Lung mesenchyme is a critical determinant of the shape and size of the lung, the extent and patterning of epithelial branching, and the formation of the pulmonary vasculature and interstitial mesenchymal components of the adult lung. Fibroblast growth factor 9 (FGF9) is a critical regulator of lung mesenchymal growth; however, upstream mechanisms that modulate the FGF mesenchymal signal and the...

To identify molecular and cellular mechanisms that determine when bone forms, and to elucidate the role played by osteogenic mesenchyme, we employed an avian chimeric system that draws upon the divergent embryonic maturation rates of quail and duck. Pre-migratory neural crest mesenchyme destined to form bone in the mandible was transplanted from quail to duck. In resulting chimeras, quail donor...

Three different kinds of carcinoma cell, human breast tumours, mouse lung tumour and rat bladder tumours have been implanted into the developing chick wing to assay their invasive behaviour. We found that the majority of the carcinoma cells did not invade the mesenchyme but were positioned in the ectoderm. We examined the ultrasturcture of the interaction of the carcinoma cells with both the ec...

We have isolated a chick Twist gene (cTwist) and examined its expression pattern during development by whole mount in situ hybridization. In early embryos, cTwist transcripts are found in the developing somites, lateral plate mesoderm, limb mesenchyme, branchial arches and head mesenchyme. At later stages, cTwist expression is found in the sclerotome and dermatome, limb bud mesenchyme, interdig...

Vertebrate members of the zinc finger transcription factor family related to Drosophila snail are expressed in neural crest and paraxial mesoderm along the left-right axis of the embryo. As simple deuterostomes, echinoderms are an important sister phylum for the chordates. We have identified populations of patterned, nonskeletogenic mesenchyme in the sea urchin Lytechinus variegatus by their ex...

We studied the effect of fibronectin (FN) on the behavior of primary mesenchyme cells isolated from sea urchin mesenchyme blastulae in vitro using a time-lapse technique. The migration of isolated primary mesenchyme cells reconstituted in seawater and horse serum is dependent on the presence or absence of exogenous FN in the culture media. The cells in FN, 4 and 40 micrograms/ml, show a high pe...

Conversion of the nephrogenic mesenchyme into epithelial tubules requires an inductive stimulus from the ureter bud . Here we show with immunofluorescence techniques that the undifferentiated mesenchyme before induction expresses uniformly type I and type III collagens. Induction both in vivo and in vitro leads to a loss of these proteins and to the appearance of basement membrane components in...

Previous studies have suggested that Bmp4 is a key Msx1-dependent mesenchymal odontogenic signal for driving tooth morphogenesis through the bud-to-cap transition. Whereas all tooth germs were arrested at the bud stage in Msx1(-/-) mice, we show that depleting functional Bmp4 mRNAs in the tooth mesenchyme, through neural crest-specific gene inactivation in Bmp4(f/f);Wnt1Cre mice, caused mandibu...

An extracellular signaling molecule acts on several types of cells, evoking characteristic and different responses depending on intrinsic factors in the signal-receiving cells. In ascidian embryos, notochord and mesenchyme are induced in the anterior and posterior margins, respectively, of the vegetal hemisphere by the same FGF signal emanating from endoderm precursors. The difference in the re...