Role of hepatocyte nuclear factor-3α and hepatocyte nuclear factor-3β in Clara cell secretory protein gene expression in the bronchiolar epithelium

Abstract

The 5' flanking region of the Clara cell secretory protein (CCSP) gene contains two cis-acting elements which bind hepatocyte nuclear factor (HNF)-3 alpha and HNF-3 beta in vitro. To determine the role of these proteins in mediating CCSP gene expression in the bronchiolar epithelium, chimeric CCSP-reporter gene constructs containing various regions of the CCSP 5' flanking region were co-transfected into H-441 cells with HNF-3 alpha or HNF-3 beta expression plasmids. These studies indicate that each of these transcription factors positively regulates CCSP gene expression and revealed that CCSP region I (-132 to -76) is sufficient to mediate this effect. Gel-mobility-shift assays with oligonucleotides corresponding to CCSP region I, nuclear extract from bronchiolar epithelial cells and HNF-3-specific antibodies indicate that HNF-3 alpha and HNF-3 beta are the only proteins in bronchiolar epithelial cells which directly interact with this region. Consistent with these observations, HNF-3 alpha and HNF-3 beta transcripts were found to be enriched in this cell population and in situ hybridization of adult lung revealed HNF-3 gene expression in non-ciliated bronchiolar epithelial cells expressing the CCSP gene. Finally, experiments with CCSP region I and a heterologous promoter indicate that this region acts in a promoter-specific context, suggesting that additional factors interacting via the minimal CCSP promoter region are essential in determining the effects of HNF-3 on cell-specific CCSP gene expression in the bronchiolar epithelium.

Compensatory Roles of Foxa1 and Foxa2 during Lung Morphogenesis

“…Expression of epithelial cell markers, including SP-A, SP-B, and CCSP, was decreased, but their expression was not entirely dependent on Foxa2 (21). In contrast, immunostaining for the epithelial cell differentiation markers, SP-B, SP-C, CCSP, and Foxj1 was absent in the relatively immature columnar and cuboidal cells lining the enlarged tubules in the (21,52,53). A number of genes that are expressed in the lung are regulated by both Foxa1 and Foxa2, including Sftpb (51), Scgbla1 (52,53), lysozyme M, and lysozyme P (54).…”

“…In contrast, immunostaining for the epithelial cell differentiation markers, SP-B, SP-C, CCSP, and Foxj1 was absent in the relatively immature columnar and cuboidal cells lining the enlarged tubules in the (21,52,53). A number of genes that are expressed in the lung are regulated by both Foxa1 and Foxa2, including Sftpb (51), Scgbla1 (52,53), lysozyme M, and lysozyme P (54). However, the distinct phenotypes in Foxa1 Ϫ/Ϫ and Foxa2 ⌬/⌬ mice (21-23) and the distinct expression patterns of Foxa1 and Foxa2 in many organs (13) suggest that Foxa1 and Foxa2 may also differentially regulate gene expression during embryogenesis and lung development.…”

Foxa2 regulates alveolarization and goblet cell hyperplasia

“…Because FOXA2 influences the transcription of the Titf1, Sftpb, and Scgb1a1 genes in vitro (Bingle and Gitlin, 1993;Bingle et al, 1995;Bohinski et al, 1994;Ikeda et al, 1996), S1-nuclease protection assays were utilized to quantitate mRNA encoding surfactant protein A (SP-A), SP-B, SP-C and Clara cell secretory protein (CCSP) at E17.5. When SP-C-rtTA compound mice were maintained on doxycycline from E0 to E17.5-18, mRNAs encoding CCSP, SP-A and SP-B were decreased significantly (data not shown).…”

“…After birth, FOXA2 is detected in subsets of conducting airway cells and in type II epithelial cells in the alveoli of mice and humans (Stahlman et al, 1998;Zhou et al, 1996). Functional analyses of the regulatory regions of several lung-specific genes have demonstrated a role of Foxa2 in regulating the transcription of several genes that play important roles in lung morphogenesis and homeostasis, including Titf1 (Ikeda et al, 1996), Sftpb (which encodes SP-B) (Bohinski et al, 1994) and Scgblal (Bingle and Gitlin, 1993;Bingle et al, 1995).…”

The Winged Helix Transcriptional Activator HFH-3 Is Expressed in the Distal Tubules of Embryonic and Adult Mouse Kidney

“…Because transcription factors play a central role in regulating cellular differentiation, the analysis of their molecular structure and expression patterns has facilitated elucidation of regulatory pathways involved in establishing tissue-specific gene transcription. In combination with other cell-specific transcription factors, the hepatocyte nuclear factor-3␣ (HNF-3␣) 1 and -3␤ proteins regulate cell-specific transcription in hepatocytes (4) and in respiratory (5)(6)(7)(8) and intestinal epithelium (9). The HNF-3/fork head homolog (HFH) proteins are an extensive family of transcription factors that share homology in the winged helix DNA binding domain (10).…”