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.

Smith-Magenis syndrome: Clinical and behavioral characteristics in a large retrospective cohort

Smith-Magenis syndrome (SMS), characterized by dysmorphic features, neurodevelopmental disorder, and sleep disturbance, is due to an interstitial deletion of chromosome 17p11.2 (90%) or to point mutations in the RAI1 gene. In this retrospective cohort, we studied the clinical, cognitive, and behavioral profile of 47 European patients with SMS caused by a 17p11.2 deletion. We update the clinical and neurobehavioral profile of SMS. Intrauterine growth was normal in most patients. Prenatal anomalies were reported in 15%. 60% of our patients older than 10 years were overweight. Prevalence of heart defects (6.5% tetralogy of Fallot, 6.5% pulmonary stenosis), ophthalmological problems (89%), scoliosis (43%), or deafness (32%) were consistent with previous reports. Epilepsy was uncommon (2%). We identified a high prevalence of obstipation (45%). All patients had learning difficulties and developmental delay, but ID range was wide and 10% of patients had IQ in the normal range. Behavioral problems included temper tantrums and other difficult behaviors (84%) and night-time awakenings (86%). Optimal care of SMS children is multidisciplinary and requires important parental involvement. In our series, half of patients were able to follow adapted schooling, but 70% of parents had to adapt their working time, illustrating the medical, social, educative, and familial impact of having a child with SMS.