Laboratory of Clinical and Developmental Genomics, National Institute of Child Health and Human Development, National Institutes of Health, 49 Convent Drive, Building 49, Room 2C078, Bethesda, MD 20814, USA.
University of Florida College of Medicine, 1600 SW Archer Rd, Gainesville, FL 32603, USA.
Mol Autism. 2014 Jan 10;5(1):3. doi: 10.1186/2040-2392-5-3.
The cellular mechanism(s) underlying autism spectrum disorders (ASDs) are not completely understood, but ASDs are thought to ultimately result from disrupted synaptogenesis. However, studies have also shown that glial cell numbers and function are abnormal in post-mortem brain tissue from autistic patients. Direct assessment of glial cells in post-mortem human brain tissue is technically challenging, limiting glial research in human ASD studies. Therefore, we attempted to determine if glial cell-type specific markers may be altered in autistic brain tissue in a manner that is consistent with known cellular findings, such that they could serve as a proxy for glial cell numbers and/or activation patterns.
We assessed the relative expression of five glial-specific markers and two neuron-specific markers via qRT-PCR. We studied tissue samples from the prefrontal cortex (PFC) and cerebellum of nine post-mortem autistic brain samples and nine neurologically-normal controls. Relative fold-change in gene expression was determined using the ΔΔCt method normalized to housekeeping gene β-actin, with a two-tailed Student's t-test P <0.05 between groups considered as significant.
Both astrocyte- and microglial-specific markers were significantly more highly expressed in autistic PFC as compared to matched controls, while in the cerebellum only astrocyte markers were elevated in autistic samples. In contrast, neuron-specific markers showed significantly lower expression in both the PFC and cerebellum of autistic patients as compared to controls.
These results are in line with previous findings showing increased glial cell numbers and up-regulation of glial cell gene expression in autistic post-mortem brain tissue, particularly in the PFC, as well as decreased number of neurons in both the PFC and cerebellum of autistic patients. The concordance of these results with cell-level studies in post-mortem autistic brain tissue suggests that expression of glial cell-type specific markers may serve as a useful alternative to traditional cellular characterization methods, especially when appropriately-preserved post-mortem tissue is lacking. Additionally, these results demonstrate abnormal glial-specific gene expression in autistic brains, supporting previous studies that have observed altered glial cell numbers or activation patterns in ASDs. Future work should directly assess the correlation between cell-type specific marker levels and cell number and activation patterns.
自闭症谱系障碍（ASD）的细胞机制尚不完全清楚，但 ASD 最终被认为是由于突触发生异常所致。然而，研究还表明，自闭症患者死后脑组织中的神经胶质细胞数量和功能异常。直接评估死后人脑组织中的神经胶质细胞在技术上具有挑战性，限制了人类 ASD 研究中的神经胶质细胞研究。因此，我们试图确定神经胶质细胞特异性标志物是否可能以与已知细胞发现一致的方式在自闭症脑组织中发生改变，从而可以作为神经胶质细胞数量和/或激活模式的替代物。
我们通过 qRT-PCR 评估了五个神经胶质特异性标志物和两个神经元特异性标志物的相对表达。我们研究了来自九个死后自闭症脑样本和九个神经正常对照的前额叶皮层（PFC）和小脑组织样本。使用 ΔΔCt 方法并归一化为管家基因β-肌动蛋白，通过双侧学生 t 检验确定基因表达的相对折叠变化，组间 P<0.05 被认为具有统计学意义。
与匹配的对照相比，自闭症患者的 PFC 中星形胶质细胞和小胶质细胞特异性标志物的表达明显更高，而在小脑，只有星形胶质细胞标志物在自闭症样本中升高。相比之下，神经元特异性标志物在自闭症患者的 PFC 和小脑中的表达均明显低于对照组。
这些结果与先前的研究结果一致，即在死后自闭症脑组织中，星形胶质细胞数量增加和神经胶质细胞基因表达上调，尤其是在 PFC 中，以及自闭症患者的 PFC 和小脑中神经元数量减少。这些结果与死后自闭症脑组织中的细胞水平研究结果一致，表明神经胶质细胞特异性标志物的表达可能是传统细胞特征分析方法的有用替代方法，特别是在缺乏适当保存的死后组织时。此外，这些结果表明自闭症大脑中存在异常的神经胶质特异性基因表达，支持先前观察到的 ASD 中神经胶质细胞数量或激活模式改变的研究。未来的工作应直接评估细胞特异性标志物水平与细胞数量和激活模式之间的相关性。
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