The researchers have combined several gene manipulation techniques and incorporated them into a single lentiviral vector – a gene delivery system partly derived from HIV. When injected into living cells – either in vitro or in vivo – the genetic material aboard the lentiviral vector joins the genetic material in the nucleus of the cell, causing the cell to express the protein encoded by the new gene. This versatile package can also carry bits of RNA that stop the cell from expressing one of its own genes, by way of RNA interference. But the cargo that makes this tool really novel and exciting is a fusion protein that acts as a kind of remote control. By administering an antibiotic, the genetic manipulation – either the transgenic material introduced by the lentivirus, or the gene silencing via RNA interference--can be switched on or off at will.
An all-in-one tool like this – efficiently combining techniques that each previously required separate delivery – will likely see wide use in genetic research and in clinical gene therapy applications. It is particularly applicable for use in stem cells, embryonic cells and tissues and organs that are amenable to genetic transduction.
"It's a flexible way to regulate the expression of genes in a cell," says EPFL professor Didier Trono. "The lentiviral vector integrates in an irreversible fashion into the cell and is then part of its genetic cargo and part of the genetic cargo of all its progeny."
The efficiency of the lentiviral vector will make it easier to create transgenic animals used in studying human genetic diseases such as Parkinson's, Alzheimer's or Huntington's diseases. The expression of the gene can be turned on and off by feeding the animal an antibiotic. Likewise genes that express pathogenic proteins can be conditionally silenced, allowing researchers to study possible new therapeutic approaches.
In cancer research this tool could be used to study gene function in tumor cells and for generating in vivo tumor models for drug screening and delivery.
In another application, dying cells (such as neurons) can be rescued by introducing a gene that expresses a growth factor. Thanks to the remote control carried in the lentivirus the expression of this growth factor can now be turned off when the desired effect is achieved, thus preventing unharnessed growth – otherwise known as cancer.
"It's an extremely polymorphic tool, useful in testing therapies and in preclinical studies," says Trono. "Using it we can control the gene expression in vivo in an extraordinary and sensitive way."
"A Versatile too for conditional gene expression and knockdown", Jolanta Szulc, Maciej Wiznerowicz, Marc-Olivier Sauvain, Didier Trono and Patrick Aebischer; Nature Methods, vol 3 no 2, February 2006.