ESPE Abstracts (2018) 89 RFC3.4

Functional Characterization of a Novel KLF11 Mutation Identified in a Family with Autoantibody-Negative Type 1 Diabetes

Kikumi Ushijimaa, Tomoyuki Kawamurab, Tsutomu Ogatac, Ichiro Yokotad, Shigetaka Sugiharae, Satoshi Narumia & Maki Fukamia

aNational Research Institute for Child Health and Development, Tokyo, Japan; bOsaka City University School of Medicine, Osaka, Japan; cHamamatsu University School of Medicine, Hamamatsu, Japan; dShikoku Medical Center for Children and Adults, Kagawa, Japan; eTokyo Women’s Medical University Medical Center East, Tokyo, Japan

Objectives: KLF11 is a member of the Sp1/KLF family transcription factor which contains three C2H2 zinc finger domains. To date, two KLF11 mutations (p.T220M and p.A347S) have been identified in three families clinically diagnosed with type 2 diabetes. The aim of our study is to report clinical and molecular characteristics of a KLF11 mutation-carrying family clinically diagnosed with type 1 diabetes (T1D).

Methods: The proband was a 10-year-old girl. She was accidentally found to have hyperglycemia when she was suffered from upper respiratory infection at age 1 year. She was subsequently diagnosed as T1D although she was negative for diabetes-associated autoantibodies. Her elder brother and mother also had been diagnosed with autoantibody-negative T1D at 1 and 4 years of age, respectively. All of them required insulin therapy. To clarify the etiology of diabetes, we performed whole exome sequencing in this family. To evaluate the pathogenicity of the identified KLF11 variant, we performed functional analyses including western blotting, immunofluorescence and luciferase reporter assay.

Results: A heterozygous missense variant in KLF11 p.H418Q was identified in three affected family members. Three-dimensional structure modeling suggested that the H418Q variant affects a functionally important histidine residue in the C2H2 zinc finger domain. The protein expression level and intracellular localization of H418Q-KLF11 were comparable with wildtype-KLF11. To analyze the transcriptional regulatory activity of wildtype and mutant KLF11, CHO cells were transiently transfected with the KLF11 expression constructs (wildtype, H418Q, A347S and T220M) along with the luciferase reporter which contains six tandem GC box of KLF11-binding sites. H418Q-KLF11 and A347S-KLF11 demonstrated significantly decreased transcriptional repression activities as compared with wildtype-KLF11. Furthermore, co-expression of H418Q-KLF11 with wildtype-KLF11 caused significant loss of repression, indicating that H418Q-KLF11 had a dominant-negative effect. The dominant negative effect was not observed in A347S-KLF11.

Conclusions: This is the first report of a KLF11 mutation identified in patients clinically diagnosed with T1D. Functional analyses provided evidence for a dominant-negative effect of H418Q-KLF11 that could explain severer phenotypes observed in our patients. Our findings expand the phenotypic spectrum of KLF11 mutation-carrying patients.

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