Schmauss C
Department of Psychiatry and Brookdale Center for Molecular Biology, Mount Sinai School of Medicine, New York, New York 10029, USA.
J Neurosci. 1996 Dec 15;16(24):7902-9. doi: 10.1523/JNEUROSCI.16-24-07902.1996.
The D2-class of dopamine receptors (D2, D3, and D4) is a target for typical and atypical neuroleptic drugs. They have been considered, therefore, as factors that may contribute to the pathophysiology of psychotic disorders. Interestingly, in cortical brain tissues obtained postmortem form patients with chronic schizophrenia D3 mRNA was found to be significantly lower than in the corresponding anatomic regions of controls. Because the expression of a truncated D3-like mRNA (named D3nf) appeared to be unaffected in schizophrenic brains, these findings suggest the possibility that the loss of D3 mRNA results from an abnormal splicing of D3 pre-mRNA in schizophrenia that is accompanied by an increased accumulation of the truncated D3nf mRNA. To test this, three approaches were taken. (1) Substrate D3 pre-mRNA was spliced in vitro in HeLa nuclear extracts. Results from these experiments show that D3nf mRNA results from the alternative removal of a short spliceosomal intron in D3 pre-mRNA that has a noncanonical 3' splice site. (2) Substrate D3 pre-mRNA was spliced in vivo in stably transfected rat GH3 cells. Despite the atypical 3' cleavage that is necessary to generate D3nf mRNA, D3 and D3nf mRNA were found to be processed at similar amounts. (3) The relative D3/D3nf splicing efficiencies were then determined in the anterior cingulate cortex of postmortem brains obtained from controls and from patients with chronic schizophrenia. Significant differences were found between the relative levels of D3 and D3nf mRNA, suggesting that an enhanced D3nf-specific splicing of D3 pre-mRNA in schizophrenia leads to a decreased expression of D3 mRNA.
多巴胺受体的D2类（D2、D3和D4）是典型和非典型抗精神病药物的作用靶点。因此，它们被认为可能是导致精神障碍病理生理学的因素。有趣的是，在慢性精神分裂症患者死后获得的大脑皮质组织中，发现D3 mRNA显著低于对照组相应的解剖区域。由于截短的D3样mRNA（命名为D3nf）的表达在精神分裂症大脑中似乎未受影响，这些发现提示了一种可能性，即精神分裂症中D3 mRNA的缺失是由于D3前体mRNA异常剪接所致，同时伴有截短的D3nf mRNA积累增加。为了验证这一点，采用了三种方法。（1）底物D3前体mRNA在HeLa细胞核提取物中进行体外剪接。这些实验结果表明，D3nf mRNA是由D3前体mRNA中一个具有非经典3'剪接位点的短剪接体内含子的选择性去除产生的。（2）底物D3前体mRNA在稳定转染的大鼠GH3细胞中进行体内剪接。尽管产生D3nf mRNA需要非典型的3'切割，但发现D3和D3nf mRNA的加工量相似。（3）然后在对照组和慢性精神分裂症患者死后获得的大脑前扣带回皮质中测定相对的D3/D3nf剪接效率。发现D3和D3nf mRNA的相对水平存在显著差异，表明精神分裂症中D3前体mRNA的D3nf特异性剪接增强导致D3 mRNA表达降低。
