To further investigate the epigenetic regulation of FBN1 in cells with one mutated FBN1-null allele, which is similar to human Marfan syndrome, an experimental tool for allele-distinguished DNA methylation analysis was designed by producing FBN1 het KO pigs in which the FBN1 CpG island shores of the WT and KO alleles have a single nucleotide polymorphism (SNP). The gene discussed is FBN1; the disease is Marfan syndrome.