Effects of EGF and TGF?1 onc-myc gene expression and DNA synthesis in embryonic hamster palate mesenchymal cells
✍ Scribed by Izadnegahdar, Mehrnaz F. ;Rathanaswami, Palaniswami ;Shah, Ravindra M.
- Publisher
- John Wiley and Sons
- Year
- 1999
- Tongue
- English
- Weight
- 237 KB
- Volume
- 254
- Category
- Article
- ISSN
- 0003-276X
No coin nor oath required. For personal study only.
✦ Synopsis
Previous work has shown that cell proliferation is a major contributor to the early palate morphogenesis in mammals. The present study was undertaken to examine the effect of EGF, TGF 1 and their combination on proliferation (measured by DNA synthesis) and on the expression of a growth related proto-oncogene, c-myc, in embryonic hamster palate mesenchymal cells (HPMC).
Vertically developing hamster palatal shelves were dissected on day 11 of gestation, and trypsinized, and primary cultures were grown in DMEM ϩ 10% serum at 37°C and 5% CO 2 . Following appropriate growth factor treatment of HPMC, DNA synthesis was measured by scintillation counting and extracted RNA was subjected to Northern blot analysis.
In serum-starved, pre-confuent cultures treated with EGF (20 ng/ml), DNA synthesis was stimulated in the presence of 2.5% serum. In contrast, treatment of HPMC with TGF 1 (10 ng/ml) in the presence or absence of EGF/serum for 24 hr, or HPMC pre-treatment with TGF 1 (30 min) followed by EGF/serum (24 hr), resulted in an arrest of DNA synthesis. Northern blot analysis of RNA extracted from HPMC showed that as serum-starved, growth-arrested cells progressed through G0 to G1 phase of the cell cycle, following EGF treatment, c-myc was expressed by 1 hr and declined thereafter. In contrast, TGF 1 did not support expression of c-myc. Following pre-or co-treatment with TGF 1 , the EGF Ϯ serum-induced expression of c-myc was seen between 1 and 6 hr.
It appears that EGF-induced expression of c-myc may be involved in advancing the HPMC in G1, and thus may contribute to the onset of DNA synthesis in HPMC. Since co-or pre-treatment with TGF 1 did not inhibit EGF/serum induced expression of c-myc, it is possible that growth arresting effect of TGF 1 may not be exerted directly through inhibition or blockage of c-myc expression.