These results demonstrate efficient delivery of intact, large (up to 157 kb) DNA constructs for in vitro gene expression and in vivo gene therapy applications.

Background: BAC clones containing entire mammalian genes including all the transcribed region and long range controlling elements are very useful for functional analysis. Sequenced BACs are available for most of the human and mouse genomes and in many cases these contain intact genes. However, large genes often span more than one BAC, and single BACs covering the entire region of interest are not available. Here we describe a system for linking two or more overlapping BACs into a single clone by homologous recombination.

No abstract

The use of genomic DNA rather than cDNA or mini-gene constructs in gene therapy might be advantageous as these contain intronic and long-range control elements vital for accurate expression. For gene therapy of cystic fibrosis though, no bacterial artificial chromosome (BAC), containing the whole CFTR gene is available. We have used Red homologous recombination to add a to a previously described vector to construct a new BAC vector with a 250.3-kb insert containing the whole coding region of the CFTR gene along with 40.1 kb of DNA 5′ to the gene and 25 kb 3′ to the gene. This includes all the known control elements of the gene. We evaluated expression by RT-PCR in CMT-93 cells and showed that the gene is expressed both from integrated copies of the BAC and also from episomes carrying the oriP/EBNA-1 element. Sequencing of the human CFTR mRNA from one clone showed that the BAC is functional and can generate correctly spliced mRNA in the mouse background. The BAC described here is the only CFTR genomic construct available on a convenient vector that can be readily used for gene expression studies or in vivo studies to test its potential application in gene therapy for cystic fibrosis.