Molecular basis of neurodegeneration in a mouse model of Polr3-related disease (tRNA)
Pathogenic variants in subunits of RNA polymerase (Pol) III cause a spectrum of neurodegenerative diseases including 4H leukodystrophy. We developed a postnatal whole-body mouse model expressing pathogenic mutations in Polr3a to examine the molecular mechanisms by which reduced Pol III activity results primarily in central nervous system phenotypes. Polr3a mutant mice exhibit behavioral deficits, exocrine pancreatic atrophy and cerebral pathology. Transcriptome and immunohistochemistry analyses of cerebra show a reduction in most Pol III transcripts, induction of innate immune and integrated stress responses and cell type-specific gene expression changes reflecting neuron and oligodendrocyte loss and microglial activation. A global decrease in mature tRNA levels and an altered tRNA profile preceded cerebral neurodegeneration suggesting a causal role in disease initiation. In cerebella, heart and kidney, Pol III transcripts other than tRNAs were generally unaffected. The results suggest tissue-specific thresholds of sensitivity to defects in Pol III transcription. Overall design: Transcriptome analysis of tamoxifen-induced expression of Polr3a mutation in mouse cerebrum and cerebellum