Laura Attardi

Research/Lab website:   http://www.stanford.edu/group/attardi/

The p53 tumor suppressor gene plays a crucial role in protecting organisms from developing cancer. Our research is aimed at dissecting the mechanism of p53 action and the role of target genes it activates in apoptosis and tumor suppression, using the mouse as a model system. Our strategy is to use combination of biochemical, cell biological, and mouse genetic approaches, starting by generating hypotheses about p53 using primary mouse embryo fibroblasts (MEFs), and then testing them using knockout technology in the mouse. An understanding of p53 function in the mouse will ultimately be useful for understanding how inactivation of p53 in humans leads to cancer and for designing therapies for the many tumors disrupted in the p53 pathway.

Specific projects include:

1) Analysis of PERP, a p53 apoptosis-specific target gene

In a screen to identify genes activated during p53-mediated apoptosis but not G1 arrest, we previously isolated a novel gene known as PERP (P53 apoptosis Effector Related to PMP-22). PERP induction correlates with p53-dependent apoptosis and not p53-independent cell death, and PERP overexpression can induce cell death in p53-deficient MEFs, suggesting that it could be a downstream mediator of p53 function in apoptosis. PERP displays sequence similarity to PMP-22/gas3 (Peripheral Myelin Protein 22/growth arrest specific 3), a tetraspan membrane protein that is commonly mutated in human hereditary peripheral neuropathies (i.e. Charcot Marie Tooth), and that appears to function in part by regulating cell proliferation and apoptosis. We are currently characterizing PERP and its encoded protein in two ways. We are constructing a PERP conditional knockout mouse to examine the function of PERP in development and tumorigenesis. We are also dissecting the mechanism by which overexpression of PERP induces cell death. PERP is a multipass transmembrane protein that could act potentially either as a signalling molecule or as an ion channel. The generation and analysis of PERP mutants will be helpful for determining how PERP exerts its effects on known steps of the apoptotic process, thus defining a link between p53 and the execution of apoptosis.

2) Characterization of additional targets of p53 in apoptosis

Another research direction will to be to identify and characterize other components of the p53-activated cell death pathway. A comprehensive search for additional p53 apoptosis-specific target genes will be carried out by the hybridization of G1-arrested and apoptotic MEF RNA populations to DNA microarrays. Genes upregulated in apoptotic cells will be characterized similarly to PERP, first in vitro, by cell biological and biochemical approaches to identify those that are most interesting, and then ultimately in vivo by gene targeting approaches.

3) Generation of p53 knock-in mice and cells