Project description: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.
Project description: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.
Project description:Loss of function of FMR2 due to either hypermethylation of the CpG island as a consequence of the expansion of the CCG repeat near its transcription start site, or internal deletion of FMR2 is considered to be the major cause of FRAXE fragile site associated intellectual disability. FMR2 was shown to be a potent transcription activator as well as an RNA binding protein capable of regulating alternative splicing. Using whole transcriptome approach, we aimed to identify genes regulated by FMR2 and to study their contribution to the underlying causes of intellectual disability in the patients. We subjected total RNA extracted from fibroblasts of FRAXE patients (n=8), and unrelated controls (n=4) to Affymetrix Human Exon 1.0 ST array
Project description:Large Xq22.3 deletion in Czech family inherited from unaffaceted mother leading to manifestation of X-linked contiguous gene deletion syndrome known as Alport syndrome with intellectual disability (ATS-ID) or AMME complex (OMIM #300194)
Project description:The Tousled-like kinases 1 and 2 (TLK1/TLK2) regulate DNA replication, repair and chromatin maintenance. TLK2 variants are associated with ‘Intellectual Disability, Autosomal Dominant 57’ (MRD57), a neurodevelopmental disorder (NDD) characterized by intellectual disability (ID), autism spectrum disorder (ASD) and microcephaly. Several TLK1 variants have been reported in NDDs but their functional significance is unknown. A male patient presenting with ID, seizures, global developmental delay, hypothyroidism, and primary immunodeficiency was determined to have a novel, heterozygous variant in TLK1 (c.1435C>G, p.Q479E) by genome sequencing (GS). Transcriptome sequencing in patient-derived cells confirmed expression of TLK1 transcripts carrying the p.Q479E variant and revealed alterations in genes involved in class switch recombination and cytokine signaling.
Project description:The Tousled-like kinases 1 and 2 (TLK1/TLK2) regulate DNA replication, repair and chromatin maintenance. TLK2 variants are associated with ‘Intellectual Disability, Autosomal Dominant 57’ (MRD57), a neurodevelopmental disorder (NDD) characterized by intellectual disability (ID), autism spectrum disorder (ASD) and microcephaly. Several TLK1 variants have been reported in NDDs but their functional significance is unknown. A male patient presenting with ID, seizures, global developmental delay, hypothyroidism, and primary immunodeficiency was determined to have a heterozygous TLK1 variant (c.1435C>G, p.Q479E), as well as a mutation in MDM1 (c.1197dupT, p.K400*). Cells expressing TLK1 p.Q479E exhibited reduced cytokine responses and elevated DNA damage, but not increased radiation sensitivity or DNA repair defects. The TLK1 p.Q479E variant impaired kinase activity but not proximal protein interactions.
Project description:Kynureninase is a member of a large family of catalytically diverse but structurally homologous pyridoxal 5'-phosphate (PLP) dependent enzymes known as the aspartate aminotransferase superfamily or alpha-family. The Homo sapiens and other eukaryotic constitutive kynureninases preferentially catalyze the hydrolytic cleavage of 3-hydroxy-l-kynurenine to produce 3-hydroxyanthranilate and l-alanine, while l-kynurenine is the substrate of many prokaryotic inducible kynureninases. The human enzyme was cloned with an N-terminal hexahistidine tag, expressed, and purified from a bacterial expression system using Ni metal ion affinity chromatography. Kinetic characterization of the recombinant enzyme reveals classic Michaelis-Menten behavior, with a Km of 28.3 +/- 1.9 microM and a specific activity of 1.75 micromol min-1 mg-1 for 3-hydroxy-dl-kynurenine. Crystals of recombinant kynureninase that diffracted to 2.0 A were obtained, and the atomic structure of the PLP-bound holoenzyme was determined by molecular replacement using the Pseudomonas fluorescens kynureninase structure (PDB entry 1qz9) as the phasing model. A structural superposition with the P. fluorescens kynureninase revealed that these two structures resemble the "open" and "closed" conformations of aspartate aminotransferase. The comparison illustrates the dynamic nature of these proteins' small domains and reveals a role for Arg-434 similar to its role in other AAT alpha-family members. Docking of 3-hydroxy-l-kynurenine into the human kynureninase active site suggests that Asn-333 and His-102 are involved in substrate binding and molecular discrimination between inducible and constitutive kynureninase substrates.