The Dual-Specificity Protein Phosphatase DUSP9/MKP-4 Is Essential for Placental Function but Is Not Required for Normal Embryonic Development

Abstract

To elucidate the physiological role(s) of DUSP9 (dual-specificity phosphatase 9), also known as MKP-4 (mitogen-activated protein kinase [MAPK] phosphatase 4), the gene was deleted in mice. Crossing male chimeras with wild-type females resulted in heterozygous (DUSP9^+/−) females. However, when these animals were crossed with wild-type (DUSP9^+/y) males none of the progeny carried the targeted DUSP9 allele, indicating that both female heterozygous and male null (DUSP9^−/y) animals die in utero. The DUSP9 gene is on the X chromosome, and this pattern of embryonic lethality is consistent with the selective inactivation of the paternal X chromosome in the extraembryonic tissues of the mouse, suggesting that DUSP9/MKP4 performs an essential function during placental development. Examination of embryos between 8 and 10.5 days postcoitum confirmed that lethality was due to a failure of labyrinth development, and this correlates exactly with the normal expression pattern of DUSP9/MKP-4 in the trophoblast giant cells and labyrinth of the placenta. Finally, when the placental defect was rescued, male null (DUSP9^−/y) embryos developed to term, appeared normal, and were fertile. Our results indicate that DUSP9/MKP-4 is essential for placental organogenesis but is otherwise dispensable for mammalian embryonic development and highlights the critical role of dual-specificity MAPK phosphatases in the regulation of developmental outcomes in vertebrates.

SUPPLEMENTAL MATERIAL

Supplemental material for this article may be found at http://mcb.asm.org/.

ACKNOWLEDGMENTS

We acknowledge Iain Goldsmith for oligonucleotide synthesis, Andy Cassidy for DNA sequencing, Janet Macdonald and Sara Chalk for technical assistance, Stewart Macpherson (Department of Pathology, Ninewells Hospital, Dundee) for tissue processing and wax embedding, and George Thomson (Department of Surgical and Molecular Oncology, Ninewells Hospital, Dundee) for cutting tissue sections. We also thank Austin Smith (Institute for Stem Cell Research, University of Edinburgh) for providing the en2A-IRESβgeoPA cassette, Stewart Fleming (Division of Pathology and Neuroscience, Ninewells Hospital, Dundee) for valuable advice on tissue morphology, Colin Henderson and Leslie Dickmann for assistance with microscopy, and Maria Karlsson for preparing the illustrations and figures.

This work was supported by Cancer Research UK.