Absence of beta-actin during primitive erythropoiesis correlates with reduced Gata2 expression levels in the yolk sac.

<p>(A) Relative E8.5 yolk sac mRNA levels measured by qRT-PCR of <i>Gata1</i>, <i>Gata2</i>, Hbb-y, Hbb-bh1, Hba and Hbb. We found a 90% decrease of <i>Gata2</i> expression level in <i>Actb−/−</i> embryos versus <i>Actb+/+</i> embryos. (B) Relative E8.5 yolk sac mRNA levels measured by qRT-PCR of <i>Gata2</i> target genes: <i>Runx1</i>, Tal1/Scl, <i>c-kit</i> and <i>EpoR</i>. <i>c-kit</i> and <i>EpoR</i> show 50% reduced expression levels in <i>Actb−/−</i> embryos versus <i>Actb+/+</i> embryos. (C) <i>Gata2</i> immunohistochemistry on E9.5 yolk sac sections. <i>Gata2</i> expression was detected only in the endoderm of the yolk sac (white arrows). No difference in <i>Gata2</i> expression could be seen between <i>Actb−/−</i> embryos and <i>Actb+/+</i> embryos. 60× magnification. (D) Relative E8.5 and E10.25 yolk sac mRNA levels measured by qRT-PCR of Vegf. At E10.25, we could demonstrate a 50% increase of Vegf mRNA expression. Error bars represent mean ±SEM; *P<.05. Immunofluorescence sections were imaged using an Olympus IX81 confocal microscope with Fluoview FV10 software.