@article {57, title = {Enrichment of mutations in chromatin regulators in people with Rett syndrome lacking mutations in MECP2.}, journal = {Genet Med}, volume = {19}, year = {2017}, month = {2017 01}, pages = {13-19}, abstract = {

PURPOSE: Rett syndrome (RTT) is a neurodevelopmental disorder caused primarily by de novo mutations in MECP2 and sometimes in CDKL5 and FOXG1. However, some RTT patients lack mutations in these genes.

METHODS: Twenty-two RTT patients without apparent MECP2, CDKL5, and FOXG1 mutations were subjected to both whole-exome sequencing and single-nucleotide polymorphism array-based copy-number variant (CNV) analyses.

RESULTS: Three patients had MECP2 mutations initially missed by clinical testing. Of the remaining 19, 17 (89.5\%) had 29 other likely pathogenic intragenic mutations and/or CNVs (10 patients had 2 or more). Interestingly, 13 patients had mutations in a gene/region previously reported in other neurodevelopmental disorders (NDDs), thereby providing a potential diagnostic yield of 68.4\%. These mutations were significantly enriched in chromatin regulators (corrected P = 0.0068) and moderately enriched in postsynaptic cell membrane molecules (corrected P = 0.076), implicating glutamate receptor signaling.

CONCLUSION: The genetic etiology of RTT without MECP2, CDKL5, and FOXG1 mutations is heterogeneous, overlaps with other NDDs, and complicated by a high mutation burden. Dysregulation of chromatin structure and abnormal excitatory synaptic signaling may form two common pathological bases of RTT.Genet Med 19 1, 13-19.

}, keywords = {Adolescent, Adult, Child, Child, Preschool, Chromatin, DNA Copy Number Variations, Female, Forkhead Transcription Factors, Humans, Infant, Male, Methyl-CpG-Binding Protein 2, Mutation, Nerve Tissue Proteins, Polymorphism, Single Nucleotide, Protein-Serine-Threonine Kinases, Rett Syndrome, Whole Exome Sequencing}, issn = {1530-0366}, doi = {10.1038/gim.2016.42}, author = {Sajan, Samin A and Jhangiani, Shalini N and Muzny, Donna M and Gibbs, Richard A and Lupski, James R and Glaze, Daniel G and Kaufmann, Walter E and Skinner, Steven A and Annese, Fran and Friez, Michael J and Lane, Jane and Percy, Alan K and Neul, Jeffrey L} } @article {59, title = {Identification of Intellectual Disability Genes in Female Patients with a Skewed X-Inactivation Pattern.}, journal = {Hum Mutat}, volume = {37}, year = {2016}, month = {2016 08}, pages = {804-11}, abstract = {

Intellectual disability (ID) is a heterogeneous disorder with an unknown molecular etiology in many cases. Previously, X-linked ID (XLID) studies focused on males because of the hemizygous state of their X chromosome. Carrier females are generally unaffected because of the presence of a second normal allele, or inactivation of the mutant X chromosome in most of their cells (skewing). However, in female ID patients, we hypothesized that the presence of skewing of X-inactivation would be an indicator for an X chromosomal ID cause. We analyzed the X-inactivation patterns of 288 females with ID, and found that 22 (7.6\%) had extreme skewing (>90\%), which is significantly higher than observed in the general population (3.6\%; P~=~0.029). Whole-exome sequencing of 19 females with extreme skewing revealed causal variants in six females in the XLID genes DDX3X, NHS, WDR45, MECP2, and SMC1A. Interestingly, variants in genes escaping X-inactivation presumably cause both XLID and skewing of X-inactivation in three of these patients. Moreover, variants likely accounting for skewing only were detected in MED12, HDAC8, and TAF9B. All tested candidate causative variants were de novo events. Hence, extreme skewing is a good indicator for the presence of X-linked variants in female patients.

}, keywords = {Carrier Proteins, Cell Cycle Proteins, Chromosomal Proteins, Non-Histone, DEAD-box RNA Helicases, Exome, Female, Genetic Variation, Humans, Intellectual Disability, Methyl-CpG-Binding Protein 2, Nuclear Proteins, Sequence Analysis, DNA, X Chromosome Inactivation}, issn = {1098-1004}, doi = {10.1002/humu.23012}, author = {Fieremans, Nathalie and Van Esch, Hilde and Holvoet, Maureen and Van Goethem, Gert and Devriendt, Koenraad and Rosello, Monica and Mayo, Sonia and Martinez, Francisco and Jhangiani, Shalini and Muzny, Donna M and Gibbs, Richard A and Lupski, James R and Vermeesch, Joris R and Marynen, Peter and Froyen, Guy} }