Enhanced C/EBPα Function Extends Healthspan and Lifespan in the African Turquoise Killifish.

The transcription factor CCAAT/enhancer binding protein alpha (C/EBPα) regulates cell differentiation, proliferation, and function in various tissues, including the liver, adipose tissue, skin, lung, and hematopoietic system. Studies in rats, mice, humans, and chickens have shown that CEBPA mRNA undergoes alternative translation initiation, producing three C/EBPα isoforms. Two of these isoforms act as full-length transcription factors with N-terminal transactivation domains and a C-terminal dimerization and DNA-binding domain. The third isoform is an N-terminally truncated variant, translated from a downstream AUG codon. It competes with full-length isoforms for DNA binding, thereby antagonizing their activity. Expression of the truncated C/EBPα isoform depends on the initial translation of a short upstream open reading frame (uORF) in the CEBPA mRNA and subsequent re-initiation at a downstream AUG codon, a process stimulated by mTORC1 signaling. We investigated whether the ortholog of the CEBPA gene in the evolutionarily distant, short-lived African turquoise killifish (Nothobranchius furzeri) is regulated by similar mechanisms. Our findings reveal that the uORF-mediated regulation of C/EBPα isoform expression is conserved in killifish. Disruption of the uORF selectively eliminates the truncated isoform, leading to unrestrained activity of the full-length C/EBPα isoforms. This genetic modification significantly extended both the median and maximum lifespan and improved the healthspan(definition) of male N. furzeri. Furthermore, comparative transcriptome analysis revealed an upregulation of genes and pathways that are associated with healthspan and lifespan regulation in other species. These results highlight a conserved mechanism of CEBPA gene regulation across species and its potential role in modulating the lifespan and aging phenotypes.