Understanding how cells are able to rebuild cellular components and re-establish global patterning holds the promise of shedding new light on the largely unanswered fundamental question of how cells perform morphogenesis and pattern formation.Ī second reason to study regeneration in single cells is to identify the mechanisms by which cells repair and recover from wounds. How does a cell create and maintain pattern? Historically, study of regeneration has played a key role in revealing mechanisms of animal development, because regeneration allows specific developmental processes to be induced experimentally ( Morgan, 1901a). While much is known about the molecular composition of cells, the mechanism by which those components are arranged into complex patterns and structures is far less understood ( Kirschner et al., 2000 Shulman and St Johnston, 1999 Harold, 2005 Marshall, 2020). This work allows us to classify regeneration genes into groups based on their potential role for regeneration in distinct cell regeneration paradigms, and provides insight into how a single cell can coordinate complex morphogenetic pathways to regenerate missing structures.
E2F is involved in the completion of regeneration but is dispensable for earlier steps. RNAi-mediated knockdown experiments indicate that Pumilio is required for regenerating oral structures of the correct size. Among the early-expressed genes, we identified an E2F transcription factor and the RNA-binding protein Pumilio as potential regulators of regeneration based on the expression pattern of their predicted target genes. By measuring gene expression after blocking translation, we show that the sequential waves of gene expression involve a cascade mechanism in which later waves of expression are triggered by translation products of early-expressed genes. By comparing transcriptional profiles of different regeneration events, we identified distinct modules of gene expression corresponding to oral apparatus regeneration, posterior holdfast regeneration, and recovery after wounding. We used RNA sequencing (RNAseq) to assay the dynamic changes in Stentor’s transcriptome during regeneration, after both oral apparatus shedding and bisection, allowing us to identify distinct temporal waves of gene expression including kinases, RNA -binding proteins, centriole biogenesis factors, and orthologs of human ciliopathy genes.
If a cell is cut in half, each half regenerates an intact cell.
#Great expressions cascade series
The anterior of the cell is marked by an array of cilia, known as the oral apparatus, which can be induced to shed and regenerate in a series of reproducible morphological steps, previously shown to require transcription. The giant ciliate Stentor coeruleus is a classical model system for studying regeneration and morphogenesis in a single cell.
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