Identification of a Novel β-Cell Glucokinase (GCK) Promoter Mutation (−71G>C) That Modulates GCK Gene Expression Through Loss of Allele-Specific Sp1 Binding Causing Mild Fasting Hyperglycemia in HumansDiabetes August 2009 58:1929-1935; published ahead of print May 1, 2009, doi:10.2337/db09-0070