Biology subjects

Smith-Bolton, R. K.

Publications and source records attributed to Smith-Bolton, R. K..

4 recordsLinked to original sources

bioRxiv2026

Draper-mediated efferocytosis by Drosophila imaginal disc epithelial cells clears cellular debris during regeneration.

Article summaryTissue regeneration requires organized responses to damage, including clearance of cellular debris. Using a genetic ablation system in Drosophila wing imaginal discs, we show that most debris is cleared within two days despite the absence of immune cell recruitment, which is restricted by the basement membrane. In the absence of immune cells, debris clearance occurs through Draper-mediated efferocytosis and lysosomal processing by epithelial cells. Disruption of this pathway delays debris removal and impacts regeneration. Residual debris consists of a heterogeneous mix of cellular components, indicating non-selective clearance. Together, our findings identify epithelial cells as key non-professional phagocytes during regeneration. Regeneration is a coordinated process that restores tissue integrity following damage. Following injury, tissues initiate early responses, including epithelial remodeling and clearance of cellular debris. However, how debris clearance is coordinated with regenerative growth to ensure efficient tissue repair remains poorly understood. To address how early damage responses, particularly debris clearance, are coordinated with regeneration, we used a genetic ablation system in Drosophila wing imaginal discs to induce apoptosis in the pouch region. Targeted damage generates cellular debris that localizes to both the apical and basal sides of the epithelium. We show that most cellular debris is cleared within two days after damage, although some debris persists apical to the regenerating epithelium. Notably, immune cells are not recruited to the damaged tissue due to restricted access by an intact basement membrane. Instead, we discovered that debris clearance is mediated by efferocytosis, whereby neighboring hinge epithelial cells activate JNK signaling and engulf debris via lysosomal formation. Reduction of efferocytosis by mutation of the phagocytic receptor Draper delays debris removal and increases debris persistence. This impairment has a modest impact on regeneration, as measured by adult wing size. Finally, our data indicate that residual debris consists of a heterogeneous mixture of cellular components, suggesting no preferential targeting by the clearance machinery. Together, our results reveal a previously unappreciated role for epithelial cells as non-professional phagocytes for debris clearance during regeneration.

developmental biology↗

bioRxiv2019

The gene brain tumor constrains growth to ensure proper patterning during regeneration in Drosophila imaginal discs

Some animals respond to injury by inducing new growth to regenerate the lost structures. This regenerative growth must be carefully controlled and constrained to prevent overgrowth and to allow correct organization of the regenerating tissue. However, the factors that restrict regenerative growth have not been identified. Using a genetic ablation system in the Drosophila wing imaginal disc, we have identified one mechanism that constrains regenerative growth, impairment of which also leads to erroneous patterning of the final appendage. Regenerating discs with reduced levels of the RNA-regulator Brain tumor (Brat) exhibit enhanced regeneration, but produce adult wings with disrupted margins that are missing extensive tracts of sensory bristles. In these mutants, aberrantly high expression of the pro-growth factor Myc and its downstream targets likely contributes to this loss of cell-fate specification. Thus, Brat constrains the expression of pro-regeneration genes and ensures that the regenerating tissue forms the proper final structure. Author SummaryWhile much has been published about the signals that stimulate regeneration, the mechanisms that constrain and/or terminate regeneration have not been well characterized. Thus, we do not understand what limits may exist on the rate of regenerative growth, what mechanisms constrain regeneration, and what the consequences might be of enhancing regrowth. Here, we detail our discovery and characterization of a mechanism that constrains regeneration, and the deleterious effects of reducing that constraint. In this manuscript, we describe our identification of the RNA regulator Brat as a factor that constrains regenerative growth. Without this constraint on regenerative growth, patterning mistakes occur leading to a malformed regenerated structure. We demonstrate that the patterning errors are not due to faster growth itself, but are due to the overexpression of the pro-growth transcription factor Myc.

developmental biology↗

bioRxiv2018

The Drosophila SWI/SNF chromatin-remodeling complexes play separate roles in regulating growth and cell fate during regeneration

To regenerate, damaged tissue must heal the wound, regrow to the proper size, replace the correct cell types, and return to the normal gene-expression program. However, the mechanisms that temporally and spatially control the activation or repression of important genes during regeneration are not fully understood. To determine the role that chromatin modifiers play in regulating gene expression after tissue damage, we induced ablation in Drosophila imaginal wing discs, and screened for chromatin regulators that are required for epithelial tissue regeneration. Here we show that many of these genes are indeed important for promoting or constraining regeneration. Specifically, the two SWI/SNF chromatin-remodeling complexes play distinct roles in regulating different aspects of regeneration. The PBAP complex regulates regenerative growth and developmental timing, and is required for the expression of JNK signaling targets and the growth promoter Myc. By contrast, the BAP complex ensures correct patterning and cell fate by stabilizing expression of the posterior gene engrailed. Thus, both SWI/SNF complexes are essential for proper gene expression during tissue regeneration, but they play distinct roles in regulating growth and cell fate. Summary statementDuring regeneration of the Drosophila wing disc, the SWI/SNF PBAP complex is required for regenerative growth and expression of JNK signaling targets, while the BAP complex maintains posterior cell fate.

developmental biology↗

bioRxiv2017

A Positive Feedback Loop Ensures Propagation of ROS Production and JNK Signaling Throughout Drosophila Tissue Regeneration

Regenerating tissue must initiate the signaling that drives regenerative growth, and sustain that signaling long enough for regeneration to complete. How these key signals are sustained is unclear. To gain a comprehensive view of the changes in gene expression that occur during regeneration, we performed wholegenome mRNAseq of actively regenerating tissue from damaged Drosophila wing imaginal discs. We used genetic tools to ablate the wing primordium to induce regeneration, and carried out transcriptional profiling of the regeneration blastema by fluorescent labeling and sorting the blastema cells, thus identifying differentially expressed genes. Importantly, by using genetic mutants of several of these differentially expressed genes we have confirmed that they have roles in regeneration. Using this approach, we show that high expression of the gene moladietz (mol), which encodes the Duox-maturation factor NIP, is required during regeneration to produce reactive oxygen species (ROS), which in turn sustain JNK signaling during regeneration. We also show that JNK signaling upregulates mol expression, thereby activating a positive feedback signal that ensures the prolonged JNK activation required for regenerative growth. Thus, by wholegenome transcriptional profiling of regenerating tissue we have identified a positive feedback loop that regulates the extent of regenerative growth.\n\nAuthor summaryRegenerating tissue must initiate the signaling that drives regenerative growth, and then sustain that signaling long enough for regeneration to complete. Drosophila imaginal discs, the epithelial structures in the larva that will form the adult animal during metamorphosis, have been an important model system for tissue repair and regeneration for over 60 years. Here we show that damage-induced JNK signaling leads to the upregulation of a gene called moladietz, which encodes a co-factor for an enzyme, NADPH dual oxidase (DUOX), that generates reactive oxygen species (ROS), a key tissue-damage signal. High expression of moladietz induces continuous production of ROS in the regenerating tissue. The sustained production of ROS then continues to activate JNK signaling throughout the course of regeneration, ensuring maximal tissue regrowth.

developmental biology↗