ERK1 and ERK2 MAPK are key regulators of distinct gene sets in zebrafish embryogenesis

Sf Gabby Krens,B Ewa Snaar-Jagalska,Shuning He,Herman P Spaink,Maximiliano Corredor-Adámez

doi:10.1186/1471-2164-9-196

Abstract

BackgroundThe MAPK signaling proteins are involved in many eukaryotic cellular processes and signaling networks. However, specific functions of most of these proteins in vertebrate development remain elusive because of potential redundancies. For instance, the upstream activation pathways for ERK1 and ERK2 are highly similar, and also many of their known downstream targets are common. In contrast, mice and zebrafish studies indicate distinct roles for both ERKs in cellular proliferation, oncogenic transformation and development. A major bottleneck for further studies is that relatively little is known of in vivo downstream signaling specific for these kinases.ResultsMicroarray based gene expression profiling of ERK1 and ERK2 knockdown zebrafish embryos at various stages of early embryogenesis resulted in specific gene expression signature sets that showed pronounced differences in gene ontology analyses. In order to predict functions of these genes, zebrafish specific in silico signaling pathways involved in early embryogenesis were constructed using the GenMAPP program. The obtained transcriptome signatures were analyzed in the BMP, FGF, Nodal and Wnt pathways. Predicted downstream effects of ERK1 and ERK2 knockdown treatments on key pathways responsible for mesendoderm development were confirmed by whole mount in situ hybridization experiments.ConclusionThe gene ontology analyses showed that ERK1 and ERK2 target common and distinct gene sets, confirming the difference in knockdown phenotypes and diverse roles for these kinases during embryogenesis. For ERK1 we identified specific genes involved in dorsal-ventral patterning and subsequent embryonic cell migration. For ERK2 we identified genes involved in cell-migration, mesendoderm differentiation and patterning.The specific function of ERK2 in the initiation, maintenance and patterning of mesoderm and endoderm formation was biologically confirmed.

Highlights

The mitogen activated protein kinase (MAPK) signaling proteins are involved in many eukaryotic cellular processes and signaling networks
For ERK1 knockdown we identified a connection with genes involved in dorsal-ventral patterning and subsequent embryonic cell migration
For ERK2 knockdown we identified a connection with genes involved in mesoderm and endoderm initiation, differentiation and patterning

Summary

Introduction

The MAPK signaling proteins are involved in many eukaryotic cellular processes and signaling networks. A major bottleneck for further studies is that relatively little is known of in vivo downstream signaling specific for these kinases. Despite much effort and their biological and medical importance, still relatively few in vivo downstream targets of these kinases have been identified conclusively, especially when considering the numerous cellular events and signaling networks they are involved in [1]. Most of the target proteins and downstream genes have been identified by in vitro studies using cell culture systems. Specific roles for both ERKs are described for cellular proliferation, as mouse embryos fibroblasts (MEF) isolated from erk1-/mice grew faster than wild type cells. Divergent roles for ERK1 and ERK2 were already shown by the different effect of the knockout studies performed in mice since erk1-/- mice are viable and fertile [5], while erk2-/mice die in utero before embryonic day (E) 8.5 [6]

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