Search

In the present study, we aimed to establish and characterize a mature cortical spheroid model system for Kleefstra syndrome (KS) using patient-derived iPSC. We identified key differences in the growth behavior of KS spheroids determined by reduced proliferation marked by low Ki67 and high E-cadherin expression. Conversely, in the spheroid-based neurite outgrowth assay KS outperformed the control neurite outgrowth due to higher BDNF expression. KS spheroids were highly enriched in VGLUT1/2-expressing glutamatergic and ChAT-expressing cholinergic neurons, while TH-positive catecholamine neurons were significantly underrepresented. Furthermore, high NMDAR1 expression was also detected in the KS spheroid, similarly to other patients-derived neuronal cultures, denoting high NMDAR1 expression as a general, KS-specific marker. Control and KS neuronal progenitors and neurospheres were exposed to different toxicants (paraquat, rotenone, bardoxolone, and doxorubicin), and dose-response curves were assessed after acute exposure. Differentiation stage and compound-specific differences were detected with KS neurospheres being the most sensitive to paraquat. Altogether this study describes a robust 3D model system expressing the disease-specific markers and recapitulating the characteristic pathophysiological traits. This platform is suitable for testing developing brain-adverse environmental effects interactions, drug development, and screening towards individual therapeutic strategies. [ABSTRACT FROM AUTHOR]

Mutations in the Euchromatic Histone Methyltransferase 1 (EHMT1) gene cause Kleefstra syndrome, a rare form of intellectual disability (ID) with strong autistic traits and sensory processing deficits. Proper development of inhibitory interneurons is crucial for sensory function. Here we report a timeline of Parvalbumin-positive (PV+) interneuron development in the three most important sensory cortical areas in the Ehmt1+/− mouse. We find a hitherto unreported delay of PV+ neuron maturation early in sensory development, with layer- and region-specific variability later in development. The delayed PV+ maturation is also reflected in a delayed maturation of GABAergic transmission in Ehmt1+/− auditory cortex, where we find a reduced GABA release probability specifically in putative PV+ synapses. Together with earlier reports of excitatory impairments in Ehmt1+/− neurons, we propose a shift in excitatory-inhibitory balance towards overexcitability in Ehmt1+/− sensory cortices as a consequence of early deficits in inhibitory maturation. [ABSTRACT FROM AUTHOR]

Both copy number losses and gains occur within subtelomeric 9q34 region without common breakpoints. The microdeletions cause Kleefstra syndrome (KS), whose responsible gene is EHMT1. A 9q34 duplication syndrome (9q34 DS) had been reported in literature, but it has never been characterized by a detailed molecular analysis of the gene content and endpoints. To the best of our knowledge, we report on the first patient carrying the smallest 9q34.3 duplication containing EHMT1 as the only relevant gene. We compared him with 21 reported patients described here as carrying 9q34.3 duplications encompassing the entire gene and extending within ~ 3 Mb. By surveying the available clinical and molecular cytogenetic data, we were able to discover that similar neurodevelopmental disorders (NDDs) were shared by patient carriers of even very differently sized duplications. Moreover, some facial features of the 9q34 DS were more represented than those of KS. However, an accurate in silico analysis of the genes mapped in all the duplications allowed us to support EHMT1 as being sufficient to cause a NDD phenotype. Wider patient cohorts are needed to ascertain whether the rearrangements have full causative role or simply confer the susceptibility to NDDs and possibly to identify the cognitive and behavioral profile associated with the increased dosage of EHMT1. [ABSTRACT FROM AUTHOR]