PABPN1 and oculopharyngeal muscular dystrophy: We propose that the Ala-stretch length larger than the threshold (e.g., 17A ∼ 24A) may trigger PABPN1 phase transition to aggregates and sequester cellular essential factors especially the components of pre-mRNA 3′-UTR processing complexes, being implicated in a unique proteinopathy of the pathogenic PABPN1-17A in OPMD, a muscle-specific disease.