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Jade J Dyson1, Fatima Abbasi1, Prajakta Varadkar1
1FDA Center for Biologics Evaluation and Research Silver Spring Maryland USA.
Abstract:
Protein phosphatase 2A (PP2A) is a heterotrimeric phosphatase that controls a wide range of cellular functions. The catalytic activity and intracellular location of PP2A are modulated by its association with regulatory B subunits, including B56 proteins, which are encoded by five separate genes in humans and mice. The specific effects of each B56 protein on PP2A activity and function are largely unknown. As part of an effort to identify specific PP2A-B56 functions, we created knockout strains of B56β, B56δ, and B56ε using CRISPR/Cas9n. We found that none of the individual B56 genes are essential for mouse survival. However, mice that have both B56δ and B56γ inactivated (B56δγ-), arrest fetal development around Day E12. The hearts of B56δγ- mice have a single outflow vessel rather than having both an aorta and a pulmonary artery. Thus, there appears to be strong genetic interaction between B56δ and B56γ, and together they are necessary for heart development. Of note, both these proteins have been shown to localize to the nucleus and have the most related peptide sequences of the B56 family members. Our results suggest there are B56 subfamilies, which work in conjunction to regulate specific PP2A functions.
Insights
Protein phosphatase 2A (PP2A) regulates cellular functions via B56 subunits. Inactivating B56δ and B56γ together is essential for mouse heart development, revealing functional B56 protein subfamilies.
Area of Science:
- Molecular Biology
- Developmental Biology
- Genetics
Background:
- Protein phosphatase 2A (PP2A) is a crucial enzyme controlling diverse cellular processes.
- PP2A's activity and localization are modulated by regulatory B subunits, including the B56 family.
- The specific roles of individual B56 proteins in PP2A function remain largely uncharacterized.
Purpose of the Study:
- To investigate the specific functions of PP2A-B56 protein interactions.
- To generate and analyze knockout mouse models for key B56 subunits.
Main Methods:
- CRISPR/Cas9n gene editing was employed to create knockout mouse strains for B56β, B56δ, and B56ε.
- Phenotypic analysis of individual and combined B56 gene knockouts was performed.
Main Results:
- Individual B56 gene knockouts did not result in essential lethality.
- Combined inactivation of B56δ and B56γ (B56δγ-) led to embryonic lethality around Day E12.
- B56δγ- mouse embryos exhibited severe cardiac defects, including a single outflow vessel instead of distinct aorta and pulmonary artery.
Conclusions:
- B56δ and B56γ subunits exhibit a critical genetic interaction essential for normal mouse heart development.
- These findings suggest the existence of functional B56 subfamilies within the PP2A regulatory network.
- Specific B56 protein combinations are necessary for regulating distinct PP2A-dependent cellular functions.
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