Julie S. Cohen

Clinical whole exome sequencing in child neurology practice.

Whole exome sequencing (WES) represents a significant breakthrough in clinical genetics as a powerful tool for etiological discovery in neurodevelopmental disorders. To better characterize the genetic landscape of neurodevelopmental disorders, we analyzed patients in our pediatric neurogenetics clinic who underwent WES.

De novo KCNB1 mutations in epileptic encephalopathy

Numerous studies have demonstrated increased load of de novo copy number variants or single nucleotide variants in individuals with neurodevelopmental disorders, including epileptic encephalopathies, intellectual disability, and autism.

MEF2C Haploinsufficiency features consistent hyperkinesis, variable epilepsy, and has a role in dorsal and ventral neuronal developmental pathways

MEF2C haploinsufficiency syndrome is an emerging neurodevelopmental disorder associated with intellectual disability, autistic features, epilepsy, and abnormal movements. We report 16 new patients with MEF2C haploinsufficiency, including the oldest reported patient with MEF2C deletion at 5q14.3. We detail the neurobehavioral phenotype, epilepsy, and abnormal movements, and compare our subjects with those previously reported in the literature. We also investigate Mef2c expression in the developing mouse forebrain. A spectrum of neurofunctional deficits emerges, with hyperkinesis a consistent finding. Epilepsy varied from absent to severe, and included intractable myoclonic seizures and infantile spasms. Subjects with partial MEF2C deletion were statistically less likely to have epilepsy. Finally, we confirm that Mef2c is present both in dorsal primary neuroblasts and ventral gamma-aminobutyric acid(GABA)ergic interneurons in the forebrain of the developing mouse. Given interactions with several key neurodevelopmental genes such as ARX, FMR1, MECP2, and TBR1, it appears that MEF2C plays a role in several developmental stages of both dorsal and ventral neuronal cell types.

High epidermal growth factor receptor immunohistochemical expression in urothelial carcinoma of the bladder is not associated with EGFR mutations in exons 19 and 21: a study using formalin-fixed, paraffin-embedded archival tissues

Epidermal growth factor receptor (EGFR) is a member of the erbB tyrosine kinase family reported to be overexpressed in a variety of solid malignancies. Mutations in exons 19 to 21 of the tyrosine kinase domain have been detected in a subset of these tumors and its presence associated with a better response to EGFR inhibitors. Several clinical trials are currently underway to evaluate the performance of such drugs in patients with bladder cancer, but data on EGFR mutation status are limited. The current study assesses EGFR immunohistochemical expression and the presence of mutations in exons 19 and 21 by polymerase chain reaction in 19 bladder urothelial carcinomas from formalin-fixed, paraffin-embedded tissues. Representative paraffin sections were microdissected for DNA extraction using a pinpoint isolation system. Parallel sections were immunostained using a monoclonal anti-EGFR antibody. No mutations in exons 19 and 21 of EGFR were identified in any of the cases. Immunohistochemical EGFR positivity was observed in 14 of 19 cases. In summary, we found EGFR protein expression in 74% of urothelial carcinomas, but we failed to detect EGFR mutations at exons 19 to 21, suggesting that EGFR overexpression is not related to the presence of mutations in the tyrosine kinase domain of the gene. Mutation analysis of EGFR exons 19 and 21 is feasible in microdissected paraffin sections from archival tissues. Immunohistochemical expression of EGFR may not be useful to predict therapeutic response to EGFR inhibitors in patients with urothelial carcinomas. To explain EGFR immunohistochemical overexpression, other mechanisms besides mutations in the EGFR kinase domain should be investigated in future studies.

A novel variant in GABRB2 associated with intellectual disability and epilepsy

The γ‐aminobutyric acid type A (GABAA) receptor is one of the three main classes of receptors activated by GABA, the principal inhibitory neurotransmitter in the central nervous system. Mutations in genes encoding various subunits of this receptor (GABRA1, GABRA2, GABRA4, GABRA5, GABRA6, GABRB1, GABRB3, GABRG1, GABRG2, GABRG3, and GABRD) are implicated in a number of neurological and developmental disorders, including epilepsy and autism. To date, no human genetics studies have implicated mutations in GABRB2, encoding the β2 subunit of the GABAA receptor, with neurodevelopmental disorders. Here we present a 12‐year‐old girl with intellectual disability and epilepsy, who was discovered by whole exome sequencing to have a de novo heterozygous missense variant in exon 4 of GABRB2 (c.236T > C; p.M79T). This variant is likely pathogenic, based on in silico analyses, as well as the fact that it results in the non‐conservative substitution of a non‐polar amino acid with a polar amino acid at a position that is evolutionarily conserved across multiple species. Our findings underscore the need for further investigation into the mechanisms by which mutations in GABRB2 contribute to neurological and developmental dysfunction.

ELP2 is a novel gene implicated in neurodevelopmental disabilities

Elongator is a multi‐subunit protein complex essential to transcription elongation, histone acetylation, and tRNA modification. The complex consists of six highly conserved protein subunits, called Elongator Proteins (ELP) 1–6. Apart from an association with intellectual disability (ID), there is limited clinical information about patients with ELP2 variants. Here we report on two brothers with severe ID, spastic diplegia, and self‐injury whose presentation eluded a diagnosis for over 20 years. In both brothers, whole exome sequencing revealed a likely pathogenic, compound heterozygous missense variant in ELP2. We describe the phenotype and natural history of the ELP2‐related disorder in these brothers.

A Diagnostic Approach for Cerebral Palsy in the Genomic Era

An ongoing challenge in children presenting with motor delay/impairment early in life is to identify neurogenetic disorders with a clinical phenotype, which can be misdiagnosed as cerebral palsy (CP). To help distinguish patients in these two groups, conventional magnetic resonance imaging of the brain has been of great benefit in “unmasking” many of these genetic etiologies and has provided important clues to differential diagnosis in others. Recent advances in molecular genetics such as chromosomal microarray and next-generation sequencing have further revolutionized the understanding of etiology by more precisely classifying these disorders with a molecular cause. In this paper, we present a review of neurogenetic disorders masquerading as cerebral palsy evaluated at one institution. We have included representative case examples children presenting with dyskinetic, spastic, and ataxic phenotypes, with the intent to highlight the time-honored approach of using clinical tools of history and examination to focus the subsequent etiologic search with advanced neuroimaging modalities and molecular genetic tools. A precise diagnosis of these masqueraders and their differentiation from CP is important in terms of therapy, prognosis, and family counseling. In summary, this review serves as a continued call to remain vigilant for current and other to-be-discovered neurogenetic masqueraders of cerebral palsy, thereby optimizing care for patients and their families.

Novel TUBB4A mutations and expansion of the neuroimaging phenotype of hypomyelination with atrophy of the basal ganglia and cerebellum (H-ABC).

Hypomyelination with atrophy of the basal ganglia and cerebellum (H‐ABC) has recently been associated with a single heterozygous p.D249N mutation in TUBB4A. We describe two novel mutations in this gene. A p.C239F mutation was found in one of the originally described H‐ABC patients, for whom we provide follow‐up 11 years after the original publication. The second novel mutation, p.R262H, was found in a patient with a typical clinical presentation for H‐ABC, but with a novel neuroimaging phenotype, given the absence of atrophy of the putamen and caudate nucleus despite 7 years of follow‐up. The recent recognition of TUBB4A mutations as the underlying etiology of H‐ABC will likely lead to the identification of subtler clinical and neuroimaging presentations of this disorder, like in our third patient. Thus mutations in this gene should be suspected in any patient with hypomyelination, regardless of the long‐term presence of neostriatal atrophy.

Depression among adults with neurofibromatosis type 1: prevalence and impact on quality of life

Neurofibromatosis type 1 (NF1) carries a significant psychosocial burden for affected individuals. The objective of this study was to measure the prevalence of depressive symptoms among a large sample of adults with NF1 and to quantify the impact of depressive symptoms on quality of life (QoL). This cross‐sectional study used an Internet‐based questionnaire to collect data from 498 adults who self‐reported as having NF1. Using the Center for Epidemiologic Studies Depression (CESD) scale, 55% of all participants (61% of females and 43% of males) scored above 16, indicating a high likelihood of clinical depression. In a multivariate regression model controlling for demographics and potential confounders, depressive symptoms accounted for 32% of the variance in QoL as measured by the Quality of Life Index. This study is the largest to date and found the highest prevalence of depression compared to prior studies. Our data provide more compelling evidence that individuals with NF1 are at increased risk for psychiatric morbidity and suggest that this population should be routinely screened for depression. Because depression was found to be strongly associated with QoL and accounted for nearly one‐third of the variance in QoL, it is likely that effectively treating depression may significantly enhance QoL for individuals with NF1.

Deletion 12p12 Involving SOX5 in Two Children With Developmental Delay and Dysmorphic Features

The SOX5 gene encodes a transcription factor involved in the regulation of nervous system development and chondrogenesis. This article reports on two cases of 12p12.1 deletion involving SOX5 presenting with global developmental delay, intellectual disability, expressive language delay, mild motor impairment, distinct features, and multiorgan involvement. The first case involves a 32-month-old boy with de novo 53-kilobase interstitial deletion at 12p12.1, representing the smallest deletion reported, and presents with severe symptomatology. The second case is a 31-month-old girl with 3.2-megabase deletion at 12p12.2 p12.1 with severe neurodevelopmental disability and minimal organ involvement. These patients bear many of the characteristics previously reported in patients with SOX5 mutations. We propose a neurodevelopmental approach to a novel syndrome with dose- and location-sensitive SOX5 gene expression.