No abstract

Individuals with methyl CpG binding protein 2 (MECP2) duplication syndrome (MDS) have varying degrees of severity in their mobility, hand use, developmental skills, and susceptibility to infections. In the present study, we examine the relationship between duplication size, gene content, and overall phenotype in MDS using a clinical severity scale. Other genes typically duplicated within Xq28 (eg, GDI1, RAB39B, FLNA) are associated with distinct clinical features independent of MECP2. We additionally compare the phenotype of this cohort (n = 48) to other reported cohorts with MDS. Utilizing existing indices of clinical severity in Rett syndrome, we found that larger duplication size correlates with higher severity in total clinical severity scores (r = 0.36; P = 0.02), and in total motor behavioral assessment inventory scores (r = 0.31; P = 0.05). Greater severity was associated with having the RAB39B gene duplicated, although most of these participants also had large duplications. Results suggest that developmental delays in the first 6 months of life, hypotonia, vasomotor disturbances, constipation, drooling, and bruxism are common in MDS. This is the first study to show that duplication size is related to clinical severity. Future studies should examine whether large duplications which do not encompass RAB39B also contribute to clinical severity. Results also suggest the need for creating an MDS specific severity scale.

Purpose Deep phenotyping is an emerging trend in precision medicine for genetic disease. The shape of the face is affected in 30–40% of known genetic syndromes. Here, we determine whether syndromes can be diagnosed from 3D images of human faces. Methods We analyzed variation in three-dimensional (3D) facial images of 7057 subjects: 3327 with 396 different syndromes, 727 of their relatives, and 3003 unrelated, unaffected subjects. We developed and tested machine learning and parametric approaches to automated syndrome diagnosis using 3D facial images. Results Unrelated, unaffected subjects were correctly classified with 96% accuracy. Considering both syndromic and unrelated, unaffected subjects together, balanced accuracy was 73% and mean sensitivity 49%. Excluding unrelated, unaffected subjects substantially improved both balanced accuracy (78.1%) and sensitivity (56.9%) of syndrome diagnosis. The best predictors of classification accuracy were phenotypic severity and facial distinctiveness of syndromes. Surprisingly, unaffected relatives of syndromic subjects were frequently classified as syndromic, often to the syndrome of their affected relative. Conclusion Deep phenotyping by quantitative 3D facial imaging has considerable potential to facilitate syndrome diagnosis. Furthermore, 3D facial imaging of “unaffected” relatives may identify unrecognized cases or may reveal novel examples of semidominant inheritance.

Mutations in the X-linked gene MECP2 are associated with a severe neurodevelopmental disorder, Rett syndrome, primarily in girls. It had been suspected that mutations in MECP2 led to embryonic lethality in males, however such males have been reported. To enhance understanding of the phenotypic spectrum present in these individuals, we identified thirty males with MECP2 mutations in the RTT Natural History Study databases. A wide phenotypic spectrum was observed, ranging from severe neonatal encephalopathy to cognitive impairment. Two males with a somatic mutation in MECP2 had classic RTT. Of the remaining 28 subjects, 16 had RTT-causing MECP2 mutations, 9 with mutations that are not seen in females with RTT but are likely pathogenic, and 3 with uncertain variants. Two subjects with RTT-causing mutations were previously diagnosed as having atypical RTT; however, careful review of the clinical history determined that an additional 12/28 subjects met criteria for atypical RTT, but with more severe clinical presentation and course, and less distinctive RTT features, than females with RTT, leading to the designation of a new diagnostic entity, Male RTT Encephalopathy. Increased awareness of the clinical spectrum and widespread comprehensive genomic testing in boys with neurodevelopmental problems will lead to improved identification.

The response of nerve cels to synaptic inputs and the propagation of this activation is critically dependent on the cell-surface distribution of ion channels. In the hippocampus, Ca2+ influx through N-methyl-D-aspartate receptors (NMDAR) and/or voltage-dependent calcium channels on dendrites is thought to be critically involved in long-term potentiation, neurite outgrowth, epileptogenesis, synaptognesis, and cell death. We report that conantokin-G (CntxG), a peptide from Conus geographus venom, competitively blocked with high ainity and specificty NMDAR-mediated currents in hippocampal neurons and is a reliable probe for exploring NMDAR distribution. Fluorescent derivatives of CntxG were prepared and used to dhietly determine NMDAR distribution on living hippocampal neurons by digital imaging and confocal fluorescence microscopy. In hippocampal slices, the CAl dendritic subfield was strongly labeled by CntxG, whereas the CA3 mossy fiber region was not. On CAl hippocampal neurons in culture, dendritic CntkG-sensitive NMDAR were clutered at sites of synaptic contacts, whereas somatic NMDAR were distributed difsely and in patches. NMDAR distribution differed from the distribution of voltage-dependent calcium channels. A significant fraction of labeled NMDAR on somata and dendrites was found to be highiy mobile: rates were consistent with the possible rapid recruitment ofNMDAR to specific synaptic locations. The llization of NMDAR and modulation of this dbution demonstrated here may have important implications for the events that underlie neuronal processing and synaptic remodeling during aative synaptic modition.