Translation initiation factor eIF2Bε promotes Wnt-mediated clonogenicity and global translation in intestinal epithelial cells.

Modulation of global mRNA translation, which is essential for intestinal stem cell function, is controlled by Wnt signaling. Loss of tumor supressor APC in stem cells drives adenoma formation through hyperactivion of Wnt signaling and dysregulated translational control. It is unclear whether factors that coordinate global translation in the intestinal epithelium are needed for APC-driven malignant transformation. Here we identified nucleotide exchange factor eIF2Bε as a translation initiation factor involved in Wnt-mediated intestinal epithelial stemness. Using eIF2BεArg191His mice with a homozygous point mutation that leads to dysfunction in the enzymatic activity, we demonstrate that eIF2Bε is involved in small intestinal crypt formation, stemness marker expression, and secreted Paneth cell-derived granule formation. Wnt hyperactivation in ex vivo eIF2BεArg191His organoids, using a GSK3ß inhibitor to mimic Apc driven transformation, shows that eIF2Bε is essential for Wnt-mediated clonogenicity and associated increase of the global translational capacity. Finally, we observe high eIF2Bε expression in human colonic adenoma tissues, exposing eIF2Bε as a potential target of CRC stem cells with aberrant Wnt signaling.

Bergmann glia translocation: a new disease marker for vanishing white matter identifies therapeutic effects of Guanabenz treatment.

AIM: Vanishing White Matter (VWM) is a devastating leucoencephalopathy without effective treatment options. Patients have mutations in the EIF2B1-5 genes, encoding the five subunits of eIF2B, a guanine exchange factor that is an important regulator of protein translation. We recently developed mouse models for VWM that replicate the human disease. To study disease improvement after treatment in these mice, it is essential to have sensitive biomarkers related to disease stage. The Bergmann glia of the cerebellum, an astrocytic subpopulation, translocate into the molecular layer in symptomatic VWM mice and patients. This study looked at the prospects of using Bergmann glia pathology as an objective disease marker for VWM. METHODS: We defined a new quantitative measurement of Bergmann glia pathology in the cerebellum of VWM mice and patients. To test the sensitivity of this new marker for improvement, VWM mutant mice received long-term treatment with Guanabenz, an FDA-approved anti-hypertensive agent affecting eIF2B activity. RESULTS: Bergmann glia translocation was significantly higher in symptomatic VWM mice and VWM patients than in controls and worsened over the disease course. Both Bergmann glia pathology and cerebellar myelin pathology improved with Guanabenz treatment in mice, showing that Bergmann glia translocation is a sensitive measurement for improvement. CONCLUSIONS: Bergmann glia translocation can be used to objectively assess effects of treatment in VWM mice. Future treatment strategies involving compounds regulating eIF2 phosphorylation might benefit VWM patients.