Counts Lab
Lab Personnel
- Scott E. Counts, PhD, Primary Investigator
- John Beck
- Mahsa Gifani, MD
- Betul Kara
- Moumita Hore
Overview
Noradrenergic Pathology in MCI and AD
Pontine noradrenergic locus coeruleus (LC) projection neurons mediate attention and memory, and we recently demonstrated that LC neuron loss occurs in MCI and correlates with poorer cognitive function. The goal of this project is to test the extent to which LC degeneration promotes cognitive impairment in AD by driving forebrain cerebrovascular dysfunction. We are approaching this goal in three ways.
First, we are using selective immunotoxins to lesion the LC in Tg344-19 AD rats, a well-characterized rodent model of AD, in the presence or absence of the norepinephrine (NE) pro-drug L-DOPS or the NE reuptake inhibitor atomoxetine. These animals are then assessed for 1) memory function in behavioral tasks, 2) cortical perfusion and neurovascular coupling by MRI, 3) ex vivo vessel physiology (Dorrance link), 5) neurochemical analysis via HPLC (Lipton link) and 4) postmortem quantification of vascular (e,g., blood-brain barrier [BBB] permeability), and AD-like pathology.
Second, microvessels from control and lesioned Tg344-19 AD rats–as well as microvessels from NCI, MCI and AD subjects–will be accessed by laser capture microdissection and queried by RNA sequencing. Target genes and pathways that are dysregulated in both lesioned rat and MCI/AD microvessels will be validated quantitatively for protein expression alterations and cell subtype specificity.
Third, validated target genes and pathways will be tested for their role in vascular dysfunction and/or protection pathways via mechanistic assays in 3D cell culture models.
If successful, these studies will show that 1) LC degeneration impacts AD clinical symptomology via the dysregulation of cerebrovascular function and pathology during the earliest stages of AD, and that 2) targeting noradrenergic mechanistic pathways in microvessels may allow for more comprehensive disease modification in AD by reducing vascular contributions to cognitive impairment.
Basocortical Pathology in MCI and AD
This project is part of the NIH-funded Program Project Grant (PPG), “Neurobiology of mild cognitive impairment (MCI) in the elderly,” which has been continuously funded since 1997 and has produced over 250 papers on the molecular pathology of MCI and preclinical AD (*LINK*).
Our current goal is to understand key mechanisms underlying the spread of tau-mediated neurofibrillary tangle (NFT) pathology within the highly integrated, selectively vulnerable cholinergic nucleus basalis-default mode network (Ch4-DMN) connectome during the transition from no cognitive impairment (NCI) to MCI. We are approaching this goal in three ways.
First, we are quantifying the spatiotemporal evolution of tau pathology within the Ch4-DMN connectome by using site-specific tau antibodies and unbiased stereology in postmortem tissue from subjects categorized as low pathology (LP)-NCI, high pathology (HP)-NCI, MCI, or AD.
Second, we are identifying dysregulated microRNAs targeting tau metabolism in HP-NCI and MCI by using laser capture microdissection of pre-tangle-bearing DMN cortical neurons, followed by RNA sequencing, bioinformatics, and validation studies.
Third, we are homing in on microRNA interactions with tau and tau metabolic pathways that either promote or rescue tau pathology, using multiple in vitro and in vivo techniques.
We are also interrogating cholinergic, synaptic, amyloid, inflammatory, RNA splicing, and novel pathways in collaboration with other PPG projects. If successful, these studies will identify critical upstream regulators of tau metabolism related to the pathological aggregation and circuit-based spread of tau pathology within the Ch4-DMN connectome prior to MCI, thus revealing new targets for therapy.
AD Biomarker Studies
We are currently engaged in multiple efforts with the Michigan AD Research Center, Mercy Health Saint Mary’s Hospital, and Spectrum Hospital to identify blood biomarkers that differentiate healthy control patients from those in the early stages of AD. Strategies include both targeted and unbiased transcriptomic and proteomic analyses of patient samples. The identification of people at greatest risk for conversion to AD would allow for interventions during the therapeutic window for disease modification.