Expression of homeobox genes in a proximal tubular cell line derived from adult mice

Abstract

We have been studying the expression of several homeobox genes in cultures of proximal tubular epithelium (MCT cells) harvested from adult mus musculus. Hox genes 2.1, 2.3, and 3.3, in particular, are all expressed at low levels in resting MCT cells. The expression of Hox 2.1 and 3.3 were not influenced by mitogenic (epidermal growth factor: EGF, and platelet-derived growth factor: PDGF) nor by hypertrophogenic cytokines (angiotensin II: Ang II) in serum-free media. Transcripts for Hox 2.3, however, were elevated in MCT cells by Ang II. EGF, and serum treatment, as early as 30 minutes after their addition, whereas no change, or slight reductions were observed with transforming growth factor beta (TGF beta), PDGF, and gamma-interferon (gamma IFN). Hox 2.3 was also super-induced by serum, in the presence of cycloheximide, in cells rested previously in serum-free media, suggesting that new protein synthesis was not required for expressive augmentation. The induction of Hox 2.3, moreover, was not specific for tubular epithelium, since the gene could be activated in tubulointerstitial fibroblasts after treatment with EGF. These experiments collectively represent a first report regarding the characterization of transcripts encoding homeoboxes in adult cells derived from renal tissue. The putative DNA-binding properties of homeobox proteins in general, the prompt and rapid induction of Hox 2.3 by morphogenic cytokines in tubulointerstitial cells, and the observed effect of cycloheximide on this gene, all indicate that Hox 2.3 might have a role in the general activation of mature somatic cells, as an immediate early event. probably in the capacity of a nuclear trans-acting factor.

Angiotensin II as a Morphogenic Cytokine Stimulating Renal Fibrogenesis

“…19 Although there are similarities between EGF and Ang II in the induction of immediate early genes, EGF stimulates mitogenesis whereas Ang II induces hypertrophy in these proximal tubular cells. 127 These early findings provide evidence of a potential interaction between Ang II and EGF-mediated signaling, and Chen and colleagues recently found evidence for a role of heparin-binding EGF (HB-EGF) in Ang II-induced tubular hypertrophy. 128 Axel Ulrich's group discovered a pathway in 1996 for how G-protein coupled receptors such as the AT1R could phosphorylate and activate the EGFR.…”

Angiotensin II-induced hypertrophy of cultured murine proximal tubular cells is mediated by endogenous transforming growth factor-beta.

“…To corroborate the stimulation of TGF-f, mRNA by ANG II, we used semi-quantitative cDNA amplification as a sensitive method to assess the level of TGF-,B transcripts and the time-course of the ANG II-induced stimulation (29,30). cDNA was synthesized from 10 Mg of total RNA using 0.7 Mg of poly-d(T) primer (Pharmacia-LKB, Freiburg, Germany) with 500 U of Moloney murine leukemia virus reverse transcriptase diluted in 50…”

“…The GeneAMP kit (Perkin Elmer Cetus, Ueberlingen, Germany) was used for all amplification reactions. Reactions were performed exactly as described before (29,30) dNTP and 2.5 U of Taq polymerase in the supplied amplification buffer (20 mM Tris-HCl, pH 8.3, 25 mM KC1, 2.0 mM MgCl2, and 0.05% Tween 20). 40 cycles with an annealing temperature of 550C for 1.5 min, an extension step at 720C for 2 min, and a denaturing temperature of 920C for 1 min were performed.…”

“…A normalization quotient between TGF-l,1 and GAPDH was calculated as described previously (29)(30)(31) ( 12,15). Since TGF-fI is a well-known inhibitor of cellular proliferation in epithelial cells including MCT cells ( 10, 33), we wondered whether ANG II-induced endogenous production of TGF-3 may be responsible for this inhibition of mitogenesis.…”

Homobox Genes Mediates the Biological Functions of Human Chorionic Gonadotropin (hCG) in Human Breast Epithelial Cells

“…Despite extensive literature on the role in embryonic and fetal development, HOX gene expression in adult cells has been reported only recently in a few tissues, including kidney, intestine, testis, colon, and the mouse mammary gland [20,21,22,23]. Our study provides evidence for the first time Free probe remodeling and in reestablishing ductal branching [22]. The transduction of H0XB7 has been shown to induce bFGF expression and alter growth characteristic of human breast cancer cells [23].…”