A novel de novo 1.8 Mb microdeletion of 17q21.33 associated with intellectual disability and dysmorphic features

Voltage-gated calcium channels in genetic epilepsies

Voltage-gated calcium channels (VGCC) are abundant in the central nervous system and serve a broad spectrum of functions, either directly in cellular excitability or indirectly to regulate Ca2+ homeostasis. Ca2+ ions act as one of the main connections in excitation-transcription coupling, muscle contraction and excitation-exocytosis coupling, including synaptic transmission. In recent years, many genes encoding VGCCs main α or additional auxiliary subunits have been associated with epilepsy. This review sums up the current state of knowledge on disease mechanisms and provides guidance on disease-specific therapies where applicable.

Integrated analysis of plasma proteome and cortex single-cell transcriptome reveals the novel biomarkers during cortical aging

Background

With the increase of age, multiple physiological functions of people begin gradually degenerating. Regardless of natural aging or pathological aging, the decline in cognitive function is one of the most obvious features in the process of brain aging. Brain aging is a key factor for several neuropsychiatric disorders and for most neurodegenerative diseases characterized by onset typically occurring late in life and with worsening of symptoms over time. Therefore, the early prevention and intervention of aging progression are particularly important. Since there is no unified conclusion about the plasma diagnostic biomarkers of brain aging, this paper innovatively employed the combined multi-omics analysis to delineate the plasma markers of brain aging.

Methods

In order to search for specific aging markers in plasma during cerebral cortex aging, we used multi-omics analysis to screen out differential genes/proteins by integrating two prefrontal cortex (PFC) single-nucleus transcriptome sequencing (snRNA-seq) datasets and one plasma proteome sequencing datasets. Then plasma samples were collected from 20 young people and 20 elder people to verify the selected differential genes/proteins with ELISA assay.

Results

We first integrated snRNA-seq data of the post-mortem human PFC and generated profiles of 65,064 nuclei from 14 subjects across adult (44-58 years), early-aging (69-79 years), and late-aging (85-94 years) stages. Seven major cell types were classified based on established markers, including oligodendrocyte, excitatory neurons, oligodendrocyte progenitor cells, astrocytes, microglia, inhibitory neurons, and endotheliocytes. A total of 93 cell-specific genes were identified to be significantly associated with age. Afterward, plasma proteomics data from 2,925 plasma proteins across 4,263 young adults to nonagenarians (18-95 years old) were combined with the outcomes from snRNA-seq data to obtain 12 differential genes/proteins (GPC5, CA10, DGKB, ST6GALNAC5, DSCAM, IL1RAPL2, TMEM132C, VCAN, APOE, PYH1R, CNTN2, SPOCK3). Finally, we verified the 12 differential genes by ELISA and found that the expression trends of five biomarkers (DSCAM, CNTN2, IL1RAPL2, CA10, GPC5) were correlated with brain aging.

Conclusion

Five differentially expressed proteins (DSCAM, CNTN2, IL1RAPL2, CA10, GPC5) can be considered as one of the screening indicators of brain aging, and provide a scientific basis for clinical diagnosis and intervention.

Neuronal Cav3 channelopathies: recent progress and perspectives

T-type, low-voltage activated, calcium channels, now designated Cav3 channels, are involved in a wide variety of physiological functions, especially in nervous systems. Their unique electrophysiological properties allow them to finely regulate neuronal excitability and to contribute to sensory processing, sleep, and hormone and neurotransmitter release. In the last two decades, genetic studies, including exploration of knock-out mouse models, have greatly contributed to elucidate the role of Cav3 channels in normal physiology, their regulation, and their implication in diseases. Mutations in genes encoding Cav3 channels (CACNA1G, CACNA1H, and CACNA1I) have been linked to a variety of neurodevelopmental, neurological, and psychiatric diseases designated here as neuronal Cav3 channelopathies. In this review, we describe and discuss the clinical findings and supporting in vitro and in vivo studies of the mutant channels, with a focus on de novo, gain-of-function missense mutations recently discovered in CACNA1G and CACNA1H. Overall, the studies of the Cav3 channelopathies help deciphering the pathogenic mechanisms of corresponding diseases and better delineate the properties and physiological roles Cav3 channels.

A novel homozygous SACS mutation identified by whole exome sequencing-genotype phenotype correlations of all published cases

ARSACS is an autosomal recessive disorder characterized by ataxia, spasticity, and polyneuropathy. A plethora of worldwide distributed mutations have been described so far. Here, we report two brothers, born to non-consanguineous parents, presenting with cerebellar ataxia and peripheral neuropathy. Whole-exome sequencing revealed the presence of a novel homozygous variant in the SACS gene. The variant was confirmed by Sanger sequencing and found at heterozygous state in both parents. This is the first reported mutation in this gene, in Greek population. This case report further highlights the growing trend of identifying genetic diseases previously restricted to single, ethnically isolated regions in many different ethnic groups worldwide. Additionally, we performed a systematic review of all published cases with SACs mutations. ARSACS seems to be an important cause of ataxia and many different types of mutations have been identified, mainly located in exon 10. We evaluated the mutation pathogenicity in all previously reported cases to investigate possible phenotype-genotype correlations. We managed to find a correlation between the pathogenicity of mutations, severity of the phenotype, and age of onset of ARSACS. Greater mutation numbers in different populations will be important and mutation-specific functional studies will be essential to identify the pathogenicity of the various ARSACS variants.

Clinical and molecular description of a 17q21.33 microduplication in a girl with severe kyphoscoliosis and developmental delay

High proportion of disease-associated copy number variant maps to chromosome 17. Genomic studies have provided an insight into its complex genomic structure such as relative abundance of segmental duplication and intercepted repetitive elements. 17q21.31, 17q11.2 and 17q12 loci are well known on this chromosome and are associated with microdeletion and microduplication syndrome. No syndrome associated with 17q21.33 locus have been described. We report clinical, cytogenetic and molecular investigations of a 13 years-old girl admitted for evaluation of microcephaly, scoliosis, skeletal defects and learning difficulties. We carried out detailed analysis of the clinical phenotype of this patient and investigated the genetic basis using Agilent 180K Array Comparative Genomic Hybridization. We identified a ∼0.9 Mb de novo microduplication on chromosome 17q21.33. Four genes, COL1A1, SGCA, PPP1R9B and CHAD located within the duplicated region are possible candidates for clinical features present in our patients. Gene expression studies by real-time RT-PCR assay only showed an overexpression of SGCA (P < 0.01), a component of the dystrophin glycoprotein complex. Defect of SGCA was previously shown to lead to severe childhood autosomal recessive muscular dystrophy (LGMD2D) which result in progressive muscle weakness and can also be associated with hyperlordosis or scoliosis. Further cases with similar duplications are expected to be diagnosed. This will contribute to the delineation of this potential new microduplication syndrome and to improve genetic counseling.

Considering specific clinical features as evidence of pathogenic copy number variants

Since the introduction of high-resolution microarray technologies, it has become apparent that structural chromosomal rearrangements can lead to a wide variety of clinical manifestations, including developmental delay/intellectual disability (DD/ID). It has been shown previously that the diagnostic yield of genome-wide array-based identification of submicroscopic alterations in patients with ID varies widely and depends on the patient selection criteria. More attempts have recently been made to define the phenotypic clues of pathogenic copy number variants (CNVs). The aim of this study was to investigate a well-phenotyped cohort of patients with DD/ID and determine whether certain clinical features may serve as indicators for pathogenic CNVs. A retrospective analysis was conducted for patients with DD/ID (n = 211) who were tested using genome-wide chromosomal microarray technologies and a review of the clinical data was performed. Pathogenic CNVs were detected in 29 patients. In comparison with individuals who had normal molecular karyotyping results (n = 182), malformations of the musculoskeletal system; congenital malformations of the CNS (particularly hydrocephalus and congenital malformations of the corpus callosum); minor anomalies of the eye, face, and neck subgroup (particularly downward-slanting palpebral fissures, minor anomalies of the ear, and micrognathia); brachydactyly; and umbilical hernia were more common in patients with chromosomal alterations. A multivariate logistic regression analysis allowed the identification of three independent pathogenic CNV predictors: congenital malformations of the corpus callosum, minor anomalies of the ear, and brachydactyly. Insights into the chromosomal phenotype may help to increase the diagnostic yield of microarray technologies and sharpen the distinction between chromosomal alterations and other conditions.

ECM receptors in neuronal structure, synaptic plasticity, and behavior

During central nervous system development, extracellular matrix (ECM) receptors and their ligands play key roles as guidance molecules, informing neurons where and when to send axonal and dendritic projections, establish connections, and form synapses between pre- and postsynaptic cells. Once stable synapses are formed, many ECM receptors transition in function to control the maintenance of stable connections between neurons and regulate synaptic plasticity. These receptors bind to and are activated by ECM ligands. In turn, ECM receptor activation modulates downstream signaling cascades that control cytoskeletal dynamics and synaptic activity to regulate neuronal structure and function and thereby impact animal behavior. The activities of cell adhesion receptors that mediate interactions between pre- and postsynaptic partners are also strongly influenced by ECM composition. This chapter highlights a number of ECM receptors, their roles in the control of synapse structure and function, and the impact of these receptors on synaptic plasticity and animal behavior.

Genetics of recessive cognitive disorders

Most severe forms of intellectual disability (ID) have specific genetic causes. Numerous X chromosome gene defects and disease-causing copy-number variants have been linked to ID and related disorders, and recent studies have revealed that sporadic cases are often due to dominant de novo mutations with low recurrence risk. For autosomal recessive ID (ARID) the recurrence risk is high and, in populations with frequent parental consanguinity, ARID is the most common form of ID. Even so, its elucidation has lagged behind. Here we review recent progress in this field, show that ARID is not rare even in outbred Western populations, and discuss the prospects for improving its diagnosis and prevention.

Osteogenesis imperfecta, tricho-dento-osseous syndrome and intellectual disability: a familial case with 17q21.33-q22 (COL1A1 and DLX3) deletion and 7q32.3-q33 duplication resulting from a reciprocal interchromosomal insertion

We report on a 22-year-old woman with features of osteogenesis imperfecta (OI), tricho-dento-osseous (TDO) syndrome and intellectual disability. Whole genome oligonucleotide microarray analysis revealed a copy number gain of 3 Mb in 7q32.3-q33 and a loss of 3.4 Mb in 17q21.33-q22. FISH analysis showed that the third copy of 7q32 was inserted into the long arm of one chromosome 17, exactly in the region 17q21.33-q22 that was deleted. The maternal uncle presented with clinical features similar to the proposita and had the same chromosomal anomalies. The mother of the proposita and two other family members were balanced carriers of this rearrangement, interpreted as an interchromosomal reciprocal insertion. Reciprocal insertion/four-break rearrangement is a very rare chromosomal event. The deleted region on chromosome 17 contains 39 genes, including COL1A1 and DLX3 involved in OI and TDO syndrome respectively. The CACNA1G gene on the deleted segment of chromosome 17 may be a good candidate gene to explain the intellectual impairment. © 2013 Wiley Periodicals, Inc.

Integrin α3 is required for late postnatal stability of dendrite arbors, dendritic spines and synapses, and mouse behavior

Most dendrite branches and a large fraction of dendritic spines in the adult rodent forebrain are stable for extended periods of time. Destabilization of these structures compromises brain function and is a major contributing factor to psychiatric and neurodegenerative diseases. Integrins are a class of transmembrane extracellular matrix receptors that function as αβ heterodimers and activate signaling cascades regulating the actin cytoskeleton. Here we identify integrin α3 as a key mediator of neuronal stability. Dendrites, dendritic spines, and synapses develop normally in mice with selective loss of integrin α3 in excitatory forebrain neurons, reaching their mature sizes and densities through postnatal day 21 (P21). However, by P42, integrin α3 mutant mice exhibit significant reductions in hippocampal dendrite arbor size and complexity, loss of dendritic spine and synapse densities, and impairments in hippocampal-dependent behavior. Furthermore, gene-dosage experiments demonstrate that integrin α3 interacts functionally with the Arg nonreceptor tyrosine kinase to activate p190RhoGAP, which inhibits RhoA GTPase and regulates hippocampal dendrite and synapse stability and mouse behavior. Together, our data support a fundamental role for integrin α3 in regulating dendrite arbor stability, synapse maintenance, and proper hippocampal function. In addition, these results provide a biochemical and structural explanation for the defects in long-term potentiation, learning, and memory reported previously in mice lacking integrin α3.