Recently, it was reported that patients with AD who also suffer from low sleep quality have increased Aβ deposition in the brain compared to patients with AD that experience normal sleep patterns. Experiments in mice showed that sleep is associated with a 60% increase in the interstitial space in the brain and greatly increases the rate at which Aβ is cleared. In a recent Genome Wide Association Study (GWAS), the KCTD2 locus in humans was implicated in Alzheimer’s disease. Interestingly, homologs of this locus are present in many animal models, such as the insomniac locus in Drosophila. Loss-of-function mutations in insomniac result in severe sleep deprivation. This raises the possibility that mutations in the KCTD2 locus may contribute to Alzheimer’s disease through sleep deprivation. This combination may exacerbate the effects of the disease. Thus, the symptoms of Alzheimer’s disease may be caused by the accumulation of abnormally folded proteins that accumulate due to sleep deprivation. Currently, little is known about the functional need for sleep, and even less is known about the effect of sleep on the pathology of AD.
Our short-term goal is to determine whether genetically induced sleep deprivation exacerbates AD-like pathology in Drosophila. If so, we could use Drosophila as a model to study the effects of sleep deprivation on AD. Our objective is to use a Drosophila AD model that expresses human Aβ42. In addition to this AD background we will also knock down Insomniac levels using siRNA, in order to study the behavioral and molecular effects of sleep deprivation on AD-like pathology.
We utilize various methods and techniques to quantify the severity of AD-like symptoms in Drosophila. These methods include behavioral analyses to assess the phenotypic symptoms of the disease as well as several molecular techniques to assess the progression of disease pathology. Our behavioral analyses include a Drosophila Activity Monitor to observe Drosophila activity patterns throughout the day and night, climbing assays to assess the integrity of locomotor function, and longevity analysis to observe any deviations in Drosophila survivorship. Molecular techniques we use include qRT-PCR to confirm the knockdown of Insomniac mRNA, western blotting to confirm Insomniac protein knockdown and to quantify the degree of Aβ accumulation over weeks of sleep deprivation, and several immunoassays of whole mount and sectioned Drosophila brains to localize and determine which brain regions have been affected by Aβ accumulation.
Our central hypothesis is that increasing sleep deprivation as a result of knocking down Insomniac will accelerate and increase Aβ deposition, resulting in more severe AD-like pathology including decreased lifespan and several more severe behavioral deficits.