The next strongest locus involved in genetic susceptibility to T1D is IDDM2 on the short arm of chromosome 11. This locus encodes the insulin gene (INS). Additional information about the insulin gene (and other genes) can be found by searching the OMIM database (Online Mendelian Inheritance in Man) on the National Center for Biotechnology Information web site (www.ncbi.nlm.nih.gov). The OMIM number for the insulin gene is 176730.

The 5’ regulatory region of INS contains a variable number of tandem repeat (VNTR) locus that has been associated with T1D. There are 3 classes of VNTR alleles: class I (26-63 repeats), class II (~80 repeats), and class III (141-209 repeats). The next slide illustrates the location of the VNTR. A person who carries two class I alleles has about a two-fold increase risk of developing T1D compared to those who carry no class I VNTRs. Class III alleles seem to provide dominant protection against developing T1D. Class II alleles are virtually non-existent in Caucasian populations and have no effect on T1D risk.

The insulin locus and the other candidate regions identified by genome screens require further evaluation studies before they can be used for genetic screening for T1D.