Mef2 promotes spine elimination in absence of δ-catenin

Involvement of myocyte enhancer factor 2c in the pathogenesis of autism spectrum disorder

Myocyte enhancer factor 2 (MEF2), a family of transcription factor of MADS (minichromosome maintenance 1, agamous, deficiens and serum response factor)-box family needed in the growth and differentiation of a variety of human cells, such as neural, immune, endothelial, and muscles. As per existing literature, MEF2 transcription factors have also been associated with synaptic plasticity, the developmental mechanisms governing memory and learning, and several neurologic conditions, like autism spectrum disorders (ASDs). Recent genomic findings have ascertained a link between MEF2 defects, particularly in the MEF2C isoform and the ASD. In this review, we summarized a concise overview of the general regulation, structure and functional roles of the MEF2C transcription factor. We further outlined the potential role of MEF2C as a risk factor for various neurodevelopmental disorders, such as ASD, MEF2C Haploinsufficiency Syndrome and Fragile X syndrome.

Identification of Gene Loci That Overlap Between Schizophrenia and Educational Attainment

There is evidence for genetic overlap between cognitive abilities and schizophrenia (SCZ), and genome-wide association studies (GWAS) demonstrate that both SCZ and general cognitive abilities have a strong polygenic component with many single-nucleotide polymorphisms (SNPs) each with a small effect. Here we investigated the shared genetic architecture between SCZ and educational attainment, which is regarded as a "proxy phenotype" for cognitive abilities, but may also reflect other traits. We applied a conditional false discovery rate (condFDR) method to GWAS of SCZ (n = 82 315), college completion ("College," n = 95 427), and years of education ("EduYears," n = 101 069). Variants associated with College or EduYears showed enrichment of association with SCZ, demonstrating polygenic overlap. This was confirmed by an increased replication rate in SCZ. By applying a condFDR threshold <0.01, we identified 18 genomic loci associated with SCZ after conditioning on College and 15 loci associated with SCZ after conditioning on EduYears. Ten of these loci overlapped. Using conjunctional FDR, we identified 10 loci shared between SCZ and College, and 29 loci shared between SCZ and EduYears. The majority of these loci had effects in opposite directions. Our results provide evidence for polygenic overlap between SCZ and educational attainment, and identify novel pleiotropic loci. Other studies have reported genetic overlap between SCZ and cognition, or SCZ and educational attainment, with negative correlation. Importantly, our methods enable identification of bi-directional effects, which highlight the complex relationship between SCZ and educational attainment, and support polygenic mechanisms underlying both cognitive dysfunction and creativity in SCZ.

Making chromosome abnormalities treatable conditions

Individuals affected by the classic chromosome deletion syndromes which were first identified at the beginning of the genetic age, are now positioned to benefit from genomic advances. This issue highlights five of these conditions (4p-, 5p-, 11q-, 18p-, and 18q-). It focuses on the increased in understanding of the molecular underpinnings and envisions how these can be transformed into effective treatments. While it is scientifically exciting to see the phenotypic manifestations of hemizygosity being increasingly understood at the molecular and cellular level, it is even more amazing to consider that we are now on the road to making chromosome abnormalities treatable conditions.

Differential regulation of apical-basolateral dendrite outgrowth by activity in hippocampal neurons

Hippocampal pyramidal neurons have characteristic dendrite asymmetry, characterized by structurally and functionally distinct apical and basolateral dendrites. The ability of the neuron to generate and maintain dendrite asymmetry is vital, since synaptic inputs received are critically dependent on dendrite architecture. Little is known about the role of neuronal activity in guiding maintenance of dendrite asymmetry. Our data indicate that dendrite asymmetry is established and maintained early during development. Further, our results indicate that cell intrinsic and global alterations of neuronal activity have differential effects on net extension of apical and basolateral dendrites. Thus, apical and basolateral dendrite extension may be independently regulated by cell intrinsic and network neuronal activity during development, suggesting that individual dendrites may have autonomous control over net extension. We propose that regulated individual dendrite extension in response to cell intrinsic and neuronal network activity may allow temporal control of synapse specificity in the developing hippocampus.

5p deletions: Current knowledge and future directions

Disorders resulting from 5p deletions (5p-) were first recognized by Lejeune et al. in 1963 [Lejeune et al. (1963); C R Hebd Seances Acad Sci 257:3098-3102]. 5p- is caused by partial or total deletion of the short arm of chromosome 5. The most recognizable phenotype is characterized by a high-pitched cry, dysmorphic features, poor growth, and developmental delay. This report reviews 5p- disorders and their molecular basis. Hemizygosity for genes located within this region have been implicated in contributing to the phenotype. A review of the genes on 5p which may be dosage sensitive is summarized. Because of the growing knowledge of these specific genes, future directions to explore potential targeted therapies for individuals with 5p- are discussed. © 2015 Wiley Periodicals, Inc.

δ-Catenin Regulates Spine Architecture via Cadherin and PDZ-dependent Interactions

The ability of neurons to maintain spine architecture and modulate it in response to synaptic activity is a crucial component of the cellular machinery that underlies information storage in pyramidal neurons of the hippocampus. Here we show a critical role for δ-catenin, a component of the cadherin-catenin cell adhesion complex, in regulating spine head width and length in pyramidal neurons of the hippocampus. The loss of Ctnnd2, the gene encoding δ-catenin, has been associated with the intellectual disability observed in the cri du chat syndrome, suggesting that the functional roles of δ-catenin are vital for neuronal integrity and higher order functions. We demonstrate that loss of δ-catenin in a mouse model or knockdown of δ-catenin in pyramidal neurons compromises spine head width and length, without altering spine dynamics. This is accompanied by a reduction in the levels of synaptic N-cadherin. The ability of δ-catenin to modulate spine architecture is critically dependent on its ability to interact with cadherin and PDZ domain-containing proteins. We propose that loss of δ-catenin during development perturbs synaptic architecture leading to developmental aberrations in neural circuit formation that contribute to the learning disabilities in a mouse model and humans with cri du chat syndrome.