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RNA polymerase III drives alternative splicing of the potassium channel-interacting protein contributing to brain complexity and neurodegeneration.

Massone S, Vassallo I, Castelnuovo M, Fiorino G, Gatta E, Robello M, Borghi R, Tabaton M, Russo C, Dieci G, Cancedda R, Pagano A - J. Cell Biol. (2011)

Bottom Line: We found that IL1-α-dependent up-regulation of 38A, a small ribonucleic acid (RNA) polymerase III-transcribed RNA, drives the synthesis of an alternatively spliced form of the potassium channel-interacting protein (KCNIP4).Notably, synthesis of the variant KCNIP4 isoform is also detrimental to brain physiology, as it results in the concomitant blockade of the fast kinetics of potassium channels.This alternative splicing shift is observed at high frequency in tissue samples from Alzheimer's disease patients, suggesting that RNA polymerase III cogenes may be upstream determinants of alternative splicing that significantly contribute to homeostasis and pathogenesis in the brain.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Oncology, Biology, and Genetics, National Institute for Cancer Research, 16132 Genoa, Italy.

ABSTRACT
Alternative splicing generates protein isoforms that are conditionally or differentially expressed in specific tissues. The discovery of factors that control alternative splicing might clarify the molecular basis of biological and pathological processes. We found that IL1-α-dependent up-regulation of 38A, a small ribonucleic acid (RNA) polymerase III-transcribed RNA, drives the synthesis of an alternatively spliced form of the potassium channel-interacting protein (KCNIP4). The alternative KCNIP4 isoform cannot interact with the γ-secretase complex, resulting in modification of γ-secretase activity, amyloid precursor protein processing, and increased secretion of β-amyloid enriched in the more toxic Aβ x-42 species. Notably, synthesis of the variant KCNIP4 isoform is also detrimental to brain physiology, as it results in the concomitant blockade of the fast kinetics of potassium channels. This alternative splicing shift is observed at high frequency in tissue samples from Alzheimer's disease patients, suggesting that RNA polymerase III cogenes may be upstream determinants of alternative splicing that significantly contribute to homeostasis and pathogenesis in the brain.

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38A promoter variants analysis. (A) A schematic representation of 38A promoter genetic variants. (B) Relative frequencies of genetic configurations. α/α genetic configuration versus α/Σ genetic configuration in AD cases and in nADcs (C).
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fig8: 38A promoter variants analysis. (A) A schematic representation of 38A promoter genetic variants. (B) Relative frequencies of genetic configurations. α/α genetic configuration versus α/Σ genetic configuration in AD cases and in nADcs (C).

Mentions: To assess the relevance of KCNIP4 alternative splicing in neurodegeneration and with the final aim to identify 38A genetic variations associated with its unusual expression in AD samples, we sequenced the 38A genomic regions of 39 cerebral cortex samples from diseased and nondiseased cases. Results showed that, although the transcribed portion of 38A did not harbor major genetic alterations that might support its increased stability, 38A promoters contain recurrent genetic variations that could be responsible for its altered expression activation in AD cases. In detail, we isolated and cloned four different promoter variants, hereafter referred to as α, β, γ, and δ (Fig. 8 A and Table S2). Considering the α variant as the wild type (wt) and α/α being the canonical wt genotype, we found a significant number of heterozygous genotypes (hereafter referred to as α/Σ) in the cerebral cortices that we analyzed (Σ being β, γ, or δ alleles). Interestingly, we found that in nADcs, the frequency of α/α homozygous and that of heterozygous genotypes was rather similar (47 and 53% of the cases, respectively); alternatively, this ratio is altered in AD samples in which the α/α genotype was associated with 27% of the individuals, whereas the α/Σ heterozygous genotype was found in 73% of the diseased cases (Fig. 8 B). Although, because of the restricted number of samples in our collection (n = 39), the different frequencies of promoter variants are not statistically significant to derive a detailed genetic determination of the impact of different promoters in the disease (χ2 = 1.63, g = 1, and P = 80%), the genetic data obtained by this screening suggest that 38A overexpression is not an individual single determinant of the disease but rather is part of a multifactorial network of events. The transcriptional properties of 38A promoter variants were then investigated to identify an allele-specific regulation of transcription that might explain the increased frequency of the heterozygous haplotype among AD cases (Table S2). We found that the expression of the ncRNA is dependent on the PolIII promoter variant that drives its synthesis in a cell type–specific manner, leading to functionally active 38A ncRNA (Fig. S4). Altogether, these data demonstrate the occurrence of cell type–specific expression of 38A promoter variants that is compatible with a possible individual susceptibility to 38A transcriptional stimuli that might occur differentially in diseased and control cases.


RNA polymerase III drives alternative splicing of the potassium channel-interacting protein contributing to brain complexity and neurodegeneration.

Massone S, Vassallo I, Castelnuovo M, Fiorino G, Gatta E, Robello M, Borghi R, Tabaton M, Russo C, Dieci G, Cancedda R, Pagano A - J. Cell Biol. (2011)

38A promoter variants analysis. (A) A schematic representation of 38A promoter genetic variants. (B) Relative frequencies of genetic configurations. α/α genetic configuration versus α/Σ genetic configuration in AD cases and in nADcs (C).
© Copyright Policy - openaccess
Related In: Results  -  Collection

License 1 - License 2
Show All Figures
getmorefigures.php?uid=PMC3105541&req=5

fig8: 38A promoter variants analysis. (A) A schematic representation of 38A promoter genetic variants. (B) Relative frequencies of genetic configurations. α/α genetic configuration versus α/Σ genetic configuration in AD cases and in nADcs (C).
Mentions: To assess the relevance of KCNIP4 alternative splicing in neurodegeneration and with the final aim to identify 38A genetic variations associated with its unusual expression in AD samples, we sequenced the 38A genomic regions of 39 cerebral cortex samples from diseased and nondiseased cases. Results showed that, although the transcribed portion of 38A did not harbor major genetic alterations that might support its increased stability, 38A promoters contain recurrent genetic variations that could be responsible for its altered expression activation in AD cases. In detail, we isolated and cloned four different promoter variants, hereafter referred to as α, β, γ, and δ (Fig. 8 A and Table S2). Considering the α variant as the wild type (wt) and α/α being the canonical wt genotype, we found a significant number of heterozygous genotypes (hereafter referred to as α/Σ) in the cerebral cortices that we analyzed (Σ being β, γ, or δ alleles). Interestingly, we found that in nADcs, the frequency of α/α homozygous and that of heterozygous genotypes was rather similar (47 and 53% of the cases, respectively); alternatively, this ratio is altered in AD samples in which the α/α genotype was associated with 27% of the individuals, whereas the α/Σ heterozygous genotype was found in 73% of the diseased cases (Fig. 8 B). Although, because of the restricted number of samples in our collection (n = 39), the different frequencies of promoter variants are not statistically significant to derive a detailed genetic determination of the impact of different promoters in the disease (χ2 = 1.63, g = 1, and P = 80%), the genetic data obtained by this screening suggest that 38A overexpression is not an individual single determinant of the disease but rather is part of a multifactorial network of events. The transcriptional properties of 38A promoter variants were then investigated to identify an allele-specific regulation of transcription that might explain the increased frequency of the heterozygous haplotype among AD cases (Table S2). We found that the expression of the ncRNA is dependent on the PolIII promoter variant that drives its synthesis in a cell type–specific manner, leading to functionally active 38A ncRNA (Fig. S4). Altogether, these data demonstrate the occurrence of cell type–specific expression of 38A promoter variants that is compatible with a possible individual susceptibility to 38A transcriptional stimuli that might occur differentially in diseased and control cases.

Bottom Line: We found that IL1-α-dependent up-regulation of 38A, a small ribonucleic acid (RNA) polymerase III-transcribed RNA, drives the synthesis of an alternatively spliced form of the potassium channel-interacting protein (KCNIP4).Notably, synthesis of the variant KCNIP4 isoform is also detrimental to brain physiology, as it results in the concomitant blockade of the fast kinetics of potassium channels.This alternative splicing shift is observed at high frequency in tissue samples from Alzheimer's disease patients, suggesting that RNA polymerase III cogenes may be upstream determinants of alternative splicing that significantly contribute to homeostasis and pathogenesis in the brain.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Oncology, Biology, and Genetics, National Institute for Cancer Research, 16132 Genoa, Italy.

ABSTRACT
Alternative splicing generates protein isoforms that are conditionally or differentially expressed in specific tissues. The discovery of factors that control alternative splicing might clarify the molecular basis of biological and pathological processes. We found that IL1-α-dependent up-regulation of 38A, a small ribonucleic acid (RNA) polymerase III-transcribed RNA, drives the synthesis of an alternatively spliced form of the potassium channel-interacting protein (KCNIP4). The alternative KCNIP4 isoform cannot interact with the γ-secretase complex, resulting in modification of γ-secretase activity, amyloid precursor protein processing, and increased secretion of β-amyloid enriched in the more toxic Aβ x-42 species. Notably, synthesis of the variant KCNIP4 isoform is also detrimental to brain physiology, as it results in the concomitant blockade of the fast kinetics of potassium channels. This alternative splicing shift is observed at high frequency in tissue samples from Alzheimer's disease patients, suggesting that RNA polymerase III cogenes may be upstream determinants of alternative splicing that significantly contribute to homeostasis and pathogenesis in the brain.

Show MeSH
Related in: MedlinePlus