ABSTRACT
Using exome sequencing and linkage analysis in a three-generation family with a unique dominant myoclonus-dystonia-like syndrome with cardiac arrhythmias, we identified a mutation in the CACNA1B gene, coding for neuronal voltage-gated calcium channels CaV2.2. This mutation (c.4166G>A;p.Arg1389His) is a disruptive missense mutation in the outer region of the ion pore. The functional consequences of the identified mutation were studied using whole-cell and single-channel patch recordings. High-resolution analyses at the single-channel level showed that, when open, R1389H CaV2.2 channels carried less current compared with WT channels. Other biophysical channel properties were unaltered in R1389H channels including ion selectivity, voltage-dependent activation or voltage-dependent inactivation. CaV2.2 channels regulate transmitter release at inhibitory and excitatory synapses. Functional changes could be consistent with a gain-of-function causing the observed hyperexcitability characteristic of this unique myoclonus-dystonia-like syndrome associated with cardiac arrhythmias.
Subject(s)
Calcium Channels, N-Type/genetics , Dystonic Disorders/genetics , Genetic Association Studies , Mutation , Action Potentials , Calcium Channels, N-Type/metabolism , Calcium Signaling , Dystonic Disorders/diagnosis , Exome , Female , Genetic Linkage , High-Throughput Nucleotide Sequencing , Humans , Male , Patch-Clamp Techniques , Pedigree , PhenotypeABSTRACT
Primrose syndrome and 3q13.31 microdeletion syndrome are clinically related disorders characterized by tall stature, macrocephaly, intellectual disability, disturbed behavior and unusual facial features, with diabetes, deafness, progressive muscle wasting and ectopic calcifications specifically occurring in the former. We report that missense mutations in ZBTB20, residing within the 3q13.31 microdeletion syndrome critical region, underlie Primrose syndrome. This finding establishes a genetic link between these disorders and delineates the impact of ZBTB20 dysregulation on development, growth and metabolism.
Subject(s)
Abnormalities, Multiple/genetics , Calcinosis/genetics , Ear Diseases/genetics , Intellectual Disability/genetics , Muscular Atrophy/genetics , Mutation, Missense , Nerve Tissue Proteins/genetics , Transcription Factors/genetics , Amino Acid Sequence , Base Sequence , Cell Line , Chromosome Deletion , Chromosomes, Human, Pair 3 , Developmental Disabilities/genetics , Female , Genetic Predisposition to Disease , HEK293 Cells , Humans , Male , Models, Molecular , Molecular Sequence Data , Sequence Homology, Amino AcidABSTRACT
Small virus-derived interfering RNAs (viRNAs) play an important role in antiviral defence in plants, insects and nematodes by triggering the RNA interference (RNAi) pathway. The role of RNAi as an antiviral defence mechanism in mammalian cells has been obscure due to the lack of viRNA detection. Although viRNAs from different mammalian viruses have recently been identified, their functions and possible impact on viral replication remain unknown. To identify viRNAs derived from HIV-1, we used the extremely sensitive SOLiD(TM) 3 Plus System to analyse viRNA accumulation in HIV-1-infected T lymphocytes. We detected numerous small RNAs that correspond to the HIV-1 RNA genome. The majority of these sequences have a positive polarity (98.1%) and could be derived from miRNAs encoded by structured segments of the HIV-1 RNA genome (vmiRNAs). A small portion of the viRNAs is of negative polarity and most of them are encoded within the 3'-UTR, which may represent viral siRNAs (vsiRNAs). The identified vsiRNAs can potently repress HIV-1 production, whereas suppression of the vsiRNAs by antagomirs stimulate virus production. These results suggest that HIV-1 triggers the production of vsiRNAs and vmiRNAs to modulate cellular and/or viral gene expression.
Subject(s)
HIV-1/genetics , MicroRNAs/chemistry , RNA, Small Interfering/chemistry , RNA, Viral/chemistry , Base Sequence , Cells, Cultured , High-Throughput Nucleotide Sequencing , Humans , MicroRNAs/genetics , MicroRNAs/metabolism , Molecular Sequence Data , RNA Interference , RNA, Antisense/chemistry , RNA, Small Interfering/genetics , RNA, Small Interfering/metabolism , RNA, Transfer, Lys/chemistry , RNA, Viral/genetics , RNA, Viral/metabolism , Sequence Analysis, RNAABSTRACT
Growth factors, such as ciliary neurotrophic factor (CNTF), have been implicated in neuronal survival and proliferation. About 2% of the human population is homozygous for a polymorphism that induces truncated and biologically inactive CNTF but does not obviously change the phenotype. In a population of patients with hereditary neuropathy, a higher rate of the CNTF null mutation would indicate greater susceptibility for clinically significant disease, and a recent report attributes early onset and rapid deterioration in a case of familial ALS (FALS) to this mutation. We have, therefore, genotyped the CNTF polymorphism in a large group of patients with CMT 1a, HNPP, sporadic ALS, in one pedigree with FALS, and controls. All groups exhibited a similar distribution of the polymorphism. We conclude that absence of CNTF does not increase susceptibility for these disorders and confirm that it does not affect onset and course of familial and sporadic ALS.
