HRG Tokushima: Molecular and Cellular Characterization of
Histidine-Rich Glycoprotein (HRG) Deficiency
Toshio Shigekiyo,
Hidemasa Yoshida,
Kazuya Matsumoto,
Hiroyuki Azuma,
Sadao Wakabayashi,
Shiro Saito,
Kazuo Fujikawa, and
Takehiko Koide
From the First Department of Internal Medicine, School of Medicine,
The University of Tokushima, Tokushima; Department of Life Science,
Faculty of Science, Himeji Institute of Technology, Hyogo, Japan; and
Department of Biochemistry, University of Washington, Seattle, WA.
Previously, we found the first congenital deficiency of
histidine-rich glycoprotein (HRG) in a Japanese woman with thrombosis. To elucidate the genetic basis of this deficiency, we first performed Southern blot analysis and found no gross deletion or insertion in the
proband's HRG gene. We then examined the nucleotide sequences of all
seven exons of the proband's HRG gene. A single nucleotide substitution, G to A at nucleotide position 429, which mutates Gly85 to
Glu in the first cystatin-like domain, was found in exon 3 in 13 of 22 amplified clones. This mutation generates a unique Taq I site.
Exon 3 was amplified from the proband, her family members, and 50 unrelated normal Japanese individuals, and Taq I fragmentation
was examined. Fragmentation of exon 3 was observed in one allele of the
genes from the proband and the family members who also have decreased
plasma levels of HRG. Fifty unrelated normal Japanese individuals had a
normal HRG gene, indicating that the G to A mutation is not a common
polymorphism. To elucidate the identified mutation as a
cause for the secretion defect of HRG in the proband's
plasma, we constructed and transiently expressed the recombinant
Tokushima-type HRG mutant (Gly85 to Glu) in baby hamster kidney (BHK)
cells, and examined an intracellular event of the mutant protein. The
results showed that only about 20% of the Tokushima-type HRG was
secreted into the culture medium, and intracellular degradation of the
mutant was observed. Thus, the present study strongly suggests that the
HRG deficiency is caused by intracellular degradation of the Gly85 to
Glu mutant of HRG in the proband.
Blood, Vol. 91 No. 1 (January 1), 1998:
pp. 128-133
© 1998 by The American Society of Hematology.
