Inflammatory cytokines, goblet cell hyperplasia and altered lung mechanics in Lgl1+/- mice

<p>Abstract</p> <p>Background</p> <p>Neonatal lung injury, a leading cause of morbidity in prematurely born infants, has been associated with arrested alveolar development and is often accompanied by goblet cell hyperplasia. Genes that regulate alveolarization and inflammation are likely to contribute to susceptibility to neonatal lung injury. We previously cloned <it>Lgl1</it>, a developmentally regulated secreted glycoprotein in the lung. In rat, O₂toxicity caused reduced levels of <it>Lgl1</it>, which normalized during recovery. We report here on the generation of an <it>Lgl1 </it>knockout mouse in order to determine whether deficiency of <it>Lgl1 </it>is associated with arrested alveolarization and contributes to neonatal lung injury.</p> <p>Methods</p> <p>An <it>Lgl1 </it>knockout mouse was generated by introduction of a neomycin cassette in exon 2 of the <it>Lgl1 </it>gene. To evaluate the pulmonary phenotype of <it>Lgl1</it>^+/-mice, we assessed lung morphology, <it>Lgl1 </it>RNA and protein, elastin fibers and lung function. We also analyzed tracheal goblet cells, and expression of mucin, interleukin (IL)-4 and IL-13 as markers of inflammation.</p> <p>Results</p> <p>Absence of <it>Lgl1 </it>was lethal prior to lung formation. Postnatal <it>Lgl1</it>^+/-lungs displayed delayed histological maturation, goblet cell hyperplasia, fragmented elastin fibers, and elevated expression of T_H2 cytokines (IL-4 and IL-13). At one month of age, reduced expression of <it>Lgl1 </it>was associated with elevated tropoelastin expression and altered pulmonary mechanics.</p> <p>Conclusion</p> <p>Our findings confirm that <it>Lgl1 </it>is essential for viability and is required for developmental processes that precede lung formation. <it>Lgl1</it>^+/-mice display a complex phenotype characterized by delayed histological maturation, features of inflammation in the post-natal period and altered lung mechanics at maturity. <it>Lgl1 </it>haploinsufficiency may contribute to lung disease in prematurity and to increased risk for late-onset respiratory disease.</p

Transcription profiling of lung adenocarcinomas of c-myc-transgenic mice: Identification of the c-myc regulatory gene network

<p>Abstract</p> <p>Background</p> <p>The transcriptional regulator c-Myc is the most frequently deregulated oncogene in human tumors. Targeted overexpression of this gene in mice results in distinct types of lung adenocarcinomas. By using microarray technology, alterations in the expression of genes were captured based on a female transgenic mouse model in which, indeed, c-Myc overexpression in alveolar epithelium results in the development of bronchiolo-alveolar carcinoma (BAC) and papillary adenocarcinoma (PLAC). In this study, we analyzed exclusively the promoters of induced genes by different in silico methods in order to elucidate the c-Myc transcriptional regulatory network.</p> <p>Results</p> <p>We analyzed the promoters of 361 transcriptionally induced genes with respect to c-Myc binding sites and found 110 putative binding sites in 94 promoters. Furthermore, we analyzed the flanking sequences (+/- 100 bp) around the 110 c-Myc binding sites and found Ap2, Zf5, Zic3, and E2f binding sites to be overrepresented in these regions. Then, we analyzed the promoters of 361 induced genes with respect to binding sites of other transcription factors (TFs) which were upregulated by c-Myc overexpression. We identified at least one binding site of at least one of these TFs in 220 promoters, thus elucidating a potential transcription factor network. The analysis correlated well with the significant overexpression of the TFs Atf2, Foxf1a, Smad4, Sox4, Sp3 and Stat5a. Finally, we analyzed promoters of regulated genes which where apparently not regulated by c-Myc or other c-Myc targeted TFs and identified overrepresented Oct1, Mzf1, Ppargamma, Plzf, Ets, and HmgIY binding sites when compared against control promoter background.</p> <p>Conclusion</p> <p>Our in silico data suggest a model of a transcriptional regulatory network in which different TFs act in concert upon c-Myc overexpression. We determined molecular rules for transcriptional regulation to explain, in part, the carcinogenic effect seen in mice overexpressing the c-Myc oncogene.</p