Single-cell analysis of somatic mutation rates, mechanisms, and impacts in human ataxia telangiectasia cerebellum

The National Institute of Neurological Disorders and Stroke awarded the University of Massachusetts Medical School $137,828 on November 1, 2025, under the Extramural Research Programs in the Neurosciences and Neurological Disorders program (CFDA 93.853) to conduct single-cell analysis of somatic mutation rates, mechanisms, and impacts in human ataxia telangiectasia cerebellum.

The research characterizes how loss-of-function mutations in the ATM locus impact Purkinje cell genome stability and transcriptome at the single-cell level in post-mortem human cerebellar tissue. Ataxia telangiectasia is a life-limiting DNA damage repair disorder marked by cerebellar degeneration, immunodeficiency, and cancer susceptibility; the study addresses how ATM loss-of-function affects Purkinje cell function and longevity, using human brain tissue rather than animal models because existing mammalian ataxia telangiectasia models fail to reproduce human cerebellar pathology.

Performance takes place in Worcester, Massachusetts. The period of performance extends from November 1, 2025, through October 31, 2028. The assistance type is a Project Grant.

Abstract

Genome maintenance is crucial to cellular and organismal health. In conditions where DNA damage repair (DDR) pathways are disrupted, patients develop severe multisystem disorders. While these diseases impact distinct repair pathways, they share some phenotypic overlap, such as premature aging and neurodegeneration. This observation suggests that genome instability promotes aging and neuronal death. One such DDR disease is ataxia telangiectasia (a-t), a life-limiting DDR disease characterized by cerebellar degeneration, immunodeficiency, and susceptibility to cancer. A-t is caused by biallelic loss-of-function (LOF) mutations at the a-t mutated (ATM) locus, which encodes ATM kinase. A-t relevant mutations are thought to interfere with one or more of its functions, most prominently ATM's role orchestrating DDR and sensing reactive oxygen species. Loss of these functions results in increased DNA damage and higher ROS in a-t patient cells. Ataxia in a-t coincides with loss of cerebellar volume while sparing other brain regions. Histology shows that purkinje cells (PCS), the sole output of the cerebellar cortex, and cerebellar granule neurons DIE over the course of a-t. Our preliminary data shows that deletion burden is higher in a-t neurons from the pre- frontal cortex, but mutation burden analysis is lacking from disease-affected cell types. How ATM LOF impacts PC genome stability, and consequently PC function and longevity, remains unknown. I propose to characterize how ATM LOF impacts the PC genome and transcriptome at the single-cell level in the human cerebellum. Post-mortem human brain was chosen over animal models because a-t mammalian models fail to phenocopy human cerebellar pathology. This experiment requires a single-cell analysis because PCS are very rare, comprising