Pathogenicity analysis and splicing rescue of a classical splice site variant (c.1343+1G>T) of CNOT1 gene associated...

Mutations in the CNOT1 gene lead to an incurable rare neurological disorder mainly manifested as a clinical spectrum of intellectual disability, developmental delay, seizures, and behavioral problems. In this study, we investigated a classical splice site variant of CNOT1 (c.1343+1G>T) associated with neurodevelopmental disorders, which was a master regulator, orchestrating gene expression, RNA deadenylation, and protein ubiquitination. To link CNOT1 dysfunction with the neurodevelopmental phenotype observed in a patient, in vitro minigene assay was used to verify the effect of CNOT1 gene splice site variant c.1343+1G>T on mRNA splicing. We also explored the impact of transient transfection introducing modified U1 snRNA on correcting the splicing variant. Through minigene expression in mammalian cells, we demonstrated that the variant induced complete exon 12 skipping, which explained the patient's clinical condition and provided additional genetic diagnosis evidence for the clinical significance of the variant. Moreover, we confirmed that the aberrant splice pattern could be partially corrected by the modified U1 snRNA at the mRNA level, which provided strong evidence for the therapeutic potential of modified U1 snRNA in neutralizing the hazardous effect of incorrect splicing patterns.