RESUMEN
BACKGROUND: Imprinting disorders are rare diseases resulting from altered expression of imprinted genes, which exhibit parent-of-origin-specific expression patterns regulated through differential DNA methylation. A subgroup of patients with imprinting disorders have DNA methylation changes at multiple imprinted loci, a condition referred to as multi-locus imprinting disturbance (MLID). MLID is recognised in most but not all imprinting disorders and is also found in individuals with atypical clinical features; the presence of MLID often alters the management or prognosis of the affected person. Some cases of MLID are caused by trans-acting genetic variants, frequently not in the patients but their mothers, which have counselling implications. There is currently no consensus on the definition of MLID, clinical indications prompting testing, molecular procedures and methods for epigenetic and genetic diagnosis, recommendations for laboratory reporting, considerations for counselling, and implications for prognosis and management. The purpose of this study is thus to cover this unmet need. METHODS: A comprehensive literature search was conducted resulting in identification of more than 100 articles which formed the basis of discussions by two working groups focusing on clinical diagnosis (n = 12 members) and molecular testing (n = 19 members). Following eight months of preparations and regular online discussions, the experts from 11 countries compiled the preliminary documentation and determined the questions to be addressed during a face-to-face meeting which was held with the attendance of the experts together with four representatives of patient advocacy organisations. RESULTS: In light of available evidence and expert consensus, we formulated 16 propositions and 8 recommendations as interim guidance for the clinical and molecular diagnosis of MLID. CONCLUSIONS: MLID is a molecular designation, and for patients with MLID and atypical phenotypes, we propose the alternative term multi-locus imprinting syndrome. Due to the intrinsic variability of MLID, the guidelines underscore the importance of involving experts from various fields to ensure a confident approach to diagnosis, counselling, and care. The authors advocate for global, collaborative efforts in both basic and translational research to tackle numerous crucial questions that currently lack answers, and suggest reconvening within the next 3-5 years to evaluate the research advancements and update this guidance as needed.
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Metilación de ADN , Impresión Genómica , Humanos , Impresión Genómica/genética , Metilación de ADN/genética , Pruebas Genéticas/métodosRESUMEN
PURPOSE: Disorders/differences of sex development (DSD) result from variants in many different human genes but, frequently, have no detectable molecular cause. METHODS: Detailed clinical and genetic phenotyping was conducted on a family with three children. A Sec31a animal model and functional studies were used to investigate the significance of the findings. RESULTS: By trio whole-exome DNA sequencing we detected a heterozygous de novo nonsense SEC31A variant, in three children of healthy non-consanguineous parents. The children had different combinations of disorders that included complete gonadal dysgenesis and multiple pituitary hormone deficiency. SEC31A encodes a component of the COPII coat protein complex, necessary for intracellular anterograde vesicle-mediated transport between the endoplasmic reticulum (ER) and Golgi. CRISPR-Cas9 targeted knockout of the orthologous Sec31a gene region resulted in early embryonic lethality in homozygous mice. mRNA expression of ER-stress genes ATF4 and CHOP was increased in the children, suggesting defective protein transport. The pLI score of the gene, from gnomAD data, is 0.02. CONCLUSIONS: SEC31A might underlie a previously unrecognised clinical syndrome comprising gonadal dysgenesis, multiple pituitary hormone deficiencies, dysmorphic features and developmental delay. However, a variant that remains undetected, in a different gene, may alternatively be causal in this family.
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Disgenesia Gonadal , Hipopituitarismo , Animales , Niño , Preescolar , Femenino , Humanos , Masculino , Ratones , Disgenesia Gonadal/genética , Hipopituitarismo/genética , Hipopituitarismo/metabolismo , Ratones Noqueados , Linaje , Hormonas Hipofisarias/deficiencia , Hormonas Hipofisarias/genética , Proteínas de Transporte Vesicular/genéticaRESUMEN
PLAGL1 is one of a group of imprinted genes, whose altered expression causes imprinting disorders impacting growth, development, metabolism, and behavior. PLAGL1 over-expression causes transient neonatal diabetes mellitus (TNDM type 1) and, based on murine models, under-expression would be expected to cause growth restriction. However, only some reported individuals with upd(6)mat have growth restriction, giving rise to uncertainty about the role of PLAGL1 in human growth. Here we report three individuals investigated for growth restriction, two with upd(6)mat and one with a mosaic deletion of the paternally-inherited allele of PLAGL1. These cases add to evidence of its involvement in pre- and early post-natal human growth.
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Impresión Genómica , Disomía Uniparental , Recién Nacido , Humanos , Animales , Ratones , Impresión Genómica/genética , Factores de Transcripción/genética , Proteínas de Ciclo Celular/genética , Proteínas Supresoras de Tumor/genéticaRESUMEN
Background: Complications are frequently reported after hypospadias repair and there is a need to understand the factors that influence their occurrence. Methods: Data from boys with hypospadias born between 2000 and 2020 were obtained from the International Disorders of Sex Development (I-DSD) Registry. Logistic regressions, fisher's exact tests and spearman's correlation tests were performed on the data to assess associations between clinical factors and complication rates. Results: Of the 551 eligible boys, data were available on 160 (29%). Within the cohort, the median (range) External Masculinization Score (EMS) was 6 (2, 9). All presented with one or more additional genital malformation and 61 (38%) presented with additional extragenital malformations. Disorders of androgen action, androgen synthesis and gonadal development were diagnosed in 28 (18%), 22 (14%) and 9 (6%) boys, respectively. The remaining 101 (62%) patients were diagnosed as having non-specific 46,XY Disorders of Sex Development. Eighty (50%) boys had evidence of abnormal biochemistry, and gene variants were identified in 42 (26%). Median age at first hypospadias surgery was 2 years (0, 9), and median length of follow-up was 5 years (0, 17). Postsurgical complications were noted in 102 (64%) boys. There were no significant associations with postsurgical complications. Conclusions: Boys with proximal hypospadias in the I-DSD Registry have high rates of additional comorbidities and a high risk of postoperative complications. No clinical factors were significantly associated with complication rates. High complication rates with no observable cause suggest the involvement of other factors which need investigation.
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The TRIO gene encodes a rho guanine exchange factor, the function of which is to exchange GDP to GTP, and hence to activate Rho GTPases, and has been described to impact neurodevelopment. Specific genotype-to-phenotype correlations have been established previously describing striking differentiating features seen in variants located in specific domains of the TRIO gene that are associated with opposite effects on RAC1 activity. Currently, 32 cases with a TRIO gene alteration have been published in the medical literature. Here, we report an additional 25, previously unreported individuals who possess heterozygous TRIO variants and we review the literature. In addition, functional studies were performed on the c.4394A > G (N1465S) and c.6244-2A > G TRIO variants to provide evidence for their pathogenicity. Variants reported by the current study include missense variants, truncating nonsense variants, and an intragenic deletion. Clinical features were previously described and included developmental delay, learning difficulties, microcephaly, macrocephaly, seizures, behavioral issues (aggression, stereotypies), skeletal problems including short, tapering fingers and scoliosis, dental problems (overcrowding/delayed eruption), and variable facial features. Here, we report clinical features that have not been described previously, including specific structural brain malformations such as abnormalities of the corpus callosum and ventriculomegaly, additional psychological and dental issues along with a more recognizable facial gestalt linked to the specific domains of the TRIO gene and the effect of the variant upon the function of the encoded protein. This current study further strengthens the genotype-to-phenotype correlation that was previously established and extends the range of phenotypes to include structural brain abnormalities, additional skeletal, dental, and psychiatric issues.
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Microcefalia , Malformaciones del Sistema Nervioso , Humanos , Fenotipo , Mutación , Mutación Missense , Microcefalia/genéticaRESUMEN
The RhoGEF TRIO is known to play a major role in neuronal development by controlling actin cytoskeleton remodeling, primarily through the activation of the RAC1 GTPase. Numerous de novo mutations in the TRIO gene have been identified in individuals with neurodevelopmental disorders (NDDs). We have previously established the first phenotype/genotype correlation in TRIO-associated diseases, with striking correlation between the clinical features of the individuals and the opposite modulation of RAC1 activity by TRIO variants targeting different domains. The mutations hyperactivating RAC1 are of particular interest, as they are recurrently found in patients and are associated with a severe form of NDD and macrocephaly, indicating their importance in the etiology of the disease. Yet, it remains unknown how these pathogenic TRIO variants disrupt TRIO activity at a molecular level and how they affect neurodevelopmental processes such as axon outgrowth or guidance. Here we report an additional cohort of individuals carrying a pathogenic TRIO variant that reinforces our initial phenotype/genotype correlation. More importantly, by performing conformation predictions coupled to biochemical validation, we propose a model whereby TRIO is inhibited by an intramolecular fold and NDD-associated variants relieve this inhibition, leading to RAC1 hyperactivation. Moreover, we show that in cultured primary neurons and in the zebrafish developmental model, these gain-of-function variants differentially affect axon outgrowth and branching in vitro and in vivo, as compared to loss-of-function TRIO variants. In summary, by combining clinical, molecular, cellular and in vivo data, we provide compelling new evidence for the pathogenicity of novel genetic variants targeting the TRIO gene in NDDs. We report a novel mechanism whereby the fine-tuned regulation of TRIO activity is critical for proper neuronal development and is disrupted by pathogenic mutations.
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Orientación del Axón , Trastornos del Neurodesarrollo , Animales , Trastornos del Neurodesarrollo/genética , Neuronas , Factores de Intercambio de Guanina Nucleótido Rho , Pez Cebra , HumanosRESUMEN
Bosch-Boonstra-Schaaf optic atrophy syndrome (BBSOAS) is a rare congenital syndrome characterized by a range of phenotypes including optic atrophy and intellectual disability among other features. Pathogenic variants in the NR2F1 (nuclear receptor subfamily 2 group F member 1) gene have been linked to this condition. A recent report has shown that pathogenic variants in the start codon lead to decreased expression of the NR2F1 protein and a relatively mild phenotype, similar to that seen in whole gene deletions, and due to the lack of the dominant negative effect. Here we describe a severe case of BBSOAS with an initiation codon missense variant. The developmental delay, seizures, optic atrophy are in keeping with features observed in this condition, however this is the first report to describe colobomas and septo-optic dysplasia as associated features potentially extending the phenotype linked to BBSOAS. In addition, this is the first description of a severe phenotype linked to a de novo missense variant in the start codon of the NR2F1 gene.
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Coloboma , Discapacidad Intelectual , Atrofias Ópticas Hereditarias , Atrofia Óptica , Displasia Septo-Óptica , Factor de Transcripción COUP I/genética , Codón Iniciador , Coloboma/genética , Humanos , Discapacidad Intelectual/genética , Atrofias Ópticas Hereditarias/genética , Atrofia Óptica/diagnóstico , Atrofia Óptica/genética , Displasia Septo-Óptica/diagnóstico , Displasia Septo-Óptica/genéticaRESUMEN
Zhu-Tokita-Takenouchi-Kim (ZTTK) syndrome is caused by de novo loss-of-function variants in the SON gene (MIM #617140). This multisystemic disorder is characterized by intellectual disability, seizures, abnormal brain imaging, variable dysmorphic features, and various congenital anomalies. The wide application and increasing accessibility of whole exome sequencing (WES) has helped to identify new cases of ZTTK syndrome over the last few years. To date, there have been approximately 45 cases reported in the literature. Here, we describe 15 additional individuals with variants in the SON gene, including those with missense variants bringing the total number of known cases to 60. We have reviewed the clinical and molecular data of these new cases and all previously reported cases to further delineate the most common as well as emerging clinical findings related to this syndrome. Furthermore, we aim to delineate any genotype-phenotype correlations specifically for a recurring pathogenic four base pair deletion (c.5753_5756del) along with discussing the impact of missense variants seen in the SON gene.
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Anomalías Congénitas/genética , Proteínas de Unión al ADN/genética , Discapacidad Intelectual/genética , Antígenos de Histocompatibilidad Menor/genética , Convulsiones/genética , Encéfalo/diagnóstico por imagen , Encéfalo/patología , Anomalías Congénitas/diagnóstico , Anomalías Congénitas/patología , Femenino , Estudios de Asociación Genética , Predisposición Genética a la Enfermedad , Genotipo , Humanos , Discapacidad Intelectual/diagnóstico , Discapacidad Intelectual/patología , Masculino , Mutación Missense/genética , Fenotipo , Convulsiones/diagnóstico , Convulsiones/patología , Secuenciación del ExomaRESUMEN
The objective of our study was to use an established cohort of boys to investigate common patterns of malformations in those with hypospadias. We performed a retrospective review of the phenotype of participants in the Deciphering Developmental Disorders Study with neurodevelopmental delay and an 'Abnormality of the genital system'. This group was divided into two subgroups: those with hypospadias and without hypospadias. Associated phenotypes of the two subgroups were compared and analysed. Of the 166 Deciphering Developmental Disorders participants with hypospadias and neurodevelopmental delay, 47 (28%) had cardiovascular and 40 (24%) had structural brain abnormalities. The rate of cardiovascular abnormalities in those with neurodevelopmental delay and genital abnormalities other than hypospadias (N = 645) was lower at 19% (P = 0.001). In addition, structural brain malformations were higher at 24% in the hypospadias group versus 15% in the group without hypospadias (P = 0.002). The constellation of these features occured at a higher rate in the hypospadias group versus the no hypospadias group (P = 0.038). In summary, this is the first study to indicate that cardiovascular and brain abnormalities are frequently encountered in association with hypospadias in children with neurodevelopmental disorders. Not only do these associations provide insight into the underlying aetiology but also they highlight the multisystem involvement in conditions with hypospadias.
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Hipospadias/complicaciones , Hipospadias/fisiopatología , Trastornos del Neurodesarrollo/fisiopatología , Encéfalo/anomalías , Anomalías Cardiovasculares/etiología , Niño , Preescolar , Femenino , Humanos , Masculino , Trastornos del Neurodesarrollo/complicaciones , Trastornos del Neurodesarrollo/etiología , Fenotipo , Estudios Retrospectivos , Anomalías Urogenitales/complicacionesRESUMEN
In the last 3 years de novo sequence variants in the ARID2 (AT-rich interaction domain 2) gene, a subunit of the SWI/SNF complex, have been linked to intellectual disabilities in 3 case reports including one which describes frameshift mutations in ARID2 in 2 patients with features resembling Coffin-Siris syndrome. Coffin-Siris syndrome (CSS) is a rare congenital syndrome characterized by intellectual deficit, coarse facial features and hypoplastic or absent fifth fingernails and/or toenails among other features. Mutations in a number of different genes encoding SWI/SNF chromatin remodelling complex proteins have been described but the underlying molecular cause remains unknown in approximately 40% of patients with CSS. Here we describe 7 unrelated individuals, 2 with deletions of the ARID2 region and 5 with de novo truncating mutations in the ARID2 gene. Similarities to CSS are evident. Although hypertrichosis and hypoplasia of the fifth finger nail and distal phalanx do not appear to be common in these patients, toenail hypoplasia and the presence of Wormian bones might support the involvement of ARID2.
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Anomalías Múltiples/genética , Cara/anomalías , Deformidades Congénitas de la Mano/genética , Discapacidad Intelectual/genética , Micrognatismo/genética , Cuello/anomalías , Fenotipo , Factores de Transcripción/genética , Anomalías Múltiples/patología , Adolescente , Niño , Preescolar , Cara/patología , Femenino , Deformidades Congénitas de la Mano/patología , Humanos , Discapacidad Intelectual/patología , Masculino , Micrognatismo/patología , Cuello/patologíaAsunto(s)
Anodoncia/patología , Quiste Dermoide/patología , Incisivo/anomalías , Nariz/patología , Anodoncia/diagnóstico por imagen , Preescolar , Quiste Dermoide/diagnóstico por imagen , Familia , Femenino , Humanos , Incisivo/diagnóstico por imagen , Incisivo/patología , Lactante , Recién Nacido , Masculino , Nariz/diagnóstico por imagen , Linaje , Fenotipo , Tomografía Computarizada por Rayos XRESUMEN
A range of phenotypes that are associated with disorders of sex development (DSD) may also be encountered in patients with neurodevelopmental delay. In this study we have undertaken a collaborative retrospective review of anonymised phenotypic and genotypic data from the UK-wide Deciphering Developmental Disorders (DDD) study. Our objectives were to determine the frequency and range of DSD phenotypes observed in participants in the DDD study and to identify novel genetic associations. We found that of 7,439 DDD participants, 603 (8%) had at least one genital abnormality. In addition, we found that DSD occurs in 5% of patients with learning difficulties. Causative mutations were found in 13 developmental genes, of which, crucially, 6 had no previous reported association with DSD. Our findings indicate that recognition of these associations should not be overlooked in the management of patients with complex conditions and that exomic sequencing through projects like DDD increases diagnostic yield.