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, Hypersen sitive sites (HS) located 3' of the IgH, HS1-4, has been suggested to act a s a locus control region (LCR) in cell lines, To assess the proposed role o f HS1-4 acting as an LCR, we generated transgenic mice harboring a V-H prom oter-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 independe nt but not copy number dependent. Thus, additional sequences are required t o,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 l ineage cells.