Novel intramolecular base-pairing of the U8 snoRNA underlies a Mendelian form of cerebral small vessel disease

Abstract

How mutations in the non-coding U8 snoRNA cause the neurological disorder leukoencephalopathy with calcification and cysts (LCC) is poorly understood. We report the first vertebrate mutant U8 animal model for interrogating LCC-associated pathology. Mutant U8 zebrafish exhibit defective central nervous system development and ribosomal RNA (rRNA) biogenesis, with tp53 activation which monitors ribosome biogenesis. Importantly, LCC patient fibroblasts demonstrate rRNA processing defects. Human precursor-U8 (pre-U8) containing a 3´ extension rescued mutant U8 zebrafish, indicating conserved biological function. Analysis of LCCassociated U8 alleles in zebrafish revealed that one null and one hypomorphic, but still functional, allele combine to cause LCC. Mutations involving any one of seven nucleotides within the human pre-U8 3´ extension, or 5´ region of U8, alter processing of pre-U8, and identify a novel basepairing interaction between the 5´ end and 3´ extension of human pre-U8. Variants in these seven nucleotides, one of which is present on a single allele in almost all patients, act as hypomorphic mutations. Given that biallelic null U8 alleles are likely incompatible with human development, identification of hypomorphic mutations mediating viable embryogenesis furthers understanding of LCC molecular pathology and cerebral vascular homeostasis.

Antisense pairing and SNORD13 structure guide RNA cytidine acetylation

“…S3). The formation of stem IV and stem V requires that transcription of SNORD13 gene goes beyond its mature 3 ′ -end, which has been previously observed (Ohno et al 2000;Boulon et al 2004;Badrock et al 2022). These external stems may be important to formation of the kink-turn motif by bringing together the C-and D-boxes (Darzacq and Kiss 2000), or serve as signal that delineates the mature 3 ′ -end.…”

Antisense pairing and SNORD13 structure guide RNA cytidine acetylation

“…The formation of stem IV and stem V requires that transcription of SNORD13 gene goes beyond its mature 3'end, which has been previously observed. [20][21][22] These external stems may be important to…”

“…The formation of stem IV and stem V requires that transcription of SNORD13 gene goes beyond its mature 3'end, which has been previously observed. [20][21][22] These external stems may be important to formation of the kink-turn motif by bringing together the C-and D-boxes, 23 or serve as signal that delineates the mature 3'-end. Of note, a process analogous to the latter has been recently found to play a role in regulating expression of SNORD118.…”