Sb. Jakowlew et al., EXPRESSION OF TRANSFORMING GROWTH-FACTOR-BETA-2 AND BETA-3 MESSENGER-RNAS AND PROTEINS IN THE DEVELOPING CHICKEN-EMBRYO, Differentiation, 55(2), 1994, pp. 105-118
Specific cDNA probes and antibodies for chicken transforming growth fa
ctor (TGF)-beta 2 and beta 3 were used to study expression of TGF-beta
2 and beta 3 mRNAs and proteins in the developing chicken embryo. Exp
ression of the mRNAs for both TGF-beta isoforms was detected by day 1.
5 of incubation (Hamburger and Hamilton stage 10) by RNA Northern blot
analysis and increased with developmental age. Expression of TGF-beta
2 and beta 3 mRNAs was detected in every embryonic tissue examined, w
ith the level of expression of both isoforms being high in heart, brai
n and muscle and low in kidney and liver. Coordinate unidirectional up
regulation of expression of TGF-beta 2 and beta 3 mRNAs occurred in mo
st embryonic tissues with development except the heart, where the stea
dy-state level of expression of TGF-beta 2 mRNA decreased with age, wh
ile that of TGF-beta 3 mRNA increased. In situ hybridization analysis
detected TGF-beta 2 and beta 3 mRNAs as early as the definitive primit
ive streak stage (stage 4). During neurulation (stage 10), TGF-beta 2
and beta 3 mRNAs were detected in cells of all three germ layers; TGF-
beta 3 mRNA was detected in neurectoderm as well. Following neurulatio
n, TGF-beta 3 mRNA was detected in the neural tube, notochord, ectoder
m, endoderm, sclerotome and dermomyotome at stage 16; expression of TG
F-beta 2 mRNA was not as prominent as TGF-beta 3 mRNA in these structu
res. By stage 29, both TGF-beta 2 and beta 3 mRNAs were localized in s
everal tissues including heart, lung, gizzard and feathers. Immunohist
ochemical staining analysis detected immunoreactive TGF-beta 2 and bet
a 3 proteins in all three germ layers of stage 4 embryos. Staining for
TGF-beta 2 and beta 3 proteins was detected in several cell types and
tissues in the early developing embryo frequently in the same locatio
ns as TGF-beta 2 and beta 3 mRNAs, with staining for TGF-beta 2 being
less intense than TGF-beta 3. However, in some cases, localization of
TGF-beta 2 and beta 3 proteins was different from that of the mRNAs, i
ndicating that a complex mechanism of transcription, translation and s
ecretion exits during chicken embryogenesis. These and other results s
uggest that TGF-beta 2 and beta 3 may play important roles and act thr
ough both autocrine and paracrine mechanisms in the development of man
y tissues in the chicken.