title: Genetic compensation induced by deleterious mutations but not gene knockdowns.
abstract: Cells sense their environment and adapt to it by fine-tuning their transcriptome. Wired into this network of gene expression control are mechanisms to compensate for gene dosage. The increasing use of reverse genetics in zebrafish, and other model systems, has revealed profound differences between the phenotypes caused by genetic mutations and those caused by gene knockdowns at many loci, an observation previously reported in mouse and Arabidopsis. To identify the reasons underlying the phenotypic differences between mutants and knockdowns, we generated mutations in zebrafish egfl7, an endothelial extracellular matrix gene of therapeutic interest, as well as in vegfaa. Here we show that egfl7 mutants do not show any obvious phenotypes while animals injected with egfl7 morpholino (morphants) exhibit severe vascular defects. We further observe that egfl7 mutants are less sensitive than their wild-type siblings to Egfl7 knockdown, arguing against residual protein function in the mutants or significant off-target effects of the morpholinos when used at a moderate dose. Comparing egfl7 mutant and morphant proteomes and transcriptomes, we identify a set of proteins and genes that are upregulated in mutants but not in morphants. Among them are extracellular matrix genes that can rescue egfl7 morphants, indicating that they could be compensating for the loss of Egfl7 function in the phenotypically wild-type egfl7 mutants. Moreover, egfl7 CRISPR interference, which obstructs transcript elongation and causes severe vascular defects, does not cause the upregulation of these genes. Similarly, vegfaa mutants but not morphants show an upregulation of vegfab. Taken together, these data reveal the activation of a compensatory network to buffer against deleterious mutations, which was not observed after translational or transcriptional knockdown.
authors.affiliation: Max Planck Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany.
authors.forename: Andrea
authors.initials: A
authors.lastname: Rossi
authors.affiliation: Max Planck Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany.
authors.forename: Zacharias
authors.initials: Z
authors.lastname: Kontarakis
authors.affiliation: Max Planck Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany.
authors.forename: Claudia
authors.initials: C
authors.lastname: Gerri
authors.affiliation: Max Planck Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany.
authors.forename: Hendrik
authors.initials: H
authors.lastname: Nolte
authors.affiliation: Max Planck Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany.
authors.forename: Soraya
authors.initials: S
authors.lastname: Hölper
authors.affiliation: Max Planck Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany.
authors.forename: Marcus
authors.initials: M
authors.lastname: Krüger
authors.affiliation: Max Planck Institute for Heart and Lung Research, 61231 Bad Nauheim, Germany.
authors.forename: Didier Y R
authors.initials: DY
authors.lastname: Stainier
mesh_terms: D000483:Alleles; D000818:Animals; D001921:Brain / Q000378:metabolism / Q000473:pathology; D064113:CRISPR-Cas Systems / Q000235:genetics; D055785:Gene Knockdown Techniques; D007814:Larva / Q000235:genetics; D008562:Membrane Glycoproteins / Q000235:genetics; D060172:Morpholinos / Q000235:genetics; D009154:Mutation / Q000235:genetics*; D010641:Phenotype; D020543:Proteome / Q000032:analysis; D034622:RNA Interference; D013489:Suppression, Genetic / Q000235:genetics*; D059467:Transcriptome / Q000235:genetics; D015854:Up-Regulation / Q000235:genetics*; D042461:Vascular Endothelial Growth Factor A / Q000235:genetics; D015027:Zebrafish / Q000196:embryology / Q000235:genetics* / Q000378:metabolism; D029961:Zebrafish Proteins / Q000235:genetics
chemical_list: C484962:Egfl7 protein, zebrafish; D008562:Membrane Glycoproteins; D060172:Morpholinos; D020543:Proteome; D042461:Vascular Endothelial Growth Factor A; C583604:Vegfaa protein, zebrafish; D029961:Zebrafish Proteins; C030340:elastin microfibril interface located protein