6 Retrovirus-mediated Cell Labeling

Abstract

Replication-incompetent recombinant retroviruses allow specific labeling of dividing cells and their progeny. Retrovirus-mediated cell labeling was first applied in the field of neurogenesis to understand the lineage relationship of different cell types and the migration pattern of clonally related cells. The combination of retrovirus vectors and live cell markers enables functional studies of newborn neurons in the adult mammalian brain. In addition, retrovirus vectors can be modified to manipulate the expression of a gene of interest, thus determining its role in the process of neurogenesis. This chapter summarizes our current understanding of neurogenesis based on studies using retrovirus-mediated cell labeling.

A BRIEF INTRODUCTION OF RETROVIRUSES
Retroviruses are (+)-stranded RNA viruses that are characterized by their ability to generate double-stranded DNA (dsDNA) from their RNA genome through reverse transcription. On entry into host cells through the specific interaction between viral surface glycoprotein and host-cell membrane receptor, the retroviral RNA genome is transcribed into a dsDNA in the cytoplasm of the host cell. The newly synthesized dsDNA enters the nucleus, where it integrates into the chromosomal DNA of the host cell and becomes a provirus. Although retroviruses package two copies of RNA genomes in their virions, it is believed that each virion makes a single provirus (Coffin et al. 1997).

Retroviruses have been classified in different ways. They are now divided into three subfamilies: orthoretrovirinae, spumaretrovirinae, and unclassified retroviridae (http://www.ncbi.nlm.nih.gov/Taxonomy/Browser/). There are six genera in the orthoretrovirinae subfamily, including alpharetrovirus, betaretrovirus, gammaretrovirus, deltaretrovirus, episilonretrovirus, and lentivirus, of which the first five were...