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CUL-4A is critical for early embryonic development
Binghui Li1, Joseph C Ruiz, Kristin T Chun
1Department of Pediatric, Herman B Wells Center for Pediatric Research, Indiana University School of Medicine, 1044 W Walnut Street, Indianapolis, IN 46202, USA.
Abstract:
Ubiquitin-mediated degradation targets cell cycle regulators for proteolysis. Much of the ubiquitin pathway's substrate specificity is conferred by E3 ubiquitin ligases, and cullins are core components of some E3s. CUL-4A encodes one of six mammalian cullins and is amplified and/or overexpressed in breast cancer, which suggests a role in regulating cell cycle progression. To examine CUL-4A's physiologic function, we generated a CUL-4A deletion mutation in mice. No viable CUL-4A(-/-) pups and no homozygous mutant embryos as early as 7.5 days postcoitum (dpc) were recovered. However, CUL-4A(-/-) blastocysts are viable, hatch, form an inner cell mass and trophectoderm, and implant (roughly 4.5 dpc), indicating that CUL-4A(-/-) embryos die between 4.5 and 7.5 dpc. Despite 87% similarity between the Cul-4A and Cul-4B cullins, the CUL-4A(-/-) lethal phenotype indicates that CUL-4A has one or more distinct function(s). Surprisingly, 44% fewer heterozygous pups were recovered than expected by Mendelian genetics, indicating that many heterozygous embryos also die during gestation due to haploinsufficiency. Taken together, our findings indicate that appropriate CUL-4A expression is critical for early embryonic development.
Insights
Cullin-4A (CUL-4A) is essential for early embryonic development in mice. Loss of CUL-4A causes embryonic lethality, highlighting its critical role in cell cycle regulation and development.
Area of Science:
- Cell Biology
- Developmental Biology
- Genetics
Background:
- Ubiquitin-mediated degradation regulates cell cycle progression via E3 ubiquitin ligases.
- Cullins are core components of E3 ubiquitin ligases, with CUL-4A being one of six mammalian cullins.
- CUL-4A amplification/overexpression in breast cancer suggests a role in cell cycle regulation.
Purpose of the Study:
- To investigate the physiological function of CUL-4A in early embryonic development.
- To determine the consequences of CUL-4A loss-of-function in a mammalian model system.
Main Methods:
- Generation of CUL-4A deletion mutant mice.
- Analysis of embryonic development in CUL-4A knockout and heterozygous embryos.
- Assessment of embryonic viability and developmental stages.
Main Results:
- No viable CUL-4A(-/-) pups or homozygous mutant embryos were recovered beyond 7.5 days postcoitum.
- CUL-4A(-/-) blastocysts were viable and implanted, but embryos died between 4.5 and 7.5 days postcoitum.
- Haploinsufficiency was observed, with significantly fewer heterozygous pups recovered than expected, indicating embryonic lethality.
Conclusions:
- CUL-4A plays a critical and indispensable role in early embryonic development.
- The lethal phenotype of CUL-4A(-/-) embryos underscores its distinct functions, despite similarity to CUL-4B.
- Appropriate CUL-4A expression levels are crucial for successful embryonic development, with haploinsufficiency also proving detrimental.