The role of microglia in TRPV4 mediated neurodegeneration

The National Institute of Neurological Disorders and Stroke awarded The Johns Hopkins University $131,569 on December 1, 2025, under the Extramural Research Programs in the Neurosciences and Neurological Disorders program (CFDA 93.853) to investigate the role of microglia in TRPV4-mediated motor neuron degeneration.

The research characterizes specific subpopulations of microglia and determines their contributions to transient receptor potential vanilloid 4 (TRPV4)-mediated motor neuron degeneration in the context of spinal muscular atrophy. The work builds on laboratory findings that gain-of-function TRPV4 mutations cause motor neuron loss and muscle weakness through spontaneous blood-central nervous system barrier opening in the ventral horn of the spinal cord. Preliminary data identified two distinct activated microglial populations: one at early disease stages around leaking vessels and another at late stages clustering around degenerating motor neurons. The research aims to further characterize these populations and elucidate their roles in disease progression using a mutant TRPV4 mouse model.

Performance occurs in Baltimore, Maryland. The award period runs from December 1, 2025, through December 1, 2026. This is a project grant, an assistance type supporting discrete research investigations. The NINDS program supports extramural research exploring fundamental brain and nervous system structure and function, with emphasis on reducing the burden of neurological disease.

Abstract

Microglia play diverse roles in neurodegenerative disorders such as alzheimer's disease, multiple sclerosis, and the motor neuron diseases amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA). Recent studies have revealed subtypes of microglia with varying molecular signatures and functions, indicating differential responses to stimuli and environmental cues. This heterogeneity suggests that microglia have distinct downstream effects on disease progression. Importantly, breakdown of blood-CNS barriers (bcnsbs; e.g., blood-brain and blood-spinal cord barrier) and leakage of serum proteins into the CNS can activate microglia. However, the identity of these microglial subpopulations and their disease contributions are incompletely understood due to the multifactorial etiologies of many neurodegenerative disorders, where bcnsb breakdown plays only a contributing role. My research aims to characterize specific subpopulations of microglia and determine their contributions to transient receptor potential vanilloid 4 (TRPV4)-mediated motor neuron degeneration. Gain-of-function mutations of TRPV4 causes forms of distal SMA. Recently our laboratory has demonstrated that mutant TRPV4 mice develop severe muscle weakness, motor neuron loss, and lethality due to spontaneous bcnsb opening in the ventral horn of the spinal cord. These deficits can be prevented by genetic ablation of TRPV4 from vascular endothelial cells or pharmacological inhibition of TRPV4. This model provides a unique opportunity to understand the microglial subpopulations activated by bcnsb breakdown in the spinal cord and their role in motor neuron degeneration. In preliminary data, i have observed two distinct, activated microglial populations: one at early disease stages around leaking vessels and another at late stages clustering around degenerating motor neurons. In specific aim 1, i will further characterize the spatial patterns of microglia activation in relation to vascular leak and motor neuron degeneration in mutant TRPV4 mice at various time points and following treatment with a TRPV4 antagonist. In specific aim 2, i will define the evolution of molecular subtypes of microglia post-bcnsb breakdown using single-cell RNA sequencing. In specific aim 3, i will investigate the functional contributions of microglia to bcnsb breakdown and motor neuron dysfunction. By dissecting the interplay between microglial activation, bcnsb dysfunction, and motor neuron degeneration, i aim to unravel mechanisms driving neuroinflammatory degenerative processes in the spinal cord, which might ultimately offer novel therapeutic approaches. This work will not only shed light on the pathogenesis of TRPV4- mediated motor neuron disease, but will offer insights into other neurodegenerative disorders in which bcnsb breakdown triggers neuroinflammation.