Analysis of G alpha 4, a G-protein subunit required for multicellular development in Dictyostelium.

Abstract

The Dictyostelium G^4 gene encodes a G-protein a subunit that is primarily expressed during the muhicellular stages of development. g^4 null mutants, created by gene disruption, show aberrant morphological differentiation, reduced levels of prespore gene expression, and a loss of the ability to produce spores. These developmental phenotypes can be rescued by complementation with the wild-type gene. Cells that overexpress the G"4 gene {0^4^^*^) also show reduced spore production but display an aberrant morphological phenotype distinct from that of g"4 cells. The g"4 phenotype can be partially rescued by the presence of wild-type or Gjfi^^ cells in chimeric organisms, suggesting that G"4-expressing cells produce an intercellular signal that is essential for multicellular development.

Identification and functional analysis of a developmentally regulated extracellular signal-regulated kinase gene in Dictyostelium discoideum.

“…In the migrating slug, ERKJ/lacZ-expressing cells are scattered throughout the organism with a higher concentration toward the posterior (Fig. 8E), a pattern that has been previously seen for Ga4 (32,33) or the gene encoding the phosphotyrosine phosphatase PTP2 (42). As culmination initiates, staining is more concentrated in the anterior tip and the cells migrating to form the lower cap of the sorus (Fig.…”

“…We assume that the spatial pattern reflects the expression pattern of the late promoter since RNA blots with the ERKJ/ERK1 construct show a developmentally regulated shift in transcript size, as does the endogenous ERK1 mRNA. Previous studies in our laboratory have shown that the ,B-Gal produced from our constructs is unstable (25,32,33,43). Several other genes that have been studied in our laboratory have a similar ALC-like pattern of expression during the multicellular stages and are also expressed during growth, such as Ga4 and PTP1 (32,33,43) or rasD, which shows a prestalk-enriched pattern of expression and is also expressed in ALCs (25).…”

“…1B (see Materials and Methods for a description of the other constructs). Two independent constructs for homologous recombination were then linearized and transformed by electroporation into JH10 cells, a thymidine auxotroph (32,56 To further examine the possibility that ERK1 is essential for growth, we made an ERK1 antisense construct with the discoidin I-y (Discly) promoter, whose expression can be regulated by exogenous folate during vegetative growth (3,66). This gene is not expressed in cells grown on bacteria or in axenic culture when cells are maintained at a very low density (15,66).…”

“…During the multicellular stages, ERKl/lacZ has an expression pattern similar to that of ALCs (28,32,47). We assume that the spatial pattern reflects the expression pattern of the late promoter since RNA blots with the ERKJ/ERK1 construct show a developmentally regulated shift in transcript size, as does the endogenous ERK1 mRNA.…”

“…Biochemical and molecular genetic analyses over the last few years have identified components required for various aspects of these processes and have led to a further understanding of the regulatory pathways controlling development. Genes encoding membrane receptors, coupled GP and Got subunits, the effectors adenylyl cyclase and phospholipase C, and the transcription factor GBF have been cloned and analyzed at a molecular level (12,17,32,65,72,81,82 the membrane to those in the nucleus is cAMP-dependent protein kinase (PKA). PKA has been shown to be essential for aggregation, cell-type-specific expression of the ecmB gene, the induction of prespore cell differentiation, and the induction of sporulation and spore cell-specific gene expression (1, 27, 35, 36, 40, 56-58, 76, 77 (8, 21-23, 61, 79, 84).…”