Cutting edge:: Ig heavy chain 3′ HS1-4 directs correct spatial position-independent expression of a linked transgene to B lineage cells

The Ig H chain locus is regulated by a set of cis-acting elements, Hypersensitive sites (HS) located 3' of the IgH, HS1-4, has been suggested to act as a locus control region (LCR) in cell lines, To assess the proposed role of HS1-4 acting as an LCR, we generated transgenic mice harboring a V-H promoter-beta-globin reporter gene linked to the Ig H chain HS1-4 3'-regulatory sequences. Transgene expression is strictly confined to B 12-lymphocytes, vith no detectable expression outside the B cell lineage in all transgenic founder lines. Furthermore, reporter gene activity is integration independent but not copy number dependent. Thus, additional sequences are required to,allow the HS1-4 regulatory region to act as a classical LCR in mice. Our data are discussed in the contest of tissue-specific gene expression in B lineage cells.