The process of regeneration is immensely complicated and requires the exquisitely precise orchestration of growth, patterning and cell-fate specification. Drosophila melanogaster larval tissues have recently emerged as a useful model organism to study this process. These larval tissues are simple but experience complex gene expression to finally form the adult tissue. As such, Drosophila is an ideal model organism to study the complicated process of regeneration. In this study we have used the experimental tractability of Drosophila to investigate how growth, patterning, cell-fate specification and fate plasticity are regulated in regenerating imaginal discs.
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. In this study, we have identified one mechanism that constrains regenerative growth, impairment of which 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. The loss of cell-fate specification is due to the aberrantly high expression of the pro-growth factor Myc and the self-renewal factor Chinmo. Thus, Brat ensures that the regenerating tissue forms the proper final structure by constraining expression of pro-regeneration genes.
Dissociation of imaginal disc cells has previously been carried out to enable flow cytometry and cell sorting to analyze cell cycle progression, cell size, gene expression, and other aspects of imaginal tissues. However, the lengthy dissociation protocols employed may alter gene expression, cell behavior and overall viability. In this study, we developed a new rapid and gentle method of dissociating the cells of wing imaginal discs that significantly enhanced cell viability and reduced the likelihood of gene expression changes. This method was successfully used to create a transcriptional profile of the regenerating tissue leading to the identification of many novel regulators of regeneration. We have also extended our investigation of regeneration to the antennal imaginal disc.
Drosophila imaginal discs have also been used to study cell-fate specification and plasticity, including homeotic changes and regeneration-induced transdetermination. In this study, we identified a change from antennal fate to eye fate induced by a Distal-less-GAL4 (DllGAL4) P-element insertion that is a mutant allele of Dll and expresses GAL4 in the antennal imaginal disc. While this fate change was not induced by tissue damage, it appeared to be a hybrid of transdetermination and homeosis. This plasticity appears to be unique to the DllGAL4 line, possibly due to cellular stress induced by the high GAL4 expression combined with the severity of the Dll mutation. Thus, we propose that even in the absence of tissue damage, other forms of cellular stress caused by high GAL4 expression can induce determined cell fates to change, and selector gene mutations can sensitize the tissue to these transformations.U of I OnlyAuthor requested U of Illinois access only (OA after 2yrs) in Vireo ETD syste
