Rp. Tucker et al., IN-SITU LOCALIZATION OF THROMBOSPONDIN-1 AND THROMBOSPONDIN-3 TRANSCRIPTS IN THE AVIAN EMBRYO, Developmental dynamics, 208(3), 1997, pp. 326-337
Two novel cDNA probes to chicken thrombospondin-1 (TSP-1) and TSP-3 we
re used to determine by in situ hybridization the origins of these ext
racellular matrix proteins during embryogenesis. Both TSP-1 and TSP-3
are expressed in embryonic cartilage. TSP-1 expression is limited to e
arly chondrocytes, in contrast to TSP-3 mRNAs that are found in older
proliferative and hypertrophic chondrocytes. TSP-1 and TSP-3 are expre
ssed consecutively during neurogenesis as well, with the TSP-1 probe h
ybridizing in proliferating neuroblasts, and TSP-3 expressed by neuron
s as they are actively extending processes. A TSP-1 hybridization sign
al reappears in subpopulations of neurons in the spinal cord and brain
after the periods of active neurite extension and programmed cell dea
th are complete. TSP-1 is also expressed in the spinal cord floor plat
e, in mesenchyme surrounding the developing paramesonephric duct, at t
he tips of growing lung bronchioles, in lens, and in corneal endotheli
um. These observations indicate that there is little overlap in the ex
pression patterns of TSP-1 and TSP-3 and that they are expressed conse
cutively during the development of cartilage and neurons. The pattern
of TSP-1 expression in avascular tissues and in the floor plate is con
sistent with possible roles for this glycoprotein in regulating angiog
enesis and establishing morphogenetic gradients. (C) 1997 Wiley-Liss,
Inc.