Teloblast
A teloblast is a large cell in the embryos of
Developmental role and morphology
All teloblasts are specified from the D quadrant
Teloblasts have two separate
O/P specification
The O and P teloblasts are specified from two separate but identical precursors, which form an equivalence group These two precursor cells are termed O/P cells for their ability to become either O or P teloblasts. Signals from the surrounding cells act to specify which fate the teloblasts and their progeny take on. Interactions with the q bandlet, however transient, can induce the p fate in the adjacent o/p bandlet.[2] The M bandlet has been shown to In some species (i.e. Helobdella triserialis), the provisional epithelium covering the cells plays a role in inducing the O fate.[3] In the absence of cell-cell interactions, the O/P precursors will become O teloblasts. O and P bandlets exhibit very different mitotic patterns (see figure) which are used to identify them in experimental manipulations.
Segmental fates
The N and Q teloblasts contribute two blast cells per segment, one making up the anterior half of the segment, the second making up the posterior half of the segment. The O, P, and M lineages contribute one blast cell per segment, but the contributions from each blast cell spans a segmental boundary. These segmental boundaries were discovered by injecting teloblasts with cell lineage tracers after a few blast cells have already been generated. During development, the N and Q bandlets, which eventually have 64 blast cells each, slide past the O,P,and M bandlet, which only have 32 cells. Thus, the segmental boundaries within each bandlet are already specified before all the bandlets come into complete register.[5]
References
- PMID 7409309.)
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: CS1 maint: multiple names: authors list (link - PMID 2869529.