Figure 2

A BAC-based strategy to assess the requirement of highly conserved non-coding regions (HMCO1-3) for Grem1 expression in mouse limb buds. (A) A 250 kb BAC spanning the genomic region from Fmn1 exon 19 to 150 kb up-stream of the Grem1 transcription is able to drive expression of a LacZ transgene (blue arrow; inserted in-frame into the Grem1 ORF) into the posterior limb bud mesenchyme in transgenic founder embryos. (B) Deletion of the HMCO1 core region (520 bp) abolishes the LacZ expression. (C, D) Deletion of the core HMCO2 region (1279 bp) results in reduced LacZ expression, while deletion of HMCO3 (924 bp) does not alter the LacZ distribution. ß-galactosidase activity colours expressing cells blue.