Copine A plays a role in the differentiation of stalk cells and the initiation of culmination in Dictyostelium development

Abstract

BackgroundCopines are calcium-dependent phospholipid-binding proteins found in diverse eukaryotic organisms. We are studying the function of copines in Dictyostelium discoideum, a single-celled amoeba that undergoes cell differentiation and morphogenesis to form multicellular fruiting bodies when placed in starvation conditions. Previously, we showed that Dictyostelium cells lacking the copine A (cpnA) gene are not able to complete the developmental cycle, arresting at the slug stage. The aim of this study is to further characterize the developmental defect of the cpnA- cells.ResultsTime-lapse imaging revealed that cpnA- cells exhibited delayed aggregation and made large mounds that formed one large slug as compared to the smaller slugs of the wild-type cells. While the prespore cell patterning appeared to be normal within the cpnA- slugs, the prestalk cell patterning was different from wild-type. When cpnA- cells were mixed with a small percentage of wild-type cells, chimeric fruiting bodies with short stalks formed. When a small percentage of cpnA- cells was mixed with wild-type cells, the cpnA- cells labeled with GFP were found located throughout the chimeric slug and in both the stalk and sporehead of the fruiting bodies. However, there appeared to be a small bias towards cpnA- cells becoming spore cells. When cpnA- cells were developed in buffer containing EGTA, they were also able to differentiate into either stalk or spore cells to form fruiting bodies with short stalks.ConclusionsOur results indicate that CpnA is involved in the regulation of aggregation, slug size, and culmination during Dictyostelium development. More specifically, CpnA appears to be involved in the function and differentiation of prestalk cells and plays a role in a calcium-regulated signaling pathway critical to triggering the initiation of culmination.

Copine A is expressed in prestalk cells and regulates slug phototaxis and thermotaxis in developing Dictyostelium

“…In a previous study, we found that mixing 5% or more wild‐type cells with cpnA‐ cells was able to rescue this culmination defect and that wild‐type cells within these mixed chimerics were located throughout the slug (Damer et al. 2007; Smith et al. 2010).…”

“…Previous studies on Dictyostelium cells lacking the cpnA gene indicate that cpnA plays a role in regulating aggregation, slug size, and culmination (Damer et al. 2007; Smith et al. 2010).…”

“…Previously we showed that Dictyostelium cells lacking the cpnA gene were arrested at the slug stage of development and the slugs formed from cpnA‐ cells appeared to be much bigger than those formed from cells of the parental wild‐type strain (Smith et al. 2010).…”

“…Dictyostelium cells were prepared for development as previously described (Smith et al. 2010), except that cells were plated on white nitrocellulose filters.…”

“…Previously, we found that cells lacking cpnA are arrested in the slug stage and do not culminate into fruiting bodies (Damer et al. 2007; Smith et al. 2010).…”