Expansion of the neurodevelopmental phenotype of individuals with EEF1A2 variants and genotype-phenotype study.

Translation elongation factor eEF1A2 constitutes the alpha subunit of the elongation factor-1 complex, responsible for the enzymatic binding of aminoacyl-tRNA to the ribosome. Since 2012, 21 pathogenic missense variants affecting EEF1A2 have been described in 42 individuals with a severe neurodevelopmental phenotype including epileptic encephalopathy and moderate to profound intellectual disability (ID), with neurological regression in some patients. Through international collaborative call, we collected 26 patients with EEF1A2 variants and compared them to the literature. Our cohort shows a significantly milder phenotype. 83% of the patients are walking (vs. 29% in the literature), and 84% of the patients have language skills (vs. 15%). Three of our patients do not have ID. Epilepsy is present in 63% (vs. 93%). Neurological examination shows a less severe phenotype with significantly less hypotonia (58% vs. 96%), and pyramidal signs (24% vs. 68%). Cognitive regression was noted in 4% (vs. 56% in the literature). Among individuals over 10 years, 56% disclosed neurocognitive regression, with a mean age of onset at 2 years. We describe 8 novel missense variants of EEF1A2. Modeling of the different amino-acid sites shows that the variants associated with a severe phenotype, and the majority of those associated with a moderate phenotype, cluster within the switch II region of the protein and thus may affect GTP exchange. In contrast, variants associated with milder phenotypes may impact secondary functions such as actin binding. We report the largest cohort of individuals with EEF1A2 variants thus far, allowing us to expand the phenotype spectrum and reveal genotype-phenotype correlations.

3q29 duplications: A cohort of 46 patients and a literature review.

Duplications of the 3q29 cytoband are rare chromosomal copy number variations (CNVs) (overlapping or recurrent ~1.6 Mb 3q29 duplications). They have been associated with highly variable neurodevelopmental disorders (NDDs) with various associated features or reported as a susceptibility factor to the development of learning disabilities and neuropsychiatric disorders. The smallest region of overlap and the phenotype of 3q29 duplications remain uncertain. We here report a French cohort of 31 families with a 3q29 duplication identified by chromosomal microarray analysis (CMA), including 14 recurrent 1.6 Mb duplications, eight overlapping duplications (>1 Mb), and nine small duplications (<1 Mb). Additional genetic findings that may be involved in the phenotype were identified in 11 patients. Focusing on apparently isolated 3q29 duplications, patients present mainly mild NDD as suggested by a high rate of learning disabilities in contrast to a low proportion of patients with intellectual disabilities. Although some are de novo, most of the 3q29 duplications are inherited from a parent with a similar mild phenotype. Besides, the study of small 3q29 duplications does not provide evidence for any critical region. Our data suggest that the overlapping and recurrent 3q29 duplications seem to lead to mild NDD and that a severe or syndromic clinical presentation should warrant further genetic analyses.

Phenotypic and genotypic characterization of 1q21.1 copy number variants: A report of 34 new individuals and literature review.

Recurrent 1q21.1 copy number variants (CNVs) have been associated with a wide spectrum of clinical features, ranging from normal phenotype to moderate intellectual disability, with congenital anomalies and dysmorphic features. They are often inherited from unaffected parents and the pathogenicity is difficult to assess. We describe the phenotypic and genotypic data for 34 probands carrying CNVs in the 1q21.1 chromosome region (24 duplications, 8 deletions and 2 triplications). We also reviewed 89 duplications, 114 deletions and 5 triplications described in the literature, at variable 1q21.1 locations. We aimed to identify the most highly associated clinical features to determine the phenotypic expression in affected individuals. Developmental delay or learning disabilities and neuropsychiatric disorders were common in patients with deletions, duplications and triplications of 1q21.1. Mild dysmorphic features common in these CNVs include a prominent forehead, widely spaced eyes and a broad nose. The CNVs were mostly inherited from apparently unaffected parents. Almost half of the CNVs were distal, overlapping with a common minimal region of 1.2 Mb. We delineated the clinical implications of 1q21.1 CNVs and confirmed that these CNVs are likely pathogenic, although subject to incomplete penetrance and variable expressivity. Long-term follow-up should be performed to each newly diagnosed case, and prenatal genetic counseling cautiously discussed, as it remains difficult to predict the phenotype in the event of an antenatal diagnosis.