Transcription-Independent Heritability of Induced Histone Modifications in the Mouse Preimplantation Embryo
Figure 1
Effects of valproic acid (VPA) on developmental progression, morphology and expression of key regulator genes in cultured mouse embryos.
A. Cryopreserved 2-cell Balb/c mouse embryos were thawed and cultured with or without 1 mM sodium valproate (VPA) as shown. Pooled embryos were harvested for CChIP at the times indicated. Photographs show representative examples of embryos at the stages indicated. EM = early morula, LM = late morula, EC = early cavitating blastocyst, EB = early blastocyst, MB = mid-expanded blastocyst, LB = late-expanded blastocyst. Bar = 40 µm. B. Intranuclear distribution of acetylated histone H4 in 8-cell, morula and blastocyst stage embryos treated or untreated with 1 mM VPA at the 8-cell to morula stage. C. Effect of VPA treatment on expression of Cdx2, Nanog and Pou5f1, relative to ActB, in cultured embryos assayed by RTQ-PCR. Cryopreserved 2-cell embryos were grown to the morula (42 h), blastocyst (66 h) or hatching blastocyst (90 h) either untreated (VPA -) or after growth for 18 h in 1 mM VPA from the 8-cell to morula stage (+ VPA). In this series of experiments, embryos were grown for longer than usual (up to 90 h, see text). VPA treatment enhanced expression of Nanog and Pou5f1 at the morula stage (42 h), but this was lost by the blastocyst stage, with a fall of several-fold in transcript levels in both treated and untreated embryos. Cdx2 expression was unaffected by VPA and showed a slight progressive increase as embryos progressed from morula to hatching blastocyst.