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Fig. 4. Brg1fl/fl:Tie2-Cre+/0 primitive
erythroblasts have embryonic globin deficits. (A-H) Cryosections
from an E9.5 control Brg1fl/fl embryo (A,C,E,G) and a
mutant Brg1fl/fl:Tie2-Cre+/0 embryo (B,D,F,H)
were subjected to in situ hybridization with probes against embryonic and
adult  -globins and embryonic β-globins. Almost all embryonic blood
cells from the control embryo express embryonic -globin  (A),
adult 1/2-globins (C), embryonic β-globin
 y (E) and embryonic βH1-globin (G). In the mutant
embryo, adult 1/2-globin expression is normal (D), but many
embryonic blood cells can be detected that express little or no embryonic
(B), y (F) or βH1 (H), as indicated by the
arrowheads in the respective insets. Scale bars: 40 µm. (I) Mean
percentages of globin-expressing blood cells from multiple serial sections of
two control and two mutant embryos at E9.5, as detected by in situ
hybridization in three independent experiments. Total blood cells counted from
control/mutant sections with each probe were: , 1521/907;
1/2, 1292/635; y; 977/721; and
βH1, 492/818. Errors were calculated as s.e.m. (J) ChIP
assay demonstrating that BRG1 is recruited to the β-globin LCR DNAse I
hypersensitive site 3 (HS3) and the promoter in primitive erythrocytes.
No evidence of BRG1 recruitment is detected at the 1/2
promoter. MW, 100 bp molecular weight standard; Pos, wild-type genomic DNA
served as a positive control for the PCR; Neg, no DNA was amplified as a
negative control; Input, total chromatin, sheared but not immunoprecipitated;
Ac-H3, ChIP material immunoprecipitated with an antibody against pan-acetyl
histone 3 (H3), a mark of an open chromatin structure; BRG1, ChIP material
immunoprecipitated with an antibody against BRG1; Mock, mock
immunoprecipitation in which the sample was not treated with antibody but was
otherwise handled identically to the ChIP samples.
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