Calcium influx drives m6A-dependent RUNX1T1 splicing to promote adipogenic commitment.

Intermuscular fat infiltration driven by fibro-adipogenic progenitors contributes to the irreversible progression of sarcopenia and reflects a fate shift associated with altered calcium signaling. Using FAP-based adipogenesis models, structural and biochemical analyses, transcriptomic profiling, and in vivo drug exposure studies, we found that Ca2+ influx dyshomeostasis promotes adipogenic commitment by triggering calmodulin remodeling, dissociation of the KCNQ1-CaM-FTO complex, nuclear translocation of FTO, and m6A-dependent alternative splicing of RUNX1T1. This cascade reduces the lipogenesis-restrictive RUNX1T1-L isoform and reinforces the C/EBPα-PPARγ positive feedback loop. RUNX1T1-L restoration corrected adipogenesis, stemness, and senescence defects more broadly than FTO inhibition, whereas amlodipine increased mesenteric fat accumulation and was associated with steatotic liver change in mice. These findings link calcium signaling to RNA processing-dependent fate control and highlight potential metabolic liabilities of broad calcium channel blockade.