Characterization and comparison of the human and mouse dist1l α-globin complex reveals a tightly packed multiple gene cluster containing differentially expressed transcription units

In this paper, we describe the detailed analysis of about 75 kb of genomic DNA flanking the 5′ end of the mouse α-globin region and complete the transcription map of the human region. Previously, we established the homology of the human and mouse α-globin upstream flanking regions (αUFR) and characterized in detail the mouse α-globin major regulatory element (αMRE) and the mMPG DNA repair gene. Here, we extend our analysis with the construction of a detailed restriction map, the mapping and isolation of two nonglobin genes, named mDist1 and mProx1, the distribution of 18 DNase hypersensitive sites (HSSs) in erythroid and fibroblast cells, and the analysis of the mDist1, mMPG, and mProx1 expression levels in several adult tissues and during fetal development. In addition, the hDist1 gene is exactly localized 1.9 kb from the hMPG gene. The mapping results show that the Dist1, MPG, and Prox1 genes, together with the α-globin genes and the αMRE, form a tightly packed multiple gene cluster that is 50% more compact in mouse than in human. The expression results show that each of the genes present in this locus displays a characteristic expression pattern in adult tissues and during fetal development. The 18 DNase HSSs observed were scattered over this region. Interestingly, all the erythroid-sensitive HSSs were associated with the Prox1 transcription unit, whereas the only two pairs of fibroblast-sensitive HSSs present in this locus were located in the promoter regions of the mProx1 and mDist1/mMPG genes. The possible role of the erythroid- and fibroblastsensitive sites in the regulation of the mouse α-globin and nonglobin gene expression is discussed. The characterization of the mouse αUFR identifies most, if not all, of the structural elements possibly involved in the regulation of mα-globin gene expression and sheds light on the organization and evolution of the telomere-associated, GC-rich isochore family H3