The significance of F139V mutation on thrombotic events in compound heterozygous and homozygous protein C deficiency

Two heterozygous mutations associated with type I protein C deficiency in two Chinese independent families

To explore the pathogenesis of protein C (PC) deficiency in two independent families by mutations detection and bioinformatics analysis. The PC activity (PC:A) and PC antigen (PC:Ag) were detected by chromogenic substrate and ELISA, respectively. The PROC sequencing was performed to identify the mutational sites. The molecular pathogenesis of the mutations were studied by the conservation, bioinformatics and model analysis. The PC:A and PC:Ag of the proband 1 were observably reduced at 35 and 44%, respectively. Gene sequencing analysis revealed the p.Leu278Pro derived from a heterozygous c.833T>C point mutations in exon 9 of PROC gene. For proband 2, the PC:A and PC:Ag were decreased to 40 and 51%, respectively, caused p.Ala178Pro missense mutation by a heterozygous point mismatch of c.532G>C in exon 5 of PROC gene. Bioinformatics and model analysis indicated that it was the Leu278Pro and Ala178Pro that caused clinical PC deficiency (PCD). The heterozygous mutations Leu278Pro and Ala178Pro were observed in two independent families. The Leu278Pro mutation in the PROC gene has not been described elsewhere. The two mutations can both lead to the type I hereditary PCD, and probably be the major causes of PCD in the families.

Protein C deficiency (a novel mutation: ala291Thr) with systemic lupus erythematosus leads to the deep vein thrombosis

: The current study aims to explore the phenotype and genotype of a mutation Ala291Thr, which responsible for type I protein C (PC) deficiency in a Chinese woman. The PROC antigen was tested with chromogenic substrate method. PROC gene were amplified by PCR with direct sequencing. Bioinformatics and model analysis were used to study the harm of the mutation. PC activity (PC: A) levels of three members were reduced to 39, 57 and 56%, respectively, PC: antigen was decreased parallelly same as PC: A. Sequencing analysis showed proband with a novel heterozygous c.997G>A point mutation in exon 9 of PROC gene resulting in Ala291Thr. The Ala291Thr mutation is responsible for the decrease of PC: A, which is cross-reacting material negative deficiency and the first reported in the world. This mutation alone may not have significant clinical symptoms, whereas it will cause deep vein thrombosis when combined with systemic lupus erythematosus.

The clinical presentation and genotype of protein C deficiency with double mutations of the protein C gene

BACKGROUND

Severe protein C (PC) deficiency is a rare heritable thrombophilia leading to thromboembolic events during the neonatal period. It remains unclear how individuals with complete PC gene (PROC) defects develop or escape neonatal stroke or purpura fulminans (PF).

PROCEDURE

We studied the onset of disease and the genotype of 22 PC-deficient patients with double mutations in PROC based on our cohort (n = 12) and the previous reports (n = 10) in Japan.

RESULTS

Twenty-two patients in 20 unrelated families had 4 homozygous and 18 compound heterozygous mutations. Sixteen newborns presented with PF (n = 11, 69%), intracranial thromboembolism and hemorrhage (n = 13, 81%), or both (n = 8, 50%), with most showing a plasma PC activity of <10%. Six others first developed overt thromboembolism when they were over 15 years of age, showing a median PC activity of 31% (range: 19-52%). Fifteen of the 22 patients (68%) had the five major mutations (G423VfsX82, V339M, R211W, M406I, and F181V) or two others (E68K and K193del) that have been reported in Japan. Three of the six late-onset cases, but none of the 16 neonatal cases, had the K193del mutation, which has been reported to be the most common variant of Chinese thrombophilia. A novel mutation of A309V was determined in a family of two patients with late onset.

CONCLUSIONS

The genotype of double-PROC mutants might show less diversity than heterozygous mutants in terms of the timing of the onset of thrombophilia (newborn onset or late onset).