CLN3
Battenin precursor (Batten disease protein) (Protein CLN3) [BTS]
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Melanoma is an aggressive skin cancer that can rapidly metastasize to become fatal, if not diagnosed early. Despite recent therapeutic advances, management of melanoma remains difficult. Therefore, novel molecular targets and strategies are required to manage this neoplasm. This study was undertaken to determine the role of the sirtuin SIRT6 in melanoma. Employing a panel of human melanoma cells and normal human melanocytes, we found significant SIRT6 mRNA and protein upregulation in melanoma cells. Further, using a tissue microarray coupled with quantitative Vectra analysis, we demonstrated significant SIRT6 overexpression in human melanoma tissues. Lentiviral short hairpin RNA-mediated knockdown of SIRT6 in A375 and Hs 294T human melanoma cells significantly decreased cell growth, viability, and colony formation, induced G1-phase arrest and increased senescence-associated beta-galactosidase staining. As autophagy is important in melanoma and is associated with SIRT6, we used a qPCR array to study SIRT6 knockdown in A375 cells. We found significant modulation in several genes and/or proteins (decreases in AKT1, ATG12, ATG3, ATG7, BAK1, BCL2L1, CLN3, CTSB, CTSS, DRAM2, HSP90AA1, IRGM, NPC1, SQSTM1, TNF, and BECN1; increases in GAA, ATG10). Our data suggests that increased SIRT6 expression may contribute to melanoma development and/or progression, potentially via senescence-and autophagy-related pathways.
Keywords
- SIRT6
- autophagy
- melanoma
- senescence
- sirtuins
Juvenile Neuronal Ceroid Lipofuscinosis (JNCL) is a fatal lysosomal storage disease caused by autosomal recessive mutations in CLN3. JNCL is typified by progressive neurodegeneration that has been suggested to occur from excessive excitatory and impaired inhibitory synaptic input; however, no studies to date have directly evaluated neuronal function. To examine changes in neuronal activity with advancing disease, electrophysiological recordings were performed in the CA1 hippocampus (HPC) and visual cortex (VC) of acute brain slices from Cln3 mice at 1, 4, 8, and 12months of age. Basic electrophysiological parameters, such as field excitatory post-synaptic potential (fePSP) and population spike (PS) amplitudes, were not altered in Cln3 CA1 and VC neurons at any age. However, fiber volley (FV) amplitudes were significantly increased in Cln3 neurons in the HPC at 1month as well as layer II/III of the VC at 1 and 4months, suggesting increased axonal excitability. In older Cln3 mice (8 and 12months), FV amplitude in the CA1 HPC and VC reached levels that were equal to or significantly lower than WT animals. Significant alterations in the synaptic strength of Cln3 CA1 neurons were also linked to age-dependent changes in axonal responses. Additionally, paired-pulse and 12-pulse facilitation responses calculated from PS recordings were significantly decreased in the CA1 HPC and layer II/III of the VC of Cln3 mice at all ages, suggesting permanent alterations in neuronal short-term plasticity. Collectively, our study has identified novel age- and region-dependent alterations in axonal excitability as well as synaptic and non-synaptic neuronal activity in Cln3 mice during disease progression, which may inform neurodegenerative mechanisms in JNCL.
MeSH Terms
- Aging
- Animals
- Disease Models, Animal
- Hippocampus
- Membrane Glycoproteins
- Mice, Transgenic
- Molecular Chaperones
- Neuronal Ceroid-Lipofuscinoses
- Neurons
- Temporal Lobe
- Visual Cortex
Keywords
- Axonal activity
- CLN3
- Electrophysiology
- Fiber volley
- Field potential
- Hippocampus
- Juvenile Batten disease
- Neocortex
- Neuron
- Short-term plasticity
Retinal degeneration and visual impairment are the first signs of juvenile neuronal ceroid lipofuscinosis caused by CLN3 mutations, followed by inevitable progression to blindness. We investigated retinal degeneration in Cln3(Δex1-6) null mice, revealing classic 'fingerprint' lysosomal storage in the retinal pigment epithelium (RPE), replicating the human disease. The lysosomes contain mitochondrial F0-ATP synthase subunit c along with undigested membranes, indicating a reduced degradative capacity. Mature autophagosomes and basal phagolysosomes, the terminal degradative compartments of autophagy and phagocytosis, are also increased in Cln3(Δex1) (-6) RPE, reflecting disruption to these key pathways that underpin the daily phagocytic turnover of photoreceptor outer segments (POS) required for maintenance of vision. The accumulated autophagosomes have post-lysosome fusion morphology, with undigested internal contents visible, while accumulated phagosomes are frequently docked to cathepsin D-positive lysosomes, without mixing of phagosomal and lysosomal contents. This suggests lysosome-processing defects affect both autophagy and phagocytosis, supported by evidence that phagosomes induced in Cln3(Δex1) (-) (6)-derived mouse embryonic fibroblasts have visibly disorganized membranes, unprocessed internal vesicles and membrane contents, in addition to reduced LAMP1 membrane recruitment. We propose that defective lysosomes in Cln3(Δex1) (-) (6) RPE have a reduced degradative capacity that impairs the final steps of the intimately connected autophagic and phagocytic pathways that are responsible for degradation of POS. A build-up of degradative organellar by-products and decreased recycling of cellular materials is likely to disrupt processes vital to maintenance of vision by the RPE.
MeSH Terms
- Aging
- Animals
- Autophagy
- Brain
- Disease Models, Animal
- Lysosomes
- Membrane Fusion
- Membrane Glycoproteins
- Mice
- Mice, Inbred C57BL
- Mice, Knockout
- Microspheres
- Mitochondrial Proton-Translocating ATPases
- Molecular Chaperones
- Neuronal Ceroid-Lipofuscinoses
- Neurons
- Phagosomes
- Retinal Pigment Epithelium
Mutations in the CLN3 gene cause a fatal neurodegenerative disorder: juvenile CLN3 disease, also known as juvenile Batten disease. The two most commonly utilized mouse models of juvenile CLN3 disease are Cln3-knockout (Cln3(-/-)) and Cln3(Δex7/8)-knock-in mice, the latter mimicking the most frequent disease-causing human mutation. To determine which mouse model has the most pronounced neurological phenotypes that can be used as outcome measures for therapeutic studies, we compared the exploratory activity, motor function and depressive-like behavior of 1-, 3- and 6-month-old Cln3(-/-) and Cln3(Δex7/8)-knock-in mice on two different genetic backgrounds (129S6/SvEv and C57BL/6J). Although, in many cases, the behavior of Cln3(-/-) and Cln3(Δex7/8) mice was similar, we found genetic-background-, gender- and age-dependent differences between the two mouse models. We also observed large differences in the behavior of the 129S6/SvEv and C57BL/6J wild-type strains, which highlights the strong influence that genetic background can have on phenotype. Based on our results, Cln3(-/-) male mice on the 129S6/SvEv genetic background are the most appropriate candidates for therapeutic studies. They exhibit motor deficits at 1 and 6 months of age in the vertical pole test, and they were the only mice to show impaired motor coordination in the rotarod test at both 3 and 6 months. Cln3(-/-) males on the C57BL/6J background and Cln3(Δex7/8) males on the 129S6/SvEv background also provide good outcome measures for therapeutic interventions. Cln3(-/-) (C57BL/6J) males had serious difficulties in climbing down (at 1 and 6 months) and turning downward on (at 1, 3 and 6 months) the vertical pole, whereas Cln3(Δex7/8) (129S6/SvEv) males climbed down the vertical pole drastically slower than wild-type males at 3 and 6 months of age. Our study demonstrates the importance of testing mouse models on different genetic backgrounds and comparing males and females in order to find the most appropriate disease model for therapeutic studies.
MeSH Terms
- Aging
- Animals
- Body Weight
- Depression
- Disease Models, Animal
- Exploratory Behavior
- Female
- Gene Knock-In Techniques
- Genetic Background
- Immobilization
- Male
- Membrane Glycoproteins
- Mice, Inbred C57BL
- Molecular Chaperones
- Motor Activity
- Neuronal Ceroid-Lipofuscinoses
- Phenotype
- Rotarod Performance Test
- Sex Characteristics
- Time Factors
Keywords
- 129S6/SvEv
- Batten disease
- C57BL/6J
- CLN3
- Cln3Δex7/8-knock-in mouse model
- Cln3−/− mouse model
- Juvenile neuronal ceroid lipofuscinosis
Pure populations of quiescent yeast can be obtained from stationary phase cultures that have ceased proliferation after exhausting glucose and other carbon sources from their environment. They are uniformly arrested in the G1 phase of the cell cycle, and display very high thermo-tolerance and longevity. We find that G1 arrest is initiated before all the glucose has been scavenged from the media. Maintaining G1 arrest requires transcriptional repression of the G1 cyclin, CLN3, by Xbp1. Xbp1 is induced as glucose is depleted and it is among the most abundant transcripts in quiescent cells. Xbp1 binds and represses CLN3 transcription and in the absence of Xbp1, or with extra copies of CLN3, cells undergo ectopic divisions and produce very small cells. The Rad53-mediated replication stress checkpoint reinforces the arrest and becomes essential when Cln3 is overproduced. The XBP1 transcript also undergoes metabolic oscillations under glucose limitation and we identified many additional transcripts that oscillate out of phase with XBP1 and have Xbp1 binding sites in their promoters. Further global analysis revealed that Xbp1 represses 15% of all yeast genes as they enter the quiescent state and over 500 of these transcripts contain Xbp1 binding sites in their promoters. Xbp1-repressed transcripts are highly enriched for genes involved in the regulation of cell growth, cell division and metabolism. Failure to repress some or all of these targets leads xbp1 cells to enter a permanent arrest or senescence with a shortened lifespan.
MeSH Terms
- Binding Sites
- Cell Cycle
- Cell Cycle Proteins
- Cell Division
- Checkpoint Kinase 2
- Cyclins
- G1 Phase
- Gene Expression Regulation, Fungal
- Longevity
- Promoter Regions, Genetic
- Repressor Proteins
- Saccharomyces cerevisiae
- Saccharomyces cerevisiae Proteins
- Transcription, Genetic