Symptomatic type 1 protein C deficiency caused by a de novo Ser270Leu mutation in the catalytic domain

• Published in: British journal of haematology 2001-06, Vol.113 (3), p.642-648
• Main Authors: Lind, Bent, Koefoed, Pernille, Thorsen, Sixtus
• Format: Article
• Language: English
• Subjects: Adult; Antigens - blood; Biological and medical sciences; Blotting, Northern; catalytic domain; Catalytic Domain - genetics; Cell Line; Child; Culture Media; de novo mutation; Female; Hematologic and hematopoietic diseases; Hematology; Heterozygote; Humans; Male; Medical sciences; Middle Aged; Platelet diseases and coagulopathies; Point Mutation; Protein C - genetics; Protein C - immunology; protein C deficiency; Protein C Deficiency - genetics; Recurrence; serine proteinase; Transgenes; venous thromboembolism; Venous Thrombosis - genetics
• ISSN: 0007-1048; 1365-2141
• DOI: 10.1046/j.1365-2141.2001.02809.x

Heterozygosity for a C8524T transition in the protein C gene converting Ser270(TCG) to Leu(TTG) in the protease domain was identified in a family with venous thrombosis. The mutation was associated with parallel reduction in plasma levels of protein C anticoagulant activity and protein C antigen, which is consistent with a type 1 deficiency. Transient expression of mutant protein C cDNA in human kidney 293 cells and analysis of protein C antigen in culture media and cell lysates showed that the secretion of mutant protein compared with wild‐type protein was reduced by at least 97% while the intracellular content of mutant and wild‐type protein was similar. Northern blot analysis of total mRNA from transfected cells showed no reduction of the mutant protein C mRNA compared with wild‐type protein C mRNA. Collectively, these results indicate that the Ser270Leu mutation in the affected family caused the plasma protein C deficiency and are consistent with a disease mechanism that involves synthesis of mutant protein followed by intracellular degradation before its secretion into the extracellular space. The mutation was not present in the parents of the proband, suggesting a de novo mutation. Non‐paternity was excluded after the analysis of three intragenic protein C polymorphisms and six dinucleotide repeat allele sets located in five different chromosomes.