The establishment of a predictive mutational model of the forkhead domain through the analyses of FOXC2 missense mutations identified in patients with hereditary lymphedema with distichiasis.
The FOX family of transcription factor genes is an evolutionary conserved, yet functionally diverse class of transcription factors that are important for regulation of energy homeostasis, development and oncogenesis. The proteins encoded by FOX genes are characterized by a conserved DNA-binding domain known as the forkhead domain (FHD). To date, disease-causing mutations have been identified in eight human FOX genes. Many of these mutations result in single amino acid substitutions in the FHD. We analyzed the molecular consequences of two disease-causing missense mutations (R121H and S125L) occurring in the FHD of the FOXC2 gene that were identified in patients with hereditary lymphedema with distichiasis (LD) to test the predictive capacity of a FHD structure/function model. On the basis of the FOXC2 solution structure, both FOXC2 missense mutations are located on the DNA-recognition helix of the FHD. A mutation model based on the parologous FOXC1 protein predicts that these FOXC2 missense mutations will impair the DNA-binding and transcriptional activation ability of the FOXC2 protein. When these mutations were analyzed biochemically, we found that both mutations did indeed reduce the DNA binding and transcriptional capacity. In addition, the R121H mutation affected nuclear localization of FOXC2. Together, these data indicate that these FOXC2 missense mutations are functional nulls and that FOXC2 haploinsufficiency underlies hereditary LD and validates the predictive ability of the FOXC1-based FHD mutational model.
Berry
Fred B
FB
Department of Ophthalmology, University of Alberta, Edmonton, Alberta, Canada T6G 2H7. fberry@ualberta.ca
Tamimi
Yahya
Y
Carle
Michelle V
MV
Lehmann
Ordan J
OJ
Walter
Michael A
MA
D000595:Amino Acid Sequence; D017931:DNA Primers; D024202:Electrophoretic Mobility Shift Assay; D005140:Eyelashes / Q000002:abnormalities*; D005455:Fluorescent Antibody Technique; D051858:Forkhead Transcription Factors / Q000235:genetics*; D006801:Humans; D008156:Luciferases; D008209:Lymphedema / Q000150:complications / Q000235:genetics*; D008957:Models, Genetic; D008958:Models, Molecular; D008969:Molecular Sequence Data; D016297:Mutagenesis, Site-Directed; D020125:Mutation, Missense / Q000235:genetics*; D017422:Sequence Analysis, DNA
D017931:DNA Primers; D051858:Forkhead Transcription Factors; C082078:mesenchyme fork head 1 protein; D008156:Luciferases