RESUMO
Zfp423/OAZ, a multi-zinc finger protein, is proposed to participate in neuronal differentiation through interactions with the Olf/EBF (O/E) family of transcription factors and mediate extrinsic BMP signaling pathways. These activities are associated with distinct domains of the Olf/EBF-associated zinc finger (OAZ) protein. Sustained OAZ expression arrests olfactory sensory neurons (OSNs) at an immature state and alters olfactory receptor expression, but the mechanism remains elusive. We show here that constitutive expression of a C-terminal mutant OAZ (OAZΔC) in mice that selectively disrupts OAZ-O/E interaction while retaining other activities, exhibits apparently normal OSN differentiation. Additionally, interfering with potential BMP signaling pathways by inducible Follistatin expression in adult mice does not alter the neuronal lineage or differentiation status. Our results indicate that O/E-mediated processes are essential for the differentiation of OSNs and the establishment of a mature phenotype. BMP signaling pathways, if they are active in normal adult olfactory epithelium, may play a minor role in this tissue.
Assuntos
Fatores de Transcrição Hélice-Alça-Hélice Básicos/fisiologia , Proteínas de Ligação a DNA/genética , Neurogênese/genética , Neurônios Receptores Olfatórios/citologia , Mutação Puntual , Receptores Odorantes/fisiologia , Fatores de Transcrição/genética , Transcrição Gênica , Dedos de Zinco/genética , Animais , Proteínas Morfogenéticas Ósseas/fisiologia , Linhagem da Célula , Proteínas de Ligação a DNA/química , Proteínas de Ligação a DNA/fisiologia , Folistatina/biossíntese , Folistatina/genética , Folistatina/fisiologia , Regulação da Expressão Gênica no Desenvolvimento , Genes Reporter , Sequências Hélice-Alça-Hélice , Camundongos , Camundongos Endogâmicos C57BL , Mucosa Olfatória/citologia , Neurônios Receptores Olfatórios/metabolismo , Fenótipo , Ligação Proteica , Mapeamento de Interação de Proteínas , Estrutura Terciária de Proteína , Receptores Odorantes/genética , Proteínas Recombinantes de Fusão/fisiologia , Transdução de Sinais/fisiologia , Relação Estrutura-Atividade , Fatores de Transcrição/química , Fatores de Transcrição/fisiologia , Dedos de Zinco/fisiologiaRESUMO
The worldwide epidemic of obesity has increased the urgency to develop a deeper understanding of physiological systems related to energy balance and energy storage, including the mechanisms controlling the development of fat cells (adipocytes). The differentiation of committed preadipocytes to adipocytes is controlled by PPARgamma and several other transcription factors, but the molecular basis for preadipocyte determination is not understood. Using a new method for the quantitative analysis of transcriptional components, we identified the zinc-finger protein Zfp423 as a factor enriched in preadipose versus non-preadipose fibroblasts. Ectopic expression of Zfp423 in non-adipogenic NIH 3T3 fibroblasts robustly activates expression of Pparg in undifferentiated cells and permits cells to undergo adipocyte differentiation under permissive conditions. Short hairpin RNA (shRNA)-mediated reduction of Zfp423 expression in 3T3-L1 cells blunts preadipocyte Pparg expression and diminishes the ability of these cells to differentiate. Furthermore, both brown and white adipocyte differentiation is markedly impaired in Zfp423-deficient mouse embryos. Zfp423 regulates Pparg expression, in part, through amplification of the BMP signalling pathway, an effect dependent on the SMAD-binding capacity of Zfp423. This study identifies Zfp423 as a transcriptional regulator of preadipocyte determination.