Megumi Kubota

THE POLYMORPHISM IN THE CAUDAL-RELATED HOMEODOMAIN PROTEIN Cdx-2 BINDING ELEMENT IN THE HUMAN VITAMIN D RECEPTOR GENE

The major physiological activity of 1,25‐dihydroxyvitamin D3 [1,25(OH)2D3] is the regulation of calcium absorption in the small intestine, and the level of vitamin D receptor (VDR) is an important factor in this regulation. In a previous study, we indicated that the caudal‐related homeodomain Cdx‐2 played an important role in the intestine‐specific transcription of the human VDR gene. In this study, the polymorphism was identified in the core sequence 5′‐ATAAAAACTTAT‐3′ in the Cdx‐2 binding site in the VDR gene promoter. In 261 Japanese women with genotyped VDR polymorphisms, 48 were genotype Cdx‐A (adenine at −3731 nucleotides [nt] relative to the transcription start site of human VDR gene 5‐ATAAAAACTTAT), 82 were genotype Cdx‐G (guanine at −3731 nt, 5′‐GTAAAAACTTAT‐3′), and 131 were genotype Cdx‐A/G (heterozygote). In postmenopausal Japanese women, the bone mineral density (BMD) in the lumbar spine (L2‐L4) with the Cdx‐G homozygote was 12% lower than that with the Cdx‐A homozygote (p < 0.05). In electrophoretic gel mobility shift assay (EMSA), the oligonucleotide with Cdx‐G allele markedly decreased the binding to Cdx‐2 compared with that in the Cdx‐A allele. The transcriptional activity of the VDR promoter with Cdx‐G allele was decreased to 70% of the Cdx‐A allele. In addition, in the herpes simplex virus thymidine kinase promoter, the Cdx‐2 binding element with the G allele showed significantly lower transcriptional activity than that of the A allele. Thus, the polymorphism in the Cdx‐2 binding site of the VDR gene (Cdx‐polymorphism) would affect the expression of VDR in the small intestine. In addition, this polymorphism may modulate BMD in postmenopausal Japanese women.

Novel monoclonal antibody, SO-MU1, against human gastric MUC5AC apomucin☆

Human gastric mucins were chemically deglycosylated with trifluoromethanesulfonic acid. A mouse monoclonal antibody (MoAb), SO-MU1, was established against the deglycosylated mucins. SO-MU1 recognized not only the deglycosylated mucins but also the native gastric mucins. Periodate treatment of the native mucins increased the SO-MU1 reactivity. Trypsin digestion abolished the antigenicity. Human gastric cDNA expression library was screened with SO-MU1 and a mucin cDNA clone was obtained. Its sequence contained the MUC5AC tandem repeat domain. We studied gastrointestinal distribution of the SO-MU1-reactive antigen immunohistochemically. Gastric surface epithelial cells and parietal cells expressed the antigen, but the glandular cells did not. The antigen was also detected in the small intestine and biliary tract but not in the colon and pancreas. In summary, (1) MoAb SO-MU1 was raised against human gastric mucins, (2) it recognized human gastric MUC5AC apomucin, and (3) the SO-MU1-reactive antigen showed characteristic distribution in the organs of endodermal origin. MoAb SO-MU1 is the first MoAb against MUC5AC.

Association between two types of vitamin D receptor gene polymorphism and bone status in premenopausal Japanese women

Polymorphisms in the vitamin D receptor (VDR) gene using ultrasound (US) bone mass and bone metabolic markers were investigated as potential genetic markers for osteoporosis in 126 premenopausal Japanese women aged 27.2 ± 10.1 (mean ± SD) years. The relationship between their VDR gene polymorphisms and bone states was determined. VDR genotypes were based on the absence (B) or presence (b) of the Bsm I restriction site (B polymorphism), and ATG (the M allele) and ACG (the m allele) sequences at the translation initiation site (M polymorphism). Genotype frequencies were 73.8%, bb; 24.6%, Bb; 1.6%, BB; 15.1%, MM; 51.6%, Mm and 33.3%, mm. The stiffness index of calcaneal bone minerals measured by an US bone densitometer was significantly higher in the mm types (P<0.05 versus MM) than in the Mm types (P<0.01 versus MM) and MM types. There was no significant difference between in B polymorphisms. Furthermore, bone mass was correlated with serum bone type alkaline phosphatase (ALP) activity and urinary deoxypyridinoline concentration in M polymorphisms. Because the distribution of B polymorphisms in each M polymorphism genotype did not differ, M polymorphisms were affected independently from B polymorphisms to bone mass or bone metabolic markers. No significant difference was observed in nutritional intake and food consumption among genotypes. In the MM and Mm types, the bone mass was closely related to the frequency of milk intake during the periods of elementary and junior high school. In contrast, bone mass was not associated with nutritional intake or the frequency of past milk intake in B polymorphisms. Therefore, the M polymorphism of the VDR gene is a stronger genetic indicator of osteoporosis than the B polymorphism in premenopausal Japanese woman.