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R R Kay

Publications and source records attributed to R R Kay.

63 records · Page 4Linked to original sources
PubMed1978

Effects of BUdR on developmental functions of Dictyostelium discoideum.

The development of Dictyostelium discoideum cells, as measured by spore yield, is somewhat more sensitive to the presence of BUdR during vegetative growth than is growth itself. Observations on the development of control and BUdR-grown cells, their protein labelling patterns and assays of 4 developmentally regulated proteins all reveal a consistent picture. BUdR appears to block spore formation by partially inhibiting several or many different earlier events during development. The relative sensitivity of development compared to growth to inhibition by the drug may be a consequence of the nature of the developmental process rather than of some unique specificity of the inhibitor.

3',5'-Cyclic-AMP Phosphodiesterases↗
PubMedDate not supplied

A possible morphogen controlling differentiation in Dictyostelium.

The complex morphology of a higher organism is generated partly by such developmental processes as cell movement and cohesion but also by a social interaction between cells in small areas of embryonic tissue known as morphogenetic fields. The initially similar cells within such a field organize themselves and differentiate, forming a discrete spatial pattern which is remarkably independent of field size and which can regenerate after some part is removed. Although it is believed that a cell signalling system must underlie this behaviour, the putative signals--or morphogens--have so far proved elusive. Perhaps the simplest known morphogenetic field arises within the multicellular aggregate formed by developing cells of the slime mould Dictyostelium discoideum. As the amorphous aggregate transforms into a cylindrical slug, a simple pattern emerges, with prestalk cells differentiating in the anterior and prespores in the posterior. One great difficulty in identifying any morphogen has been to predict properties that could form the basis of a bioassay. However, in Dictyostelium it is almost essential that the morphogens should dictate to cells their choice of differentiation pathway. We have described previously a crude factor termed DIF which stimulates the differentiation of isolated amoebae into stalk cells. We now show that purified DIF also inhibits spore formation and so switches cells to stalk cell formation. Thus, we believe that DIF is a morphogen which regulates the choice of differentiation pathway of cells in the Dictyostelium slug.

Cell Differentiation↗
PubMedDate not supplied

Intracellular pH and the control of cell differentiation in Dictyostelium discoideum.

During development in the cellular slime mould Dictyostelium discoideum starved amoebae aggregate to form multicellular structures that display a simple antero-posterior pattern: prestalk cells occupy the front 20% of the aggregate, and prespore cells occupy the remainder. We have attempted to elucidate the nature of the mechanism regulating the proportions of the two cell types by examining the factors that influence the pathway of differentiation of amoebae in vitro. Amoebae of D. discoideum strain V12 M2 form stalk cells efficiently in appropriate conditions and 'sporogenous' derivatives produce spores as well as stalk cells. Mature spores are formed in a medium containing only cyclic AMP and salts, whereas formation of stalk cells requires, in addition, a low molecular weight hydrophobic factor (DIF). Recent observations have led us to propose that DIF is a morphogen responsible for activating stalk cell differentiation. Here we present evidence that ammonia is a second morphogen, that acts antagonistically to DIF, and that the choice of differentiation pathway is mediated by intracellular pH.

Ammonia↗
PubMedDate not supplied

Chemical structure of the morphogen differentiation inducing factor from Dictyostelium discoideum.

Morphogens are signal molecules presumed to exist in embryos and to be involved in establishing the spatial pattern of cells during development. Differentiation inducing factor (DIF) has the properties of a morphogen required for producing the prestalk/prespore pattern in the aggregate formed by cells of the slime mould Dictyostelium in response to starvation. DIF-1, the major bioactive species after purification, has now been identified using a combined microchemical, spectroscopic and synthetic approach. The structure is defined as 1-(3,5-dichloro-2,6-dihydroxy-4-methoxyphenyl)-1-hexanone, and represents a new class of effector molecule. The availability of relatively large quantities of synthetic and isotopically labelled materials should now allow progress towards a detailed understanding of the pattern-forming processes in Dictyostelium development.

Cell Differentiation↗