Hypoxia-inducible factor-dependent histone deacetylase activity determines stem cell fate in the placenta

Abstract

Hypoxia-inducible factor (HIF) is a heterodimeric transcription factor composed of HIFα and the arylhydrocarbon receptor nuclear translocator(ARNT/HIF1β). Previously, we have reported that ARNT function is required for murine placental development. Here, we used cultured trophoblast stem (TS)cells to investigate the molecular basis of this requirement. In vitro, wild-type TS cell differentiation is largely restricted to spongiotrophoblasts and giant cells. Interestingly, Arnt-null TS cells differentiated into chorionic trophoblasts and syncytiotrophoblasts, as demonstrated by their expression of Tfeb, glial cells missing 1 (Gcm1) and the HIV receptor CXCR4. During this process, a region of the differentiating Arnt-null TS cells underwent granzyme B-mediated apoptosis,suggesting a role for this pathway in murine syncytiotrophoblast turnover. Surprisingly, HIF1α and HIF2α were induced during TS cell differentiation in 20% O2; additionally, pVHL levels were modulated during the same time period. These results suggest that oxygen-independent HIF functions are crucial to this differentiation process. As histone deacetylase(HDAC) activity has been linked to HIF-dependent gene expression, we investigated whether ARNT deficiency affects this epigenetic regulator. Interestingly, Arnt-null TS cells had reduced HDAC activity,increased global histone acetylation, and altered class II HDAC subcellular localization. In wild-type TS cells, inhibition of HDAC activity recapitulated the Arnt-null phenotype, suggesting that crosstalk between the HIFs and the HDACs is required for normal trophoblast differentiation. Thus, the HIFs play important roles in modulating the developmental plasticity of stem cells by integrating physiological, transcriptional and epigenetic inputs.

p45NF-E2 represses Gcm1 in trophoblast cells to regulate syncytium formation, placental vascularization and embryonic growth

“…Although it remains unknown whether the thrombocytopenia observed in p45NF-E2-deficient mice is related to altered acetylation, we establish that the placental phenotype and IUGR of p45NF-E2 -/-embryos are mechanistically linked to acetylation-dependent syncytiotrophoblast differentiation. This role of acetylation in trophoblast cells is in agreement with the acetylation-dependent syncytiotrophoblast formation in aryl hydrocarbon receptor nuclear translocator (Arnt, or Hif1)-deficient trophoblast cells in vitro (Maltepe et al, 2005). The activity of HDACs, which are also referred to as lysine deacetylases (KDACs) or protein deacetylases (PDACs), was reduced in the absence of p45NF-E2.…”

“…Syncytiotrophoblast formation was monitored in nearly confluent TS cells differentiated for 6 days. In some cases, TS cells were differentiated in the presence of HDAC inhibitor [100 nM trichostatin A (TSA) or 2.5 mM sodium butyrate] (Maltepe et al, 2005) or HAT inhibitor (30 nM curcumin or 5 M EGCG) (Balasubramanyam et al, 2004;Tachibana et al, 2004). For quantification of syncytiotrophoblast formation, cells were incubated with 2.5 m CellMask Deep Red (Invitrogen) for 5 minutes at 37°C and then fixed for 3 minutes in 3.75% formaldehyde at room temperature.…”

Essential role of B-Raf in ERK activation during extraembryonic development

“…HIF-1␣ stabilization is the rate-limiting event in HIF-1 activation and is strongly induced by low oxygen tension but also, under normoxic conditions, by a variety of growth factors and cytokines (31). Functional HIF-1 is required for mouse placental development, and it has been implicated in murine (32,33) and human trophoblast differentiation (34). In human cytotrophoblasts, inhibition of ERK activation impairs both HIF-1␣ accumulation and VEGF synthesis induced under normoxic conditions by IL-1␤ and TGF-␤ (28,29).…”

Evaluation of Placental Epigenetic Changes due to Morphine Consumption

“…The placenta performs vital functions such as nutrient transport between the circulatory systems of the mother and embryo during intra-uterus growth and development. Normal genesis of the embryo is reliant on constant interactions between transcriptional factors, epigenetic and environmental factors (Esteller & Herman, 2002;Grayson et al, 2005;Maltepe et al, 2005;Simmons et al, 2001). Morphine is a meddlesome factor in normal embryonic development, and the mother's dependency to opiates is a growing concern because of various epigenetic factors including stress.…”