Translatome profiling in fatal familial insomnia implicates TOR signaling in somatostatin neurons

Abstract

Selective neuronal vulnerability is common in neurodegenerative diseases but poorly understood. In genetic prion diseases, including fatal familial insomnia (FFI) and Creutzfeldt–Jakob disease (CJD), different mutations in the Prnp gene manifest as clinically and neuropathologically distinct diseases. Here we report with electroencephalography studies that theta waves are mildly increased in 21 mo old knock-in mice modeling FFI and CJD and that sleep is mildy affected in FFI mice. To define affected cell types, we analyzed cell type–specific translatomes from six neuron types of 9 mo old FFI and CJD mice. Somatostatin (SST) neurons responded the strongest in both diseases, with unexpectedly high overlap in genes and pathways. Functional analyses revealed up-regulation of neurodegenerative disease pathways and ribosome and mitochondria biogenesis, and down-regulation of synaptic function and small GTPase-mediated signaling in FFI, implicating down-regulation of mTOR signaling as the root of these changes. In contrast, responses in glutamatergic cerebellar neurons were disease-specific. The high similarity in SST neurons of FFI and CJD mice suggests that a common therapy may be beneficial for multiple genetic prion diseases.

Cerebellar granule neurons induce Cyclin D1 in an early stage of Huntington’s disease

“…This may partially explain the high number of DEGs in cerebellar vGluT2 + neurons, arguably the least heterogeneous cell type analyzed in this study. However, in a previous study using the same experimental approach, we did not observe strong changes in the cerebellar vGluT2 + neurons (Bauer et al, 2022), indicating this result is not an artifact but reflects the biological response of this cell type in HD. A third limitation is the use of a genetic background not widely used in HD research.…”

“…For RiboTag samples, cell type-specific mRNA was immunoprecipitated from brain tissue homogenates of flash-frozen cerebellum or cerebrum hemispheres, as described here (Bauer et al, 2022). In brief, homogenate was precleared by centrifugation and incubation with IgG isotype antibody-bound protein-G dynabeads (PGDB; 1009D, Invitrogen, Waltham MA).…”

“…CC-BY-NC-ND 4.0 International license perpetuity. It is made available under a preprint (which was not certified by peer review) is the author/funder, who has granted bioRxiv a license to display the preprint in The copyright holder for this this version posted November 9, 2022. ; https://doi.org/10.1101/2022.11.08.515613 doi: bioRxiv preprint Preparation of RNA samples: For RiboTag samples, cell type-specific mRNA was immunoprecipitated from brain tissue homogenates of flash-frozen cerebellum or cerebrum hemispheres, as described here (Bauer et al, 2022). In brief, homogenate was precleared by centrifugation and incubation with IgG isotype antibody-bound protein-G dynabeads (PGDB; 1009D, Invitrogen, Waltham MA).…”

Therapeutic Trial of anle138b in Mouse Models of Genetic Prion Disease

“…However, subsequent studies did not identify a clear increase in Gfap mRNA levels in the whole-brain homogenates from these animals (W. S. Jackson, unpublished observations), mirroring our results. Specific changes in mRNA translation have been observed in these knock-in lines ( 26 ), distinct from those observed in RML-inoculated mice ( 27 ), but these findings are more recent and were not leveraged here. Various histopathological abnormalities have also been identified in these knock-in mouse lines by 20 months (~600 days) ( 8 , 9 ), some of which we replicate here.…”

Therapeutic trial of anle138b in mouse models of genetic prion disease

“…However, subsequent studies did not identify a clear increase in Gfap mRNA levels in whole brain homogenates in these animals (Walker Jackson, personal communication), mirroring our results. Specific changes in mRNA translation have been observed in these knock-in lines 27 , distinct from those observed in RML-inoculated mice 28 , but these findings are more recent and were not leveraged here. Various histopathological abnormalities have also been identified in these knock-in mouse lines by 20 months (∼600 days) 8,9 , some of which we replicate here.…”