Screening of chromosomal region 21q22.3 for mutations in genes associated with neuronal Ca2+ signalling in bipolar affective disorder
ACTA BIOCHIMICA POLONICA
Authors: Kostyrko, Andrzej; Hauser, Joanna; Rybakowski, Janusz K.; Trzeciak, Wieslaw H.
Abstract
The therapeutic effect of lithium in bipolar affective disorder may be connected with decreasing intracellular Ca2+ concentrations. Several linkage studies have identified a potential bipolar affective disorder susceptibility locus within chromosomal region 21q22.3. This locus contains two genes expressed in the brain - ADARB1 and TRPM2 - involved in regulating intracellular Ca2+ concentrations. The aim of this study was an identification of mutations in the coding sequences of ADARB1 and TRPM2 and their association with bipolar affective disorder. For that purpose we screened 60 patients with bipolar affective disorder and a control group of 66 subjects using single strand conformation polymorphism and sequence analysis. For rapid screening we performed restriction fragment length polymorphism analysis. Screening of bipolar affective disorder patients for mutations in TRPM2 led to identification of three novel and four known transitions. Two transitions resulted in the substitutions: R755C and A890V. Screening of the coding sequence of ADARB1 did not reveal any mutations except one already known transition. A comparison of the transition frequency in patients and controls does not support association of the detected mutations with bipolar affective disorder. According to our results, bipolar affective disorder may not be caused by mutations in ADARB1. However, this study does not exclude TRPM2 as a candidate gene since we have screened only about 30 per cent of the entire coding sequence of this large gene.
Accumulation of nuclear ADAR2 regulates adenosine-to-inosine RNA editing during neuronal development
JOURNAL OF CELL SCIENCE
Authors: Behm, Mikaela; Wahlstedt, Helene; Widmark, Albin; Eriksson, Maria; Ohman, Marie
Abstract
Adenosine to inosine (A-to-I) RNA editing is important for a functional brain, and most known sites that are subject to selective RNA editing have been found to result in diversified protein isoforms that are involved in neurotransmission. In the absence of the active editing enzymes ADAR1 or ADAR2 (also known as ADAR and ADARB1, respectively), mice fail to survive until adulthood. Nuclear A-to-I editing of neuronal transcripts is regulated during brain development, with low levels of editing in the embryo and a dramatic increase after birth. Yet, little is known about the mechanisms that regulate editing during development. Here, we demonstrate lower levels of ADAR2 in the nucleus of immature neurons than inmature neurons. We show that importin-alpha 4 (encoded by Kpna3), which increases during neuronal maturation, interacts with ADAR2 and contributes to the editing efficiency by bringing it into the nucleus. Moreover, we detect an increased number of interactions between ADAR2 and the nuclear isomerase Pin1 as neuronsmature, which contribute to ADAR2 protein stability. Together, these findings explain how the nuclear editing of substrates that are important for neuronal function can increase as the brain develops.
COA
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