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Loss of Apela peptide in mice causes low penetrance embryonic lethality and defects in early mesodermal derivatives

ABSTRACT: Apela (also referred to as Elabela, Ende and Toddler) is a small signaling peptide that activates the G protein-coupled receptor Aplnr. We used CRISPR/Cas9 to generate a null, reporter-expressing allele, in order to study the role of Apela in the developing mouse embryo. We found that loss of Apela results in low penetrance cardiovascular defects that manifest after the onset of circulation. Targeted Apela null alleles exhibited different transcriptional activity depending on the presence or absence of a Neomycin selection cassette. These are referred to as Apela KO NEO-IN and Apela KO NEO-OUT strains, respectively. Despite subtle phenotypic characteristics that were unique to the NEO-OUT mutants, both Apela null strains shared the same variable expressivity of cardiovascular defects and the same penetrance of embryonic lethality. To investigate the earliest regulatory events leading to physical abnormalities in Apela mutants, we performed RNA-Seq on whole stage-matched and morphologically normal E7.5 embryos (3 wild-type, 6 Apela KO NEO-IN, and 6 Apela KO NEO-OUT individuals). We chose this stage because Apela is initially expressed in the embryo at late gastrulation, shortly after the emergence of extraembryonic mesoderm progenitors. Since modification of the Apela locus may influence the expression of neighboring genes, we examined the expression of upstream and downstream sequences and found no significant difference in their expression. Downregulated genes of interest included several mitochondrial genes, Ceacam2, Ulk4, and Mov10l1. Upregulated genes included the vascular endothelial growth factor Vegfc. Principal component analysis identified outliers (KO1 and KO9), both of which expressed lower levels of mesoderm markers. KO9 was further characterized by aberrant upregulation of erythroid and myeloid markers. This finding was confirmed in our study by qRT-PCR analysis of additional Apela null individuals.

ORGANISM(S): Mus musculus

PROVIDER: GSE101748 | GEO | 2017/08/01

SECONDARY ACCESSION(S): PRJNA395343

REPOSITORIES: GEO

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Project description:Delta-like 3 (Dll3) is a divergent ligand and modulator of the Notch signaling pathway only identified so far in mammals. Null mutations of Dll3 disrupt cycling expression of Notch targets Hes1, Hes5, and Lfng, but not of Hes7. Compared with Dll1 or Notch1, the effects of Dll3 mutations are less severe for gene expression in the presomitic mesoderm, yet severe segmentation phenotypes and vertebral defects result in both human and mouse. Reasoning that Dll3 specifically disrupts key regulators of somite cycling, we carried out functional analysis to identify targets accounting for the segmental phenotype. Using microdissected embryonic tissue from somitic and presomitic mesodermal tissue, we identified new genes enriched in these tissues, including Limch1, Rphn2, and A130022J15Rik. Surprisingly, we only identified a small number of genes disrupted by the Dll3 mutation. These include Uncx, a somite gene required for rib and vertebral patterning, and Nrarp, a regulator of Notch/Wnt signaling in zebrafish and a cycling gene in mouse. To determine the effects of Dll3 mutation on Nrarp, we characterized the cycling expression of this gene from early (8.5 dpc) to late (10.5 dpc) somitogenesis. Nrarp displays a distinct pattern of cycling phases when compared to Lfng and Axin2 (a Wnt pathway gene) at 9.5 dpc but appears to be in phase with Lfng by 10.5 dpc. Nrarp cycling appears to require Dll3 but not Lfng modulation. In Dll3 null embryos, Nrarp displayed static patterns. However, in Lfng null embryos, Nrarp appeared static at 8.5 dpc but resumed cycling expression by 9.5 and dynamic expression at 10.5 dpc stages. By contrast, in Wnt3a null embryos, Nrarp expression was completely absent in the presomitic mesoderm. Towards identifying the role of Dll3 in regulating somitogenesis, Nrarp emerges as a potentially important regulator that requires Dll3 but not Lfng for normal function. Experiment Overall Design: To enrich for genes in the presomitic mesoderm that are specifically disrupted by Dll3 mutation, we compared microdissected tissues from wild-type and Dll3 mutant embryos. We generated biological replicate pools from Dll3+/+ (wild-type) or Dll3neo/neo embryos for a total of six pools. Microarray analysis using Affymetrix MOE430A arrays was carried out on the biological pool triplicates for both wild-type and mutant genotypes.

Project description:Delta-like 3 (Dll3) is a divergent ligand and modulator of the Notch signaling pathway only identified so far in mammals. Null mutations of Dll3 disrupt cycling expression of Notch targets Hes1, Hes5, and Lfng, but not of Hes7. Compared with Dll1 or Notch1, the effects of Dll3 mutations are less severe for gene expression in the presomitic mesoderm, yet severe segmentation phenotypes and vertebral defects result in both human and mouse. Reasoning that Dll3 specifically disrupts key regulators of somite cycling, we carried out functional analysis to identify targets accounting for the segmental phenotype. Using microdissected embryonic tissue from somitic and presomitic mesodermal tissue, we identified new genes enriched in these tissues, including Limch1, Rphn2, and A130022J15Rik. Surprisingly, we only identified a small number of genes disrupted by the Dll3 mutation. These include Uncx, a somite gene required for rib and vertebral patterning, and Nrarp, a; regulator of Notch/Wnt signaling in zebrafish and a cycling gene in mouse. To determine the effects of Dll3 mutation on Nrarp, we characterized the cycling expression of this gene from early (8.5 dpc) to late (10.5 dpc) somitogenesis. Nrarp displays a distinct pattern of cycling phases when compared to Lfng and Axin2 (a Wnt pathway gene) at 9.5 dpc but appears to be in phase with Lfng by 10.5 dpc. Nrarp cycling appears to require Dll3 but not Lfng modulation. In Dll3 null embryos, Nrarp displayed static patterns. However, in Lfng null embryos, Nrarp appeared static at 8.5 dpc but resumed cycling expression by 9.5 and dynamic expression at 10.5 dpc stages. By contrast, in Wnt3a null embryos, Nrarp expression was completely absent in the presomitic mesoderm. Towards identifying the role of Dll3 in regulating somitogenesis, Nrarp emerges as a potentially important regulator that requires Dll3 but not Lfng for normal function. Experiment Overall Design: To enrich for genes in the somite level tissues that are specifically disrupted by Dll3 mutation, we compared microdissected tissues from wild-type and Dll3 mutant embryos. We generated biological replicate pools from Dll3+/+ (wild-type) or Dll3neo/neo embryos for a total of six pools. Microarray analysis using Affymetrix MOE430A arrays was carried out on the biological pool triplicates for both wild-type and mutant genotypes.

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Loss of Apela peptide in mice causes low penetrance embryonic lethality and defects in early mesodermal derivatives

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