GJB2 c.35del variant up-regulates GJA1 gene expression and affects differentiation of human stem cells.

Pathogenic DNA alterations in GJB2 are present in nearly half of non-syndromic hearing loss cases with autosomal recessive inheritance. The most frequent variant in GJB2 causing non-syndromic hearing loss is the frameshifting c.35del. GJB2 encodes Cx26, a protein of the connexin family that assembles hemichannels and gap junctions. The expression of paralogous proteins is believed to compensate for the loss of function of specific connexins. As Cx26 has been involved in cell differentiation in distinct tissues, we employed stem cells derived from human exfoliated deciduous teeth (SHEDs), homozygous for the c.35del variant, to assess GJB2 roles in stem cell differentiation and the relationship between its loss of function and the expression of paralogous genes. Primary SHED cultures from patients and control individuals were compared. SHEDs from patients had significantly less GJB2 mRNA and increased amount of GJA1 (Cx43), but not GJB6 (Cx30) or GJB3 (Cx31) mRNA. In addition, they presented higher induced differentiation to adipocytes and osteocytes but lower chondrocyte differentiation. Our results suggest that GJA1 increased expression may be involved in functional compensation for GJB2 loss of function in human stem cells, and it may explain changes in differentiation properties observed in SHEDs with and without the c.35del variant.

Neuropsychological profile in tuberous sclerosis complex: a study of clinical and cognitive variables in a cohort from Brazil.

BACKGROUND: Tuberous sclerosis complex (TSC) is an autosomal dominant genetic disorder with a wide clinical, cognitive, and behavioral expressivity. OBJECTIVE: To assess the neuropsychological profile of individuals clinically diagnosed with TSC and the factors that could significantly impact their cognitive development. METHODS: A total of 62 individuals with ages ranging from 3 to 38 years were followed up in a tertiary attention hospital in Southern Brazil, and they were assessed using a standard battery and the Vineland Adaptive Behavior Scales, when intellectual disability was observed. RESULTS: History of epilepsy was found in 56 participants (90.3%), and 31 (50%) presented an intellectual disability. Among the other half of TSC individuals without intellectual disability, 8 (12.9%) presented borderline classification, 20 (32.2%) presented average scores, and 3 (4.8%) were above average. In total, 17 participants (27.4%) fulfilled the diagnostic criteria for autism spectrum disorder. The results of the multiple linear regression analysis suggested that seizures, age at diagnosis, visual perception, and general attention significantly impact cognitive performance indexes. CONCLUSION: The present study suggests that the occurrence of epileptic seizures and older age at diagnosis contribute to higher impairment in the domains of cognitive development, underlining the importance of early diagnosis and the prevention of epileptic seizures or their rapid control. The development of attentional skills, visual perception, and executive functions must be followed up.

ANTECEDENTES: O complexo da esclerose tuberosa (CET) é uma doença genética autossômica dominante com ampla expressividade clínica, cognitiva e comportamental. OBJETIVO: Avaliar o perfil neuropsicológico de indivíduos com diagnóstico clínico de CET e os fatores que poderiam impactar significativamente o seu desenvolvimento cognitivo. MéTODOS: Ao todo, 62 indivíduos com idades entre 3 e 38 anos foram acompanhados em um hospital terciário do Sul do Brasil e avaliados por meio de uma bateria padrão e das Escalas de Comportamento Adaptativo Vineland, quando observada deficiência intelectual. RESULTADOS: Encontrou-se histórico de epilepsia em 56 participantes (90,3%) e de deficiência intelectual em 31 (50%). Quanto à outra metade dos indivíduos com CET sem deficiência intelectual, 8 (12,9%) apresentaram classificação limítrofe, 20 (32,2%) apresentaram pontuações médias e 3 (4,8%) estavam acima da média. No total, 17 participantes (27,4%) preenchiam os critérios diagnósticos para o transtorno do espectro autista. Os resultados da análise de regressão linear múltipla sugeriram que as crises epilépticas, a idade ao diagnóstico, a percepção visual e a atenção geral impactam significativamente os índices de desempenho cognitivo. CONCLUSãO: Este estudo sugere que a ocorrência de crises epilépticas e a maior idade ao diagnóstico contribuem para um maior comprometimento nos domínios do desenvolvimento cognitivo, e destaca-se a importância do diagnóstico precoce e da prevenção das crises epilépticas ou do seu rápido controle. O desenvolvimento de habilidades de atenção, percepção visual e funções executivas deve ser acompanhado.

A dermatological assessment of pediatric patients with tuberous sclerosis complex (TSC).

BACKGROUND: Tuberous sclerosis complex (TSC) is a multisystem neurocutaneous syndrome with variable phenotypes. Recent updates of TSC diagnostic criteria reaffirmed the defined genetic diagnostic criterion as the finding of a pathogenic DNA alteration in either TSC1 or TSC2 genes. It also slightly modified definite clinical diagnostic criteria. TSC-associated skin lesions in infancy are important clinical signs to select individuals with possible TSC for a closer clinical follow-up and genetic testing. OBJECTIVE: To raise awareness of the updated TSC diagnosis criteria; to assess the frequency of skin lesions in TSC patients as well as the first dermatological presentation; and to associate the findings with either TSC1 or TSC2 mutations. METHODS: Observational cross-sectional study. Clinical and genetic data were retrospectively collected from 37 TSC patients from a Brazilian University Hospital. Patients with skin signs were examined and prospectively assessed for 12 months. RESULTS: The earliest cutaneous lesions were hypomelanotic macules, which together with angiofibromas were the most frequent dermatological lesions. The total pathogenic DNA alteration ratio between TSC2 and TSC1 genes was 8:1. The frequency of a TSC2 pathogenic variant was 10-fold greater in the presence of ungual fibromas. STUDY LIMITATIONS: Small sample and a limited number of patients with TSC1 pathogenic variants. CONCLUSION: Clinicians should be knowledgeable about TSC updated diagnostic criteria. Patients need to be followed up by a multidisciplinary team and treated accordingly. Early detection of cutaneous lesions is important for TSC diagnosis. A significant association between TSC2 gene pathogenic alterations and ungual fibromas is described.

Clinical Characterization and Underlying Genetic Findings in Brazilian Patients with Syndromic Microcephaly Associated with Neurodevelopmental Disorders.

Microcephaly is characterized by an occipitofrontal circumference at least two standard deviations below the mean for age and sex. Neurodevelopmental disorders (NDD) are commonly associated with microcephaly, due to perturbations in brain development and functioning. Given the extensive genetic heterogeneity of microcephaly, managing patients is hindered by the broad spectrum of diagnostic possibilities that exist before conducting molecular testing. We investigated the genetic basis of syndromic microcephaly accompanied by NDD in a Brazilian cohort of 45 individuals and characterized associated clinical features, as well as evaluated the effectiveness of whole-exome sequencing (WES) as a diagnostic tool for this condition. Patients previously negative for pathogenic copy number variants underwent WES, which was performed using a trio approach for isolated index cases (n = 31), only the index in isolated cases with parental consanguinity (n = 8) or affected siblings in familial cases (n = 3). Pathogenic/likely pathogenic variants were identified in 19 families (18 genes) with a diagnostic yield of approximately 45%. Nearly 86% of the individuals had global developmental delay/intellectual disability and 51% presented with behavioral disturbances. Additional frequent clinical features included facial dysmorphisms (80%), brain malformations (67%), musculoskeletal (71%) or cardiovascular (47%) defects, and short stature (54%). Our findings unraveled the underlying genetic basis of microcephaly in half of the patients, demonstrating a high diagnostic yield of WES for microcephaly and reinforcing its genetic heterogeneity. We expanded the phenotypic spectrum associated with the condition and identified a potentially novel gene (CCDC17) for congenital microcephaly.

FMRP ribonucleoprotein complexes and RNA homeostasis.

The Fragile Mental Retardation 1 gene (FMR1), at Xq27.3, encodes the fragile mental retardation protein (FMRP), and displays in its 5'-untranslated region a series of polymorphic CGG triplet repeats that may undergo dynamic mutation. Fragile X syndrome (FXS) is the leading cause of inherited intellectual disability among men, and is most frequently due to FMR1 full mutation and consequent transcription repression. FMR1 premutations may associate with at least two other clinical conditions, named fragile X-associated primary ovarian insufficiency (FXPOI) and tremor and ataxia syndrome (FXTAS). While FXPOI and FXTAS appear to be mediated by FMR1 mRNA accumulation, relative reduction of FMRP, and triplet repeat translation, FXS is due to the lack of the RNA-binding protein FMRP. Besides its function as mRNA translation repressor in neuronal and stem/progenitor cells, RNA editing roles have been assigned to FMRP. In this review, we provide a brief description of FMR1 transcribed microsatellite and associated clinical disorders, and discuss FMRP molecular roles in ribonucleoprotein complex assembly and trafficking, as well as aspects of RNA homeostasis affected in FXS cells.

Understanding human DNA variants affecting pre-mRNA splicing in the NGS era.

Pre-mRNA splicing, an essential step in eukaryotic gene expression, relies on recognition of short sequences on the primary transcript intron ends and takes place along transcription by RNA polymerase II. Exonic and intronic auxiliary elements may modify the strength of exon definition and intron recognition. Splicing DNA variants (SV) have been associated with human genetic diseases at canonical intron sites, as well as exonic substitutions putatively classified as nonsense, missense or synonymous variants. Their effects on mRNA may be modulated by cryptic splice sites associated to the SV allele, comprehending exon skipping or shortening, and partial or complete intron retention. As splicing mRNA outputs result from combinatorial effects of both intrinsic and extrinsic factors, in vitro functional assays supported by computational analyses are recommended to assist SV pathogenicity assessment for human Mendelian inheritance diseases. The increasing use of next-generating sequencing (NGS) targeting full genomic gene sequence has raised awareness of the relevance of deep intronic SV in genetic diseases and inclusion of pseudo-exons into mRNA. Finally, we take advantage of recent advances in sequencing and computational technologies to analyze alternative splicing in cancer. We explore the Catalog of Somatic Mutations in Cancer (COSMIC) to describe the proportion of splice-site mutations in cis and trans regulatory elements. Genomic data from large cohorts of different cancer types are increasingly available, in addition to repositories of normal and somatic genetic variations. These are likely to bring new insights to understanding the genetic control of alternative splicing by mapping splicing quantitative trait loci in tumors.

Unilateral giant renal angiomyolipoma and pulmonary lymphangioleiomyomatosis.

Angiomyolipomas (AMLs) are mesenchymal neoplasms, named so because of the complex tissue composition represented by variable proportions of mature adipose tissue, smooth muscle cells, and dysmorphic blood vessels. Although AMLs may rise in different sites of the body, they are mostly observed in the kidney and liver. In the case of renal AMLs, they are described in two types: isolated AMLs and AMLs associated with tuberous sclerosis (TS). While most cases of AMLs are found incidentally during imaging examinations and are asymptomatic, others may reach huge proportions causing symptoms. Pulmonary lymphangioleiomyomatosis (LAM) is a rare benign disease characterized by cystic changes in the pulmonary parenchyma and smooth muscle proliferation, leading to a mixed picture of interstitial and obstructive disease. AML and LAM constitute major features of tuberous sclerosis complex (TSC), a multisystem autosomal dominant tumor-suppressor gene complex diagnosis. The authors report the case of a young female patient who presented a huge abdominal tumor, which at computed tomography (CT) show a fat predominance. The tumor displaced the right kidney and remaining abdominal viscera to the left. Chest CT also disclosed pulmonary lesions compatible with lymphangioleiomyomatosis. Because of sudden abdominal pain accompanied by a fall in the hemoglobin level, the patient underwent an urgent laparotomy. The excised tumor was shown to be a giant renal AML with signs of bleeding in its interior. The authors call attention to the diagnosis of AML and the huge proportions that the tumor can reach, as well as for ruling out the TSC diagnosis, once it may impose genetic counseling implications..