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Microbead Implantation in the Zebrafish Embryo
Published on: July 30, 2015
Protein turnover downstream of the Nipbl/CRL4 axis contributes to abnormal development in zebrafish embryos
Annie C Sanchez1, Niusha Banoukh1, Fiona Mensching1
1Department of Biological Sciences, Lehigh University, Bethlehem, Pennsylvania, USA.
Background:
Mutations in cohesins cause cohesinopathies such as Cornelia de Lange Syndrome (CdLS) and Roberts Syndrome (RBS). Prior findings demonstrate that Esco2 (a cohesin activator) and Smc3 (a core cohesin subunit) regulate the CRL4 E3 ubiquitin ligase. SMC3 mutations, however, account for a small percentage of CdLS. Here, we test whether NIPBL, which when mutated is responsible for 65% of CdLS cases, also regulates CRL4.
Results:
We report that Nipbl knockdown in zebrafish embryos produces developmental abnormalities and reduces the transcription of ddb1, which encodes a key component of CRL4 E3 ligase. The severity of phenotypes in Nipbl knockdown embryos is partially rescued by exogenous ddb1 mRNA, demonstrating that CRL4 ligase function is downstream of Nipbl. These findings suggest that aberrant accumulation of CRL4 ligase substrates contributes to developmental abnormalities. To test this model, we identified candidate CRL4 substrates in zebrafish embryos by LC-MS. The results reveal that elevated expression of one of these candidates, pparαa, is sufficient to produce developmental defects in zebrafish embryos.
Conclusions:
Nipbl impacts CRL4 ligase activity via regulation of ddb1 expression. We provide evidence that the aberrant accumulation of substrates is sufficient to produce developmental abnormalities consistent with those observed in RBS and CdLS models.
Insights
NIPBL regulates the CRL4 E3 ligase by controlling ddb1 expression, impacting cohesinopathies like Cornelia de Lange Syndrome. Aberrant substrate accumulation causes developmental abnormalities.
Area of Science:
- Genetics
- Molecular Biology
- Developmental Biology
Background:
- Cohesinopathies, including Cornelia de Lange Syndrome (CdLS) and Roberts Syndrome (RBS), arise from mutations in cohesins.
- Esco2 and Smc3 are known regulators of the CRL4 E3 ubiquitin ligase.
- SMC3 mutations are infrequent in CdLS, prompting investigation into other key genes like NIPBL.
Purpose of the Study:
- To investigate whether NIPBL, a gene frequently mutated in CdLS, also regulates the CRL4 E3 ubiquitin ligase.
- To elucidate the mechanism by which NIPBL influences CRL4 ligase activity and its downstream consequences.
Main Methods:
- Zebrafish embryos were used to study the effects of Nipbl knockdown.
- Quantitative analysis of ddb1 transcription was performed.
- Rescue experiments with exogenous ddb1 mRNA were conducted.
- Liquid chromatography-mass spectrometry (LC-MS) was employed to identify CRL4 substrates.
Main Results:
- Nipbl knockdown in zebrafish caused developmental abnormalities and reduced ddb1 transcription.
- Exogenous ddb1 mRNA partially rescued the phenotypes, confirming CRL4 ligase function downstream of Nipbl.
- Elevated expression of the identified CRL4 substrate candidate, pparαa, was sufficient to induce developmental defects.
Conclusions:
- Nipbl regulates CRL4 ligase activity through modulation of ddb1 expression.
- Aberrant accumulation of CRL4 substrates contributes to developmental abnormalities seen in cohesinopathies.
- These findings provide a mechanistic link between NIPBL function and CRL4 ligase activity in the context of CdLS and RBS.
