[Mutation of the activin receptor-like kinase 1(ALK1) gene and the expression of plasma thrombomodulin in type-2 hereditary hemorrhagic telangiectasia: a study of a Chinese family].
OBJECTIVE
To analysis and define the clinical phenotype and related mutation of hereditary hemorrhagic telangiectasia. (HHT).


METHODS
The proband of a Chinese HHT family, female, aged 48, and 2 of her family members: her father, aged 74, and her brother, aged 44 underwent nasal cavity endoscopy and automatic photochonography to observe the capillaries in nasal mucosa. Samples of peripheral blood were collected. The exons 3, 7, and 8 of the activin receptor-like kinase 1 (ALK1) gene of the proband and her family members and 2 healthy people as contrds were amplified by polymerase chain reaction, and the PCR products were sequenced. The levels of plasma thrombomodulin (TM) of the proband and her family members were detected by Western blotting combined with density screening.


RESULTS
Except the mother and sister-in-law, other 4 of the family members had epistaxis or bleeding in other sites. The proband and her father had obvious telangiectasis of nasal mucosa or finger skin respectively. ALK1 gene analysis confirmed that a C1231T mutation (CGG-->TGG) in the exon 8 existed in the proband, her brother, and her father, no mutation was found in her sister in law, her nephew, and the healthy persons. Six bands were shown in the expression of plasma thrombomodulin. Density screening was conducted for the 2 bands with differential expression: those with the molecular masses of 56,000 and 28,000. The result of density screening showed that the average value of screening at the 56,000 band was 218.3 in the normal controls, significantly higher than that of the HTT patients (145.1); and the average value of screening at the 28,000 band was 222.0 in the normal controls, significantly higher than that in the HTT patients (145.1).


CONCLUSION
ALK1 gene mutation, a C1231T variation on exon 8, exists in Chinese type 2 HHT individuals. The levels of plasma thrombomodulin levels at the 56,000 and 28,000 fragments of the HTT patients are lower than of normal subjects whose significance and mechanism remain to be elucidated.