As. Law et al., EXPRESSION OF THE GENE FOR TRANSFORMING GROWTH-FACTOR-BETA IN AVIAN DYSCHONDROPLASIA, Research in Veterinary Science, 61(2), 1996, pp. 120-124
Previous immunolocalisation studies of dyschondroplasia have indicated
that there is a reduction in the number of growth plate chondrocytes
containing the protein transforming growth factor beta 3 (TGF-beta 3).
The reduction in TGF-beta 3 in dyschondroplasia is likely to be a dir
ect result of a reduction in the expression of the TGF-beta 3 gene. mR
NA was extracted from small (0 . 09 g) samples of growth cartilage fro
m the proximal tibiotarsus of three-week-old broiler chicks. The carti
lage samples contained cells from all three zones of the growth plate
(proliferative, transitional and upper hypertrophic) and were collecte
d from normal and dyschondroplastic growth plates. The dyschondroplast
ic growth plates were identified by an accumulation of transitional ch
ondrocytes which were considered to be a result of a failure to differ
entiate to the hypertrophic phenotype. A semi-quantitative polymerase
chain reaction (PCR) was used to estimate the quantity of mRNA specifi
c for glyceraldehyde-3-phosphate dehydrogenase (GAPDH) and for each of
the three isoforms of TGF beta (TGF-beta 1, TGF-beta 2, and TGF-beta
3) in each of the cartilage samples. The levels of expression of mRNA
for GAPDH, TGF-beta 1 and TGF-beta 2 were similar in the two groups, b
ut the expression of TGF-beta 3 mRNA was significantly reduced in the
samples from the dyschondroplastic growth plates. The reduction in TGF
-beta 3 levels is thought to be associated with the failure of chondro
cyte hypertrophy in dyschondroplasia, and provides in vivo evidence th
at TGF-beta 3 is part of the cascade of events associated with the dif
ferentiation of chondrocytes during endochondral ossification in the c
hick.