Related Experiment Video
Updated: Jun 2, 2026
Separation of Mouse Embryonic Facial Ectoderm and Mesenchyme
Published on: April 12, 2013
The molecular and cellular basis of variable craniofacial phenotypes and their genetic rescue in Twisted gastrulation
Charles J Billington1, Brandon Ng, Cynthia Forsman
1Department of Pediatrics, University of Minnesota, Minneapolis, MN 55455-0356, USA.
Abstract:
The severity of numerous developmental abnormalities can vary widely despite shared genetic causes. Mice deficient in Twisted gastrulation (Twsg1(-/-)) display such phenotypic variation, developing a wide range of craniofacial malformations on an isogenic C57BL/6 strain background. To examine the molecular basis for this reduced penetrance and variable expressivity, we used exon microarrays to analyze gene expression in mandibular arches from several distinct, morphologically defined classes of Twsg1(-/-) and wild type (WT) embryos. Hierarchical clustering analysis of transcript levels identified numerous differentially expressed genes, clearly distinguishing severely affected and unaffected Twsg1(-/-) mutants from WT embryos. Several genes that play well-known roles in craniofacial development were upregulated in unaffected Twsg1(-/-) mutant embryos, suggesting that they may compensate for the loss of TWSG1. Imprinted genes were overrepresented among genes that were differentially expressed particularly between affected and unaffected mutants. The most severely affected embryos demonstrated increased p53 signaling and increased expression of its target, Trp53inp1. The frequency of craniofacial defects significantly decreased with a reduction of p53 gene dosage from 44% in Twsg1(-/-)p53(+/+) pups (N=675) to 30% in Twsg1(-/-)p53(+/-) (N=47, p=0.04) and 15% in Twsg1(-/-)p53(-/-) littermates (N=39, p=0.001). In summary, these results demonstrate that phenotypic variability in Twsg1(-/-) mice is associated with differential expression of certain developmentally regulated genes, and that craniofacial defects can be partially rescued by reduced p53 levels. We postulate that variable responses to stress may contribute to variable craniofacial phenotypes by triggering differential expression of genes and variable cellular apoptosis.
Insights
Genetic mutations in mice cause varied craniofacial defects. Gene expression analysis revealed compensatory gene upregulation and identified p53 signaling as a key factor in defect severity, suggesting stress responses influence developmental abnormalities.
Area of Science:
- Developmental Biology
- Genetics
- Molecular Biology
Background:
- Phenotypic variation in developmental abnormalities can occur despite identical genetic causes.
- Mice lacking Twisted gastrulation (Twsg1(-/-)) exhibit variable craniofacial malformations on a consistent genetic background.
Purpose of the Study:
- To investigate the molecular mechanisms underlying the variable expressivity and reduced penetrance of craniofacial defects in Twsg1(-/-) mice.
- To identify specific genes and pathways associated with phenotypic variability.
Main Methods:
- Exon microarrays were employed to compare gene expression profiles in mandibular arches of Twsg1(-/-) and wild-type (WT) embryos.
- Hierarchical clustering was used to identify differentially expressed genes.
- Statistical analysis was performed to assess the impact of p53 gene dosage on craniofacial defect frequency.
Main Results:
- Differential gene expression patterns were identified, distinguishing affected and unaffected Twsg1(-/-) mutants from WT embryos.
- Upregulation of craniofacial development genes was observed in unaffected mutants, suggesting a compensatory role.
- Imprinted genes were overrepresented among differentially expressed genes between mutant groups.
- Increased p53 signaling and Trp53inp1 expression correlated with more severe defects.
- Reducing p53 gene dosage significantly decreased the frequency of craniofacial defects in Twsg1(-/-) mice.
Conclusions:
- Phenotypic variability in Twsg1(-/-) mice is linked to differential expression of developmental genes.
- p53 signaling pathway plays a crucial role in the severity of craniofacial abnormalities.
- Variable cellular apoptosis, potentially triggered by stress responses, may contribute to the observed phenotypic variability.
