Development of stable cell lines for production or regulated expression using matrix attachment regions

One of the major hurdles of isolating stable, inducible or constitutive hig h-level producer cell lines is the time-consuming selection procedure. Give n the variation in the expression levels of the same construct in individua l clones, hundreds of clones must be isolated and tested to identify one or more with the desired characteristics. Various boundary elements (BEs), ma trix attachment regions, and locus control regions (LCRs) were screened for their ability to augment the expression of heterologous genes in Chinese h amster ovary (CHO) cells. Of the chromatin elements assayed, the chicken ly sozyme matrix-attachment region (MAR) was the only element to significantly increase stable reporter expression. We found that the use of the MAR incr eases the proportion of high-producing clones. thus reducing the number of clones that need to be screened. These benefits are observed both for const ructs with MARs flanking the transgene expression cassette, as well as when constructs are co-transfected with the MAR on a separate plasmid. Moreover , the MAR was co-transfected with a multicomponent regulatable beta -galact osidase expression system in C2C12 cells and several clones exhibiting regu lated expression were identified. Hence, MARs are useful in the development of stable cell lines for production or regulated expression. (C) 2001 Else vier Science B.V. All rights reserved.