Disruption of spatiotemporal hypoxic signaling causes congenital heart disease in mice
Xuejun Yuan, … , Yonggang Zhou, Thomas Braun
Xuejun Yuan, … , Yonggang Zhou, Thomas Braun
Published April 24, 2017
Citation Information: J Clin Invest. 2017;127(6):2235-2248. https://doi.org/10.1172/JCI88725.
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Research Article Cardiology Stem cells

Disruption of spatiotemporal hypoxic signaling causes congenital heart disease in mice

Abstract

Congenital heart disease (CHD) represents the most prevalent inborn anomaly. Only a minority of CHD cases are attributed to genetic causes, suggesting a major role of environmental factors. Nonphysiological hypoxia during early pregnancy induces CHD, but the underlying reasons are unknown. Here, we have demonstrated that cells in the mouse heart tube are hypoxic, while cardiac progenitor cells (CPCs) expressing islet 1 (ISL1) in the secondary heart field (SHF) are normoxic. In ISL1+ CPCs, induction of hypoxic responses caused CHD by repressing Isl1 and activating NK2 homeobox 5 (Nkx2.5), resulting in decreased cell proliferation and enhanced cardiomyocyte specification. We found that HIF1α formed a complex with the Notch effector hes family bHLH transcription factor 1 (HES1) and the protein deacetylase sirtuin 1 (SIRT1) at the Isl1 gene. This complex repressed Isl1 in the hypoxic heart tube or following induction of ectopic hypoxic responses. Subsequently, reduced Isl1 expression abrogated ISL1-dependent recruitment of histone deacetylases HDAC1/5, inhibiting Nkx2.5 expression. Inactivation of Sirt1 in ISL1+ CPCs blocked Isl1 suppression via the HIF1α/HES1/SIRT1 complex and prevented CHDs induced by pathological hypoxia. Our results indicate that spatial differences in oxygenation of the developing heart serve as signals to control CPC expansion and cardiac morphogenesis. We propose that physiological hypoxia coordinates homeostasis of CPCs, providing mechanistic explanations for some nongenetic causes of CHD.

Authors

Xuejun Yuan, Hui Qi, Xiang Li, Fan Wu, Jian Fang, Eva Bober, Gergana Dobreva, Yonggang Zhou, Thomas Braun

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Figure 5

Inactivation of Sirt1 in ISL1+ cells enhances Isl1 expression and promotes proliferation of ISL1+ cells after induction of hypoxia responses.

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Inactivation of Sirt1 in ISL1+ cells enhances Isl1 expression and promot...
(A) Whole-mount immunostaining of E9.5 control and Sirt1 mutant embryos for NKX2.5 and ISL1 with and without chemical induction of hypoxia responses (30 mg/kg body weight CoCl2 treatment). The pale green staining in the head and tail is due to unspecific autofluorescence. Neural tube (arrows with small arrowheads), cardiac mesoderm (arrows with big arrowheads), and heart tubes (arrowheads) are indicated. Embryos with or without chemical induction of hypoxia responses were obtained from 3 different litters. Scale bars: 100 μm. (B) Representative images of sections from control and Sirt1 mutant E9.5 embryos following whole-mount immunostaining for ISL1 and NKX2.5 with and without chemical induction of hypoxia responses (15 mg/kg body weight CoCl2 treatment). Embryos with (Sirt1fl/+ Isl1-Cre–: n = 2 Sirt1fl/– Isl1-Cre+: n = 3) or without (Sirt1fl/+ Isl1-Cre–: n = 5; Sirt1fl/– Isl1-Cre+: n = 2) chemical induction of hypoxia responses were obtained from 2 different litters. Note reduced ISL1 levels in the cardiac mesoderm (white arrows) in control, but not in Sirt1fl/– Isl1-Cre+, littermates after chemical induction of hypoxia responses. Scale bars: 200 μm. (C) Quantification of ISL1+ cell proliferation by pH3 immunostaining in control (–CoCl2: n = 4; +CoCl2: n = 5) and Sirt1fl/– Isl1-Cre+ E9.0 embryos (n = 3) after chemical induction of hypoxia responses. Note that inactivation of Sirt1 in the SHF rescues reduced proliferation of ISL1+ cells. *P < 0.05; **P < 0.01, ANOVA with Dunnett’s post hoc correction.