Takuo Kubota

Low-density lipoprotein receptor-related protein 5 (LRP5) regulates bone acquisition by controlling bone formation. Because roles of LRP6, another co-receptor for Wnts, in postnatal bone metabolism have not been fully elucidated, we studied bone phenotype in mice harboring an Lrp6 hypomorphic mutation, ringelschwanz (rs), and characterized the mutant protein. First, we performed pQCT, bone histomorphometry, and immunohistochemistry on tibias of Lrp6(rs/rs) and Lrp6(+/+) mice and determined bioch

Achondroplasia (ACH) is a skeletal dysplasia that presents with limb shortening, short stature, and characteristic facial configuration. ACH is caused by mutations of the <i>FGFR3</i> gene, leading to constantly activated FGFR3 and activation of its downstream intracellular signaling pathway. This results in the suppression of chondrocyte differentiation and proliferation, which in turn impairs endochondral ossification and causes short-limb short stature. ACH also causes characteristic clinical

Osteogenesis imperfecta (OI) is a heritable brittle bone disease mainly caused by mutations in the two type I collagen genes. Collagen synthesis is a complex process including trimer formation, glycosylation, secretion, extracellular matrix (ECM) formation, and mineralization. Using OI patient-derived fibroblasts and induced pluripotent stem cells (iPSCs), we investigated the effect of 4-phenylbutyric acid (4-PBA) on collagen synthesis to test its potential as a new treatment for OI. Endoplasmic

Wnt signaling is involved not only in embryonic development but also in maintenance of homeostasis in postnatal tissues. Multiple lines of evidence have increased understanding of the roles of Wnt signaling in bone since mutations in the LRP5 gene were identified in human bone diseases. Canonical Wnt signaling promotes mesenchymal progenitor cells to differentiate into osteoblasts. The canonical Wnt/β-catenin pathway possibly through Lrp6, a co-receptor for Wnts as well as Lrp5, in osteoblasts r

Serum FGF23 level is the most critical biochemical marker for distinguishing DR from HR and might be a good indicator of biochemical response to the intervention. Serum FGF23 levels show utility for the diagnosis of DR and in the assessment of its response to treatment.

There is concern that vitamin D deficiency is prevalent among children in Japan as well as worldwide. We conducted a nationwide epidemiologic survey of symptomatic vitamin D deficiency to observe its incidence rate among Japanese children. A questionnaire inquiring the number of new patients with vitamin D deficiency rickets and/or hypocalcemia for 3 years was sent to 855 randomly selected hospitals with a pediatrics department in Japan. In this survey, we found that 250 children were diagnosed

Recently, the reemergence of vitamin D deficiency in developed countries has been pointed out. Vitamin D deficiency is diagnosed based on the serum 25-hydroxyvitamin D (25OHD) level. However, its normal range is still controversial, making the diagnosis of vitamin D deficiency difficult. Here, we present seven Japanese patients diagnosed with vitamin D deficiency. Three patients complained of leg bowing, and the other four of tetany. The patients with leg bowing were toddlers. Radiographic surve

We present a 10-year old boy with central diabetes insipidus (CDI) showing hyperintensity in a normal-sized posterior pituitary on magnetic resonance (MR) T1-weighted image (T1WI). He complained of nocturnal enuresis and polyuria. Daily urine volume increased to 4 to 5 L, and AVP plasma level was very low. Polymerase chain reaction (PCR)-amplified exons of the arginine vasopressin (AVP)-neurophysin (NP) II gene were sequenced. Nucleotide-1884 guanine in Exon 2 was substituted with thymine, which