Limits...
De-regulation of gene expression and alternative splicing affects distinct cellular pathways in the aging hippocampus.

Stilling RM, Benito E, Gertig M, Barth J, Capece V, Burkhardt S, Bonn S, Fischer A - Front Cell Neurosci (2014)

Bottom Line: This approach enabled us to test differential expression of coding and non-coding transcripts, as well as differential splicing and RNA editing.We report a specific age-associated gene expression signature that is associated with major genetic risk factors for late-onset AD (LOAD).This signature is dominated by neuroinflammatory processes, specifically activation of the complement system at the level of increased gene expression, while de-regulation of neuronal plasticity appears to be mediated by compromised RNA splicing.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychiatry and Psychotherapy, University Medical Center Göttingen Göttingen, Germany ; Research Group for Epigenetics in Neurodegenerative Diseases, German Center for Neurodegenerative Diseases (DZNE) Göttingen Göttingen, Germany.

ABSTRACT
Aging is accompanied by gradually increasing impairment of cognitive abilities and constitutes the main risk factor of neurodegenerative conditions like Alzheimer's disease (AD). The underlying mechanisms are however not well understood. Here we analyze the hippocampal transcriptome of young adult mice and two groups of mice at advanced age using RNA sequencing. This approach enabled us to test differential expression of coding and non-coding transcripts, as well as differential splicing and RNA editing. We report a specific age-associated gene expression signature that is associated with major genetic risk factors for late-onset AD (LOAD). This signature is dominated by neuroinflammatory processes, specifically activation of the complement system at the level of increased gene expression, while de-regulation of neuronal plasticity appears to be mediated by compromised RNA splicing.

No MeSH data available.


Related in: MedlinePlus

Impaired novel object recognition memory in 24-month-old mice. (A) 3-month-old mice (3M) and 24-month-old mice (24M) were tested in the novel object recognition paradigm. To assay short-term memory, mice were first exposed to two similar objects (A+A) and then re-exposed to the testing area containing one novel object 5 min later (A+B). Preference for the novel object was significantly greater in 3-month-old mice when compared to the 24-month group, which performed at chance level (*p < 0.05 between groups, two-sided t-test; ##p < 0.01 vs. chance level, one-sample t-test; n = 11[3M]/9[24M]). (B) To test long-term memory mice were exposed to the arena 24 h later, now containing another novel object (A + C). While object preference in 3M was significantly higher than chance level (#p < 0.05, one-sample t-test, n = 10), 24M animals (n = 4) performed at chance level, indicating impaired long-term object recognition memory in aged mice. Error bars indicate s.e.m. (C) During the training session, none of the groups showed preference for any of the two equal objects (A+A).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
getmorefigures.php?uid=PMC4230043&req=5

Figure 1: Impaired novel object recognition memory in 24-month-old mice. (A) 3-month-old mice (3M) and 24-month-old mice (24M) were tested in the novel object recognition paradigm. To assay short-term memory, mice were first exposed to two similar objects (A+A) and then re-exposed to the testing area containing one novel object 5 min later (A+B). Preference for the novel object was significantly greater in 3-month-old mice when compared to the 24-month group, which performed at chance level (*p < 0.05 between groups, two-sided t-test; ##p < 0.01 vs. chance level, one-sample t-test; n = 11[3M]/9[24M]). (B) To test long-term memory mice were exposed to the arena 24 h later, now containing another novel object (A + C). While object preference in 3M was significantly higher than chance level (#p < 0.05, one-sample t-test, n = 10), 24M animals (n = 4) performed at chance level, indicating impaired long-term object recognition memory in aged mice. Error bars indicate s.e.m. (C) During the training session, none of the groups showed preference for any of the two equal objects (A+A).

Mentions: Age-associated memory impairment is the result of variable combinations of genetic pre-disposition and environmental factors, which eventually causes detrimental changes in cellular homeostasis. We therefore reasoned that a comprehensive picture of age-related changes in transcription would be most informative about the aging processes occurring in the brain. The hippocampal formation is essential for memory function in rodents and humans and has been linked to cognitive age-associated memory impairment (Fanselow, 2010). Thus, we performed deep sequencing of polyA-enriched RNA extracted from the mouse hippocampus in three different age groups (3-month-old mice, 24-month-old-mice, and 29-month-old-mice). Since C57BL/6J mice in the laboratory have a maximum life span of just above 30 months, 24-month-old mice represent a model of advanced aging, while 29-month-old represent a time point at the end of life-span. We first confirmed that the selected groups of mice indeed show age-associated memory decline (Figure 1). Due to severely impaired locomotor activity in 29-month-old mice we had to exclude these mice from any behavioral testing. A commonly employed test for hippocampus-dependent memory function in mice is the Morris water maze test. Pilot experiments however showed that in our hands even 24-month-old mice have difficulties to cope with the 2-week-lasting daily training procedure, in which the animals have to swim in a pool filled with opaque water and need to find and climb on a hidden platform. Thus, we decided to subject mice to the novel-object-recognition paradigm that does not depend on advanced motor skills and allows the measurement of short and long-term memory in a non-stressful experimental setting. Moreover, while object recognition learning recruits various brain structures, it also depends on an intact hippocampus (Broadbent et al., 2010; Antunes and Biala, 2012). As expected, we observed that both short (Figure 1A) and long-term object-recognition memory (Figure 1B) was impaired in 24-month-old mice, when compared to 3-month-old mice. This was not due to altered explorative behavior during the training, since both groups of mice explored the objects presented during the training session to a similar degree (Figure 1C).


De-regulation of gene expression and alternative splicing affects distinct cellular pathways in the aging hippocampus.

Stilling RM, Benito E, Gertig M, Barth J, Capece V, Burkhardt S, Bonn S, Fischer A - Front Cell Neurosci (2014)

Impaired novel object recognition memory in 24-month-old mice. (A) 3-month-old mice (3M) and 24-month-old mice (24M) were tested in the novel object recognition paradigm. To assay short-term memory, mice were first exposed to two similar objects (A+A) and then re-exposed to the testing area containing one novel object 5 min later (A+B). Preference for the novel object was significantly greater in 3-month-old mice when compared to the 24-month group, which performed at chance level (*p < 0.05 between groups, two-sided t-test; ##p < 0.01 vs. chance level, one-sample t-test; n = 11[3M]/9[24M]). (B) To test long-term memory mice were exposed to the arena 24 h later, now containing another novel object (A + C). While object preference in 3M was significantly higher than chance level (#p < 0.05, one-sample t-test, n = 10), 24M animals (n = 4) performed at chance level, indicating impaired long-term object recognition memory in aged mice. Error bars indicate s.e.m. (C) During the training session, none of the groups showed preference for any of the two equal objects (A+A).
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4230043&req=5

Figure 1: Impaired novel object recognition memory in 24-month-old mice. (A) 3-month-old mice (3M) and 24-month-old mice (24M) were tested in the novel object recognition paradigm. To assay short-term memory, mice were first exposed to two similar objects (A+A) and then re-exposed to the testing area containing one novel object 5 min later (A+B). Preference for the novel object was significantly greater in 3-month-old mice when compared to the 24-month group, which performed at chance level (*p < 0.05 between groups, two-sided t-test; ##p < 0.01 vs. chance level, one-sample t-test; n = 11[3M]/9[24M]). (B) To test long-term memory mice were exposed to the arena 24 h later, now containing another novel object (A + C). While object preference in 3M was significantly higher than chance level (#p < 0.05, one-sample t-test, n = 10), 24M animals (n = 4) performed at chance level, indicating impaired long-term object recognition memory in aged mice. Error bars indicate s.e.m. (C) During the training session, none of the groups showed preference for any of the two equal objects (A+A).
Mentions: Age-associated memory impairment is the result of variable combinations of genetic pre-disposition and environmental factors, which eventually causes detrimental changes in cellular homeostasis. We therefore reasoned that a comprehensive picture of age-related changes in transcription would be most informative about the aging processes occurring in the brain. The hippocampal formation is essential for memory function in rodents and humans and has been linked to cognitive age-associated memory impairment (Fanselow, 2010). Thus, we performed deep sequencing of polyA-enriched RNA extracted from the mouse hippocampus in three different age groups (3-month-old mice, 24-month-old-mice, and 29-month-old-mice). Since C57BL/6J mice in the laboratory have a maximum life span of just above 30 months, 24-month-old mice represent a model of advanced aging, while 29-month-old represent a time point at the end of life-span. We first confirmed that the selected groups of mice indeed show age-associated memory decline (Figure 1). Due to severely impaired locomotor activity in 29-month-old mice we had to exclude these mice from any behavioral testing. A commonly employed test for hippocampus-dependent memory function in mice is the Morris water maze test. Pilot experiments however showed that in our hands even 24-month-old mice have difficulties to cope with the 2-week-lasting daily training procedure, in which the animals have to swim in a pool filled with opaque water and need to find and climb on a hidden platform. Thus, we decided to subject mice to the novel-object-recognition paradigm that does not depend on advanced motor skills and allows the measurement of short and long-term memory in a non-stressful experimental setting. Moreover, while object recognition learning recruits various brain structures, it also depends on an intact hippocampus (Broadbent et al., 2010; Antunes and Biala, 2012). As expected, we observed that both short (Figure 1A) and long-term object-recognition memory (Figure 1B) was impaired in 24-month-old mice, when compared to 3-month-old mice. This was not due to altered explorative behavior during the training, since both groups of mice explored the objects presented during the training session to a similar degree (Figure 1C).

Bottom Line: This approach enabled us to test differential expression of coding and non-coding transcripts, as well as differential splicing and RNA editing.We report a specific age-associated gene expression signature that is associated with major genetic risk factors for late-onset AD (LOAD).This signature is dominated by neuroinflammatory processes, specifically activation of the complement system at the level of increased gene expression, while de-regulation of neuronal plasticity appears to be mediated by compromised RNA splicing.

View Article: PubMed Central - PubMed

Affiliation: Department of Psychiatry and Psychotherapy, University Medical Center Göttingen Göttingen, Germany ; Research Group for Epigenetics in Neurodegenerative Diseases, German Center for Neurodegenerative Diseases (DZNE) Göttingen Göttingen, Germany.

ABSTRACT
Aging is accompanied by gradually increasing impairment of cognitive abilities and constitutes the main risk factor of neurodegenerative conditions like Alzheimer's disease (AD). The underlying mechanisms are however not well understood. Here we analyze the hippocampal transcriptome of young adult mice and two groups of mice at advanced age using RNA sequencing. This approach enabled us to test differential expression of coding and non-coding transcripts, as well as differential splicing and RNA editing. We report a specific age-associated gene expression signature that is associated with major genetic risk factors for late-onset AD (LOAD). This signature is dominated by neuroinflammatory processes, specifically activation of the complement system at the level of increased gene expression, while de-regulation of neuronal plasticity appears to be mediated by compromised RNA splicing.

No MeSH data available.


Related in: MedlinePlus