Abnormal Heart Development and Lung Remodeling in Mice Lacking the Hypoxia-Inducible Factor-Related Basic Helix-Loop-Helix PAS Protein NEPAS

Abstract

Hypoxia-inducible factors (HIFs) are crucial for oxygen homeostasis during both embryonic development and postnatal life. Here we show that a novel HIF family basic helix-loop-helix (bHLH) PAS (Per-Arnt-Sim) protein, which is expressed predominantly during embryonic and neonatal stages and thereby designated NEPAS (neonatal and embryonic PAS), acts as a negative regulator of HIF-mediated gene expression. NEPAS mRNA is derived from the HIF-3α gene by alternative splicing, replacing the first exon of HIF-3α with that of inhibitory PAS. NEPAS can dimerize with Arnt and exhibits only low levels of transcriptional activity, similar to that of HIF-3α. NEPAS suppressed reporter gene expression driven by HIF-1α and HIF-2α. By generating mice with a targeted disruption of the NEPAS/HIF-3α locus, we found that homozygous mutant mice (NEPAS/HIF-3α^−/−) were viable but displayed enlargement of the right ventricle and impaired lung remodeling. The expression of endothelin 1 and platelet-derived growth factor β was increased in the lung endothelial cells of NEPAS/HIF-3α-null mice. These results demonstrate a novel regulatory mechanism in which the activities of HIF-1α and HIF-2α are negatively regulated by NEPAS in endothelial cells, which is pertinent to lung and heart development during the embryonic and neonatal stages.

ACKNOWLEDGMENTS

We thank Mitsuyasu Kato for helpful discussion and Tania O'Connor for critical reading of the manuscript. We also thank Naomi Kaneko for technical assistance.

This work was supported in part by grants from the JST-ERATO Environmental Response Project (M.Y.); the Ministry of Education, Science, Sports and Culture (M.Y.); JST-SORST (Y.F.-K.); and the Swedish Research Council and Heart-Lung Foundation (L.P.).