De novo truncating variants in the intronless IRF2BPL are responsible for developmental epileptic encephalopathy.

PURPOSE: Developmental and epileptic encephalopathies (DEEs) are severe clinical conditions characterized by stagnation or decline of cognitive and behavioral abilities preceded, accompanied or followed by seizures. Because DEEs are clinically and genetically heterogeneous, next-generation sequencing, especially exome sequencing (ES), is becoming a first-tier strategy to identify the molecular etiologies of these disorders. METHODS: We combined ES analysis and international data sharing. RESULTS: We identified 11 unrelated individuals with DEE and de novo heterozygous truncating variants in the interferon regulatory factor 2-binding protein-like gene (IRF2BPL). The 11 individuals allowed for delineation of a consistent neurodevelopmental disorder characterized by mostly normal initial psychomotor development followed by severe global neurological regression and epilepsy with nonspecific electroencephalogram (EEG) abnormalities and variable central nervous system (CNS) anomalies. IRF2BPL, also known as enhanced at puberty protein 1 (EAP1), encodes a transcriptional regulator containing a C-terminal RING-finger domain common to E3 ubiquitin ligases. This domain is required for its repressive and transactivating transcriptional properties. The variants identified are expected to encode a protein lacking the C-terminal RING-finger domain. CONCLUSIONS: These data support the causative role of truncating IRF2BPL variants in pediatric neurodegeneration and expand the spectrum of transcriptional regulators identified as molecular factors implicated in genetic developmental and epileptic encephalopathies.

The Buschke-Ollendorff syndrome: a case report of simultaneous osteo-cutaneous malformations in the hand.

BACKGROUND: We describe a male with functionally impairing radial deviation of the thumb who presented to us at 24 years of age. Two sclerotic skin lesions had been excised 7 years before because of consecutive skin contracture. Latest radiological examination showed a spotted pattern consistent with osteopoikilosis. CASE PRESENTATION: A corrective osteotomy of the thumb was carried out due to the patients discomfort. Facing the simultaneous osteo-cutaneous malformation we postulated a Buschke-Ollendorff syndrome. Buschke-Ollendorff syndrome is a rare autosomal-dominant hereditary disorder of connective tissue with typical osteo-cutaneous manifestations. To explore our hypothesis, biopsies were taken from the affected bone lesions and surrounding skin and soft tissue for histological investigation and genetic testing of the LEMD3 gene was performed on blood of the patient. The histology showed typical changes of the bone architecture and a fibrotic collagenous nodule of the skin. The genetic testing on DNA extracted from peripheral blood leucocytes confirmed a heterozygous loss of function mutation in the LEM domain-containing protein 3 (LEMD3) gene coding for the inner nuclear membrane protein MAN1, which causes osteopoikilosis by antagonizing transforming growth factor ß (TGF-ß) and bone morphogenetic protein (BMP) signalling. CONCLUSIONS: In atypical cases of simultaneous occurrence of fibrotic skin lesions and a spotted pattern in the X-ray we recommend the genetic screening of the LEMD3 gene. A correct diagnosis of Buschke-Ollendorff syndrome is necessary to spare patients from expensive investigations and to provide reassurance about the benign nature of the disease.

In-Frame Deletion and Missense Mutations of the C-Terminal Helicase Domain of SMARCA2 in Three Patients with Nicolaides-Baraitser Syndrome.

Using high-resolution molecular karyotyping with SNP arrays to identify candidate genes for etiologically unexplained intellectual disability, we identified a 32-kb de novo in-frame deletion of the C-terminal helicase domain of the SMARCA2 gene in a patient with severe intellectual disability, epilepsy, sparse hair, prominent joints, and distinct facial anomalies. Sequencing of the gene in patients with a similar phenotype revealed de novo missense mutations in this domain in 2 further patients, pointing to a crucial role of the SMARCA2 C-terminal helicase domain. The clinical features observed in all 3 patients are typical of Nicolaides-Baraitser syndrome, an only rarely reported syndrome with mainly moderate to severe intellectual disability. Notably, one of our patients with a p.Gly1132Asp mutation showed typical morphological features but an exceptional good development with borderline overall IQ and learning difficulties, thus expanding the phenotypic spectrum of Nicolaides-Baraitser syndrome.

The MEF2C-Related and 5q14.3q15 Microdeletion Syndrome.

Disorders related to the autosomal transcription factor MEF2C located in 5q14.3 were first described in 2009 and have since evolved to one of the more common microdeletion syndromes. Mutational screening in a larger cohort revealed heterozygous de novo mutations of MEF2C in about 1% of patients with moderate to severe intellectual disability, and the phenotype is similar in patients with intragenic deletions and multigenic microdeletions. Clinically, MEF2C-related disorders are characterized by severe intellectual disability with absent speech and limited walking abilities, hypotonia, seizures, and a variety of minor brain anomalies. The majority of patients show a similar facial gestalt with broad forehead, flat nasal bridge, hypotonic mouth, and small chin, as well as strabismus, but this phenotype is clinically not well recognized. The course of the disease is generally quite uniform, but patients with point mutations and smaller deletions seem to have a higher chance of walking skills and a lower risk of refractory seizures. Patients in whom the microdeletion also includes the RASA1 gene show features of the respective capillary and arterio-venous malformations and fistula syndrome. The phenotypic overlap with Rett syndrome is explained by a shared pathway and, accordingly, diminished MECP2 and CDKL5 expression is measureable in patients with MEF2C defects. Further research of this pathway may therefore eventually lead to a common therapeutic target.