PCNA and Beckwith-Wiedemann syndrome: However, lack of PCNA binding in CDKN1C per se is not directly involved in the gain-of-function phenotype observed in IMAGe syndrome patients because CDKN1C truncation mutants lacking PCNA binding, i.e., p.Phe276fs*10 (Figure 4), were also identified in BWS patients (Figure 1A) [11], [12], in whom the loss-of-function phenotype of CDKN1C was always observed.