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MEF2C orthologues from zebrafish: evolution, expression and promoter regulation

Publication . Adrião, Andreia Lúcia Gonçalves; Conceição, Natércia; Cancela, Leonor

MEF2C is a crucial transcription factor for cranial neural crest cells development. An abnormal expression of this protein leads to severe abnormalities in craniofacial features. Recently, a human disease (MRD20) was described as a consequence of MEF2C haploinsufficiency. These patients show severe developmental delay, intellectual disability and dysmorphic features. Zebrafish presents two MEF2C orthologues, mef2ca and mef2cb. In this study we demonstrate a highly conserved pattern of chromosome localization for MEF2C between human and zebrafish, a similar protein sequence and tissue expression profile. We have focused our functional analysis on the zebrafish orthologue mef2cb. We identified three new exons through 5' RACE and described two new transcriptional start sites (TSS). These alternative TSS reflect the occurrence of two alternative promoters differentially regulated by nuclear factors related to craniofacial or neuronal development such as Sox9b, Sox10 and Runx2. We also predict that mef2cb gene may be post transcriptionally regulated by analysing the structure of its 5' UTR region, conserved throughout evolution. Our study provides new insights in MEF2C conservation and provides the first evidence of mef2cb regulation by both transcriptional and post transcriptional mechanisms, thus contributing to validate zebrafish as a good model for future studies concerning MEF2C dependent pathologies. (c) 2015 Elsevier Inc. All rights reserved.

2016-02Journal article

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MEF2C: expression, regulation and interaction with target genes in health and diseases

Publication . Adrião, Andreia Lúcia Gonçalves; Cancela, Leonor; Grazina, Manuela; Conceição, Natércia

MEF2C is the first MEF2 family factor to be expressed during embryonic development. Zebrafish has been proven to be an excellent model for human genetic diseases and has two MEF2C orthologues, mef2ca and mef2cb. The involvement of MEF2C in different developmental processes was studied in zebrafish through expression analysis and usage of mutant lines as loss of function models. Alterations in this gene were related to cardiac defects and its haploinsufficiency was linked to a human disease (MRD20) whose patients show abnormal neuronal and craniofacial development. Recently this gene was reported to be involved in dementia conditions such as Alzheimer disease, Parkinson disease and amyotrophic lateral sclerosis. Our work aims to further validate zebrafish as an animal model to study MEF2C related pathologies focusing on craniofacial and neuronal issues. Our in silico analysis demonstrated a high conservation of mef2c pattern of chromosome localization, protein structure and sites of mRNA expression throughout evolution. We also identified two transcriptional start sites for mef2cb that were conserved through evolution. These are related to the occurrence of alternative promoters that appear to be differentially regulated by Sox9b, Sox10 and Runx2, three nuclear factors associated to craniofacial or neuronal development. Through the use of Mef2ca and Mef2cb loss of function mutant lines, we described the craniofacial phenotype resulting from the absence of both mef2c isoforms in zebrafish. We concluded that both orthologues are involved in cartilage, bone and brain development in zebrafish and we described the molecular profile of specific marker genes resulting from mef2c loss of function. Our results allow us to consider zebrafish as a valuable animal model for analysis concerning MEF2C related pathologies. To complement our work we performed a pilot study in which we describe for the first time an alteration in MEF2C gene in a patient with frontotemporal lobar degeneration, suggesting an association between MEF2C and this disease, a result that extends the involvement of this gene to a previously unsuspected human pathology.

2015-12-10Doctoral thesis

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