Murray State University
Inhibition of Differentiation by Chondroitin Sulfate in the Early Chick Embryo.
Institution
Murray State University
Faculty Advisor/ Mentor
David Canning
Abstract
The central area pellucida epiblast (CAPE) region of the chick blastoderm gives rise to all subsequent embryonic tissues. At gastrulation it produces axial mesoderm and endoderm under instructive influences from the marginal zone. Later, the anterior CAPE forms the head and anterior CNS due to factors secreted in the prechordal plate. However, the actual cellular mechanisms allocating epiblast cells to specific fates are largely unknown. We have examined the state of specification of CAPE cells from the onset of gastrulation through the head stage. By extirpating tissue from various stages, we have used isolation cultures, in combination with in-situ hybridization and immunocytochemistry to map the time-course of the degree of commitment of the CAPE. Our studies have revealed specific roles for molecular components of the extracellular matrix in the allocation of cell fates from the CAPE. One of these, chondroitin sulfate (CS), appears to suppress certain cell fates relative to others. In the pre-gastrula, CS inhibits N-cadherin expression and muscle differentiation, while promoting notochord differentiation. Following gastrulation, CS assists in the formation of head structures from the prechordal plate region. As the head develops, CS delineates nervous tissue areas from mesenchymal tissues. Isolates from the anterior CAPE fail to form head tissues if CS is experimentally removed. This mechanism appears to be mediated by suppression of N-cadherin activity during morphogenesis. The results are currently being confirmed by using neural markers and the genetic expression for the same process is being analyzed by in-situ hybridization of whole embryos and head cultures.
Inhibition of Differentiation by Chondroitin Sulfate in the Early Chick Embryo.
The central area pellucida epiblast (CAPE) region of the chick blastoderm gives rise to all subsequent embryonic tissues. At gastrulation it produces axial mesoderm and endoderm under instructive influences from the marginal zone. Later, the anterior CAPE forms the head and anterior CNS due to factors secreted in the prechordal plate. However, the actual cellular mechanisms allocating epiblast cells to specific fates are largely unknown. We have examined the state of specification of CAPE cells from the onset of gastrulation through the head stage. By extirpating tissue from various stages, we have used isolation cultures, in combination with in-situ hybridization and immunocytochemistry to map the time-course of the degree of commitment of the CAPE. Our studies have revealed specific roles for molecular components of the extracellular matrix in the allocation of cell fates from the CAPE. One of these, chondroitin sulfate (CS), appears to suppress certain cell fates relative to others. In the pre-gastrula, CS inhibits N-cadherin expression and muscle differentiation, while promoting notochord differentiation. Following gastrulation, CS assists in the formation of head structures from the prechordal plate region. As the head develops, CS delineates nervous tissue areas from mesenchymal tissues. Isolates from the anterior CAPE fail to form head tissues if CS is experimentally removed. This mechanism appears to be mediated by suppression of N-cadherin activity during morphogenesis. The results are currently being confirmed by using neural markers and the genetic expression for the same process is being analyzed by in-situ hybridization of whole embryos and head cultures.