The vertebrate tail bud: three germ layers from one tissue

Abstract

The tail bud of amniote embryos comprises a mass of apparently undifferentiated mesenchymal cells located at the caudal limit of the embryo, representing the remains of Hensen's node and the primitive streak. These cells have the potential to give rise to a variety of different tissues including the posterior or 'secondary' neural tube, the tail gut, and somites and their derivatives. This seemingly homogeneous accumulation of cells therefore has the capacity to differentiate into tissues which in more cranial regions of the embryo are derived from cells of different germ layers. In this review, the tissue contributions of the tail bud in various vertebrate classes are discussed, with particular attention to the mesenchymal-to-epithelial transformation that characterizes the process of secondary neurulation, and which distinguishes it from the epithelial folding that occurs during primary neurulation in more cranial regions. Recent studies suggest that the transformation is accompanied by extensive changes in the cell surface oligosaccharide complement of the differentiating cells, and that the sialyted form of N-CAM is expressed both temporally and spatially in a manner that suggests a role for it in the process. The pluripotential nature of the tail bud mesenchyme may be revealed experimentally by grafting the tissue ectopically, or by culturing it on different substrata. In the latter case, the mesenchyme can be demonstrated to give rise to myocytes, chondrocytes, neuroepithelium and neural crest derivatives such as melanocytes, depending on the nature of the culture substratum. It is concluded that the tail bud mesenchyme represents a developing system which is readily amenable to experimentation and should provide insights into the general mechanisms of cell differentiation and transformation.

In situ hybridization screen in zebrafish for the selection of genes encoding secreted proteins

“…3H-J). Varied expression of sESTs in this region is consistent with the idea that the tail bud does not constitute a blastema, or uniform population of cells (Griffith et al, 1992). Rather, cell fate restrictions have occurred and patterning events are likely to be proceeding due to communication between cells expressing different signaling molecules.…”

Maternal Diabetes Increases the Risk of Caudal Regression Caused by Retinoic Acid

“…Wnt-3a was directly involved in the genetic pathway of RA-induced caudal regression. Caudal regression induced by RA was associated with excessive apoptosis of the tail bud (11), which contains progenitor cells for the various tissues of the caudal embryonic region (17,18). It has been shown that Wnt-3a, a gene that encodes a secreted signaling molecule, is indispensable for tail bud development (19).…”

Cervicothoracic nonterminal myelocystocele with mature teratoma

“…Specifically, they suggested that pluripotent cells of the caudal cell mass may give rise to these tumors through various types of cell-signaling dysfunction. 3,6 The patient described in our case had a cervicothoracic nonterminal myelocystocele containing a teratoma located above the caudal cell mass. It has been postulated that these midline tumors may originate from rests of pluripotent cells at sites of early neural tube closure.…”