Asunto(s)
Agenesia del Cuerpo Calloso/patología , Albúminas/metabolismo , Pérdida Auditiva Sensorineural/patología , Túbulos Renales Proximales/patología , Proteína 2 Relacionada con Receptor de Lipoproteína de Baja Densidad/deficiencia , Mutación/genética , Miopía/patología , Proteinuria/patología , Agenesia del Cuerpo Calloso/genética , Agenesia del Cuerpo Calloso/metabolismo , Preescolar , Femenino , Pérdida Auditiva Sensorineural/genética , Pérdida Auditiva Sensorineural/metabolismo , Hernias Diafragmáticas Congénitas , Humanos , Túbulos Renales Proximales/metabolismo , Proteína 2 Relacionada con Receptor de Lipoproteína de Baja Densidad/genética , Miopía/genética , Miopía/metabolismo , Fenotipo , Proteinuria/genética , Proteinuria/metabolismo , Defectos Congénitos del Transporte Tubular RenalAsunto(s)
Padre , Herencia , Ictiosis Lamelar/genética , Ictiosis Lamelar/patología , Queratina-10/genética , Mosaicismo , Mutación , Piel/patología , Biopsia , Preescolar , Análisis Mutacional de ADN , Femenino , Predisposición Genética a la Enfermedad , Humanos , Masculino , Persona de Mediana Edad , Linaje , FenotipoRESUMEN
Genetic testing for pathogenic COL4A3-5 variants is usually undertaken to investigate the cause of persistent hematuria, especially with a family history of hematuria or kidney function impairment. Alport syndrome experts now advocate genetic testing for persistent hematuria, even when a heterozygous pathogenic COL4A3 or COL4A4 is suspected, and cascade testing of their first-degree family members because of their risk of impaired kidney function. The experts recommend too that COL4A3 or COL4A4 heterozygotes do not act as kidney donors. Testing for variants in the COL4A3-COL4A5 genes should also be performed for persistent proteinuria and steroid-resistant nephrotic syndrome due to suspected inherited FSGS and for familial IgA glomerulonephritis and kidney failure of unknown cause.