The Enhancer of split transcription factor Her8a is a novel dimerisation partner for Her3 that controls anterior hindbrain neurogenesis in zebrafish
- Equal contributors
1 Zebrafish Neurogenetics Department, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstr. 1, D-85764 Neuherberg, Germany
2 Department of Protein Science, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstaedter Landstr. 1; D-85764 Neuherberg, Germany
3 Division of Experimental Ophthalmology and Medical Proteome Center, Center of Ophthalmology, University of Tübingen, D-72076 Tübingen, Germany
4 Zebrafish Neurogenetics Group, Laboratory of Neurobiology and Development (N&D), CNRS UPR 3294, Institute of Neurobiology Alfred Fessard, Avenue de la Terrasse, Building 5, F-91198-Gif-sur-Yvette, France
5 Max Planck Institute for Psychiatry, Kraepelinstr. 2-10, 80804, Munich, Germany
6 Institute for Developmental Genetics, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstr.1, D-85764 Neuherberg, Germany
7 Genetics and Neurobiology of C. elegans, INSERM U1024, Institute of Biology of the Ecole Normale Supérieure, 46 rue d'Ulm, F-75005 Paris, France
8 Roche Diagnostics GmbH, Nonnenwald 2, D-82377 Penzberg, Germany
9 Eppendorf Instrumente GmbH, Barkhausenweg 1, 22339, Hamburg, Germany
10 Zebrafish Neurogenetics Group, Laboratory of Neurobiology and Development (N&D), CNRS UPR 3294, Institute of Neurobiology Alfred Fessard, Avenue de la Terrasse, Building 5, F-91198 Gif-sur-Yvette, France
BMC Developmental Biology 2011, 11:27 doi:10.1186/1471-213X-11-27Published: 17 May 2011
Neurogenesis control and the prevention of premature differentiation in the vertebrate embryo are crucial processes, allowing the formation of late-born cell types and ensuring the correct shape and cytoarchitecture of the brain. Members of the Hairy/Enhancer of Split (Hairy/E(spl)) family of bHLH-Orange transcription factors, such as zebrafish Her3, 5, 9 and 11, are implicated in the local inhibition of neurogenesis to maintain progenitor pools within the early neural plate. To better understand how these factors exert their inhibitory function, we aimed to isolate some of their functional interactors.
We used a yeast two-hybrid screen with Her5 as bait and recovered a novel zebrafish Hairy/E(spl) factor - Her8a. Using phylogenetic and synteny analyses, we demonstrate that her8a evolved from an ancient duplicate of Hes6 that was recently lost in the mammalian lineage. We show that her8a is expressed across the mid- and anterior hindbrain from the start of segmentation. Through knockdown and misexpression experiments, we demonstrate that Her8a is a negative regulator of neurogenesis and plays an essential role in generating progenitor pools within rhombomeres 2 and 4 - a role resembling that of Her3. Her8a co-purifies with Her3, suggesting that Her8a-Her3 heterodimers may be relevant in this domain of the neural plate, where both proteins are co-expressed. Finally, we demonstrate that her8a expression is independent of Notch signaling at the early neural plate stage but that SoxB factors play a role in its expression, linking patterning information to neurogenesis control. Overall, the regulation and function of Her8a differ strikingly from those of its closest relative in other vertebrates - the Hes6-like proteins.
Our results characterize the phylogeny, expression and functional interactions involving a new Her factor, Her8a, and highlight the complex interplay of E(spl) proteins that generates the neurogenesis pattern of the zebrafish early neural plate.