| Autor: |
Fogarty LC; Division of BioMedical Sciences, Memorial University, 300 Prince Philip Drive, St. John's, NF, A1B 3V6, Canada., Flemmer RT; Division of BioMedical Sciences, Memorial University, 300 Prince Philip Drive, St. John's, NF, A1B 3V6, Canada., Geizer BA; Division of BioMedical Sciences, Memorial University, 300 Prince Philip Drive, St. John's, NF, A1B 3V6, Canada., Licursi M; Division of BioMedical Sciences, Memorial University, 300 Prince Philip Drive, St. John's, NF, A1B 3V6, Canada., Karunanithy A; Division of BioMedical Sciences, Memorial University, 300 Prince Philip Drive, St. John's, NF, A1B 3V6, Canada., Opferman JT; Department of Cellular and Molecular Biology, St. Jude Children's Research Hospital, 262 Danny Thomas Place, Memphis, TN, 38105, USA., Hirasawa K; Division of BioMedical Sciences, Memorial University, 300 Prince Philip Drive, St. John's, NF, A1B 3V6, Canada., Vanderluit JL; Division of BioMedical Sciences, Memorial University, 300 Prince Philip Drive, St. John's, NF, A1B 3V6, Canada. j.vanderluit@mun.ca. |
| Abstrakt: |
During neurogenesis, proliferating neural precursor cells (NPC) exit the cell cycle and differentiate into postmitotic neurons. The proteins that regulate cell survival through the stages of differentiation, however, are still poorly understood. Here, we examined the roles of the anti-apoptotic Bcl-2 proteins, Mcl-1 and Bcl-xL, in promoting survival as cells progress through the stages of neurogenesis in the mouse embryonic central nervous system. We used Nestin-mediated, nervous system-specific conditional deletion of mcl-1, bcl-x or both to identify their distinct and overlapping roles. Individual conditional deletion of mcl-1 (MKO) and bcl-x (BKO) suggested sequential roles in promoting cell survival during developmental neurogenesis. In the MKO embryo, apoptosis begins at embryonic day 10 (E10) in the proliferating NPC population throughout the entire developing nervous system. In the BKO embryo, apoptosis begins later at E11 within the postmitotic neuron populations. In the double (mcl-1 and bcl-x) conditional knockout (DKO), cell death extended throughout both proliferating and non-proliferating cell populations resulting in embryonic lethality at E12, earlier than in either the MKO or BKO. Apoptotic cell death of the entire central nervous system in the DKO demonstrates that both genes are necessary for cell survival during developmental neurogenesis. To determine whether Mcl-1 and Bcl-xL have overlapping anti-apoptotic roles during neurogenesis, we examined the impact of gene dosage. Loss of a single bcl-x allele in the MKO embryo exasperated apoptotic cell death within the NPC population revealing a novel anti-apoptotic role for Bcl-xL in proliferating NPCs. Cells were rescued from apoptosis in both the MKO and BKO embryos by breeding with the Bax null mouse line indicating that Mcl-1 and Bcl-xL have a common pro-apoptotic target during developmental neurogenesis. Taken together, these findings demonstrate that Mcl-1 and Bcl-xL are the two essential anti-apoptotic Bcl-2 proteins required for the survival of the developing mammalian nervous system. |
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