Summary: Researchers using zebrafish models found genes with altered expression linked to mitochondrial dysfunction and reduced ATP production, suggesting early energy deficits could play a key role in the development of Alzheimer’s disease.
Source: University of Adelaide
Rethinking the Origins of Alzheimer’s Disease
Despite decades of research, the underlying cause of Alzheimer’s disease remains unclear. Many scientists believe the disease begins many years—possibly decades—before memory and cognitive symptoms appear, yet the initial triggers are still largely unknown. For a long time the accumulation of amyloid-beta peptide has dominated the field’s thinking, but this hypothesis does not explain why amyloid-beta starts to accumulate in the first place. Moreover, treatments that successfully remove amyloid-beta from the brain have not stopped the progression of cognitive decline in patients.
A Different Approach: Modeling Human Genetics in Zebrafish
Frustrated by the slow progress and limited explanatory power of current models, a team of geneticists at the University of Adelaide adopted a different strategy. Instead of relying on prevailing theories, they chose to recreate as closely as possible the genetic situation found in people who inherit a mutation that causes early-onset familial Alzheimer’s disease (EOfAD).
Most EOfAD-causing mutations are found in the PRESENILIN 1 (PSEN1) gene. Individuals with these mutations typically carry one mutated PSEN1 allele alongside a normal copy. To model this state, the Adelaide researchers introduced comparable single-copy mutations into the PSEN1-equivalent gene in zebrafish. Zebrafish offer several experimental advantages: they are genetically tractable, can be bred in large numbers, and groups of sibling fish can be raised together in the same controlled environment to reduce non-genetic variability. This approach lets researchers focus tightly on the direct effects of the mutation.
Transcriptome Analysis Reveals Early Energy Production Deficits
The team examined the entire brain transcriptome—the complete set of gene expression—from young adult mutant fish and their wild-type siblings at an age equivalent to humans who would not yet show Alzheimer’s symptoms. Comparing these closely related, similarly reared animals revealed specific changes in gene expression associated with the PSEN1-like mutation.
Computational analyses of the differentially expressed genes pointed to disrupted mitochondrial function and reduced ATP synthesis. Because ATP is the primary energy currency of cells, any impairment in its production can have wide-ranging effects on brain physiology. The findings suggest that energy metabolism defects, rather than—or in addition to—amyloid accumulation, could be an early driver of disease processes that later lead to neurodegeneration and cognitive decline.
Next Steps: Comparing Multiple Alzheimer’s-like Mutations
The Adelaide group has already created additional zebrafish lines carrying different Alzheimer’s disease–like mutations. Their plan is to compare the brain transcriptomes across these various mutant lines to find common molecular defects. Identifying a shared pathway or cellular process altered across multiple mutations could reveal the central mechanism driving Alzheimer’s disease—whether that is impaired ATP production, mitochondrial dysfunction, or a more subtle, convergent defect in cellular energetics.
Such comparative transcriptomic work aims to pinpoint early molecular changes before widespread neurodegeneration occurs, offering potential targets for interventions designed to prevent or slow disease onset rather than treating late-stage symptoms.
Publication and Research Context
The first brief report from the University of Adelaide Alzheimer’s Disease Genetics Laboratory describing these Alzheimer’s-like mutant zebrafish was published on 3 May in the journal Molecular Brain. The study analysed entire-brain transcriptomes from six-month-old zebrafish heterozygous for an EOfAD-like mutation (Q96_K97del) in the zebrafish psen1 gene and found gene ontology signals implicating mitochondrial processes, especially ATP synthesis and ATP-dependent functions such as vacuolar acidification.
Thanks to Michael Lardelli for submitting this neuroscience research news for inclusion.
Source:
University of Adelaide
Media Contacts:
Michael Lardelli – University of Adelaide
Image Source:
The image is credited to The University of Adelaide.
Original Research (open access):
“Brain transcriptome analysis of a familial Alzheimer’s disease-like mutation in the zebrafish presenilin 1 gene implies effects on energy production.” Newman M, Hin N, Pederson S & Lardelli M. Molecular Brain. doi: 10.1186/s13041-019-0467-y
Abstract (summary)
Understanding Alzheimer’s disease requires insight into its initial molecular changes. Because postmortem human tissue reflects late-stage disease and compensatory responses, modeling the genetic state of early-onset familial Alzheimer’s disease in a living organism can reveal earlier, causative changes. By analysing whole-brain transcriptomes from zebrafish heterozygous for an EOfAD-like psen1 mutation, the researchers found transcriptomic signatures suggesting mitochondrial dysfunction and impaired ATP synthesis, implicating energy metabolism as a potentially critical factor in disease initiation.