Consequences of Two Different Amino-Acid Substitutions at the Same Codon in KRT14 Indicate Definitive Roles of Structural Distortion in Epidermolysis Bullosa Simplex Pathogenesis

• Published in: Journal of investigative dermatology Vol. 131; no. 9; pp. 1869 - 1876
• Main Authors: Natsuga, Ken, Nishie, Wataru, Smith, Brian J., Shinkuma, Satoru, Smith, Thomasin A., Parry, David A.D., Oiso, Naoki, Kawada, Akira, Yoneda, Kozo, Akiyama, Masashi, Shimizu, Hiroshi
• Format: Journal Article
• Language: English
• Published: New York, NY Elsevier Inc 01.09.2011; Nature Publishing Group; Elsevier Limited
• Subjects: Amino Acid Sequence; Amino Acid Substitution - genetics; Biological and medical sciences; Bullous diseases of the skin; Cell Line; Child; Codon - genetics; Cresols; Dermatology; Dimerization; DNA Mutational Analysis; Drug Combinations; Epidermolysis Bullosa Simplex - genetics; Epidermolysis Bullosa Simplex - immunology; Epidermolysis Bullosa Simplex - pathology; Family Health; Formaldehyde; Humans; Keratin-14 - chemistry; Keratin-14 - genetics; Keratin-14 - immunology; Keratinocytes - cytology; Keratinocytes - physiology; Male; Medical sciences; Molecular Sequence Data; Mutation, Missense; Pedigree; Protein Structure, Quaternary; Resorcinols; Bullous dermatosis; Immunopathology; Skin disease; Codon; Epidermolysis bullosa; Dermatology; Pathogenesis; Aminoacid; Autoimmune disease
• ISSN: 0022-202X; 1523-1747
• DOI: 10.1038/jid.2011.143

Numerous inherited diseases develop due to missense mutations, leading to an amino-acid substitution. Whether an amino-acid change is pathogenic depends on the level of deleterious effects caused by the amino-acid alteration. We show an example of different structural and phenotypic consequences caused by two individual amino-acid changes at the same position. Epidermolysis bullosa simplex (EBS) is a genodermatosis resulting from KRT5 or KRT14 mutations. Mutation analysis of an EBS family revealed that affected individuals were heterozygous for a, to our knowledge, previously unreported mutation of c.1237G>C (p.Ala413Pro) in KRT14. Interestingly, 2 of 100 unrelated normal controls were heterozygous, and 1 of the 100 was homozygous for a different mutation in this position, c.1237G>A (p.Ala413Thr). In silico modeling of the protein demonstrated deleterious structural effects from proline substitution but not from threonine substitution. In vitro transfection studies revealed a significantly larger number of keratin-clumped cells in HaCaT cells transfected with mutant KRT14 complementary DNA (cDNA) harboring p.Ala413Pro than those transfected with wild-type KRT14 cDNA or mutant KRT14 cDNA harboring p.Ala413Thr. These results show that changes in two distinct amino acids at a locus are destined to elicit different phenotypes due to the degree of structural distortion resulting from the amino-acid alterations.