Viruses are ideal vectors to deliver cargo that can manipulate cellular gene expression in vitro and in vivo. Delivery is achieved either via a defined cellular receptor, e.g. adenovirus binds the coxsackie receptor (CAR), or for lentivirus by membrane fusion. Sertoli SK11 cells transfected with plasmid or infected with adenovirus carrying beta-galactosidase Adenovirus is very efficient at infecting cells, and has been used to successfully manipulate testicular Sertoli (SK11) cells in vitro. Previously Sertoli cells had proved intractable to genetic manipulation by conventional means, but are efficiently infected by adenovirus. However, adenovirus remains episomal, it does not integrate into the cellular DNA, and expression levels of the introduced gene/cargo eventually diminishes as cells divide, which renders them unsuitable for long term studies. Lentivirus integrates into the host genome, which makes them an excellent choice for longitudional studies of gene expression. Furthermore, lentiviral host range can be expanded by pseudotyping, which substitutes the viral envelope with an alternative capable of fusing with a wide variety of targets and species. Uterine biopsies transduced with Lentivirus tagged with emGFP and an miRNA targeted against Prokineticin 1 These properties and the ability to transduce dividing and non-dividing cells, and the manipulability of the viral genome have driven us to develop and use lentivirus as vectors to introduce DNA to mark and manipulate gene expression in cells and tissues. The facility is wholly responsible for the customised design of untagged and fluorescently tagged DNA expression constructs encoding cDNAs, short-hairpin RNAs and miRNAs and production of small and bulk and lentivirus vector preparations.