Noel, K. | Search bioRxiv

bioRxiv2026

The circadian system is affected by Alzheimers disease independently from amyloid beta deposits

Circadian disruption, notably sleep disturbances, serves as an early indicator of Alzheimers disease (AD), preceding cognitive symptoms like memory loss. The suprachiasmatic nucleus (SCN) governs biological rhythms and receives direct retinal input via melanopsin-expressing retinal ganglion cells (mRGCs) to synchronize with environmental light cycles. The anatomical and functional basis for circadian disruption in AD remains unclear. Here, we explored the multi-level relationships between gene expression, the SCN connectome, and regulations of sleep and circadian rhythms in the APP/PS1 mouse model. The sleep architecture of APP/PS1 mice displayed significantly reduced rapid eye movement sleep (REM), associated with a reduced daily core body temperature amplitude and locomotor hyperactivity. Lastly, APP/PS1 mice showed an impaired response to acute light pulse stimulation and present hyperactivity of mRGCs at a young age and hypoactivity of these cells at older ages. These physiological functions are known to be, at least in part, regulated by the SCN, the main target of mRGCs. We noted several modifications in SCN connectomics using serial blockface electron microscopy (SBEM), including a reduction of the dendro-dendritic chemical synapse (DDCS) network that receives a large part of the retinal input and is thought to be crucial for synchronicity between SCN neurons. In addition, we observed multiple signs of dystrophy, including modifications of the shape of dendrites and cell soma, accumulation of aggregated lysosomes, and swelling of axons. At the same time, we investigated the changes in gene expression using spatial transcriptomics. The SCN presents changes in the expression of genes associated with synapse formation, cell adhesion, and neurite growth. These results suggest that, despite the absence of amyloid plaques in the ventral hypothalamus, the SCN of APP/PS1 mice still undergo profound gene expression changes, impacting connectomics and physiological functions. Graphical abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=157 SRC="FIGDIR/small/744599v1_ufig1.gif" ALT="Figure 1"> View larger version (39K): org.highwire.dtl.DTLVardef@ceedb0org.highwire.dtl.DTLVardef@156cfaaorg.highwire.dtl.DTLVardef@5bc262org.highwire.dtl.DTLVardef@36df4d_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

bioRxiv2024

Mechanistic evidence of widespread insecticide resistance among Illinois West Nile virus vectors (Culex pipiens and Culex restuans)

BackgroundMosquitoes are major vectors of arboviruses and other vector-borne diseases, making them a significant public health concern worldwide. Mitigation of arboviral outbreaks relies largely on the use of insecticides, but the effectiveness of such responses is threatened by the evolution of insecticide resistance. Monitoring mosquito susceptibility to different insecticides is therefore vital for informed decisions regarding outbreak responses. In this study, we elucidate the patterns of resistance to two insecticide classes within the primary vectors of West Nile virus in the northeast and midwestern regions of the continental United States, Culex pipiens and Culex restuans. Methodology/Principal FindingsEgg collections were performed throughout Illinois from 2018-2020, and adults were tested for insecticide resistance to permethrin and malathion. Individuals from each sampling location were sequenced to determine the presence of kdr target-site mutations, and biochemical assays were performed to determine increases in detoxification enzymes and insensitive acetylcholinesterase. Results from the bottle assays indicate variable resistance rates in Illinois, however lowered mortality was found in most of the regions that were tested. The kdr mutation (L1014F) was present in 50% of Culex pipiens sequenced, and more prevalent in southern Illinois compared with northern and central (p < 0.001). Different mechanisms were predictive of resistance by species and insecticide, with permethrin resistance being affected by kdr-allele frequency and oxidase levels and malathion resistance by - and {beta}-esterases in Cx. pipiens. For Cx. restuans -esterase and oxidase levels were predictive of permethrin resistance while {beta}-esterase and insensitive acetylcholinesterase levels were predictive of malathion resistance. Conclusions/SignificanceWe documented variation in insecticide resistance levels that appear to be driven by population differences in kdr mutation rates and metabolic resistance mechanisms. The presence of different mechanisms in species and regions has implications for approaches to resistance management and highlights the need to implement and maintain insecticide resistance monitoring practices. Author SummaryMosquitoes are the vectors of many major diseases including malaria, dengue, yellow fever, zika, and West Nile virus. Insecticides are often used to control mosquitoes and the outbreaks they cause. However, evidence has shown that populations of different mosquito species worldwide have developed resistance to our most common insecticides. This study shows that West Nile virus vectors in Illinois, (Culex pipiens and Culex restuans) are no exception to this trend. Egg collections were made throughout the state during the 2018-2020 field seasons and the resulting adults were tested for resistance to two common insecticides using the CDCs bottle bioassay protocol. The results indicate that rates of resistance vary throughout the state and population differences in resistance mechanisms are driving this variation.

ecology↗