Consistent methylation differences between T1D patients and non-diabetic controls were found in 4 CpG sites (sites where cytosine and guanine appear consecutively on the same strand of nucleic acid) proximal to the transcription start site of the insulin gene, a gene that encodes preproinsulin and has the second highest odds ratio (OR) for T1D risk. The gene discussed is INS; the disease is type 1 diabetes mellitus.