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The impairment of HCCS leads to MLS syndrome by activating a non-canonical cell death pathway in the brain and eyes.

Indrieri A, Conte I, Chesi G, Romano A, Quartararo J, Tatè R, Ghezzi D, Zeviani M, Goffrini P, Ferrero I, Bovolenta P, Franco B - EMBO Mol Med (2013)

Bottom Line: Mitochondrial-dependent (intrinsic) programmed cell death (PCD) is an essential homoeostatic mechanism that selects bioenergetically proficient cells suitable for tissue/organ development.By taking advantage of a medaka model that recapitulates the MLS phenotype we demonstrate that downregulation of hccs, an essential player of the mitochondrial respiratory chain (MRC), causes increased cell death via an apoptosome-independent caspase-9 activation in brain and eyes.We also show that the unconventional activation of caspase-9 occurs in the mitochondria and is triggered by MRC impairment and overproduction of reactive oxygen species (ROS).

View Article: PubMed Central - PubMed

Affiliation: Telethon Institute of Genetics and Medicine, Naples, Italy.

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hccs downregulation induces apoptosome-independent caspase-9 activation in mitochondriaA–C. TUNEL assays on st30 embryos co-injected with hccs-MO and Apaf1-MO (A), wt embryos exposed to staurosporine (B) and embryos injected with Apaf1-MO exposed to staurosporine (C) (n = 100/each treatment). Apaf1 down-regulation was able to protect the embryos from cell death induced by staurosporine, but not from the increased cell death due to hccs knockdown.D–F. TUNEL assays on st30 embryos co-injected with hccs-MO and Bcl-xL mRNA (D) and embryos injected with hccs-MO treated with CsA (E) or vehicle alone (F). Note that Bcl-xL overexpression and CsA treatment block cell death. Scale bars: 20 µm.G. Number of TUNEL positive cells/eye (n ≥ 5 embryos/stage; Error bars are SEM; p-values were calculated by ANOVA).H. Caspase-9 activation in morphant embryos treated with CsA or vehicle alone. Histograms show the relative levels of emitted signals displayed in arbitrary units of luminescence. Values represent means of three samples. Each sample represents a group of 20 embryos (error bars are SEM; p-values were calculated by ANOVA).
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fig05: hccs downregulation induces apoptosome-independent caspase-9 activation in mitochondriaA–C. TUNEL assays on st30 embryos co-injected with hccs-MO and Apaf1-MO (A), wt embryos exposed to staurosporine (B) and embryos injected with Apaf1-MO exposed to staurosporine (C) (n = 100/each treatment). Apaf1 down-regulation was able to protect the embryos from cell death induced by staurosporine, but not from the increased cell death due to hccs knockdown.D–F. TUNEL assays on st30 embryos co-injected with hccs-MO and Bcl-xL mRNA (D) and embryos injected with hccs-MO treated with CsA (E) or vehicle alone (F). Note that Bcl-xL overexpression and CsA treatment block cell death. Scale bars: 20 µm.G. Number of TUNEL positive cells/eye (n ≥ 5 embryos/stage; Error bars are SEM; p-values were calculated by ANOVA).H. Caspase-9 activation in morphant embryos treated with CsA or vehicle alone. Histograms show the relative levels of emitted signals displayed in arbitrary units of luminescence. Values represent means of three samples. Each sample represents a group of 20 embryos (error bars are SEM; p-values were calculated by ANOVA).

Mentions: Non-canonical apoptosome-independent caspase-9 activation has been observed in few specific conditions (Hao et al, 2005; Ho et al, 2004; Katoh et al, 2008; Manns et al, 2011; Mills et al, 2006). To determine the mechanism of caspase-9 activation in hccs-morphants, we thus co-injected hccs-MO with a MO designed against Apaf1 (Apaf1-MO). Apaf1 down-regulation protected the embryos from staurosporine induced PCD but failed to rescue PCD in hccs-morphants. At st30, the large majority of co-injected embryos were in fact morphologically undistinguishable from hccs-morphants with a similar number of apoptotic cells (Fig 5A–C and G and Supporting Information Table S1). These data clearly involve non-canonical, apoptosome-independent caspase-9 activation in the pathogenesis of microphthalmia.


The impairment of HCCS leads to MLS syndrome by activating a non-canonical cell death pathway in the brain and eyes.

Indrieri A, Conte I, Chesi G, Romano A, Quartararo J, Tatè R, Ghezzi D, Zeviani M, Goffrini P, Ferrero I, Bovolenta P, Franco B - EMBO Mol Med (2013)

hccs downregulation induces apoptosome-independent caspase-9 activation in mitochondriaA–C. TUNEL assays on st30 embryos co-injected with hccs-MO and Apaf1-MO (A), wt embryos exposed to staurosporine (B) and embryos injected with Apaf1-MO exposed to staurosporine (C) (n = 100/each treatment). Apaf1 down-regulation was able to protect the embryos from cell death induced by staurosporine, but not from the increased cell death due to hccs knockdown.D–F. TUNEL assays on st30 embryos co-injected with hccs-MO and Bcl-xL mRNA (D) and embryos injected with hccs-MO treated with CsA (E) or vehicle alone (F). Note that Bcl-xL overexpression and CsA treatment block cell death. Scale bars: 20 µm.G. Number of TUNEL positive cells/eye (n ≥ 5 embryos/stage; Error bars are SEM; p-values were calculated by ANOVA).H. Caspase-9 activation in morphant embryos treated with CsA or vehicle alone. Histograms show the relative levels of emitted signals displayed in arbitrary units of luminescence. Values represent means of three samples. Each sample represents a group of 20 embryos (error bars are SEM; p-values were calculated by ANOVA).
© Copyright Policy - open-access
Related In: Results  -  Collection

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getmorefigures.php?uid=PMC3569643&req=5

fig05: hccs downregulation induces apoptosome-independent caspase-9 activation in mitochondriaA–C. TUNEL assays on st30 embryos co-injected with hccs-MO and Apaf1-MO (A), wt embryos exposed to staurosporine (B) and embryos injected with Apaf1-MO exposed to staurosporine (C) (n = 100/each treatment). Apaf1 down-regulation was able to protect the embryos from cell death induced by staurosporine, but not from the increased cell death due to hccs knockdown.D–F. TUNEL assays on st30 embryos co-injected with hccs-MO and Bcl-xL mRNA (D) and embryos injected with hccs-MO treated with CsA (E) or vehicle alone (F). Note that Bcl-xL overexpression and CsA treatment block cell death. Scale bars: 20 µm.G. Number of TUNEL positive cells/eye (n ≥ 5 embryos/stage; Error bars are SEM; p-values were calculated by ANOVA).H. Caspase-9 activation in morphant embryos treated with CsA or vehicle alone. Histograms show the relative levels of emitted signals displayed in arbitrary units of luminescence. Values represent means of three samples. Each sample represents a group of 20 embryos (error bars are SEM; p-values were calculated by ANOVA).
Mentions: Non-canonical apoptosome-independent caspase-9 activation has been observed in few specific conditions (Hao et al, 2005; Ho et al, 2004; Katoh et al, 2008; Manns et al, 2011; Mills et al, 2006). To determine the mechanism of caspase-9 activation in hccs-morphants, we thus co-injected hccs-MO with a MO designed against Apaf1 (Apaf1-MO). Apaf1 down-regulation protected the embryos from staurosporine induced PCD but failed to rescue PCD in hccs-morphants. At st30, the large majority of co-injected embryos were in fact morphologically undistinguishable from hccs-morphants with a similar number of apoptotic cells (Fig 5A–C and G and Supporting Information Table S1). These data clearly involve non-canonical, apoptosome-independent caspase-9 activation in the pathogenesis of microphthalmia.

Bottom Line: Mitochondrial-dependent (intrinsic) programmed cell death (PCD) is an essential homoeostatic mechanism that selects bioenergetically proficient cells suitable for tissue/organ development.By taking advantage of a medaka model that recapitulates the MLS phenotype we demonstrate that downregulation of hccs, an essential player of the mitochondrial respiratory chain (MRC), causes increased cell death via an apoptosome-independent caspase-9 activation in brain and eyes.We also show that the unconventional activation of caspase-9 occurs in the mitochondria and is triggered by MRC impairment and overproduction of reactive oxygen species (ROS).

View Article: PubMed Central - PubMed

Affiliation: Telethon Institute of Genetics and Medicine, Naples, Italy.

Show MeSH
Related in: MedlinePlus