Decoding Genome-wide Dysregulation of Translation in eIF2B-mutant Astrocytes: Implications for Vanishing White Matter Disease
eIF2B is a master regulator of translation initiation and mediator of the integrated stress response (ISR). Partial-loss-of function mutations are associated with eIF2B-leukodystrophy termed Vanishing White Matter Disease (VWMD), a recessive neurodegenerative disorder. Astrocytes, the brain homeostasis keepers, are central to VWMD owing to their hyper-sensitivity to eIF2B activity, as manifested by their phenotypic deficits due to the mutation. Here we used astrocytes isolated from the brains of WT and eIF2B5R132H/R132H mice to assess their transcriptome and translatome responses upon cytokine-mediated activation, an mTOR-driven process critical for brain homeostasis. We found that: (i) a mild eIF2B mutation has the power to disrupt translation regulation programs involving ~30% of the expressed genes; (ii) a common compensatory strategy to overcome the translation regulation failure is manipulation of mRNA abundance; and (iii) dysregulation of functionally related genes can be used to reliably predict deficits of corresponding cellular functions. Specifically, the study illuminates the molecular anomalies responsible for the impaired ribogenesis and mitochondrial respiration of eIF2B-mutant astrocytes. Moreover, it reliably predicts, for the first time, impaired cholesterol biosynthesis in eIF2B-mutant astrocytes. This work demonstrates the strength of combined transcriptome/translatome approach to decipher links between mild expression anomalies and downstream cellular defects associated with VWMD. Overall design: Three biological repetitions of Eif2b5-R132H-R132H mutant primary astrocytes were treated or not with 20ng/ml TNFa and 0.25ng/ml IL-1ß  for 24 hr or 48 hr. A portion of each sample was treated with RNase-I to generate ribosome footprints used for Ribo-seq analysis, while an undigested portion was used for RNA-seq.