Although Arf is broadly known as a tumor suppressor gene, it also is essential for mouse eye development. Mice lacking Arf are born blind with a severe developmental eye disease, mimicking a human eye disease known as Persistent Hyperplastic Primary Vitreous. Very little is known about basic mechanisms that control Arf transcription or the expression of its gene product, p19Arf. One of my overall goals is to use elucidate the fundamental mechanisms driving the expression of this important gene. The existing dogma holds that Arf functions as an """"""""oncogene sensor"""""""" such that its expression is induced in cells carrying abnormal or excessive proliferation signals from oncogene activation. Mechanisms by which an individual cell can discriminate between an oncogenic stimulus and an equally intense, normal proliferation signal - such as that occurring during development - are not at all clear. Recently, though, members of my laboratory and I made a surprising discovering challenging the current paradigm. Specifically, while exploring mechanisms by which p19Arf prevented primary vitreous hyperplasia in the developing mouse, we showed that its promoter is activated in an exquisitely controlled pattern during mouse development. This finding allows me to safely conclude that Arf control must extend beyond the cell intrinsic signals provided by oncogene activation. Working from our new findings that part of the Tgf22 -/- phenotype resembles that in the absence of Arf, I have established the Transforming Growth Factor 2-2 (Tgf22) as an essential regulator of p19Arf and that the latter is required for the anti-mitogenic effects of Tgf22 in vivo and in vitro. In this proposal, I will take advantage of existing mouse and cell culture models to close three critical gaps in my knowledge: Does Tgf2 directly control p19Arf expression during eye development? What are the essential intracellular signals emanating from Tgf22? What are the fundamental mechanisms acting at the Arf promoter? Studying this pathway from Tgf22 to p19Arf will deepen our understanding of how the two proteins operate in the developing eye, and better define the genetic abnormalities that can contribute to human diseases characterized by hyperplasia in the vitreous. From a broader perspective, though, this potentially sheds new light on how Arf may be controlled in cancer cells and how Tgf2s may carry out other functions during development.
The Arf gene plays an essential role to prevent primary vitreous hyperplasia and hyaloid vascular regression, processes that are critical for normal vision. We have previously defined its temporally- and spatially-restricted expression in the developing eye, but the mechanisms underlying this expression pattern are totally unknown. My Preliminary Studies in this proposal provide the first insight: Tgf22 plays a key role in the process. Experiments in this proposal define will define the cellular and molecular mechanisms by which Tgf22 accomplishes this.
|Iqbal, Nida S; Devitt, Caitlin C; Sung, Caroline Y et al. (2016) p19(Arf) limits primary vitreous cell proliferation driven by PDGF-B. Exp Eye Res 145:224-9|
|Iqbal, Nida S; Xu, Lin; Devitt, Caitlin C et al. (2014) Isolation and characterization of mammalian cells expressing the Arf promoter during eye development. Biotechniques 56:239-49|
|Iqbal, Nida; Mei, Jie; Liu, Jing et al. (2014) miR-34a is essential for p19(Arf)-driven cell cycle arrest. Cell Cycle 13:792-800|
|Mary-Sinclair, Michelle N; Wang, Xiaofei; Swanson, Douglas J et al. (2014) Varied manifestations of persistent hyperplastic primary vitreous with graded somatic mosaic deletion of a single gene. Mol Vis 20:215-30|
|Zheng, Yanbin; Devitt, Caitlin; Liu, Jing et al. (2013) A distant, cis-acting enhancer drives induction of Arf by TgfÎ² in the developing eye. Dev Biol 380:49-57|
|Zheng, Yanbin; Devitt, Caitlin; Liu, Jing et al. (2013) Arf induction by TgfÎ² is influenced by Sp1 and C/ebpÎ² in opposing directions. PLoS One 8:e70371|
|Widau, Ryan C; Zheng, Yanbin; Sung, Caroline Y et al. (2012) p19Arf represses platelet-derived growth factor receptor Ã½Ã½ by transcriptional and posttranscriptional mechanisms. Mol Cell Biol 32:4270-82|
|Zheng, Yanbin; Zhao, Yi D; Gibbons, Melissa et al. (2010) Tgfbeta signaling directly induces Arf promoter remodeling by a mechanism involving Smads 2/3 and p38 MAPK. J Biol Chem 285:35654-64|