Deficiency of SHP-1 protein-tyrosine phosphatase activity results in heightened osteoclast function and decreased bone density.
Mice homozygous for the motheaten (Hcphme) or viable motheaten (Hcphme-v) mutations are deficient in functional SHP-1 protein-tyrosine phosphatase and show severe defects in hematopoiesis. Comparison of femurs from mev/mev mice revealed significant decreases in bone mineral density (0.33 +/- 0.03 mg/mm3 for mev/mevversus 0.41 +/- 0.01 mg/mm3 for controls) and mineral content (1.97 +/- 0.36 mg for mev/mevversus 10.64 +/- 0.67 for controls) compared with littermate controls. Viable motheaten mice also showed reduced amounts of trabecular bone and decreased cortical thickness. These bone abnormalities were associated with a 14% increase in numbers of multinucleated osteoclasts and an increase in osteoclast resorption activity. In co-cultures of normal osteoblasts with mutant or control bone marrow cells, numbers of osteoclasts developing from mutant mice were increased compared with littermate control mice. Although mev/mev osteoclasts develop in the absence of colony-stimulating factor (CSF)-1, nevertheless cultured osteoclasts show increased size in the presence of CSF-1. CSF-1-deficient osteopetrosis (op/op) mutant mice develop severe osteosclerosis. However, doubly homozygous mev/mevop/op mice show an expansion of bone marrow cavities and reduced trabecular bone mass compared with op/op mice. Western blot analysis showed that several proteins that were markedly hyperphosphorylated on tyrosine residues were detected in the motheaten osteoclasts, including a novel 126-kd phosphotyrosine protein. The marked hyperphosphorylation of a 126-kd protein in motheaten osteoclasts suggests that this protein depends on SHP-1 for dephosphorylation. These findings demonstrate that the decreased SHP-1 catalytic activity in me/me and mev/mev mice results in an increased population of activated osteoclasts and consequent reduction in bone density.
Jackson Laboratory, Bar Harbor, Maine Kumamoto University of Medicine, Kumamoto, Japan.
S
S
Umeda
W G
WG
Beamer
K
K
Takagi
M
M
Naito
S
S
Hayashi
H
H
Yonemitsu
T
T
Yi
L D
LD
Shultz
D000818:Animals; D015153:Blotting, Western; D015519:Bone Density / Q000502:physiology*; D001854:Bone Marrow Cells / Q000166:cytology; D002455:Cell Division / Q000502:physiology; D018920:Coculture Techniques; D003804:Dentin / Q000473:pathology; D005269:Femur / Q000000981:diagnostic imaging / Q000473:pathology; D006720:Homozygote; D047908:Intracellular Signaling Peptides and Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D008817:Mice, Mutant Strains; D009154:Mutation / Q000502:physiology; D010006:Osteoblasts / Q000166:cytology; D010010:Osteoclasts / Q000473:pathology / Q000502:physiology*; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases / Q000172:deficiency* / Q000235:genetics; D011859:Radiography; D014054:Tomography
D047908:Intracellular Signaling Peptides and Proteins; D054592:Protein Tyrosine Phosphatase, Non-Receptor Type 11; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; D017027:Protein Tyrosine Phosphatases; C516725:Ptpn11 protein, mouse; C509248:Ptpn6 protein, mouse