PTBP1 and familial hypercholesterolemia: We proposed an adaptor system of H3-K36me3-MRG15-PTB involved in the alternative splicing of LDLR pre-mRNA, during which increased levels of H3-K36me3 around LDLR exons 4 and 12 were recognized by MRG15 which, in turn, recruited PTB protein to affect the alternative splicing of LDLR pre-mRNA in hypercholesterolemia (Figure 6).