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PURPOSE: Pediatric cholestasis is the phenotypic expression of clinically and genetically heterogeneous disorders of bile acid synthesis and flow. Although a growing number of monogenic causes of pediatric cholestasis have been identified, the majority of cases remain undiagnosed molecularly. METHODS: In a cohort of 299 pediatric participants (279 families) with intrahepatic cholestasis, we performed exome sequencing as a first-tier diagnostic test. RESULTS: A likely causal variant was identified in 135 families (48.56%). These comprise 135 families that harbor variants spanning 37 genes with established or tentative links to cholestasis. In addition, we propose a novel candidate gene (PSKH1) (HGNC:9529) in 4 families. PSKH1 was particularly compelling because of strong linkage in three consanguineous families who shared a novel hepatorenal ciliopathy phenotype. Two of the four families shared a founder homozygous variant while the third had a different homozygous variant in PSKH1. PSKH1 encodes a putative protein serine kinase of unknown function. Patient fibroblasts displayed abnormal cilia that are long and show abnormal transport. A homozygous Pskh1 mutant mouse faithfully recapitulated the human phenotype and displayed abnormally long cilia. The phenotype could be rationalized by the loss of catalytic activity observed for each recombinant PSKH1 variant using in vitro kinase assays. CONCLUSION: Our results support the use of genomics in the workup of pediatric cholestasis and reveal PSKH1-related hepatorenal ciliopathy as a novel candidate monogenic form.
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Androgen insensitivity syndrome (AIS) is a difference of sex development (DSD) characterized by different degrees of undervirilization in individuals with a 46,XY karyotype despite normal to high gonadal testosterone production. Classically, AIS is explained by hemizygous mutations in the X-chromosomal androgen receptor (AR) gene. Nevertheless, the majority of individuals with clinically diagnosed AIS do not carry an AR gene mutation. Here, we present a patient with a 46,XY karyotype, born with undervirilized genitalia, age-appropriate testosterone levels and no uterus, characteristic for AIS. Diagnostic whole exome sequencing (WES) showed a maternally inherited LINE1 (L1) retrotransposon insertion in the 5' untranslated region (5'UTR) of the AR gene. Long-read nanopore sequencing confirmed this as an insertion of a truncated L1 element of ≈ 2.7 kb and showed an increased DNA methylation at the L1 insertion site in patient-derived genital skin fibroblasts (GSFs) compared to healthy controls. The insertion coincided with reduced AR transcript and protein levels in patient-derived GSFs confirming the clinical diagnosis AIS. Our results underline the relevance of retrotransposons in human disease, and expand the growing list of human diseases associated with them.
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Síndrome de Resistência a Andrógenos , Metilação de DNA , Epigênese Genética , Elementos Nucleotídeos Longos e Dispersos , Receptores Androgênicos , Humanos , Síndrome de Resistência a Andrógenos/genética , Síndrome de Resistência a Andrógenos/metabolismo , Receptores Androgênicos/genética , Receptores Androgênicos/metabolismo , Masculino , Elementos Nucleotídeos Longos e Dispersos/genética , Feminino , Sequenciamento do Exoma , Transcrição GênicaRESUMO
Utilizing trio whole-exome sequencing and a gene matching approach, we identified a cohort of 18 male individuals from 17 families with hemizygous variants in KCND1, including two de novo missense variants, three maternally inherited protein-truncating variants, and 12 maternally inherited missense variants. Affected subjects present with a neurodevelopmental disorder characterized by diverse neurological abnormalities, mostly delays in different developmental domains, but also distinct neuropsychiatric signs and epilepsy. Heterozygous carrier mothers are clinically unaffected. KCND1 encodes the α-subunit of Kv4.1 voltage-gated potassium channels. All variant-associated amino acid substitutions affect either the cytoplasmic N- or C-terminus of the channel protein except for two occurring in transmembrane segments 1 and 4. Kv4.1 channels were functionally characterized in the absence and presence of auxiliary ß subunits. Variant-specific alterations of biophysical channel properties were diverse and varied in magnitude. Genetic data analysis in combination with our functional assessment shows that Kv4.1 channel dysfunction is involved in the pathogenesis of an X-linked neurodevelopmental disorder frequently associated with a variable neuropsychiatric clinical phenotype.
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Transtornos do Neurodesenvolvimento , Adolescente , Adulto , Criança , Pré-Escolar , Feminino , Humanos , Lactente , Masculino , Epilepsia/genética , Sequenciamento do Exoma , Doenças Genéticas Ligadas ao Cromossomo X/genética , Heterozigoto , Mutação de Sentido Incorreto/genética , Transtornos do Neurodesenvolvimento/genética , Linhagem , Fenótipo , Canais de Potássio Shal/genéticaRESUMO
Hyperpolarization activated Cyclic Nucleotide (HCN) gated channels are crucial for various neurophysiological functions, including learning and sensory functions, and their dysfunction are responsible for brain disorders, such as epilepsy. To date, HCN2 variants have only been associated with mild epilepsy and recently, one monoallelic missense variant has been linked to developmental and epileptic encephalopathy. Here, we expand the phenotypic spectrum of HCN2- related disorders by describing twenty-one additional individuals from fifteen unrelated families carrying HCN2 variants. Seventeen individuals had developmental delay/intellectual disability (DD/ID), two had borderline DD/ID, and one had borderline DD. Ten individuals had epilepsy with DD/ID, with median age of onset of 10 months, and one had epilepsy with normal development. Molecular diagnosis identified thirteen different pathogenic HCN2 variants, including eleven missense variants affecting highly conserved amino acids, one frameshift variant, and one in-frame deletion. Seven variants were monoallelic of which five occurred de novo, one was not maternally inherited, one was inherited from a father with mild learning disabilities, and one was of unknown inheritance. The remaining six variants were biallelic, with four homozygous and two compound heterozygous variants. Functional studies using two-electrode voltage-clamp recordings in Xenopus laevis oocytes were performed on three monoallelic variants, p.(Arg324His), p.(Ala363Val), and p.(Met374Leu), and three biallelic variants, p.(Leu377His), p.(Pro493Leu) and p.(Gly587Asp). The p.(Arg324His) variant induced a strong increase of HCN2 conductance, while p.(Ala363Val) and p.(Met374Leu) displayed dominant negative effects, leading to a partial loss of HCN2 channel function. By confocal imaging, we found that the p.(Leu377His), p.(Pro493Leu) and p.(Gly587Asp) pathogenic variants impaired membrane trafficking, resulting in a complete loss of HCN2 elicited currents in Xenopus oocytes. Structural 3D-analysis in depolarized and hyperpolarized states of HCN2 channels, revealed that the pathogenic variants p.(His205Gln), p.(Ser409Leu), p.(Arg324Cys), p.(Asn369Ser) and p.(Gly460Asp) modify molecular interactions altering HCN2 function. Taken together, our data broadens the clinical spectrum associated with HCN2 variants, and disclose that HCN2 is involved in developmental encephalopathy with or without epilepsy.
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Neurodevelopmental proteasomopathies represent a distinctive category of neurodevelopmental disorders (NDD) characterized by genetic variations within the 26S proteasome, a protein complex governing eukaryotic cellular protein homeostasis. In our comprehensive study, we identified 23 unique variants in PSMC5 , which encodes the AAA-ATPase proteasome subunit PSMC5/Rpt6, causing syndromic NDD in 38 unrelated individuals. Overexpression of PSMC5 variants altered human hippocampal neuron morphology, while PSMC5 knockdown led to impaired reversal learning in flies and loss of excitatory synapses in rat hippocampal neurons. PSMC5 loss-of-function resulted in abnormal protein aggregation, profoundly impacting innate immune signaling, mitophagy rates, and lipid metabolism in affected individuals. Importantly, targeting key components of the integrated stress response, such as PKR and GCN2 kinases, ameliorated immune dysregulations in cells from affected individuals. These findings significantly advance our understanding of the molecular mechanisms underlying neurodevelopmental proteasomopathies, provide links to research in neurodegenerative diseases, and open up potential therapeutic avenues.
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Phosphoinositides (PIs) are membrane phospholipids produced through the local activity of PI kinases and phosphatases that selectively add or remove phosphate groups from the inositol head group. PIs control membrane composition and play key roles in many cellular processes including actin dynamics, endosomal trafficking, autophagy, and nuclear functions. Mutations in phosphatidylinositol 4,5 bisphosphate [PI(4,5)P2] phosphatases cause a broad spectrum of neurodevelopmental disorders such as Lowe and Joubert syndromes and congenital muscular dystrophy with cataracts and intellectual disability, which are thus associated with increased levels of PI(4,5)P2. Here, we describe a neurodevelopmental disorder associated with an increase in the production of PI(4,5)P2 and with PI-signaling dysfunction. We identified three de novo heterozygous missense variants in PIP5K1C, which encodes an isoform of the phosphatidylinositol 4-phosphate 5-kinase (PIP5KIγ), in nine unrelated children exhibiting intellectual disability, developmental delay, acquired microcephaly, seizures, visual abnormalities, and dysmorphic features. We provide evidence that the PIP5K1C variants result in an increase of the endosomal PI(4,5)P2 pool, giving rise to ectopic recruitment of filamentous actin at early endosomes (EEs) that in turn causes dysfunction in EE trafficking. In addition, we generated an in vivo zebrafish model that recapitulates the disorder we describe with developmental defects affecting the forebrain, including the eyes, as well as craniofacial abnormalities, further demonstrating the pathogenic effect of the PIP5K1C variants.
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Deficiência Intelectual , Fosfatidilinositóis , Animais , Síndrome , Actinas , Peixe-Zebra/genética , Deficiência Intelectual/genética , Monoéster Fosfórico Hidrolases/genética , Fosfatos de FosfatidilinositolRESUMO
PURPOSE: SRRM2 encodes the SRm300 protein, a splicing factor of the SR-related protein family characterized by its serine- and arginine-enriched domains. It promotes interactions between messenger RNA and the spliceosome catalytic machinery. This gene, predicted to be highly intolerant to loss of function (LoF) and very conserved through evolution, has not been previously reported in constitutive human disease. METHODS: Among the 1000 probands studied with developmental delay and intellectual disability in our database, we found 2 patients with de novo LoF variants in SRRM2. Additional families were identified through GeneMatcher. RESULTS: Here, we report on 22 patients with LoF variants in SRRM2 and provide a description of the phenotype. Molecular analysis identified 12 frameshift variants, 8 nonsense variants, and 2 microdeletions of 66 kb and 270 kb. The patients presented with a mild developmental delay, predominant speech delay, autistic or attention-deficit/hyperactivity disorder features, overfriendliness, generalized hypotonia, overweight, and dysmorphic facial features. Intellectual disability was variable and mild when present. CONCLUSION: We established SRRM2 as a gene responsible for a rare neurodevelopmental disease.
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Deficiência Intelectual , Transtornos do Neurodesenvolvimento , Proteínas de Ligação a RNA/genética , Criança , Deficiências do Desenvolvimento/genética , Humanos , Deficiência Intelectual/genética , Hipotonia Muscular/genética , Transtornos do Neurodesenvolvimento/genética , FenótipoRESUMO
PURPOSE: Few studies have systematically analyzed the structure and content of laboratory exome sequencing reports from the same patient. METHODS: We merged 8 variants from patients into "normal" exomes to create virtual patient-parent trios. We provided laboratories worldwide with the data and patient phenotype information (developmental delay, dysmorphic features, and cardiac hypertrophy). Laboratories analyzed the data and issued a diagnostic exome report. Reports were scored using a coding matrix developed from existing guidelines. RESULTS: In total, 41 laboratories representing 17 countries issued reports. Reporting of quality control statistics and technical information was poor (46.3%). Although 75.6% of the reports clearly stated the classification of all reported variants, few reports listed extensive evidence supporting variant classification. Only 53.1% of laboratories that reported unsolicited or secondary findings gave advice regarding health-related follow-up and 20.5% gave advice regarding cascade testing for relatives. Of the 147 variants reported, 105 (71.4%) were classified in agreement with classifications based on American College of Medical Genetics and Genomics/Association for Molecular Pathology and Association for Clinical Genomic Science guidelines. Concordance was higher for known pathogenic variants (86.3%) than for novel unpublished variants (56.8%). CONCLUSION: The considerable variability identified in the components that laboratories included in their reports and their classification of variants suggests that existing guidelines are not being used consistently with significant implications for patient care.
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Exoma , Sequenciamento de Nucleotídeos em Larga Escala , Exoma/genética , Testes Genéticos , Genômica , Humanos , Sequenciamento do ExomaRESUMO
SPTBN1 encodes ßII-spectrin, the ubiquitously expressed ß-spectrin that forms micrometer-scale networks associated with plasma membranes. Mice deficient in neuronal ßII-spectrin have defects in cortical organization, developmental delay and behavioral deficiencies. These phenotypes, while less severe, are observed in haploinsufficient animals, suggesting that individuals carrying heterozygous SPTBN1 variants may also show measurable compromise of neural development and function. Here we identify heterozygous SPTBN1 variants in 29 individuals with developmental, language and motor delays; mild to severe intellectual disability; autistic features; seizures; behavioral and movement abnormalities; hypotonia; and variable dysmorphic facial features. We show that these SPTBN1 variants lead to effects that affect ßII-spectrin stability, disrupt binding to key molecular partners, and disturb cytoskeleton organization and dynamics. Our studies define SPTBN1 variants as the genetic basis of a neurodevelopmental syndrome, expand the set of spectrinopathies affecting the brain and underscore the critical role of ßII-spectrin in the central nervous system.
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Genes Dominantes , Predisposição Genética para Doença , Variação Genética , Transtornos do Neurodesenvolvimento/genética , Espectrina/genética , Animais , Estudos de Associação Genética/métodos , Heterozigoto , Humanos , Camundongos , Transtornos do Neurodesenvolvimento/diagnóstico , Fenótipo , Espectrina/metabolismoRESUMO
Truncating variants in exons 33 and 34 of the SNF2-related CREBBP activator protein (SRCAP) gene cause the neurodevelopmental disorder (NDD) Floating-Harbor syndrome (FLHS), characterized by short stature, speech delay, and facial dysmorphism. Here, we present a cohort of 33 individuals with clinical features distinct from FLHS and truncating (mostly de novo) SRCAP variants either proximal (n = 28) or distal (n = 5) to the FLHS locus. Detailed clinical characterization of the proximal SRCAP individuals identified shared characteristics: developmental delay with or without intellectual disability, behavioral and psychiatric problems, non-specific facial features, musculoskeletal issues, and hypotonia. Because FLHS is known to be associated with a unique set of DNA methylation (DNAm) changes in blood, a DNAm signature, we investigated whether there was a distinct signature associated with our affected individuals. A machine-learning model, based on the FLHS DNAm signature, negatively classified all our tested subjects. Comparing proximal variants with typically developing controls, we identified a DNAm signature distinct from the FLHS signature. Based on the DNAm and clinical data, we refer to the condition as "non-FLHS SRCAP-related NDD." All five distal variants classified negatively using the FLHS DNAm model while two classified positively using the proximal model. This suggests divergent pathogenicity of these variants, though clinically the distal group presented with NDD, similar to the proximal SRCAP group. In summary, for SRCAP, there is a clear relationship between variant location, DNAm profile, and clinical phenotype. These results highlight the power of combined epigenetic, molecular, and clinical studies to identify and characterize genotype-epigenotype-phenotype correlations.
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Anormalidades Múltiplas/patologia , Adenosina Trifosfatases/genética , Anormalidades Craniofaciais/patologia , Metilação de DNA , Epigênese Genética , Transtornos do Crescimento/patologia , Comunicação Interventricular/patologia , Mutação , Transtornos do Neurodesenvolvimento/patologia , Fenótipo , Anormalidades Múltiplas/genética , Estudos de Casos e Controles , Estudos de Coortes , Anormalidades Craniofaciais/genética , Feminino , Predisposição Genética para Doença , Transtornos do Crescimento/genética , Comunicação Interventricular/genética , Humanos , Recém-Nascido , Masculino , Transtornos do Neurodesenvolvimento/genéticaRESUMO
Defects in histone methyltransferases (HMTs) are major contributing factors in neurodevelopmental disorders (NDDs). Heterozygous variants of SETD1A involved in histone H3 lysine 4 (H3K4) methylation were previously identified in individuals with schizophrenia. Here, we define the clinical features of the Mendelian syndrome associated with haploinsufficiency of SETD1A by investigating 15 predominantly pediatric individuals who all have de novo SETD1A variants. These individuals present with a core set of symptoms comprising global developmental delay and/or intellectual disability, subtle facial dysmorphisms, behavioral and psychiatric problems. We examined cellular phenotypes in three patient-derived lymphoblastoid cell lines with three variants: p.Gly535Alafs*12, c.4582-2_4582delAG, and p.Tyr1499Asp. These patient cell lines displayed DNA damage repair defects that were comparable to previously observed RNAi-mediated depletion of SETD1A. This suggested that these variants, including the p.Tyr1499Asp in the catalytic SET domain, behave as loss-of-function (LoF) alleles. Previous studies demonstrated a role for SETD1A in cell cycle control and differentiation. However, individuals with SETD1A variants do not show major structural brain defects or severe microcephaly, suggesting that defective proliferation and differentiation of neural progenitors is unlikely the single underlying cause of the disorder. We show here that the Drosophila melanogaster SETD1A orthologue is required in postmitotic neurons of the fly brain for normal memory, suggesting a role in post development neuronal function. Together, this study defines a neurodevelopmental disorder caused by dominant de novo LoF variants in SETD1A and further supports a role for H3K4 methyltransferases in the regulation of neuronal processes underlying normal cognitive functioning.
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Deficiência Intelectual , Transtornos do Neurodesenvolvimento , Animais , Criança , Drosophila , Drosophila melanogaster , Haploinsuficiência/genética , Histona-Lisina N-Metiltransferase/genética , Humanos , Deficiência Intelectual/genética , Transtornos do Neurodesenvolvimento/genéticaRESUMO
PURPOSE: This study aims to provide a comprehensive description of the phenotypic and genotypic spectrum of SNAP25 developmental and epileptic encephalopathy (SNAP25-DEE) by reviewing newly identified and previously reported individuals. METHODS: Individuals harboring heterozygous missense or loss-of-function variants in SNAP25 were assembled through collaboration with international colleagues, matchmaking platforms, and literature review. For each individual, detailed phenotyping, classification, and structural modeling of the identified variant were performed. RESULTS: The cohort comprises 23 individuals with pathogenic or likely pathogenic de novo variants in SNAP25. Intellectual disability and early-onset epilepsy were identified as the core symptoms of SNAP25-DEE, with recurrent findings of movement disorders, cerebral visual impairment, and brain atrophy. Structural modeling for all variants predicted possible functional defects concerning SNAP25 or impaired interaction with other components of the SNARE complex. CONCLUSION: We provide a comprehensive description of SNAP25-DEE with intellectual disability and early-onset epilepsy mostly occurring before the age of two years. These core symptoms and additional recurrent phenotypes show an overlap to genes encoding other components or associated proteins of the SNARE complex such as STX1B, STXBP1, or VAMP2. Thus, these findings advance the concept of a group of neurodevelopmental disorders that may be termed "SNAREopathies."
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Encefalopatias , Epilepsia , Deficiência Intelectual , Transtornos do Neurodesenvolvimento , Proteína 25 Associada a Sinaptossoma/genética , Pré-Escolar , Epilepsia/genética , Humanos , Transtornos do Neurodesenvolvimento/genética , FenótipoRESUMO
PURPOSE: Existing research suggests that while some laboratories report variants of uncertain significance, unsolicited findings (UF), and/or secondary findings (SF) when performing exome sequencing, others do not. METHODS: To investigate reporting differences, we created virtual patient-parent trio data by merging variants from patients into "normal" exomes. We invited laboratories worldwide to analyze the data along with patient phenotype information (developmental delay, dysmorphic features, and cardiac hypertrophy). Laboratories issued a diagnostic exome report and completed questionnaires to explain their rationale for reporting (or not reporting) each of the eight variants integrated. RESULTS: Of the 39 laboratories that completed the questionnaire, 30 reported the HDAC8 variant, which was a partial cause of the patient's primary phenotype, and 26 reported the BICD2 variant, which explained another phenotypic component. Lack of reporting was often due to using a filter or a targeted gene panel that excluded the variant, or because they did not consider the variant to be responsible for the phenotype. There was considerable variation in reporting variants associated with the cardiac phenotype (MYBPC3 and PLN) and reporting UF/SF also varied widely. CONCLUSION: This high degree of variability has significant impact on whether causative variants are identified, with important implications for patient care.
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Testes Genéticos , Laboratórios , Exoma/genética , Histona Desacetilases , Humanos , Proteínas Repressoras , Análise de Sequência de DNA , Sequenciamento do ExomaRESUMO
Next-generation sequencing and next-generation metabolic screening are, independently, increasingly applied in clinical diagnostics of inborn errors of metabolism (IEM). Integrated into a single bioinformatic method, these two -omics technologies can potentially further improve the diagnostic yield for IEM. Here, we present cross-omics: a method that uses untargeted metabolomics results of patient's dried blood spots (DBSs), indicated by Z-scores and mapped onto human metabolic pathways, to prioritize potentially affected genes. We demonstrate the optimization of three parameters: (1) maximum distance to the primary reaction of the affected protein, (2) an extension stringency threshold reflecting in how many reactions a metabolite can participate, to be able to extend the metabolite set associated with a certain gene, and (3) a biochemical stringency threshold reflecting paired Z-score thresholds for untargeted metabolomics results. Patients with known IEMs were included. We performed untargeted metabolomics on 168 DBSs of 97 patients with 46 different disease-causing genes, and we simulated their whole-exome sequencing results in silico. We showed that for accurate prioritization of disease-causing genes in IEM, it is essential to take into account not only the primary reaction of the affected protein but a larger network of potentially affected metabolites, multiple steps away from the primary reaction.
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The ubiquitin-proteasome system is the principal system for protein degradation mediated by ubiquitination and is involved in various cellular processes. Cullin-RING ligases (CRL) are one class of E3 ubiquitin ligases that mediate polyubiquitination of specific target proteins, leading to decomposition of the substrate. Cullin 3 (CUL3) is a member of the Cullin family proteins, which act as scaffolds of CRL. Here we describe three cases of global developmental delays, with or without epilepsy, who had de novo CUL3 variants. One missense variant c.854T>C, p.(Val285Ala) and two frameshift variants c.137delG, p.(Arg46Leufs*32) and c.1239del, p.(Asp413Glufs*42) were identified by whole-exome sequencing. The Val285 residue located in the Cullin N-terminal domain and p.Val285Ala CUL3 mutant showed significantly weaker interactions to the BTB domain proteins than wild-type CUL3. Our findings suggest that de novo CUL3 variants may cause structural instability of the CRL complex and impairment of the ubiquitin-proteasome system, leading to diverse neuropsychiatric disorders.
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Proteínas Culina/genética , Proteínas Culina/metabolismo , Deficiências do Desenvolvimento/genética , Predisposição Genética para Doença , Espasmos Infantis/genética , Criança , Pré-Escolar , Deficiências do Desenvolvimento/complicações , Deficiências do Desenvolvimento/fisiopatologia , Feminino , Mutação da Fase de Leitura , Células HEK293 , Humanos , Lactente , Masculino , Mutação de Sentido Incorreto , Ligação Proteica , Espasmos Infantis/complicações , Ubiquitina-Proteína Ligases/metabolismo , Sequenciamento do ExomaRESUMO
BACKGROUND: CLN3 disease is a disorder of lysosomal homeostasis predominantly affecting the retina and the brain. The severity of the underlying mutations in CLN3 particularly determines onset and course of neurological deterioration. Given the highly conserved start codon code among eukaryotic species, we expected a variant in the start codon of CLN3 to give rise to the classical, that is, severe, phenotype. CASE SERIES: We present three patients with an identical CLN3 genotype (compound heterozygosity for the common 1 kb deletion in combination with a c.1A > C start codon variant) who all displayed a more attenuated phenotype than expected. While their retinal phenotype was similar to as expected in classical CLN3 disease, their neurological phenotype was delayed. Two patients had an early onset of cognitive impairment, but a particularly slow deterioration afterwards without any obvious motor impairment. The third patient also had a late onset of cognitive impairment. CONCLUSIONS: Contrasting our initial expectations, patients with a start codon variant in CLN3 may display a protracted phenotype. Future work will have to reveal the exact mechanism behind the assumed residual protein synthesis, and determine whether this may be eligible to start codon targeted therapy.
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RNA polymerase III (Pol III) is an essential 17-subunit complex responsible for the transcription of small housekeeping RNAs such as transfer RNAs and 5S ribosomal RNA. Biallelic variants in four genes (POLR3A, POLR3B, and POLR1C and POLR3K) encoding Pol III subunits have previously been found in individuals with (neuro-) developmental disorders. In this report, we describe three individuals with biallelic variants in POLR3GL, a gene encoding a Pol III subunit that has not been associated with disease before. Using whole exome sequencing in a monozygotic twin and an unrelated individual, we detected homozygous and compound heterozygous POLR3GL splice acceptor site variants. RNA sequencing confirmed the loss of full-length POLR3GL RNA transcripts in blood samples of the individuals. The phenotypes of the described individuals are mainly characterized by axial endosteal hyperostosis, oligodontia, short stature, and mild facial dysmorphisms. These features largely fit within the spectrum of phenotypes caused by previously described biallelic variants in POLR3A, POLR3B, POLR1C, and POLR3K. These findings further expand the spectrum of POLR3-related disorders and implicate that POLR3GL should be included in genetic testing if such disorders are suspected.
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Anodontia/genética , Osteocondrodisplasias/genética , RNA Polimerase III/genética , Adulto , Anodontia/patologia , Feminino , Humanos , Mutação com Perda de Função , Osteocondrodisplasias/patologia , Fenótipo , Splicing de RNA , SíndromeRESUMO
Intracellular cobalamin metabolism (ICM) defects can be present as autosomal recessive or X-linked disorders. Parenteral hydroxocobalamin (P-OHCbl) is the mainstay of therapy, but the optimal dose has not been determined. Despite early treatment, long-term complications may develop. We have analyzed the biochemical and clinical responses in five patients with early onset of different types of ICM defects (cblC: patients 1-3; cblA: patient 4; cblX: patient 5) following daily P-OHCbl dose intensification (DI). In patient 4, P-OHCbl was started at age 10 years and in patient 5 at age 5 years. OHCbl was formulated at either, 5, 25, or 50 mg/mL. P-OHCbl was intravenously or subcutaneously (SQ) delivered, subsequently by placement of a SQ injection port except in patient 4. In all patients, homocysteine and methylmalonic acid levels, demonstrated an excellent response to various P-OHCbl doses. After age 36 months, patients 1-3 had a close to normal neurological examination with lower range developmental quotient. In patient 3, moderate visual impairment was present. Patient 4, at age 10 years, had normal renal, visual and cognitive function. In cblX patient 5, epilepsy was better controlled. In conclusion, P-OHCbl-DI caused an excellent control of metabolites in all patients. In the three cblC patients, comparison with patients, usually harboring identical genotype and similar metabolic profile, was suggestive of a positive effect, in favor of clinical efficacy. With P-OHCbl-DI, CblA patient has been placed into a lower risk to develop renal and optic impairment. In cblX patient, lower P-OHCbl doses were administrated to improve tolerability.