Abstract
Phosphoinositide-dependent kinase-1 (PDK1) controls the activation of a subset of AGC kinases. Using a conditional knockout of PDK1 in haematopoietic cells, we demonstrate that PDK1 is essential for B cell development. B-cell progenitors lacking PDK1 arrested at the transition of pro-B to pre-B cells, due to a cell autonomous defect. Loss of PDK1 decreased the expression of the IgH chain in pro-B cells due to impaired recombination of the IgH distal variable segments, a process coordinated by the transcription factor Pax5. The expression of Pax5 in pre-B cells was decreased in PDK1 knockouts, which correlated with reduced expression of the Pax5 target genes IRF4, IRF8 and Aiolos. As a result, Ccnd3 is upregulated in PDK1 knockout pre-B cells and they have an impaired ability to undergo cell-cycle arrest, a necessary event for Ig light chain rearrangement. Instead, these cells underwent apoptosis that correlated with diminished expression of the pro-survival gene Bcl2A1. Reintroduction of both Pax5 and Bcl2A1 together into PDK1 knockout pro-B cells restored their ability to differentiate in vitro into mature B cells.
Publication types
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Research Support, Non-U.S. Gov't
MeSH terms
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3-Phosphoinositide-Dependent Protein Kinases
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Animals
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B-Lymphocytes / cytology
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B-Lymphocytes / metabolism*
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Cell Cycle Checkpoints / physiology*
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Cyclin D3 / genetics
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Cyclin D3 / metabolism
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Gene Knockdown Techniques
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Ikaros Transcription Factor
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Immunoglobulin Heavy Chains / biosynthesis*
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Immunoglobulin Heavy Chains / genetics
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Immunoglobulin Light Chains / biosynthesis*
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Immunoglobulin Light Chains / genetics
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Interferon Regulatory Factors / genetics
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Interferon Regulatory Factors / metabolism
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Mice
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Mice, Transgenic
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Minor Histocompatibility Antigens
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PAX5 Transcription Factor / genetics
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PAX5 Transcription Factor / metabolism
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Protein Serine-Threonine Kinases / genetics
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Protein Serine-Threonine Kinases / metabolism*
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Proto-Oncogene Proteins c-bcl-2 / genetics
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Proto-Oncogene Proteins c-bcl-2 / metabolism
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Trans-Activators / genetics
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Trans-Activators / metabolism
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Up-Regulation / physiology
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V(D)J Recombination / physiology*
Substances
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BCL2-related protein A1
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Ccnd3 protein, mouse
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Cyclin D3
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Ikzf3 protein, mouse
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Immunoglobulin Heavy Chains
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Immunoglobulin Light Chains
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Interferon Regulatory Factors
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Minor Histocompatibility Antigens
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PAX5 Transcription Factor
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Pax5 protein, mouse
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Proto-Oncogene Proteins c-bcl-2
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Trans-Activators
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interferon regulatory factor-4
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interferon regulatory factor-8
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Ikaros Transcription Factor
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3-Phosphoinositide-Dependent Protein Kinases
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Pdpk1 protein, mouse
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Protein Serine-Threonine Kinases