Role of circadian clock on astrocyte and dementia
- 주제(키워드) Circadian clock , astrocyte , transcriptome analysis , Tmem44 , dementia , behavioral circadian rhythm , MESOR , L5 onset time
- 발행기관 아주대학교
- 지도교수 김은영
- 발행년도 2021
- 학위수여년월 2021. 2
- 학위명 박사
- 학과 및 전공 일반대학원 의생명과학과
- 실제URI http://www.dcollection.net/handler/ajou/000000030834
- 본문언어 영어
- 저작권 아주대학교 논문은 저작권에 의해 보호받습니다.
초록/요약
The circadian clock is a system that helps organisms to adapt to changes of the external environment by day and night cycle caused by the earth's rotation. The circadian clock is preserved from the cellular level, and is regulated through the transcriptional translational feedback loop (TTFL) of the core clock genes such as Bmal1 or Nr1d1. The circadian clock at the cellular level can further lead to the circadian clock at the tissue or organism level. In mammals, suprachiasmatic nucleus (SCN), which exists in the hypothalamus, is the master circadian clock and responsible for transmitting and synchronizing circadian clock signals. Recently, it has been proposed that the circadian gene expression pattern at the cellular or tissue level is related to time dependent functional regulation of each cell type or tissue. Therefore, studies on the regulation of cellular or tissue physiology have been attempted by assessing circadian oscillating transcripts of specific cell type or tissue sample. In addition, studies on the role of the circadian clock on pathophysiology can be attempted by measuring the circadian rhythm characteristics at the organism level such as behavioral activity monitoring or multiple cortisol assessments. At the first part, I investigated circadian transcriptome in mouse cortical astrocyte culture to find crucial gene and/or pathway for regulating astrocyte physiology at cellular level. I found 412 circadian oscillating transcripts in astrocyte and found several enriched biological mechanisms such as cellular migration, glutathione metabolism, and calcium signaling pathways. I further narrowed candidate oscillating transcripts possibly regulating astrocyte physiology. Finally, I could get 38 candidate transcripts which include several transcripts already studied as possible regulator of astrocyte physiology or brain functions. I further assessed Tmem44 as a novel candidate. Tmem44 downregulation affected circadian rhythm, decreased cellular migration, and metabolic activity in astrocytes. Further research will be performed to identify the role of Tmem44 and other candidates on astrocyte physiology in vitro and in vivo. At the second part, I assessed role of circadian rhythm on pathophysiology of neurodegenerative disorder at organism level. I investigated the associations between behavioral circadian rhythm, neurodegeneration, and cognition in patients with mild cognitive impairment and mild dementia. I extracted behavioral circadian rhythm characteristics from longitudinal activity data measured by wrist actigraphy. As a result, I found that MESOR, which corresponds to the rhythm-adjusted mean activity, associated positively with frontal/executive function. Furthermore, L5 onset time, which corresponds to the time of rest period onset, associated positively with medial temporal lobe grey matter (MTL GM) volume and memory function, particularly in amyloid-negative participants. Additional path analysis revealed that MTL GM volume partially mediates the relationship between L5 onset time and memory function in amyloid-negative participants. Together, these studies suggest potential role of circadian rhythm on regulation of astrocyte physiology at cellular level and dementia pathophysiology at organism level.
more목차
I. INTRODUCTION 1
A. Circadian clock system in animal 1
B. Role of the circadian clock on astrocyte function 1
C. Circadian rhythm disruption and neurodegenerative disorder 2
D. Aims 4
II. RESULTS 6
CHAPTER 1. Circadian transcriptome analysis in primary mouse cortical astrocyte culture 6
1.1. Introdcution 6
1.2. Materials and Methods 8
1.2.1. Study approval and animal experiment 8
1.2.2. Primary astrocyte culture 8
1.2.3. Circadian synchronization and sample collection 8
1.2.4. RNA-Seq analysis and astrocyte enrichment test 9
1.2.5. Circadian oscillation detection 12
1.2.6. Downregulation of gene expression 12
1.2.7. Real-time measurement of circadian rhythm in astrocytes 13
1.2.8. Quantitative reverse transcription polymerase chain reaction (qRT-PCR) 13
1.2.9. Immunoblotting 13
1.2.10. Real-time cellular migration assessment 14
1.2.11. Measurement of metabolic activity and cell death in astrocytes 14
1.2.12. Statistical analysis 15
1.3. Results 16
1.3.1. Circadian oscillation detection in mouse cortical astrocyte transcriptome 16
1.3.2. Characterization of circadian oscillating transcripts 19
1.3.3. Enriched biological processes, pathways, and STRING protein network analysis of circadian oscillating transcripts 23
1.3.4. Narrowing down of the candidate oscillating transcripts possibly regulating astrocyte physiology 28
1.3.5. Tmem44 as possible regulator of circadian rhythm, cellular migration, and metabolic activity of mouse cortical astrocyte 31
1.4. Discussion 39
CHAPTER 2. Associations of behavioral circadian rhythms with amyloid burden, medial temporal lobe atrophy, and cognitive impairment 47
2.1. Introdcution 47
2.2. Materials and Methods 48
2.2.1. Participants 48
2.2.2. Standard protocol approval, registration, and patient consent 51
2.2.3. Measure of behavioral circadian rhythms 51
2.2.4. Cognitive function assessment 54
2.2.5. Neuroimaging biomarkers 54
2.2.6. Other measures 56
2.2.7. Statistical analysis 57
2.3. Results 58
2.3.1. Demographic characteristics of study participants 58
2.3.2. Analysis of behavioral circadian rhythms, neuroimaging biomarkers, and cognitive function 58
2.3.3. Association of MESOR with frontal/executive function and L5 onset time with memory function 64
2.3.4. Model of relationships between L5 onset time, MTL GM volume, memory function, and cortical amyloid burden 74
2.4. Discussion 76
III.CONCLUSION 84
REFERENCES 86
