LMO2 expression is predominantly driven by the proximal promoter in hematopoietic cells. (A) Pictorial representation of the human and mouse LMO2 loci, where the coding exons are represented by black boxes and the untranslated regions by white boxes. The 2 alternative promoter regions, transcribing the long (exon 1-6) and short (exons 4 to 6) mRNA variants are indicated by arrows above the exons. The positions of the oligonucleotides used to quantify the transcript isoforms are indicated underneath the loci by short arrows. (B) Expression analysis of the 2 transcript forms by real-time PCR. Total cDNAs were subjected to real-time PCR using primers that amplified either all LMO2 transcripts or only those with the distal noncoding exons. For both human and mouse, the total level of LMO2 in bone marrow, normalized by the level of actin, was assigned a value of 1. The relative abundance of the transcript variants, normalized by the level of actin in those tissues and cell lines, is depicted by ▪ (distal) and ▦ (proximal) plus or minus standard deviation (SD). BM indicates bone marrow; PB, peripheral blood; FL, fetal liver.