OTD/OTX2 functional equivalence depends on 5′ and 3′ UTR-mediated control ofOtx2mRNA for nucleo-cytoplasmic export and epiblast-restricted translation
Author:
Acampora Dario12, Boyl Pietro Pilo1, Signore Massimo1, Martinez-Barbera Juan Pedro1, Ilengo Cristina3, Puelles Eduardo1, Annino Alessandro2, Reichert Heinrich4, Corte Giorgio35, Simeone Antonio12
Affiliation:
1. MRC Centre for Developmental Neurobiology, King’s College London, Guy’s Campus, New Hunts House, London SE1 9RT, UK 2. International Institute of Genetics and Biophysics, CNR, Via G. Marconi 12, 80125 Naples, Italy 3. IST-National Institute for Cancer Research, 4. Institute of Zoology, University of Basel, Rheinsprung 9, CH-4051 Basel, Switzerland 5. Dipartimento di Oncologia Clinica e Sperimentale, Università di Genova, Largo Benzi, 16132 Genova, Italy
Abstract
How gene activity is translated into phenotype and how it can modify morphogenetic pathways is of central importance when studying the evolution of regulatory control mechanisms. Previous studies in mouse have suggested that, despite the homeodomain-restricted homology, Drosophila orthodenticle (otd) and murine Otx1 genes share functional equivalence and that translation of Otx2 mRNA in epiblast and neuroectoderm might require a cell type-specific post-transcriptional control depending on its 5′ and 3′ untranslated sequences (UTRs).In order to study whether OTD is functionally equivalent to OTX2 and whether synthesis of OTD in epiblast is molecularly dependent on the post-transcriptional control of Otx2 mRNA, we generated a first mouse model (otd2) in which an Otx2 region including 213 bp of the 5′ UTR, exons, introns and the 3′ UTR was replaced by an otd cDNA and a second mutant (otd2FL) replacing only exons and introns of Otx2 with the otd coding sequence fused to intact 5′ and 3′ UTRs of Otx2.otd2 and otd2FL mRNAs were properly transcribed under the Otx2 transcriptional control, but mRNA translation in epiblast and neuroectoderm occurred only in otd2FL mutants. Phenotypic analysis revealed that visceral endoderm (VE)-restricted translation of otd2 mRNA was sufficient to rescue Otx2 requirement for early anterior patterning and proper gastrulation but it failed to maintain forebrain and midbrain identity.Importantly, epiblast and neuroectoderm translation of otd2FL mRNA rescued maintenance of anterior patterning as it did in a third mouse model replacing, as in otd2FL, exons and introns of Otx2 with an Otx2 cDNA (Otx22c). The molecular analysis has revealed that Otx2 5′ and 3′ UTR sequences, deleted in the otd2 mRNA, are required for nucleo-cytoplasmic export and epiblast-restricted translation. Indeed, these molecular impairments were completely rescued in otd2FL and Otx22c mutants. These data provide novel in vivo evidence supporting the concept that during evolution pre-existing gene functions have been recruited into new developmental pathways by modifying their regulatory control.
Publisher
The Company of Biologists
Subject
Developmental Biology,Molecular Biology
Reference48 articles.
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