January 6, 2022
PAR-22-093 - Research on Current Topics in Alzheimer's Disease and Its Related Dementias (R01 Clinical Trial Optional)
PAR-22-094 - Research on Current Topics in Alzheimer's Disease and Its Related Dementias (R21 Clinical Trial Not Allowed)
National Institute on Aging (NIA)
Alzheimer’s disease (AD) is a progressive, degenerative disorder of the brain and is the most common form of dementia in older adults. Prominent behavioral manifestations of AD include memory impairments and decline in other cognitive domains. AD is a heterogeneous, multifactorial disease that selectively affects certain regions of the brain (e.g., the entorhinal cortex, hippocampus, and prefrontal cortex) while other areas, such as the cerebellum, remain unaffected.
Selective vulnerability in the nervous system refers to the fact that subpopulations of neurons in different brain areas may be more or less susceptible to specific types of environmental or pathological insults leading to cell dysfunction or death. The factors underlying this selectivity in AD remain unclear. Studies on the staging of AD neuropathology showed AD-related tauopathy begins in the locus coeruleus, followed by neurofibrillary tangles in the entorhinal cortex, then hippocampal pyramidal neurons, and then neocortical neurons. Why is pathology seen in the locus coeruleus and entorhinal cortex at early stages of the disease? Why are specific neuronal cell types in these and other brain regions preferentially affected? What is it about these cells and their projections that make them susceptible to amyloid, tau, or other AD pathology? Studies using an epigenetic biomarker of tissue age (known as the epigenetic clock), which is based on DNA methylation levels, showed that the cerebellum ages more slowly than other parts of the human body in a population of supercentenarians. How the cerebellum epigenetic clock compares with other brain area epigenetic biomarkers is unknown.
Neuroimaging and anatomical studies are showing shrinkage or atrophy and synaptic changes in certain regions of the brain in aging and AD. Functional imaging studies are defining changes in large-scale neural and cognitive networks in the aging human brain and have shown, for example, specific disruption of the resting-state default mode network, compared to other networks, in AD. Glia cells (e.g., astrocytes, microglia, oligodendrocytes) are critical for many normal brain functions. For example, astrocytes and microglia modulate the sculpting and turnover of synapses in development, adulthood, and aging. Glial cell function changes with age and in AD. Are specific types of glial cells or their regional diversity susceptible to AD pathological processes? Understanding the differential rate of brain cellular and regional aging should lead to novel insights into the molecular mechanisms of selective cell and network vulnerability to AD.
The selective vulnerability of specific cell types, and hence neural connectivity and network activity, is most likely due to the unique molecular properties of the affected cells. Molecular characterization of neurons at the single-cell level using immunolabeling, RNA in situ hybridization, and transgenic labeling approaches has provided unique insight into individual gene expression in different cell types in different areas of the mouse brain. Current single-cell gene expression profiling approaches can measure genome-wide transcriptomics in single cells. Integrated approaches have been described to sequence both genomic DNA and mRNA from the same cell, which would allow direct comparison of genomic variation and transcriptomic profiles in single cells. These single-cell genomic and molecular profiling approaches are critical to defining and characterizing mechanisms underlying selective cell vulnerability in aging and AD. Such molecular signatures will suggest or confirm cellular pathways that may mediate vulnerability to, or resistance against, pathological processes in specific brain cells and regions in aging and AD. For example, differential cell vulnerability might be expressed as differential adaptive responses to cell stressors (both internal and cell non-autonomous), calcium dyshomeostasis, mitochondrial/energy dysfunction, macromolecular damage, proteostasis disruption, and protein misfolding and aggregation. Differential excitability and connectivity properties of neuronal subpopulations and their sensitivity to stress and environmental factors may contribute to, and control, selective network vulnerability in AD.
The goal of this Notice of Special Interest (NOSI) is to stimulate research to define and characterize neural cell populations (e.g., neurons and glia), neural activity and circuits, structural and functional networks, and brain regions that are vulnerable (or resistant) in brain aging and AD and the mechanisms underlying such selective vulnerability. Genetic and molecular signatures of different types of neurons and glial cells across the adult lifespan, in AD compared to other dementias of aging, and in different stages of AD will implicate cell processes and pathways mediating selective vulnerability in AD. Defining cell types by physiological measures such as electrophysiology and connectivity and manipulating neural activity in circuits and networks will provide a functional index of selective vulnerability. Applicants are encouraged to use new approaches to generate sophisticated data on molecular signatures of brain cells and on structure and function of brain circuits and networks. Understanding the mechanisms underlying selective vulnerability from cells to networks in AD is critical to fully define the disease process and to develop effective therapies.
Areas of research interest and opportunity include, but are not limited to, the following:
Application and Submission Information
This notice applies to due dates on or after March 11, 2022 and subsequent receipt dates through November 13, 2024.
Submit applications for this initiative using one of the following funding opportunity announcements (FOAs) or any reissues of these announcement through the expiration date of this notice.
All instructions in the SF424 (R&R) Application Guide and the funding opportunity announcement used for submission must be followed, with the following additions:
Applications nonresponsive to terms of this NOSI will not be considered for the NOSI initiative.
Bradley C. Wise, Ph.D.
National Institute on Aging (NIA)