A novel human myo-inositol monophosphatase gene, IMP.18p, maps to a susceptibility region for bipolar disorder
作者:T Yoshikawa、G Turner、L E Esterling、A R Sanders、S D Detera-Wadleigh
DOI:10.1038/sj.mp.4000325
日期:1997.9.1
Within the broad susceptibility region for bipolar disorder on the pericentromeric portion of chromosome 18, the highest allele sharing in our 22-pedigree series has been found in markers mapping to 18p11.2. Studies by other investigators on independently ascertained pedigrees have also shown increased sharing in this region, making 18p11.2 a plausible site for a candidate gene search. We found expressed sequence tags (ESTs) mapping within this area that are homologous to the myo-inositol-1-phosphate phosphohydrolase (myo-inositol monophosphatase: IMP) gene of Xenopus laevis. Since IMP has been proposed to be the potential target of lithium, a drug commonly used for the treatment of bipolar disorder, we proceeded to characterize the cognate transcript. Northern blot analysis detected a major transcript of 1.5âkb with abundant expression in adult and fetal tissues, but minimal expression in whole brain. In subcortical brain regions, however, substantial levels of transcript were evident, most prominently in the caudate. We have isolated and sequenced the full-length cDNA. The deduced amino acid sequence revealed ~54% identity with an existing human IMP, which we found mapped to chromosome 8, and IMP of other species. The sequence also included motifs characteristic of the IMP gene family. To provide a more precise location of this gene, mapping with a panel of radiation hybrids (RH) was conducted. Multipoint RH analysis placed the gene between GNAL and D18S71 within the 18p11.2 region. We, therefore, designated this novel gene as IMP.18p. The physical position and possible function suggest that IMP.18p is an important candidate gene for bipolar disorder.
在双相情感障碍的广泛易感区内,位于 18 号染色体的近染色体部分,在我们的 22 个血统系列中,等位基因共享率最高的是映射到 18p11.2 的标记。其他研究人员对独立确定的血统进行的研究也显示,该区域的等位基因共享率也有所提高,因此 18p11.2 是候选基因搜索的一个可信的位点。我们发现在这一区域的表达序列标签(ESTs)与爪蟾的肌醇-1-磷酸磷酸水解酶(肌醇单磷酸酶:IMP)基因同源。锂是一种常用于治疗躁郁症的药物,由于 IMP 被认为是锂的潜在靶标,因此我们开始研究同源转录本的特征。Northern 印迹分析检测到了一个 1.5âkb 的主要转录本,在成体和胎儿组织中有大量表达,但在全脑中表达极少。然而,在皮层下脑区,转录本的表达水平很高,其中以尾状核最为显著。我们对全长 cDNA 进行了分离和测序。推导出的氨基酸序列显示,它与现有的人类 IMP(我们发现该 IMP 映射到第 8 号染色体上)以及其他物种的 IMP 有约 54% 的相同性。该序列还包括 IMP 基因家族特有的基序。为了更精确地确定该基因的位置,我们使用辐射杂交种(RH)进行了测绘。多点 RH 分析将该基因置于 18p11.2 区域的 GNAL 和 D18S71 之间。因此,我们将这个新基因命名为 IMP.18p。物理位置和可能的功能表明,IMP.18p 是双相情感障碍的一个重要候选基因。