Alternative splicing drives a dynamic transcriptomic response during Acanthamoeba castellanii programmed cell death.

Programmed cell death (PCD) in unicellular organisms is not well characterized. This study investigated the transcriptomic response of Acanthamoeba castellanii to G418-induced PCD, focusing on the role of alternative splicing (AS). RNA sequencing revealed extensive transcriptional changes, affecting approximately 70% of annotated genes over six hours of treatment. This analysis also highlighted significant alterations in pathways related to cell cycle, proteolysis, and RNA splicing. Analysis of AS events identified 18,748 differentially spliced events, predominantly intron retention (IR). Interestingly, retained introns displayed a 3' bias in untreated cells, a pattern that shifted towards uniform distribution throughout the gene body during PCD. Additionally, we characterized retained introns during trophozoite stage and during PCD of the amoeba. Correlational analysis revealed a significant negative correlation between IR and transcript levels, suggesting a complex interplay between transcriptional and post-transcriptional regulation. The predominance of IR, coupled with its dynamic positional shift during PCD, points to a novel regulatory mechanism in A. castellanii PCD. These findings provide insights into the molecular mechanisms underlying PCD in this organism, potentially identifying new therapeutic targets and allowing us a better understanding of such process in A. castellanii, a facultative human pathogen.