Semaphorin 6A phase separation sustains a histone lactylation–dependent lactate buildup in pathological angiogenesis

Ischemic retinal diseases are major causes of blindness worldwide and are characterized by pathological angiogenesis. Epigenetic alterations in response to metabolic shifts in endothelial cells (ECs) suffice to underlie excessive angiogenesis. Lactate accumulation and its subsequent histone lactylation in ECs contribute to vascular disorders. However, the regulatory mechanism of establishing and sustaining lactylation modification remains elusive. Here, we showed that lactate accumulation induced histone lactylations on H3K9 and H3K18 in neovascular ECs in the proliferative stage of oxygen-induced retinopathy. Joint CUT&Tag and scRNA-seq analyses identified <i>Prmt5</i> as a target of H3K9la and H3K18la in isolated retinal ECs. EC-specific deletion of <i>Prmt5</i> since the early stage of revascularization suppressed a positive feedback loop of lactate production and histone lactylation, thus inhibiting neovascular tuft formation. Mechanistically, the C-terminal intrinsically disorder region (IDR) of the transmembrane semaphorin 6A (SEMA6A) forms liquid-liquid phase separation condensates to recruit RHOA and P300, facilitating P300 phosphorylation and histone lactylation cycle. Deletion of endothelial <i>Sema6A</i> reduced H3K9la and H3K18la at the promoter of <i>PRMT5</i> and diminished its expression. The induction of histone lactylation by SEMA6A-IDR and its pro-angiogenic effect were abrogated by deletion of <i>Prmt5</i>. Our study illustrates a sustainable histone lactylation machinery driven by phase separation-dependent lactyltransferase activation in dysregulated vascularization.