Massively parallel sequencing identifies the gene Megf8 with ENU-induced mutation causing heterotaxy

• Published in: Proceedings of the National Academy of Sciences - PNAS Vol. 106; no. 9; pp. 3219 - 3224
• Main Authors: Zhang, Zhen, Alpert, Deanne, Francis, Richard, Chatterjee, Bishwanath, Yu, Qing, Tansey, Terry, Sabol, Steven L, Cui, Cheng, Bai, Yongli, Koriabine, Maxim, Yoshinaga, Yuko, Cheng, Jan-Fang, Chen, Feng, Martin, Joel, Schackwitz, Wendy, Gunn, Teresa M, Kramer, Kenneth L, De Jong, Pieter J, Pennacchio, Len A, Lo, Cecilia W
• Format: Journal Article
• Language: English
• Published: United States National Academy of Sciences 03.03.2009; National Acad Sciences
• Subjects: Active Transport, Cell Nucleus; Amino Acid Sequence; Amino acids; Animals; Antibodies; Base Sequence; Biological Sciences; Body Patterning; Cells, Cultured; Chromosomes; Danio rerio; DNA; Drosophila; Embryo, Nonmammalian - drug effects; Embryo, Nonmammalian - embryology; Embryo, Nonmammalian - metabolism; Embryos; Ethylnitrosourea - pharmacology; Gene Expression Regulation, Developmental - drug effects; Genes; Genetic mutation; Genetic screening; Genomes; Genomics; Humans; In situ hybridization; Insects; Membrane Proteins - chemistry; Membrane Proteins - genetics; Membrane Proteins - metabolism; Molecular Sequence Data; Mutation; Mutation - genetics; Nodal Protein - metabolism; Phenotypes; Proteins; Rodents; Sequence Alignment; Sequencing; Signal Transduction; Studies; Zebrafish - embryology; Zebrafish - genetics; Zebrafish - metabolism; Zebrafish Proteins - chemistry; Zebrafish Proteins - genetics; Zebrafish Proteins - metabolism
• ISSN: 0027-8424; 1091-6490
• DOI: 10.1073/pnas.0813400106

Forward genetic screens with ENU (N-ethyl-N-nitrosourea) mutagenesis can facilitate gene discovery, but mutation identification is often difficult. We present the first study in which an ENU- induced mutation was identified by massively parallel DNA sequencing. This mutation causes heterotaxy and complex congenital heart defects and was mapped to a 2.2-Mb interval on mouse chromosome 7. Massively parallel sequencing of the entire 2.2-Mb interval identified 2 single-base substitutions, one in an intergenic region and a second causing replacement of a highly conserved cysteine with arginine (C193R) in the gene Megf8. Megf8 is evolutionarily conserved from human to fruit fly, and is observed to be ubiquitously expressed. Morpholino knockdown of Megf8 in zebrafish embryos resulted in a high incidence of heterotaxy, indicating a conserved role in laterality specification. Megf8C¹⁹³R mouse mutants show normal breaking of symmetry at the node, but Nodal signaling failed to be propagated to the left lateral plate mesoderm. Videomicroscopy showed nodal cilia motility, which is required for left-right patterning, is unaffected. Although this protein is predicted to have receptor function based on its amino acid sequence, surprisingly confocal imaging showed it is translocated into the nucleus, where it is colocalized with Gfi1b and Baf60C, two proteins involved in chromatin remodeling. Overall, through the recovery of an ENU-induced mutation, we uncovered Megf8 as an essential regulator of left-right patterning.