Fig. 1: α-synuclein levels are reduced in human brain glioma.
A SNCA expression in all IDHmut-codel, IDHmut-non codel et IDHwt glioma samples from TCGA database. Violin plots of SNCA expression (FPKM, Fragment Per Kilobase Million) from RNA-seq analysis (***, P < 0.001; NT, non tumoral). B Left, SNCA expression (from TCGA) levels in Proneural, Neural, Classical and Mesenchymal glioblastoma (GBM) subtypes. Right, SNCA expression dispersion among the subgroups according to Neftel classification: oligodendroglial progenitor cell-like (OPC-like); astrocyte-like (AC-like); neural progenitor cell-like (NPC-like) and mesenchymal-like (MES-like). Each quadrant of the 2D representation (B, middle) corresponds to one cell state of Neftel classification. The exact position of adult GBM single cells (dots, n = 4916) indicates their relative score for the meta-modules and their color illustrates the expression level of SNCA (***, P < 0.001). Values above the violin corresponds to the mean expression in each subgroup. C Kaplan-Meier statistical analysis of the prognostic significance of SNCA in all gliomas (right), in GBM (middle) and in low grade glioma (right) patients. Blue lines represent low expression ( < median, (med)) and red lines represent high expression ( > median); n indicates number of samples in each low or high expression groups. (***, P = 0.0002). D Single cell RNA-seq (n = 5742) from Neftel classification by means of the t-distributed stochastic neighbor embedding (tSNE) plot, showing clustered cells based on the presence of chromosomal copy number aberrations (blue), or high expression of marker genes for macrophages (red), oligodendrocytes (green) or T-cell (purple). According to that clustering, color dots indicate SNCA expression levels (logTPM, ***, P < 0.001). Representative immunoblots and quantification of α-syn expression in non-tumoral (NT), grade II (N = 12) and III (N = 7) oligodendroglioma (E, One-way ANOVA, correlation trend analysis) or GBM biopsies (F, N = 12, Mann–Whitney test). Stain Free gel quantification method was used to normalize protein load charges. Bars represent the means ± SEM of α-syn protein expression as percent of control (NT biopsies) taken as 100. ****, P < 0.0001.
