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RNA polymerase (Pol) III synthesizes abundant short non-coding RNAs that have essential functions in protein synthesis, secretion and other processes. Despite the ubiquitous functions of these RNAs, mutations in Pol III subunits cause Pol III-related leukodystrophy, an early-onset neurodegenerative disease. The basis of this neural sensitivity and the mechanisms of disease pathogenesis are unknown. Here we show that mice expressing pathogenic mutations in the largest Pol III subunit, Polr3a, specifically in Olig2-expressing cells, have impaired growth and developmental delay, deficits in cognitive, sensory and fine sensorimotor function, and hypomyelination in multiple regions of the cerebrum and spinal cord. In contrast, the gross motor defects and cerebellar hypomyelination that are common features of severely affected patients are absent in the mice, suggesting a relatively mild form of the disease in this conditional model. Our results show that disease pathogenesis in the mice involves defects that reduce both the number of mature myelinating oligodendrocytes and the ability of these cells to produce a myelin sheath of normal thickness. Thus, the findings suggest cell-specific roles for Pol III in the development and/or survival of oligodendrocytes as well as their function in myelination.Significance StatementPathogenic mutations in subunits of RNA polymerase (Pol) III cause a prevalent autosomal recessive form of leukodystrophy. However, understanding of the mechanisms of pathogenesis, including how ubiquitously-expressed Pol III mutations affect primarily the central nervous system, has been limited by the absence of an animal model of the disease. We show that conditional knock-in of pathogenic Polr3a mutations in the Olig2 lineage in mice results in growth, neurobehavioral and hypomyelination phenotypes reflecting a subset of clinical features of Pol III-related leukodystrophy patients. Myelination defects in the mice identify neural-specific roles for Pol III transcription. The phenotypes of Pol III-related leukodystrophic mice enable genetic and pharmacological approaches aimed at mitigating the consequences of this disease in humans.

The circadian clock coordinates behavioral and circadian cues with availability and utilization of nutrients. Proteasomal degradation of clock repressors, such as cryptochrome (CRY) 1, maintains periodicity. Whether macroautophagy, a quality control pathway, degrades circadian proteins remains unknown. Here we show that circadian proteins BMAL1, CLOCK, REV-ERB alpha, and CRY1 are lysosomal targets, and that macroautophagy affects the circadian clock by selectively degrading CRY1. Autophagic degradation of CRY1, an inhibitor of gluconeogenesis, occurs in a diurnal window when rodents rely on gluconeogenesis, suggesting that CRY1 degradation is timeimprinted to maintenance of blood glucose. High-fat feeding accelerates autophagic CRY1 degradation and contributes to obesity-associated hyperglycemia. CRY1 contains several light chain 3 (LC3)-interacting region (LIR) motifs, which facilitate the interaction of cargo proteins with the autophagosome marker LC3. Using mutational analyses, we identified two distinct LIRs on CRY1 that exert circadian glycemic control by regulating CRY1 degradation, revealing LIRs as potential targets for controlling hyperglycemia.