GGC repeat expansion in NOTCH2NLC induces dysfunction in ribosome biogenesis and translation

Abstract

GGC repeat expansion in the 5′ untranslated region (UTR) of NOTCH2NLC is associated with a broad spectrum of neurological disorders, especially neuronal intranuclear inclusion disease (NIID). Studies have found that GGC repeat expansion in NOTCH2NLC induces the formation of polyglycine (polyG)-containing protein, which is involved in the formation of neuronal intranuclear inclusions. However, the mechanism of neurotoxicity induced by NOTCH2NLC GGC repeats is unclear. Here, we used NIID patient-specific iPSC-derived 3D cerebral organoids (3DCOs) and cellular models to investigate the pathophysiological mechanisms of NOTCH2NLC GGC repeat expansion. IPSC-derived 3DCOs and cellular models showed the deposition of polyG-containing intranuclear inclusions. The NOTCH2NLC GGC repeats could induce the upregulation of autophagic flux, enhance integrated stress response, and activate EIF2α phosphorylation. Bulk RNA sequencing for iPSC-derived neurons and single-cell RNA sequencing (scRNA-seq) for iPSC-derived 3DCOs revealed that NOTCH2NLC GGC repeats may be associated with dysfunctions in ribosome biogenesis and translation. Moreover, NOTCH2NLC GGC repeats could induce the NPM1 nucleoplasm translocation, increase nucleolar stress, impair ribosome biogenesis, and induce ribosomal RNA (rRNA) sequestration, suggesting dysfunction of membraneless organelles in the NIID cellular model. Dysfunctions in ribosome biogenesis and phosphorylated EIF2α and the resulting increase in the formation of G3BP1-positive stress granules may together lead to whole-cell translational inhibition, which may eventually cause cell death. Interestingly, scRNA-seq revealed that NOTCH2NLC GGC repeats may be associated with a significantly decreased proportion of immature neurons while 3DCOs were developing. Together, our results underscore the value of patient-specific iPSC-derived 3DCOs in investigating the mechanisms of polyG diseases, especially those caused by repeats in human-specific genes.

Immune Dysfunction and Systemic Inflammatory infiltration Exist in Neuronal Intranuclear Inclusion Disease

“…Previous studies have demonstrated the neurotoxicity of uN2CpolyG protein based on its reduction of cell viability, disruption of nucleocytoplasmic transport, induction of mitochondrial dysfunction, and inhibition of ribosome biogenesis and translation (3,(17)(18)(19). These ndings have offered crucial insights into the protein's detrimental effects on cellular mechanisms.…”

Adult-Type Neuronal Intranuclear Inclusion Disease with Limb Tremor Onset: Case Report and Literature Review

“…Researchers have proposed several hypotheses regarding the pathogenesis of NIID, including the toxicity of polyamino acid proteins (17)(18)(19), toxic RNA gain-offunction (19,20), and aberrant methylation of GGC repeat sequences (21). Recently, some studies have suggested that dysfunction of ribosome biogenesis and translation and mitochondrial dysfunction might be related to the pathogenesis of NIID (22,23). However, the speci c mechanisms driving the pathogenesis of NIID remain unclear, and extensive experiments in cellular and animal models are required for further studies.…”