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

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 4

Inactivation of Sirt1 in ISL1+ cells increases the number of ISL1+ cells and rescues hypoxia-induced CHDs.

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Inactivation of Sirt1 in ISL1+ cells increases the number of ISL1+ cells...
(A) FACS analysis of ISL1+ cells and their derivatives in E9.5 embryonic hearts (20–24 somites) after Sirt1 inactivation. *P < 0.05, t test (n = 3). (B) Quantification of ISL1+NKX2.5+ cells in the cardiac mesoderm by immunostaining of E9.5 embryos (20–24 somites). ***P < 0.001, t test (n = 3). (C) H&E staining of E15.5 hearts of control (Sirt1 WT), Sirt1fl/+ Isl1-Cre+ (Sirt1 hypomorphic), and Sirt1fl/– Isl1-Cre+ (Sirt1 mutant) embryos after chemical induction of hypoxia responses (15 mg CoCl2/kg body weight) at E7.5. Note the rescue of CHDs in Sirt1fl/– Isl1-Cre–, Sirt1fl/+ Isl1-Cre+, and Sirt1fl/– Isl1-Cre+ embryos compared with controls. Twenty-seven embryos from 4 litters, including 8 Sirt1fl/– Isl1-Cre+ embryos, were analyzed. Numbers of specific CHDs are listed in Supplemental Table 2. Scale bars: 200 μm. (D) Whole-mount views of E9.5 embryos (upper panels) and E15.5 embryonic hearts (lower panels) without and with chemical induction of hypoxia responses (30 mg CoCl2/kg body weight). For each time point, 1 litter was analyzed. Numbers of analyzed embryos for each condition are indicated in the figure. Representative images are shown. Inactivation of Sirt1 in the SHF ameliorates CHDs. OFT, outflow tract. Scale bars: 100 μm. (E) H&E staining of severe cardiac malformations in control, but not in Sirt1fl/– Isl1-Cre+, embryos at E15.5 after chemical induction of hypoxia responses (30 mg CoCl2/kg body weight). Arrows point to individual cardiac defects named in the figure. Scale bars: 100 μm.