title: c-Myc regulates self-renewal in bronchoalveolar stem cells.
abstract: BACKGROUND
  Bronchoalveolar stem cells (BASCs) located in the bronchoalveolar duct junction are thought to regenerate both bronchiolar and alveolar epithelium during homeostatic turnover and in response to injury. The mechanisms directing self-renewal in BASCs are poorly understood.
  
  
  METHODS
  BASCs (Sca-1(+), CD34(+), CD31(-) and, CD45(-)) were isolated from adult mouse lung using FACS, and their capacity for self-renewal and differentiation were demonstrated by immunostaining. A transcription factor network of 53 genes required for pluripotency in embryonic stem cells was assessed in BASCs, Kras-initiated lung tumor tissue, and lung organogenesis by real-time PCR. c-Myc was knocked down in BASCs by infection with c-Myc shRNA lentivirus. Comprehensive miRNA and mRNA profiling for BASCs was performed, and significant miRNAs and mRNAs potentially regulated by c-Myc were identified. We explored a c-Myc regulatory network in BASCs using a number of statistical and computational approaches through two different strategies; 1) c-Myc/Max binding sites within individual gene promoters, and 2) miRNA-regulated target genes.
  
  
  RESULTS
  c-Myc expression was upregulated in BASCs and downregulated over the time course of lung organogenesis in vivo. The depletion of c-Myc in BASCs resulted in decreased proliferation and cell death. Multiple mRNAs and miRNAs were dynamically regulated in c-Myc depleted BASCs. Among a total of 250 dynamically regulated genes in c-Myc depleted BASCs, 57 genes were identified as potential targets of miRNAs through miRBase and TargetScan-based computational mapping. A further 88 genes were identified as potential downstream targets through their c-Myc binding motif.
  
  
  CONCLUSIONS
  c-Myc plays a critical role in maintaining the self-renewal capacity of lung bronchoalveolar stem cells through a combination of miRNA and transcription factor regulatory networks.
authors.affiliation: Division of General Thoracic Surgery, Department of Surgery, Mayo Clinic, Rochester, Minnesota, United States of America.
authors.forename: Jie
authors.initials: J
authors.lastname: Dong
authors.forename: Shari
authors.initials: S
authors.lastname: Sutor
authors.forename: Guoqian
authors.initials: G
authors.lastname: Jiang
authors.forename: Yajun
authors.initials: Y
authors.lastname: Cao
authors.forename: Yan W
authors.initials: YW
authors.lastname: Asmann
authors.forename: Dennis A
authors.initials: DA
authors.lastname: Wigle
mesh_terms: D000818:Animals; D002454:Cell Differentiation / Q000235:genetics*; D049109:Cell Proliferation; D002478:Cells, Cultured; D053595:Embryonic Stem Cells / Q000378:metabolism; D005260:Female; D020869:Gene Expression Profiling; D053263:Gene Regulatory Networks / Q000235:genetics; D007150:Immunohistochemistry; D008297:Male; D051379:Mice; D008813:Mice, Inbred ICR; D035683:MicroRNAs / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D039904:Pluripotent Stem Cells / Q000378:metabolism; D011247:Pregnancy; D016271:Proto-Oncogene Proteins c-myc / Q000235:genetics* / Q000378:metabolism; D011650:Pulmonary Alveoli / Q000166:cytology / Q000378:metabolism; D034622:RNA Interference; D012333:RNA, Messenger / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013234:Stem Cells / Q000166:cytology / Q000378:metabolism*; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: D035683:MicroRNAs; C489428:Myc protein, mouse; D016271:Proto-Oncogene Proteins c-myc; D012333:RNA, Messenger; D014157:Transcription Factors