Mechanisms implied in tissues response to the oxygen partial pressure remain poorly understood as well as the role of hypoxia in developmental processes. However, the activation of transcription factors such as FoxO and HIF and the recruitment of signalling pathways including Calcineurin, PI3K, p38-MAPK and mTOR are known to be involved in hypoxia responses. Currently, little information is kno...

In vertebrates, the paraxial mesoderm already exhibits a complex Hox gene pattern by the time that segmentation occurs and somites are formed. The anterior boundaries of the Hox genes are always maintained at the same somite number, suggesting coordination between somite formation and Hox expression. To study this interaction, we used morpholinos to knockdown either the somitogenesis gene X-Del...

A strong, negative cis-element located at the first intron +502/+835 (I300) of zebrafish myf5 has been reported. To elucidate the molecular mechanism underlying this repression network, we microinjected zebrafish single-cell embryos with I300 RNA, resulting in the dramatic reduction of luciferase activity driven by the myf5 promoter. Within this I300 segment, we identified an intronic microRNA ...

The vertebrate axial skeleton (vertebral column and ribs) is derived from embryonic structures called somites. Mechanisms of somite formation and patterning are largely conserved along the length of the body axis, but segments acquire different morphologies in part through the action of Hox transcription factors. Although Hox genes' roles in axial skeletal patterning have been extensively chara...

We present measurements of the bulk Young's moduli of early chick embryos at Hamburger-Hamilton stage 10. Using a micropipette probe with a force constant k approximately 0.025 N/m, we applied a known force in the plane of the embryo in the anterior-posterior direction and imaged the resulting tissue displacements. We used a two-dimensional finite-element simulation method to model the embryo a...

Both the muscle and endothelium of the vertebrate limb derive from somites. We have used replication-defective retroviral vectors to analyze the lineage relationships of these somite-derived cells in the chick. We find that myogenic precursors in the somites or proximal limb are not committed to forming slow or fast muscle fibers, particular anatomical muscles, or muscles within specific proxim...

Mouse Foxc1 (previously Mf1) is a member of the conserved forkhead/winged helix transcription factor gene family. It is expressed in many mesodermal tissues including paraxial mesoderm of the trunk and head, prechondrogenic mesenchyme, branchial arches and developing kidney. Homozygous mutants die perinatally with hydrocephalus and skeletal, cardiovascular, ocular and genitourinary defects. Her...