Unknown,Transcriptomics,Genomics,Proteomics

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Intellectual disability and mood disorder associated with partial deletion of the Neurexin 1 Gene

ABSTRACT: Abstract Background Neurexins are proteins located in the presynaptic membrane that bind postsynaptic ligands, neuroligins, neurexophilins, and dystrophoglycan. They exert profound effects on neurological function by mediating signalling across synapses and determining synaptic characteristics through the recruitment of additional proteins for synapse formation. Alterations in neurexin-encoding genes cause cognitive disorders such as autism, developmental delay and schizophrenia. The three neurexin genes in the human genome (NRXN1, NRXN2, and NRXN3) each have two different functional promoters, producing a large (alpha) and small (beta) transcript with corresponding proteins. NRXN1 produces hundreds, perhaps thousands, of different transcripts with differential localization in the CNS. Results We report here the identification of an individual (53825) with mild dysmorphia, severe language disorder, mild intellectual disability, attention deficit hyperactivity disorder (ADHD), and a mood disorder. Genomic analysis by Affymetrix 6.0 Gene Chip and FISH (fluorescence in situ hybridization) using probes specific for NRXN1 revealed a hemizygous deletion of approximately 190 Kb, which includes exons 3-5 of NRXN1. This deletion should result in the absence of the vast majority of different NRXN1 alpha transcripts from one of the NRXN1 gene copies, without effecting NRXN1 beta transcription. Copy number analysis of Affymetrix 6.0 SNP arrays was performed according to the manufacturer's directions on DNA extracted from cryopreserved diagnostic bone marrow or peripheral blood samples for pediatric patients. One sample showed partial deletion of NRXN1 alpha; data presented in this Series.

ORGANISM(S): Homo sapiens

SUBMITTER: Patricia Bray-Ward

PROVIDER: E-GEOD-23358 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Generating sufficient DNA for high-throughput genetic analysis has always been a challenge for clinical settings where the amount of source DNA is limited. Multiple displacement amplification (MDA) has been proposed as a promising candidate for such situations. Previous work with lower-resolution arrays confirmed the utility of single-cell MDA products for large-size (~30 Mb) genome variation screening. We tested the performance of single-cell MDA products on the SNP 6.0 arrays to examine the performance of single-cell MDA in SNP genotyping, copy number polymorphism, de novo copy number variation (CNV) and loss of heterozygosity (LOH) analysis. Our data show that for SNP genotyping, single-cell MDA did not obtain complete genome coverage or high sequence fidelity. For CNV calling, single-cell MDA introduced stochastic amplification artifacts in log2 ratio profiles, reducing the robustness of CNV calling; however, by adjusting smooth window size, it is still possible to analyze large chromosomal aberrations, and homozygous deletions as small as 500 kb can still be identified from the noisy log2 ratio profiles. Our results also suggest that even with a modified protocol (reduction of reaction volume, addition of a molecular crowding reagent, minimization of reaction time), single-cell MDA presented little improvement over the unmodified protocol, but by increasing the number of cells as template to 5M-bM-^@M-^S10 cells, SNP 6.0 array results comparable to those of 10 ng genomic DNA MDA could be obtained. Algorithms like PICNIC improved the CNV calling, suggesting that better algorithms can better utilize single-cell MDA array results. Affymetrix SNP arrays were performed according to the manufacturer's directions on DNA extracted from cell line samples, and multiple displacement samples. Genotyping, Copy number and LOH analysis of Affymetrix SNP 6.0 arrays was performed for 3 samples of unamplified cell line genomic DNA, 2 samples of DNA obtained by multiple displacement amplification from 10ng genomic DNA, 3 single-cell multiple displacement amplification (MDA) products, single cell modified MDA amplification product, 5-cell modified MDA amplification product, 10-cell modified MDA amplification product.

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Intellectual disability and mood disorder associated with partial deletion of the Neurexin 1 Gene

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