DISCOVERY OF DIFFERENTIAL ISOFORM EXPRESSION DUE TO ALTERNATIVE SPLICING AFTER EX VIVO AND IN VIVO IRRADIATION AT 4 HOURS

LEBERLE, J.; BIOLATTI, V.; AUSAS, S.; NEGRIN, L.; MAZZITELLI-FUENTES, L.; CASCÓN, A.; BREZÁN, R.; IRAZOQUI, J.; ALVAREZ, A.; VENTIMIGLIA, R.; PERONA, M.; IBAÑEZ, I.L.; BELLORA, N.

Congreso; Reunión Anual de Sociedades de Biociencias 2023; 2023

Introduction and objectives: The molecular study of the radioinduced response by the massive analysis of the radiomodulated transcriptome has gained great relevance in recent years, both in the field of radioprotection and radiotherapy (RT). The aim of this study was to evaluate the transcriptome of irradiated human leukocytes in order to identify differential isoform expression at different doses of ionizing radiation (IR). Materials and methods: Leukocytes from healthy individuals were X-ray irradiated ex vivo at 25, 100 and 200 cGy and cultured for 4 hours at 37°C and 5% CO2 for RNA extraction. For in vivo studies, leukocytes were collected from cancer patients who received a single RT fraction, equivalent to a 1.6 cGy blood absorbed dose. Control samples were non-irradiated ex vivo or collected prior to the RT session. The transcriptome was sequenced by RNA-seq (Illumina Platform, 150 bp paired-end). Sequencing reads were mapped to the human genome hg38 (STAR software). A comparative analysis of isoforms was performed using SUPPA2 and BANDITS software. Results: We identified 39 genes which express different isoforms across the doses compared with the non-irradiated samples with SUPPA2. The most relevant were TNFSF4, KHNYN, MRPL36, CYCS, TRAPPC5, NR6A1 and AK6. BANDITS revealed 55 genes undergoing alternative splicing (AS) ex vivo. The most significant and biologically relevant genes in the radioinduced response were DDB2, DDIAS and TNFSF4. The latter showed an up-regulationof TNFSF4-201 transcript after IR, whereas TNFSF4-202 was down-regulated. This shows that there is an effect in the AS machinery in the cell when it is exposed to IR. Meanwhile, neither of the analyses could predict isoform changes in vivo, probably related to the low doses used. Conclusion: We determined a switch of isoforms of genes post-irradiation with potential as biomarkers of IR exposure or biodosimeters.