It has been suggested that substrate adhesion molecules of the tenascin family may be responsible for the segmented outgrowth of motor axons and neural crest cells during formation of the peripheral nervous system. We have used two monoclonal antibodies (M1B4 and 578) and an antiserum [KAF9(1)] to study the expression of J1/tenascin-related molecules within the somites of the chick embryo. Neur...

A histological technique is described which results in the differential staining of neural crest cells. This is used to describe the formation and early migration of crest cells in the head of the mouse embryo. The first indications of crest formation are seen in the midbrain/anterior hindbrain at 3--4 somites where crest cells accumulate in the basal surface of the ectodermal epithelium near t...

Tbx6 is a member of the T-box family of transcription factor genes. Two mutant alleles of this gene establish that Tbx6 is involved in both the specification and patterning of the somites along the entire length of the embryo. The null allele, Tbx6(tm1Pa), causes abnormal patterning of the cervical somites and improper specification of more posterior paraxial mesoderm, such that it forms ectopi...

Recruitment of multipotent mesodermal cells to the myogenic lineage is mediated by the transcription factor Myf5, the first of the myogenic regulatory factors to be expressed in most sites of myogenesis in the mouse embryo. Among numerous elements controlling the spatiotemporal pattern of Myf5 expression, the -58/-56 kb distal Myf5 enhancer directs expression in myogenic progenitor cells in lim...

The vertebrate body plan is organized in a segmented fashion, best illustrated by the repetition of the vertebrae. The first signs of segmentation arise during early embryogenesis when somites bud off in a rhythmic fashion from the anterior part of the presomitic mesoderm (PSM). The periodic formation of somites is proposed to be controlled by a molecular oscillator–the segmentation clock–actin...

Among other functions, the Notch signaling pathway contributes to the development of somites [4] in animals. It involves a cell signaling mechanism with a wide range of functions, including cellular differentiation [5], and the formation of the embryonic structures (embryogenesis [6]). All multicellular animals use Notch signaling, which is involved in the development, maintenance, and regenera...