Details of the region around the −^ZFbreakpoints.

The positions of the Alu elements orientated toward (Up) or away from (Down) the telomere are shown. Below this, tandem repeats, other repeats, and DNaseI HS and CpG islands (labeled F-L) are shown. The ζ, α, and θ1genes are transcribed toward the centromere, and the gene16PHQG;16 is transcribed toward the telomere. The α−^ZF deletion is shown as a black bar below the chromosome. Genomic mapping localized its 5′ breakpoint between an HpaI site (at coordinate 164 012) and a SacI site (at coordinate 164 356), beyond the polyA addition site of the α2-globin gene. Pulsed field gel electrophoresis of a Not1 α-specific fragment, approximately 380 kb, indicated that the deletion extends for approximately 18 kb (data not shown). The 3′ breakpoint was localized between a BglII site (coordinate 180 096) and a BamHI site (coordinate 182 417). Forward 280 and reverse 279 primers were designed from the breakpoint regions, and a 928-bp fragment spanning the breakpoint was amplified (data not shown) in the propositus (Z.F.) and his mother (H.F.). DNA sequence analysis demonstrated that the breakpoints lie between coordinates 164 044-45 and 182 395-96 and arose via an illegitimate recombination event (sequence available on request). Five previously described deletions that remove overlapping segments of this region are denoted a-e14; none of these silence α gene expression, although deletion a, −α^3.7, only removes 1 α gene. Cosmids described in the text are shown at the bottom of the figure. The black box attached to cDH2 represents the α-globin regulatory element (HS –40).