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During endochondral bone development, the first osteoblasts differentiate in the perichondrium surrounding avascular cartilaginous rudiments; the source of trabecular osteoblasts inside the later bone is, however, unknown. Here, we generated tamoxifen-inducible transgenic mice bred to Rosa26R-LacZ reporter mice to follow the fates of stage-selective subsets(More)
Sonic hedgehog (Shh), which regulates proliferation in many contexts, functions as a limb morphogen to specify a distinct pattern of digits. How Shh's effects on cell number relate to its role in specifying digit identity is unclear. Deleting the mouse Shh gene at different times using a conditional Cre line, we find that Shh functions to control limb(More)
We have isolated a new murine homeobox gene, Rpx (for Rathke's pouch homeobox), that is dynamically expressed in the prospective cephalic region of the embryo during gastrulation. Early expression is seen in the anterior midline endoderm and prechordal plate precursor. Expression is subsequently activated in the overlying ectoderm of the cephalic neural(More)
Despite a wealth of experimental data implicating fibroblast growth factor (FGF) signaling in various developmental processes, genetic inactivation of individual genes encoding specific FGFs or their receptors (FGFRs) has generally failed to demonstrate their role in vertebrate organogenesis due to early embryonic lethality or functional redundancy. Here we(More)
Cartilage differentiation occurs over a broad time range from early embryonic development, when the mesenchymal condensations that give rise to cartilage models for future bone first appear, and continuing through adult life, when there is ongoing maintenance of articular joint surfaces and re-activation of cartilage formation after fracture. The(More)
The mouse Brachyury (T) gene plays critical roles in the genesis of normal mesoderm during gastrulation and in the maintenance of a functioning notochord. Abrogation of Brachyury (T) expression within the chordamesoderm of homozygous null mutants nevertheless spares anterior axis formation. An intriguing possibility to explain the preservation of anterior(More)
Limb modifications are fundamental to tetrapod evolution. Adaptive digit loss enables specialized functions such as running or flight, and has repeatedly evolved in parallel. But the developmental mechanisms underlying deviation from the five-digit ground state are unclear, partly owing to the hurdles involved in analysing embryos from animals that are not(More)
Indian hedgehog (Ihh) is essential for chondrocyte and osteoblast proliferation/differentiation during prenatal endochondral bone formation. The early lethality of various Ihh-ablated mutant mice, however, prevented further analysis of its role in postnatal bone growth and development. In this study, we describe the generation and characterization of a(More)
Recombinant limb buds constructed of an ectodermal jacket containing dissociated anterior wing bud mesoderm cells form limb-like structures lacking anteroposterior polarity. Polarity can be restored by implanting a small piece of polarizing region into the recombinant limb. We used recombinant limbs to study expression of Msx1 and Msx2 and 5' Hoxd genes in(More)
Gnot1, a Not (for notochord) family homeobox gene, is expressed in the chick pregastrulation blastoderm. Gnot1 expression in the epiblast is upregulated as the posteriorly derived hypoblast moves forward anteriorly to form a layer beneath it, which is of particular interest considering the known inductive role of the hypoblast in axis formation in the(More)