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|Investigating Alzheimer’s disease using zebrafish genetic models
|School of Biological Sciences
|Early-onset familial Alzheimer’s disease (EOfAD) is promoted by autosomal, dominant mutations, enabling the generation of EOfAD-like mutations in animal models for the study of its pathogenic mechanism. This thesis has succeeded in generating an EOfAD-like mutation and an Acne Inversa-like mutation in psen1 using the CRISPR/Cas system. The EOfAD-like mutation can be used for investigation of EOfAD-specific transcriptome signatures, while the Acne Inversa-like mutation (non-EOfAD-like) will be used in transcriptome comparisons with EOfAD-like mutations to refine (by exclusion) our definition of the AD-relevant aspects of EOfAD-like brain transcriptome profiles. On the other hand, the Alzheimer’s Disease Genetics Laboratory (ADGL) has generated two EOfAD-relevant mutations in zebrafish, psen1K97fs and psen1Q96_K97del, and has performed brain transcriptome analyses on heterozygous 6-month-old and 24-month-old mutants compared to their wild type siblings to investigate gene expression changes induced by the mutations. Work by others in the ADGL had observed significant differences in gene expression due to the mutations at 6 months compared to 24 months. In the work described in this thesis, further analyses were performed on these two mutations. I analysed transcript splicing associated with the psen1K97fs mutation and found that I could not detect equivalent alternative splice products associated with the human mutation upon which this mutation model is based. This indicated that the zebrafish psen1K97fs mutation is probably not a close model of the pathological action of human PSEN2K115fs. In addition, I performed transcriptome analysis of heterozygous psen1Q96_K97del mutant larvae to test their possible utility in chemical library screening. I found that genes DE in the larvae were not consistent with those identified in 6-month-old heterozygous mutant brains, although similar cellular pathways were affected. Also, some larvae-specific effects were identified. However, these analyses encountered difficulties. I initially aimed to investigate the nature of this age-dependent transition in gene expression using quantitative PCR (qPCR). I intended to monitor the change in expression of these genes month by month. However, variability in the expression of the selected differentially expressed (DE) genes thwarted this analysis. Furthermore, I compared the behaviour of heterozygous psen1Q96_K97del mutant adult fish to their wild type siblings using the free-movement pattern (FMP) Y-maze test to assess impairments in short-term spatial working memory at 6, 12 and 24 months of age. However, no statistically significant differences in behaviour were identified.
|Thesis (Ph.D.) -- University of Adelaide, School of Biological Sciences, 2020
free-movement pattern Y-maze
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