Alunno, L.; Massignani, I.; Hamadou, M. H.; Mazza, F.; Peroni, D.; Belli, R.; Dassi, E.; Romanel, A.; Inga, A.

To prioritize germline genetic variants affecting mRNA fate at the post-transcriptional and translational levels, we leveraged sucrose-gradient-based isolation of 80S monosomes and polysomes, followed by mRNA retrieval and paired-end sequencing. Total cytoplasmic RNA was also sequenced for comparison. Experiments were performed in the non-transformed cell line RPE-1, cultured under basal conditions or upon p53 activation by Nutlin. Differential gene expression analysis confirmed a canonical p53 response. Heterozygous SNPs and SNVs were identified from the RNA-seq data, and allelic fractions (AF) were calculated for total, monosomal, and polysomal mRNAs. Variants showing reproducible AF differences across fractions beyond experimental variability were defined as tranSNPs. Among nearly 7000 heterozygous variants analyzable in polysomal or total RNA and over 5000 in monosomal mRNA, 1155 displayed a significant imbalance. Reporter assays performed in both RPE-1 and HCT116 cells validated allelic or haplotype effects for 17 selected variants in UTRs and coding regions, confirming differences in 15 cases, with evidence of cell line-specific responses. Proteomic analysis further supported allelic imbalance for selected missense variants. Overall, tranSNPs were identified in a non-transformed cell line at frequencies comparable to those in cancer cells, thereby extending their implications in human physiology. Further, monosome profiling enabled improved detection sensitivity of tranSNPs without positional bias, suggesting that 80S profiling improves detection of allele-specific translational regulation in RPE-1 cells.