Three arginine to cysteine substitutions in the pro-alpha (I)-collagen chain cause Ehlers-Danlos syndrome with a propensity to arterial rupture in early adulthood

Hum Mutat. 2007 Apr;28(4):387-95. doi: 10.1002/humu.20455.

Abstract

Mutations in the COL1A1 and COL1A2 genes, encoding the proalpha1 and 2 chains of type I collagen, cause osteogenesis imperfecta (OI) or Ehlers-Danlos syndrome (EDS) arthrochalasis type. Although the majority of missense mutations in the collagen type I triple helix affect glycine residues in the Gly-Xaa-Yaa repeat, few nonglycine substitutions have been reported. Two arginine-to-cysteine substitutions in the alpha1(I)-collagen chain are associated with classic EDS [R134C (p.R312C)] or autosomal dominant Caffey disease with mild EDS features [R836C (p.R1014C)]. Here we show alpha1(I) R-to-C substitutions in three unrelated patients who developed iliac or femoral dissection in early adulthood. In addition, manifestations of classic EDS in Patient 1 [c.1053C>T; R134C (p.R312C); X-position] or osteopenia in Patients 2 [c.1839C>T; R396C (p.R574C); Y-position] and 3 [c.3396C>T; R915C (p.R1093C); Y-position] are seen. Dermal fibroblasts from the patients produced disulfide-bonded alpha1(I)-dimers in approximately 20% of type I collagen, which were efficiently secreted into the medium in case of the R396C and R915C substitution. Theoretical stability calculations of the collagen type I heterotrimer and thermal denaturation curves of monomeric mutant alpha1(I)-collagen chains showed minor destabilization of the collagen helix. However, dimers were shown to be highly unstable. The R134C and R396C caused delayed procollagen processing by N-proteinase. Ultrastructural findings showed collagen fibrils with variable diameter and irregular interfibrillar spaces, suggesting disturbed collagen fibrillogenesis. Our findings demonstrate that R-to-C substitutions in the alpha1(I) chain may result in a phenotype with propensity to arterial rupture in early adulthood. This broadens the phenotypic range of nonglycine substitutions in collagen type I and has important implications for genetic counseling and follow-up of patients carrying this type of mutation.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adolescent
  • Adult
  • Amino Acid Substitution
  • Arginine / genetics
  • Arginine / metabolism
  • Base Sequence
  • Bone Diseases, Metabolic / complications
  • Bone Diseases, Metabolic / genetics
  • Bone Diseases, Metabolic / metabolism
  • Collagen / genetics
  • Collagen Type I / genetics*
  • Collagen Type I / metabolism
  • Collagen Type I, alpha 1 Chain
  • Collagen Type III / genetics
  • Cysteine / genetics
  • Cysteine / metabolism
  • Ehlers-Danlos Syndrome / complications*
  • Ehlers-Danlos Syndrome / genetics*
  • Ehlers-Danlos Syndrome / metabolism
  • Female
  • Femoral Artery
  • Humans
  • Iliac Artery
  • Male
  • Molecular Sequence Data
  • Mutation, Missense
  • Protein Structure, Secondary
  • RNA, Messenger / genetics
  • Rupture, Spontaneous / genetics*

Substances

  • COL3A1 protein, human
  • Collagen Type I
  • Collagen Type I, alpha 1 Chain
  • Collagen Type III
  • RNA, Messenger
  • Collagen
  • Arginine
  • Cysteine