KLF11 variant in a family clinically diagnosed with early childhood-onset type 1B diabetes

Abstract

KLF11 is the causative gene for maturity-onset diabetes of the young 7 (MODY7). KLF11 regulates insulin gene expression through binding to the GC box in the promoter. To date, only two KLF11 mutations have been identified in three families with early-onset type 2 diabetes. Here, we report a novel KLF11 variant associated with early childhood-onset type 1B diabetes. The proband and his younger sister exhibited hyperglycemia at age 1 year, and their mother developed diabetes at age 4 years. These three individuals required insulin injection from the initial phase of the disease. Being negative for islet cell autoantibodies, they were diagnosed with type 1B diabetes. Mutation screening for 30 diabetes-associated genes identified a heterozygous KLF11 variant (p.His418Gln) in the proband and his sister. The variant was also detected in the affected mother, as well as in the allegedly unaffected maternal grandmother. In silico analyses indicated that this variant involves a highly conserved histidine residue in the first C₂ H₂ zinc finger domain which ligates a zinc ion. In vitro analyses showed that expression levels and intracellular localization of His418Gln-KLF11 were comparable to those of wildtype (WT)-KLF11. Luciferase assays demonstrated that while WT-KLF11 suppressed the activity of a 6 × GC box-containing reporter, His418Gln-KLF11 lacked the suppressive effect. Notably, His418Gln-KLF11 canceled the suppressive effect of co-transfected WT-KLF11. Such a dominant-negative effect was absent in the previously reported Ala347Ser-KLF11 variant. These results indicate that specific variants of KLF11 (MODY7) with a dominant-negative effect underlie early childhood-onset type 1B diabetes with incomplete penetrance. This study documents a novel monogenic mutation associated with diabetes in children.

Keywords: GC box; MODY; childhood-onset diabetes; monogenic diabetes; mutation.