Expression and distribution of NBCn2 (Slc4a10) splice variants in mouse brain: cloning of novel variant NBCn2-D.

The SLC4A10 gene, which is highly expressed in the mammalian brain, contains two known alternative splicing units, inserts A and B, and is theoretically capable of producing four NBCn2 splice variants: NBCn2-A, -B, -C, and -D. By immunoprecipitation and western blotting, a previous study showed the putative NBCn2-D to be expressed predominantly in the subcortex (SCX) and medulla (MD) of mouse brain. However, no evidence has been provided, in any species, for the existence of a full-length transcript encoding NBCn2-D. In the present study, we report for the first time the cloning of the full-length cDNAs encoding NBCn2-D from mouse SCX and MD. Based on the frequency of bacterial colonies obtained after PCR, we conclude that in SCX, the NBCn2-A transcript is the dominant transcript, whereas in MD, NBCn2-B is dominant. NBCn2-D is the least abundant transcript in each of these two brain regions. An analysis based upon the present PCR data as well as the previous immunoprecipitation/western-blot data suggests the following prevalence of NBCn2 variants in total mouse brain: NBCn2-A (~83%), NBCn2-B (~10%), NBCn2-C (~5%), and NBCn2-D (~2%). We also estimate the prevalence of each variant in each of five brain regions (i.e, cerebral cortex, SCX, cerebellum, hippocampus, and MD). We hypothesize that the expression of different NBCn2 splice variants is characteristic of specific tissue/cells.

SLC4A10基因在哺乳动物大脑中高度表达，包含两个已知的可变剪接单元，即插入片段A和B，理论上能够产生四种NBCn2剪接变体：NBCn2 - A、 - B、 - C和 - D。通过免疫沉淀和蛋白质印迹法，先前的一项研究表明，推测的NBCn2 - D主要在小鼠大脑的皮质下（SCX）和延髓（MD）中表达。然而，在任何物种中都没有提供编码NBCn2 - D的全长转录本存在的证据。在本研究中，我们首次报道了从小鼠皮质下和延髓中克隆编码NBCn2 - D的全长cDNA。基于PCR后获得的细菌菌落频率，我们得出结论：在皮质下，NBCn2 - A转录本是主要的转录本，而在延髓中，NBCn2 - B是主要的。NBCn2 - D在这两个大脑区域中是含量最少的转录本。基于当前PCR数据以及先前的免疫沉淀/蛋白质印迹数据进行的分析表明，在小鼠全脑中NBCn2变体的普遍程度如下：NBCn2 - A（约83%），NBCn2 - B（约10%），NBCn2 - C（约5%），NBCn2 - D（约2%）。我们还估计了在五个大脑区域（即大脑皮层、皮质下、小脑、海马体和延髓）中每个变体的普遍程度。我们假设不同的NBCn2剪接变体的表达是特定组织/细胞的特征。