ER71 directs mesodermal fate decisions during embryogenesis

Abstract

SUMMARYEr71 mutant embryos are nonviable and lack hematopoietic and endothelial lineages. To further define the functional role for ER71 in cell lineage decisions, we generated genetically modified mouse models. We engineered an Er71-EYFP transgenic mouse model by fusing the 3.9 kb Er71 promoter to the EYFP reporter gene. Using FACS and transcriptional profiling, we examined the EYFP + population of cells in Er71 mutant and wild-type littermates. In the absence of ER71, we observed an increase in the number of EYFP-expressing cells, increased expression of the cardiac molecular program and decreased expression of the hematoendothelial program, as compared with wild-type littermate controls. We also generated a novel Er71-Cre transgenic mouse model using the same 3.9 kb Er71 promoter. Genetic fate-mapping studies revealed that the ER71-expressing cells give rise to the hematopoietic and endothelial lineages in the wild-type background. In the absence of ER71, these cell populations contributed to alternative mesodermal lineages, including the cardiac lineage. To extend these analyses, we used an inducible embryonic stem/embryoid body system and observed that ER71 overexpression repressed cardiogenesis. Together, these studies identify ER71 as a critical regulator of mesodermal fate decisions that acts to specify the hematopoietic and endothelial lineages at the expense of cardiac lineages. This enhances our understanding of the mechanisms that govern mesodermal fate decisions early during embryogenesis.

ER71 specifies Flk-1+ hemangiogenic mesoderm by inhibiting cardiac mesoderm and Wnt signaling

“…Our findings are consistent with recent reports that hematopoietic and endothelial versus cardiogenic output was inversely correlated by the ER71 status. 31,32 This view is also supported by a recent study showing that cardiac mesoderm from mouse and human ES cells can be identified as Flk-1 ϩ PDGFR␣ ϩ . 33 We propose that ER71 promotes Flk-1 ϩ PDGFR␣ Ϫ hemangiogenic mesoderm commitment by inhibiting Flk-1 ϩ PDGFR␣ ϩ cardiogenic mesoderm formation and that ER71-deficient Flk-1 ϩ PDGFR␣ ϩ mesoderm could represent "pure" cardiac progenitors.…”

Sox7Is Regulated by ETV2 During Cardiovascular Development

“…In the zebrafish model system, Etv2 has also been shown to be important for vascular development, initially for EPC specification, and later in hemogenic endothelial cells [49,50]. Genetic fate mapping analysis utilizing an Etv2-cre transgenic mouse model confirmed that ETV2-expressing cells give rise to both hematopoietic and endothelial lineages [45].…”

“…It was previously demonstrated that Etv2 is expressed early during embryogenesis in the endocardial/endothelial lineage and that Etv2-deficient embryos are lethal, lacking endocardial/endothelial and hematopoietic lineages [14,21,23,45]. In the zebrafish model system, Etv2 has also been shown to be important for vascular development, initially for EPC specification, and later in hemogenic endothelial cells [49,50].…”

“…Transcriptome analysis performed on E8.5 Etv2-mutant embryos compared with wild-type littermates revealed decreased expression of Sox-F family transcription factors in the Etv2 mutant embryo [45]. To further assess the temporal relationship between Etv2 and Sox7, gene expression patterns were followed in developing EBs, beginning on day 2 until day 6.…”

“…The effect of SOX7 over-expression on the production of FLK1 + /CDH5 + EPCs was assessed in EBs harvested at day 6 [42,45,47]. Induction of SOX7-MYC for 72 h (day 3-6, Fig.…”