Neuron navigator 2 (NAV2, RAINB1, POMFIL2, HELAD1, unc53H2) is essential for nervous system development. In the present study the spatial distribution of Nav2 transcript in mouse CNS during embryonic, postnatal and adult life is examined. Because multiple NAV2 proteins are predicted based on alternate promoter usage and RNA splicing, in situ hybridization was performed using probes designed to the 5′ and 3′ ends of the Nav2 transcript, and PCR products using primer sets spanning the length of the mRNA were also examined by real time PCR (qPCR). These studies support full-length Nav2 transcript as the predominant form in the wild-type mouse CNS. The developing cortex, hippocampus, thalamus, olfactory bulb, and granule cells (GC) within the cerebellum show the highest expression, with a similar staining pattern using either the 5′Nav2 or 3′Nav2 probe. Nav2 is expressed in GC precursors migrating over the cerebellar primordium as well as in the postmitotic premigratory cells of the external granule cell layer (EGL). It is expressed in the cornu ammonis (CA) and dentate gyrus (DG) throughout hippocampal development. In situ hybridization was combined with immunohistochemistry for Ki67, CTIP2 and Nissl staining to follow Nav2 transcript location during cortical development, where it is observed in neuroepithelial cells exiting the germinal compartments, as well as later in the cortical plate (CP) and developing cortical layers. The highest levels of Nav2 in all brain regions studied are observed in late gestation and early postnatal life which coincides with times when neurons are migrating and differentiating. A hypomorphic mouse that lacks the full-length transcript but expresses shorter transcript shows little staining in the CNS with either probe set except at the base of the cerebellum, where a shorter Nav2 transcript is detected. Using dual fluorescent probe in situ hybridization studies, these cells are identified as oligodendrocytes and are detected using both Olig1 and the 3′Nav2 probe. The identification of full-length Nav2 as the primary transcript in numerous brain regions suggests NAV2 could play a role in CNS development beyond that of its well-established role in the cerebellum.

神经元导航器2（NAV2，RAINB1，POMFIL2，HELAD1，unc53H2）对于神经系统发育至关重要。在本研究中，研究了小鼠CNS在胚胎，出生后和成年期间的Nav2转录本的空间分布。由于基于备用启动子的使用和RNA剪接可预测多种NAV2蛋白，因此使用针对Nav2转录本5'和3'末端设计的探针进行原位杂交，并且还使用了跨mRNA长度的引物组进行PCR产物通过实时PCR（qPCR）检查。这些研究支持全长Nav2转录本是野生型小鼠CNS中的主要形式。小脑内发育中的皮质，海马，丘脑，嗅球和颗粒细胞（GC）显示最高的表达，并且使用5'Nav2或3'Nav2探针具有相似的染色模式。Nav2在迁移到小脑原基的GC前体以及外部颗粒细胞层（EGL）的有丝分裂后迁移细胞中表达。在整个海马体发育过程中，它在角膜铵（CA）和齿状回（DG）中表达。原位杂交与免疫组化结合用于Ki67，CTIP2和Nissl染色以追踪Nav2皮质发育过程中的转录本位置，在离开生发区室的神经上皮细胞中以及后来在皮质板（CP）和发育中的皮质层中观察到。在妊娠晚期和出生后早期生命中观察到的所有大脑区域中Nav2的水平最高，这与神经元迁移和分化的时间相吻合。缺乏全长转录本但表达较短转录本的亚型小鼠，用任一探针组在中枢神经系统中几乎没有染色，但在小脑底部检测到较短的Nav2转录本。使用双荧光探针原位杂交研究，将这些细胞鉴定为少突胶质细胞，并使用OLIG1和3' NAV2探针。在许多大脑区域中，将全长Nav2作为主要转录物的鉴定表明，NAV2除了在小脑中已确立的作用外，还可能在CNS发育中发挥作用。