Pluripotency
We have shown that Cited2 is essential for mouse embryonic stem cell (ESC) self-renewal, proliferation and survival. We also demonstrated that Cited2 binds directly to Nanog, Tbx3 and Klf4 promoters in undifferentiated ESC, and controls the expression of these genes. Thus, Cited2 interacts with transcription factors that form the core of the gene regulatory network that sustains pluripotency. We are interested in understanding the molecular mechanisms that depend on the correct Cited2 function to sustain ESC stemness.
Protein stability and stem cells
We identified the FBXL5 protein, an E3 ubiquitin ligase that regulates intracellular iron homeostasis, as a CITED2 interacting protein. Overexpression of FBXL5 triggers the degradation of CITED2 in a proteasome-dependent manner, thereby giving access to transcriptional co-activators p300 and CBP to transcription factors such as HIF-1. We are studying the role played by FBXL5 in stem cell biology.
Reprogramming
We obtained results that indicate that Cited2 is important for the reprogramming of mouse embryonic fibroblasts into induced pluripotent stem cells (iPSC) by expression of Oct4, Sox2, Klf4 and Myc. We also demonstrated that overexpression of Cited2 in combination with Oct4, Sox2, Klf4 and Myc increases the efficiency of reprogramming of primary embryonic fibroblasts and led to obtaining iPSCs with less variability in the expression of genes associated with pluripotency, particularly in fibroblasts that are pre-senescent. We are investigating the potential benefits of using CITED2 to obtain iPSC from human somatic cells.
Differentiation of stem cells
Embryonic Stem Cells (ESC) differentiation events involve molecular mechanisms and signaling pathways similar to those required for the early processes of embryonic development. Cited2, a transcriptional modulator, is essential for embryonic mouse heart development, and variations in the human CITED2 gene sequence have been associated with congenital heart disease. We are using ESC to better understand the mechanisms involved in the onset of normal heart development and heart disease. We have recently shown that Cited2 associates and cooperates with the Isl1 transcription factor, which is essential for cardiogenesis.
Molecules secreted by embryonic stem cells compensate for defects in embryonic development
Failure of cardiac differentiation of Embryonic Stem Cells (ESC) due to decreased expression or loss of function of Cited2 can be compensated for by introducing molecules secreted into the culture medium by ESCs that overexpress Cited2. These molecules also rescue embryonic death and cardiovascular defects in zebrafish embryos with loss of Cited2 function.