All families were of reported or self-reported white ethnicity and of European descent, with two parents and at least one affected child. The family collection consisted of 458 families from the UK Diabetes UK Warren 1 repository, 328 families from USA Human Biological Data Interchange, 250 families from Northern Ireland, 951 Finnish families, 360 Norwegian families, 412 Romanian families and 80 families from Yorkshire, UK (Supplementary Table 6). All DNA samples were collected after approval from the relevant research ethics committees, and written informed consent was obtained from the participants or their guardians.
