There is a crucial need to better understand the effects of low-doses of ionizing radiation in fetal models. Radiation-induced adaptive response (AR) was described in mouse embryos pre-exposed in utero to low-doses of X-rays, which exhibited lower apoptotic levels in the limb bud. We previously described AR-specific gene modulations in the mouse embryo. In this study, we evaluated the role of t...

To examine the role of BMP signaling during limb pattern formation, we isolated chicken cDNAs encoding type I (BRK-1 and BRK-2) and type II (BRK-3) receptors for bone morphogenetic proteins. BRK-2 and BRK-3, which constitute dual-affinity signaling receptor complexes for BMPs, are co-expressed in condensing precartilaginous cells, while BRK-1 is weakly expressed in the limb mesenchyme. BRK-3 is...

Myogenic Regulatory Factors (MRFs) are a family of transcription factors whose expression in a cell reflects the commitment of this cell to a myogenic fate before any cytological sign of muscle differentiation is detectable. Myogenic cells in limb skeletal muscles originate from the lateral half of the somites. Cells that migrate away from the lateral part of the somites to the limb bud do not ...

To investigate the role of fibroblast growth factor-2 (basic fibroblast growth factor) in chick limb development, we constructed a replication-defective spleen necrosis virus to ectopically express fibroblast growth factor-2 in stage 20-22 chick limb bud. Because infecting cells in vivo proved to be inefficient, limb bud cells were dissociated, infected in vitro, and then grafted back into host...

The polarizing region is a major signalling tissue involved in patterning the tissues of the vertebrate limb. The polarizing region is located at the posterior margin of the limb bud and can be recognized by its ability to induce additional digits when grafted to the anterior margin of a chick limb bud. The signal from the polarizing region operates at the tip of the bud in the progress zone, a...

The ability of the anterior apical ectodermal ridge to promote outgrowth in the chick wing bud when disconnected from posterior apical ridge was examined by rotating the posterior portion of the stage-19/20 to stage-21 wing bud around its anteroposterior axis. This permitted contact between the anterior and posterior mesoderm, without removing wing bud tissue. In a small but significant number ...

Signaling through the p38 mitogen-activated protein kinases (MAPKs) is essential for cartilage formation in primary cultures of limb mesenchyme. Here we show that, concurrent with a decrease in chondrogenesis, inhibition of p38 in limb bud cultures dramatically promotes muscle development. Specifically, treatment of primary limb bud cultures with p38 inhibitors increases the expression of myoge...

The application of retinoic acid (RA) to the developing chick limb bud causes 6-digit double posterior limbs to form instead of the normal 3-digit limb. As an attempt to begin a molecular analysis of this phenomenon we have identified and characterized a soluble cytoplasmic receptor for RA, namely cytoplasmic retinoic acid-binding protein (CRABP), from the cells of the chick limb bud. It is pre...

Cell-extracellular matrix interactions play crucial roles in limb muscle development but practically nothing is known on what integrins are involved before the differentiation of muscle precursor cells (MPCs) in the limb muscle masses. In this study we determine the expression patterns of integrins during early forelimb muscle development in the mouse. alpha6beta1 integrin is downregulated in t...

BACKGROUND Sonic hedgehog (Shh), a vertebrate homolog of the Drosophila segment polarity gene hedgehog (hh), has been implicated in patterning of the developing chick limb. Such a role is suggested by the restricted expression of Shh along the posterior limb bud margin, and by the observation that heterologous cells expressing Shh have limb-polarizing activity resembling that of cells from the ...