Inherited C-terminal TREX1 variants disrupt homology-directed repair to cause senescence and DNA damage phenotypes in Drosophila, mice, and humans.

Age-related microangiopathy, also known as small vessel disease (SVD), causes damage to the brain, retina, liver, and kidney. Based on the DNA damage theory of aging, we reasoned that genomic instability may underlie an SVD caused by dominant C-terminal variants in TREX1, the most abundant 3'-5' DNA exonuclease in mammals. C-terminal TREX1 variants cause an adult-onset SVD known as retinal vasculopathy with cerebral leukoencephalopathy (RVCL or RVCL-S). In RVCL, an aberrant, C-terminally truncated TREX1 mislocalizes to the nucleus due to deletion of its ER-anchoring domain. Since RVCL pathology mimics that of radiation injury, we reasoned that nuclear TREX1 would cause DNA damage. Here, we show that RVCL-associated TREX1 variants trigger DNA damage in humans, mice, and Drosophila, and that cells expressing RVCL mutant TREX1 are more vulnerable to DNA damage induced by chemotherapy and cytokines that up-regulate TREX1, leading to depletion of TREX1-high cells in RVCL mice. RVCL-associated TREX1 mutants inhibit homology-directed repair (HDR), causing DNA deletions and vulnerablility to PARP inhibitors. In women with RVCL, we observe early-onset breast cancer, similar to patients with BRCA1/2 variants. Our results provide a mechanistic basis linking aberrant TREX1 activity to the DNA damage theory of aging, premature senescence, and microvascular disease.

[A case of chordoma presenting as recurrent bacterial meningitis with cerebrospinal fluid leakage].

A 52-year-old man was admitted to our hospital because of two episodes of bacterial meningitis within a 6-month period. CSF examination showed neutrophilic pleocytosis with marked elevation of protein and hypoglycorrhachia, but the inflammatory reaction was mild and blood and CSF cultures were negative. At the time of the second admission, intermittent watery nasal discharge caused by CSF rhinorrhea was evident. CT and MR imaging revealed a tiny clival bone defect, and transnasal endoscopic repair was performed successfully. The pathological diagnosis was chordoma based on immunohistochemical staining for brachyury. Although chordoma presenting as recurrent bacterial meningitis occurs extremely rare, asking patients detailed questions about the CSF rhinorrhea must be essential for disclosing unclear infection sources.

[A case of multiple cerebral hemorrhage caused by sudden increase of eosinophil in a patient with eosinophilic granulomatosis with polyangiitis].

A 42-year-old woman with bronchial asthma was admitted to our hospital due to sensory dominant mononeuritis multiplex lasting for more than 6 months. At that time, her eosinophil count was 761/µl and her sural nerve biopsy showed no findings suggestive of vasculitis. Four months later, she experienced sudden convulsions and right hemiparesis due to left lobular parietal subcortical hemorrhage, when her eosinophil count was elevated to 3,257/µl. Numerous microbleeds and small infarctions were also detected in the intracerebral areas of different regions with MRI. Eosinophilic granulomatosis with polyangiitis (EGPA) is a systemic necrotizing vasculitis of the small vessels, commonly affecting the peripheral nerves. Subarachnoid hemorrhage in patients with EGPA is extremely rare. Steep elevation of the eosinophil count may release certain cytokines, causing cerebral hemorrhage.