Cannon Jason R, Greenamyre J Timothy
Department of Neurology, Pittsburgh Institute for Neurodegenerative Diseases, University of Pittsburgh, Pittsburgh, PA 15260, United States.
Neurosci Lett. 2009 Oct 16;464(1):14-7. doi: 10.1016/j.neulet.2009.08.023. Epub 2009 Aug 12.
Quantification of neuronal cell number is a key endpoint in the characterization of neurodegenerative disease models and neuroprotective regimens. Immunohistochemistry for phenotypic markers, followed by unbiased stereology is often used to quantify the relevant neuronal population. To control for loss of phenotypic markers in the absence of cell death, or to determine if other types of neurons are lost, a general neuronal marker is often desired. Vertebrate neuron-specific nuclear protein (NeuN) is reportedly expressed in most mammalian neurons. In Parkinson's disease models, NeuN has been widely used to determine if there is actual nigral dopamine neuron loss or simply loss of tyrosine hydroxylase expression, a prominent phenotypic marker. To date, the qualitative value of NeuN expression as such a marker in the substantia nigra has not been assessed. Midbrain tissue sections from control rats were stained for NeuN and tyrosine hydroxylase and assessed by light or confocal microscopy. Here we report that NeuN expression level in the rat substantia nigra was highly variable, with many faintly stained cells that would not be meet stereological scoring criteria. Additionally, dopamine neurons with little or no NeuN expression were readily identified. Subcellular compartmentalization of NeuN expression was also variable, with many cells dorsal and ventral to the nigra exhibiting expression in both the nucleus and cytoplasm. NeuN expression also appeared to be much higher in non-dopamine neurons within the ventral midbrain. This characterization of nigral NeuN expression suggests that it is not useful as a quantitative general neuronal marker in the substantia nigra.
神经元细胞数量的量化是神经退行性疾病模型和神经保护方案特征描述中的一个关键终点。针对表型标志物进行免疫组织化学，随后采用无偏倚立体学方法，常用于量化相关的神经元群体。为了控制在无细胞死亡情况下表型标志物的丢失，或者确定其他类型的神经元是否丢失，通常需要一种通用的神经元标志物。据报道，脊椎动物神经元特异性核蛋白（NeuN）在大多数哺乳动物神经元中表达。在帕金森病模型中，NeuN已被广泛用于确定是否存在实际的黑质多巴胺能神经元丢失，或者仅仅是酪氨酸羟化酶表达的丢失，酪氨酸羟化酶是一种突出的表型标志物。迄今为止，NeuN表达作为黑质中此类标志物的定性价值尚未得到评估。对来自对照大鼠的中脑组织切片进行NeuN和酪氨酸羟化酶染色，并通过光学显微镜或共聚焦显微镜进行评估。在此我们报告，大鼠黑质中NeuN的表达水平高度可变，有许多染色浅的细胞不符合立体学评分标准。此外，很容易识别出几乎没有或没有NeuN表达的多巴胺能神经元。NeuN表达的亚细胞区室化也存在差异，黑质背侧和腹侧的许多细胞在细胞核和细胞质中均有表达。NeuN表达在腹侧中脑的非多巴胺能神经元中似乎也高得多。黑质NeuN表达的这种特征表明，它作为黑质中定量通用神经元标志物并无用处。
