Related Experiment Videos
Essential role of PDK1 in regulating cell size and development in mice
Margaret A Lawlor1, Alfonso Mora, Peter R Ashby
1MRC Protein Phosphorylation Unit, School of Life Sciences, MSI/WTB Complex, University of Dundee, Dow Street, Dundee DD1 5EH, UK. m.a.lawlor@dundee.ac.uk
Abstract:
PDK1 functions as a master kinase, phosphorylating and activating PKB/Akt, S6K and RSK. To learn more about the roles of PDK1, we generated mice that either lack PDK1 or possess PDK1 hypomorphic alleles, expressing only approximately 10% of the normal level of PDK1. PDK1(-/-) embryos die at embryonic day 9.5, displaying multiple abnormalities including lack of somites, forebrain and neural crest derived tissues; however, development of hind- and midbrain proceed relatively normally. In contrast, hypomorphic PDK1 mice are viable and fertile, and insulin injection induces the normal activation of PKB, S6K and RSK. Nevertheless, these mice are 40-50% smaller than control animals. The organ volumes from the PDK1 hypomorphic mice are reduced proportionately. We also establish that the volume of a number of PDK1-deficient cells is reduced by 35-60%, and show that PDK1 deficiency does not affect cell number, nuclear size or proliferation. We provide genetic evidence that PDK1 is essential for mouse embryonic development, and regulates cell size independently of cell number or proliferation, as well as insulin's ability to activate PKB, S6K and RSK.
Insights
Phosphoinositide-dependent kinase 1 (PDK1) is vital for embryonic development and cell size regulation. PDK1 deficiency in mice leads to embryonic lethality and reduced cell volume without affecting cell proliferation.
Area of Science:
- Cell Biology
- Developmental Biology
- Biochemistry
Background:
- Phosphoinositide-dependent kinase 1 (PDK1) is a crucial kinase involved in cell growth and survival pathways.
- PDK1 activates key downstream kinases including PKB/Akt, S6K, and RSK, which are central to cellular signaling.
- Understanding PDK1's precise role requires in vivo models to dissect its functions during development and in adult physiology.
Purpose of the Study:
- To investigate the essential functions of PDK1 in mouse embryonic development.
- To determine PDK1's role in regulating cell size and its impact on cell proliferation.
- To analyze the effect of PDK1 deficiency on the activation of downstream signaling pathways like PKB/Akt.
Main Methods:
- Generation of knockout (PDK1-/-) and hypomorphic (reduced PDK1 expression) mouse models.
- Detailed phenotypic analysis of embryos and adult mice, including developmental milestones and organ morphology.
- Assessment of cell size, cell number, nuclear size, and proliferation rates in PDK1-deficient cells.
- Pharmacological stimulation with insulin to evaluate signaling pathway activation.
Main Results:
- PDK1 knockout embryos exhibit embryonic lethality by day 9.5 with severe developmental defects.
- Hypomorphic PDK1 mice are viable but display significantly reduced body size (40-50% smaller) and proportionate organ volume reduction.
- PDK1 deficiency leads to a 35-60% reduction in cell volume without altering cell number, nuclear size, or proliferation rates.
- Insulin-induced activation of PKB/Akt, S6K, and RSK remains normal in hypomorphic PDK1 mice.
Conclusions:
- PDK1 is indispensable for mouse embryonic development, with complete loss causing embryonic lethality.
- PDK1 plays a critical role in regulating cell size, independent of its effects on cell proliferation.
- PDK1 is essential for mediating insulin signaling pathway activation, impacting cell growth and development.