Albizzati Elena, Florio Elena, Miramondi Federica, Sormonta Irene, Landsberger Nicoletta, Frasca Angelisa
Department of Medical Biotechnology and Translational Medicine, University of Milan, Milan, Italy.
Division of Neuroscience, IRCCS San Raffaele Scientific Institute, Milan, Italy.
Front Neurosci. 2022 Feb 15;16:823060. doi: 10.3389/fnins.2022.823060. eCollection 2022.
Rett syndrome (RTT) is a neurodevelopmental disorder that represents the most common genetic cause of severe intellectual disability in females. Most patients carry mutations in the X-linked gene, coding for the methyl-CpG-binding protein 2 (MeCP2), originally isolated as an epigenetic transcriptional factor able to bind methylated DNA and repress transcription. Recent data implicated a role for glia in RTT, showing that astrocytes express and that its deficiency affects their ability to support neuronal maturation by non-cell autonomous mechanisms. To date, some molecular, structural and functional alterations have been attributed to null astrocytes, but how they evolve over time and whether they follow a spatial heterogeneity are two aspects which deserve further investigations. In this study, we assessed cytoskeletal features of astrocytes in deficient brains by analyzing their arbor complexity and processes in reconstructed GFAP cells at different ages, corresponding to peculiar stages of the disorder, and in different cerebral regions (motor and somatosensory cortices and CA1 layer of hippocampus). Our findings demonstrate the presence of defects in null astrocytes that worsen along disease progression and strictly depend on the brain area, highlighting motor and somatosensory cortices as the most affected regions. Of relevance, astrocyte cytoskeleton is impaired also in the somatosensory cortex of symptomatic heterozygous animals, with astrocytes showing slightly more pronounced defects with respect to the null cells, emphasizing the importance of non-cell autonomous effects. We reported a temporal correlation between the progressive thinning of layer I and the atrophy of astrocytes, suggesting that their cytoskeletal dysfunctions might contribute to cortical defects. Considering the reciprocal link between morphology and function in astrocytes, we analyzed the effect of deficiency on the expression of selected astrocyte-enriched genes, which describe typical astrocytic features. qRT-PCR data corroborated our results, reporting an overall decrement of gene expression, which is area and age-dependent. In conclusion, our data show that deficiency causes structural and molecular alterations in astrocytes, which progress along with the severity of symptoms and diversely occur in the different cerebral regions, highlighting the importance of considering heterogeneity when studying astrocytes in RTT.
雷特综合征(RTT)是一种神经发育障碍,是女性严重智力残疾最常见的遗传原因。大多数患者携带X连锁基因的突变,该基因编码甲基CpG结合蛋白2(MeCP2),最初作为一种能够结合甲基化DNA并抑制转录的表观遗传转录因子被分离出来。最近的数据表明神经胶质细胞在雷特综合征中起作用,显示星形胶质细胞表达[相关蛋白],其缺乏会通过非细胞自主机制影响它们支持神经元成熟的能力。迄今为止,一些分子、结构和功能改变已归因于MeCP2缺失的星形胶质细胞,但它们如何随时间演变以及是否存在空间异质性是两个值得进一步研究的方面。在本研究中,我们通过分析不同年龄(对应于该疾病的特定阶段)以及不同脑区(运动和体感皮层以及海马体CA1层)中重建的GFAP细胞的星形胶质细胞的树突复杂性和突起,评估了MeCP2缺失大脑中星形胶质细胞的细胞骨架特征。我们的研究结果表明,MeCP2缺失的星形胶质细胞存在缺陷,这些缺陷会随着疾病进展而恶化,并且严格依赖于脑区,突出显示运动和体感皮层是受影响最严重的区域。相关的是,有症状的杂合动物的体感皮层中星形胶质细胞的细胞骨架也受损,与MeCP2缺失的细胞相比,杂合的星形胶质细胞显示出更明显的缺陷,强调了非细胞自主效应的重要性。我们报道了I层的逐渐变薄与星形胶质细胞萎缩之间的时间相关性,表明它们的细胞骨架功能障碍可能导致皮质缺陷。考虑到星形胶质细胞形态与功能之间的相互联系,我们分析了MeCP2缺乏对选定富含星形胶质细胞基因表达的影响,这些基因描述了典型的星形胶质细胞特征。qRT-PCR数据证实了我们的结果,报告了基因表达的总体下降,这与区域和年龄有关。总之,我们的数据表明,MeCP2缺乏会导致星形胶质细胞的结构和分子改变,这些改变会随着症状的严重程度而进展,并且在不同脑区中以不同方式发生,突出了在研究雷特综合征中的星形胶质细胞时考虑异质性的重要性。