This study aimed to evaluate whether the immunolocalization of fibroblast growth factor (FGF) 23 and dentin matrix protein 1 (DMP1) is associated with the spatial regularity of the osteocyte lacunar canalicular system(s) (OLCS). Femora of 12-weeks-old male ICR mice were fixed with 4% paraformaldehyde, decalcified with a 10% EDTA solution and then embedded in paraffin. We have devised a triple staining procedure that combines silver impregnation, alkaline phosphatase (ALPase) immunohistochemistry and tartrate-resistant acid phosphatase (TRAPase) enzyme histochemistry on a single paraffin section. This procedure permitted the visualization of ALPase-positive plump osteoblasts and several TRAPase-positive osteoclasts on those bone matrices featuring irregularly arranged OLCS, and of ALPase-positive bone lining cells on the bone matrix displaying the well-arranged OLCS. As observations proceeded from the metaphysis toward the diaphysis, the endosteal cortical bone displayed narrower bands of calcein labeling, accompanied by increased regularity of the OLCS. This implies that the speed of bone deposition during bone remodeling would affect the regularity of the OLCS. While DMP1 was evenly localized in all regions of the cortical bones, FGF23 was more abundantly localized in osteocytes of cortical bones with regularly arranged OLCS. In cortical bones, the endosteal area featuring regular OLCS exhibited more intense FGF23 immunoreaction when compared to the periosteal region, which tended to display irregular OLCS. In summary, FGF23 appears to be synthesized principally by osteocytes in the regularly distributed OLCS that have been established after bone remodeling.

Hypophosphatasia (HPP), a rare genetic disease characterized by reduced serum alkaline phosphatase (ALP) activity and failure in bone and tooth mineralization, is caused by mutations in tissue-nonspecific ALP (TNSALP) gene. Two missense mutations (C201Y and C489S, standardized nomenclature) of TNSALP, involved in intra-chain disulfide bonds, were reported in patients diagnosed with perinatal HPP (Taillandier A. et al. Hum. Mutat. 13 (1999) 171-172, Hum. Mutat. 15 (2000) 293). To investigate the role of the disulfide bond in TNSALP, we expressed TNSALP (C201Y) and TNSALP (C489S) in COS-1 cells transiently. Compared with the wild-type enzyme [TNSALP (W)], both the TNSALP mutants exhibited a diminished ALP activity in the cells, where a 66kDa immature form was predominant with a marginal amount of a 80kDa mature form of TNSALP. Detailed studies on Tet-On CHO established cell line expressing TNSALP (W) or TNSALP (C201Y) showed that the 66kDa form of TNSALP (C201Y) exists as a monomer in contrast to a dimer of TNSALP (W). Only a small fraction of the TNSALP (C201Y) reached cell surface as the 80kDa mature form, though most of the 66kDa form was found to be endo-β-N-acetylglucosaminidase H sensitive and rapidly degraded in proteasome following polyubiquitination. Collectively, these results indicate not only that the intra-subunit disulfide bonds are crucial for TNSALP to properly fold and assemble into the dimeric enzyme, but also that the development of HPP associated with TNSALP (C201Y) or TNSALP (C489S) is attributed to decreased cell surface appearance of the functional enzyme.

We report a 10-year-old male with relapsing Ph-like acute lymphoblastic leukemia (ALL) bearing ATF7IP/PDGFRB translocation. He was refractory to conventional therapy, and was finally treated with single-agent second-generation TKI dasatinib. The therapeutic response was prompt, with the disappearance of minimum residual disease (MRD) based on genomic PCR analysis within 3 months, and he has maintained complete molecular remission for 12 months. This case report describes an early-phase response to TKI monotherapy on Ph-like ALL, and technical tips for MRD monitoring on long-term follow-up.

No abstract

Mutations in the tissue‐nonspecific alkaline phosphatase (TNSALP) gene cause hypophosphatasia (HPP), an inborn error of metabolism characterized by defects in bone and teeth mineralization accompanying subnormal levels of serum alkaline phosphatase activity. Missense mutations at position 420 of TNSALP (standard nomenclature), which convert glycine to serine [TNSALP (G420S)] or alanine [TNSALP (G420A)], have been reported in perinatal and childhood HPP, respectively. When expressed in COS‐1 cells, both TNSALP mutants were indistinguishable from wild‐type TNSALP [TNSALP (W)] as evidenced by immunofluorescence and western blotting. Nevertheless, the two TNSALP mutants did not show substantial alkaline phosphatase activity. In agreement with transiently transfected cells, TNSALP (G420S) expressed in a Tet‐On inducible expression system lacked its alkaline phosphatase activity, although this mutant was anchored to the cell surface lipid bilayers by glycosylphosphatidylinositol as an 80 kDa mature form bearing complex‐type oligosaccharides like TNSALP (W). Importantly, TNSALP (G420S) was found to largely fail to assemble into the homodimer in contrast to TNSALP (W). Taken together, these results demonstrate that the glycine residue at position 420 is crucial for the subunit interaction of TNSALP and hence its catalytic function without affecting trafficking of monomeric TNSALP. We conclude that the dimerization defect is the molecular basis for perinatal HPP associated with the genotype G420S/G420S.