title: Timeless in lung morphogenesis.
abstract: The Clock gene, timeless, regulates circadian rhythm in Drosophila, but its vertebrate homolog is critical to embryonic development. Timeless was shown to be involved in murine urethral bud branching morphogenesis. We generated a polyclonal antibody to mouse TIMELESS (mTIM) and studied its distribution and its potential role during lung development, which also requires branching morphogenesis. In the early mouse embryo, TIM was localized to all organs, especially the neural epithelium. In embryonic day (E) 9.5 embryos, TIM was present in both epithelial and mesenchymal cells at the onset of lung morphogenesis. In E15 embryos, TIM decreased in the mesenchyme but remained pronounced in the epithelium of both large and small airways. Later, TIM was localized to a specific subset of epithelial cells with alveolar type 2 phenotype. This finding was verified by immunostaining of isolated alveolar type 2 cells. In the proximal airways, TIM was colocalized with CCSP to nonciliated columnar epithelial cells. Antisense oligonucleotides to mTim specifically inhibited branching morphogenesis of embryonic lungs in explant culture without affecting SpC expression an alveolar type 2 cell marker. In cultured lung cells, expression of TIM is independent of cell cycle and proliferation. These studies indicate that the function of Timeless is highly conserved in organs whose formation requires branching morphogenesis.
authors.affiliation: School of Medicine, University of Southern California, Los Angeles, California 90033, USA.
authors.forename: Jing
authors.initials: J
authors.lastname: Xiao
authors.forename: Changgong
authors.initials: C
authors.lastname: Li
authors.forename: Nian-Ling
authors.initials: NL
authors.lastname: Zhu
authors.forename: Zea
authors.initials: Z
authors.lastname: Borok
authors.forename: Parviz
authors.initials: P
authors.lastname: Minoo
mesh_terms: D016475:3T3 Cells; D000818:Animals; D015415:Biomarkers; D018797:Cell Cycle Proteins; D002454:Cell Differentiation; D002940:Circadian Rhythm; D004847:Epithelial Cells / Q000378:metabolism; D018507:Gene Expression Regulation, Developmental; D006367:HeLa Cells; D006801:Humans; D007150:Immunohistochemistry; D047908:Intracellular Signaling Peptides and Proteins; D008168:Lung / Q000166:cytology / Q000187:drug effects / Q000196:embryology*; D008648:Mesoderm / Q000166:cytology / Q000378:metabolism; D051379:Mice / Q000196:embryology; D009024:Morphogenesis; D016376:Oligonucleotides, Antisense / Q000494:pharmacology; D009924:Organ Culture Techniques; D013997:Time Factors; D014157:Transcription Factors / Q000378:metabolism*
chemical_list: D015415:Biomarkers; D018797:Cell Cycle Proteins; D047908:Intracellular Signaling Peptides and Proteins; D016376:Oligonucleotides, Antisense; C509769:TIMELESS protein, human; C509770:Timeless protein, mouse; D014157:Transcription Factors