| Co-Investigator(Kenkyū-buntansha) |
OKURA Masaya Osaka University, Graduate School of Dentistry, Associate Professor, 大学院歯学研究科, 助教授 (10281130)
MICHIGAMI Toshimi Research Institute, Osaka Medical Center for Maternal and Child Health, Department of Bone and Mineral Research, Director, 環境影響部門, 部長 (00301804)
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| Budget Amount *help |
¥3,500,000 (Direct Cost: ¥3,500,000)
Fiscal Year 2006: ¥1,700,000 (Direct Cost: ¥1,700,000)
Fiscal Year 2005: ¥1,800,000 (Direct Cost: ¥1,800,000)
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| Research Abstract |
SHP-2 is thought to be a positive regulator of the MAPK pathway. We thus hypothesized that changes in SHP-2 phosphatase activity might affect MAPK activity and result in retardation of growth seen in Noonan or LEOPARD syndromes. To this end we performed the following experiments.
(a) Analysis of chondrocyte differentiation
Wild type, D61N, or Q510E SHP-2s were transiently expressed in ATDC5 cells. Quantitative PCR revealed that mRNA levels of the transcription factor sox9, an early marker of chondrocyte differentiation, were increased in cell expressing either of the mutants. On the other hand, no difference in col2a1 mRNA levels, known to be upregulated by sox9/sox5/sox6 complexes, could be demonstrated. Similar results were obtained in reporter assays using a native col2al promoter linked to a luciferase reporter gene. Transduced cells cultured in alginate beads expressed lower mRNA levels of colX, a maker of hypertrophic chondrocytes.
(b) Analysis of MAPK signaling
Following transient expression of wild type, D61N, or Q510E SHP-2s in ATDC5 cells, MAPK activity in response to 50 ng/ml FGF2 was determined by Western blotting with a phospho-p44/42 MAPK antibody. While the D61N mutation demonstrated increased activity, the Q510E mutation exhibited reduced activity.
(c) Analysis of chondrocyte proliferation
ATDC5 cells expressing wild type, D61N, or Q510E SHP-2s were cultured up to 3 days and counted every day using a hemocytometer. No significant difference in cell numbers could be demonstrated regardless of genotype.
These results imply that mutant SHP-2s, via non-MAPK pathways. induce sox9 expression and delay chondrocyte maturation, possibly leading to one of the causes of growth retardation in Noonan and LEOPARD syndromes.
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