title: Temporally regulated expression of Lin-28 in diverse tissues of the developing mouse.
abstract: The gene lin-28 was originally identified through a mutant of the nematode Caenorhabditis elegans displaying defects in developmental timing. It is expressed stage-specifically in tissues throughout the animal and is required for cell fates to be expressed at the appropriate stage of larval development. lin-28 encodes a cytoplasmic protein with a unique pairing of RNA-binding motifs. Diverse animals possess Lin-28 homologues and mouse Lin-28 is expressed in embryos, embryonic stem cells and embryonal carcinoma cells, but not in some differentiated cell types. To assess whether mammalian Lin-28 may function as a developmental timing regulator, we examined adult and embryonic tissues of the mouse for its expression. We observed Lin-28 protein in many diverse tissues of the embryo through the period of organogenesis and that it persists in some tissues in the adult. In addition to an overall down-regulation during embryogenesis, in at least two tissues Lin-28 expression shows temporal regulation, as opposed to cell type or tissue-specific regulation: in the developing bronchial epithelium, where it is present in the developing lung and absent in the adult, and in a subset of cells developing along the crypt-villus axis of the intestine. Interestingly, unlike epithelia, cardiac and skeletal muscle continuously express Lin-28, suggesting an ongoing need for its activity there. We also observed that Lin-28 expression is repressed during the retinoic acid-induced differentiation of mouse P19 cells into neuronal cells, suggesting that down-regulation of Lin-28 in some tissues may occur in response to hormonal signals that govern development.
authors.affiliation: Fox Chase Cancer Center, 7701 Burholme Avenue, Philadelphia, PA 19111, USA.
authors.forename: Dong Hua
authors.initials: DH
authors.lastname: Yang
authors.forename: Eric G
authors.initials: EG
authors.lastname: Moss
mesh_terms: D000818:Animals; D045744:Cell Line, Tumor; D015536:Down-Regulation; D007150:Immunohistochemistry; D007700:Kinetics; D051379:Mice / Q000033:anatomy & histology / Q000196:embryology* / Q000378:metabolism; D016601:RNA-Binding Proteins / Q000276:immunology / Q000378:metabolism*
chemical_list: C488352:Lin-28 protein, mouse; D016601:RNA-Binding Proteins