title: Live imaging of muscle histolysis in Drosophila metamorphosis.
abstract: BACKGROUND
  The contribution of programmed cell death (PCD) to muscle wasting disorders remains a matter of debate. Drosophila melanogaster metamorphosis offers the opportunity to study muscle cell death in the context of development. Using live cell imaging of the abdomen, two groups of larval muscles can be observed, doomed muscles that undergo histolysis and persistent muscles that are remodelled and survive into adulthood.
  
  
  METHODS
  To identify and characterize genes that control the decision between survival and cell death of muscles, we developed a method comprising in vivo imaging, targeted gene perturbation and time-lapse image analysis. Our approach enabled us to study the cytological and temporal aspects of abnormal cell death phenotypes.
  
  
  RESULTS
  In a previous genetic screen for genes controlling muscle size and cell death in metamorphosis, we identified gene perturbations that induced cell death of persistent or inhibit histolysis of doomed larval muscles. RNA interference (RNAi) of the genes encoding the helicase Rm62 and the lysosomal Cathepsin-L homolog Cysteine proteinase 1 (Cp1) caused premature cell death of persistent muscle in early and mid-pupation, respectively. Silencing of the transcriptional co-repressor Atrophin inhibited histolysis of doomed muscles. Overexpression of dominant-negative Target of Rapamycin (TOR) delayed the histolysis of a subset of doomed and induced ablation of all persistent muscles. RNAi of AMPKα, which encodes a subunit of the AMPK protein complex that senses AMP and promotes ATP formation, led to loss of attachment and a spherical morphology. None of the perturbations affected the survival of newly formed adult muscles, suggesting that the method is useful to find genes that are crucial for the survival of metabolically challenged muscles, like those undergoing atrophy. The ablation of persistent muscles did not affect eclosion of adult flies.
  
  
  CONCLUSIONS
  Live imaging is a versatile approach to uncover gene functions that are required for the survival of muscle undergoing remodelling, yet are dispensable for other adult muscles. Our approach promises to identify molecular mechanisms that can explain the resilience of muscles to PCD.
authors.affiliation: Imaging Informatics Division, Bioinformatics Institute (BII), Agency for Science, Technology and Research (A*STAR), 30 Biopolis Street, #07-01 Matrix, Singapore, 138671, Republic of Singapore.|School of Computer Engineering, Nanyang Technological University, N4-2A-05, Nanyang Avenue, Singapore, 639798, Republic of Singapore.
authors.forename: Yadav
authors.initials: Y
authors.lastname: Kuleesha
authors.affiliation: Imaging Informatics Division, Bioinformatics Institute (BII), Agency for Science, Technology and Research (A*STAR), 30 Biopolis Street, #07-01 Matrix, Singapore, 138671, Republic of Singapore.
authors.forename: Wee Choo
authors.initials: WC
authors.lastname: Puah
authors.affiliation: Imaging Informatics Division, Bioinformatics Institute (BII), Agency for Science, Technology and Research (A*STAR), 30 Biopolis Street, #07-01 Matrix, Singapore, 138671, Republic of Singapore. mwasser07@gmail.com.|Present address: BioImagingMW, Block 28D Dover Crescent, #31-73, Singapore, 134028, Republic of Singapore. mwasser07@gmail.com.
authors.forename: Martin
authors.initials: M
authors.lastname: Wasser
mesh_terms: D000263:Adenylate Kinase / Q000378:metabolism; D000818:Animals; D056668:Cathepsin L / Q000378:metabolism; D016923:Cell Death; D029721:Drosophila Proteins / Q000378:metabolism; D004331:Drosophila melanogaster / Q000166:cytology* / Q000235:genetics / Q000254:growth & development*; D017344:Genes, Insect; D021621:Imaging, Three-Dimensional / Q000379:methods*; D007814:Larva / Q000235:genetics; D008675:Metamorphosis, Biological; D018613:Microscopy, Confocal; D008954:Models, Biological; D009132:Muscles / Q000166:cytology*; D010641:Phenotype; D011679:Pupa / Q000502:physiology; D034622:RNA Interference; D015203:Reproducibility of Results; D017386:Sequence Homology, Amino Acid
chemical_list: D029721:Drosophila Proteins; D000263:Adenylate Kinase; D056668:Cathepsin L
keywords: Cell death; Drosophila; Histolysis; Live imaging; Metamorphosis; Muscle atrophy; Muscle remodelling