TREX1 is expressed by microglia in normal human brain and increases in regions affected by ischemia

C-176 loaded Ce DNase nanoparticles synergistically inhibit the cGAS-STING pathway for ischemic stroke treatment

The neuroinflammatory responses following ischemic stroke cause irreversible nerve cell death. Cell free-double strand DNA (dsDNA) segments from ischemic tissue debris are engulfed by microglia and sensed by their cyclic GMP-AMP synthase (cGAS), which triggers robust activation of the innate immune stimulator of interferon genes (STING) pathway and initiate the chronic inflammatory cascade. The decomposition of immunogenic dsDNA and inhibition of the innate immune STING are synergistic immunologic targets for ameliorating neuroinflammation. To combine the anti-inflammatory strategies of STING inhibition and dsDNA elimination, we constructed a DNase-mimetic artificial enzyme loaded with C-176. Nanoparticles are self-assembled by amphiphilic copolymers (P[CL₃₅-b-(OEGMA_20.7-co-NTAMA_14.3)]), C-176, and Ce⁴⁺ which is coordinated with nitrilotriacetic acid (NTA) group to form corresponding catalytic structures. Our work developed a new nano-drug that balances the cGAS-STING axis to enhance the therapeutic impact of stroke by combining the DNase-memetic Ce⁴⁺ enzyme and STING inhibitor synergistically. In conclusion, it is a novel approach to modulating central nervus system (CNS) inflammatory signaling pathways and improving stroke prognosis.

TREX1 cytosolic DNA degradation correlates with autoimmune disease and cancer immunity

The N-terminal domain of Three Prime Repair Exonuclease 1 (TREX1) is catalytically active and can degrade dsDNA or ssDNA in the cytosol, whereas the C-terminal domain is primarily involved in protein localization. TREX1 deficiency induces cytosolic DNA accumulation as well as activation of the cGAS-STING-IFN signaling pathway, which results in tissue inflammation and autoimmune diseases. Furthermore, TREX1 expression in cancer immunity can be adaptively regulated to promote tumor proliferation, making it a promising therapeutic target.

Liver Pathology in Retinal Vasculopathy with Cerebral Leukoencephalopathy and Systemic Manifestations (RVCL-S): Vasculopathic Disease Beyond Nodular Regenerative Hyperplasia (NRH)

BACKGROUND

Retinal vasculopathy with cerebral leukoencephalopathy and systemic manifestations (RVCL-S) is a rare autosomal dominant disease resulting from a frame-shift mutation in TREX1, an intracellular 3'-5' exonuclease 1. Hepatic findings include an elevated alkaline phosphatase (ALP) and nodular regenerative hyperplasia (NRH). Affected individuals typically succumb to brain lesions prior to clinically apparent hepatic manifestations; thus, little else is known about the hepatic pathology.

DESIGN

Autopsy reports and a liver section from each (n=11) of three unrelated kindreds with the most common mutation in TREX1 (V235Gfs*6) were studied with standard and immunohistochemical stains. Cases were compared with "normal liver" controls from similar autopsy years.

RESULTS

Cases consisted of six men and five women who died at a median age of 50 yr. (range 41- 60yr.). Seven had elevated ALP. Two had liver atrophy. Foci of NRH were variably detected in all. Inhomogeneous distribution of other findings included patternless parenchymal fibrous bands, approximation of vascular structures, and commonly, architectural changes of vascular structures. Only bile duct epithelia were unaffected. Additionally, small trichrome-positive nodules were found along vein walls or isolated in the parenchyma. Rare foci of non-NRH hepatocytic nodules were noted in three. Increased CD34 and altered α-SMA IHC expression were variably noted. Periportal ductules and perivenular K7 IHC expression were increased to unpredictable degrees.

CONCLUSIONS

The extensive but inhomogeneous histopathologic findings in livers of autopsied patients with RVCL-S appear to involve hepatic vascular structures. These findings validate inclusion of vascular liver involvement beyond NRH in this complex hereditary disorder.

A path towards personalized medicine for autoinflammatory and related diseases

The human genome project led to the advancement of genetic technologies and genomic medicine for a variety of human diseases, including monogenic autoimmune and autoinflammatory diseases. As a result, the genome of an individual can now be rapidly sequenced at a low cost, and this technology is beginning to change the practice of rheumatology. In this Perspective, we describe how new sequencing technologies combined with careful clinical phenotyping have led to the discovery of rare rheumatic diseases and their corresponding disease-causing mutations. Additionally, we explore ways in which single-gene mutations, including somatic mutations, are creating opportunities to develop personalized medicines. To illustrate this idea, we focus on diseases affecting the TREX1-cGAS-STING pathway, which is associated with monogenic autoinflammatory diseases and vasculopathies. For many of the affected patients and families, there is an urgent, unmet need for the development of personalized therapies. New innovations related to small molecular inhibitors and gene therapies have the potential to benefit these families, and might help drive further innovations that could prove useful for patients with more common forms of autoimmunity and autoinflammation.

Tumor-Like Brain Lesions Associated With Variants of Uncertain Significance Compared to Previous Studies: A Case Report

TREX1 is a gene that encodes an exonuclease on the C-terminal strand at the 3 ́ end for DNA repair. Multiple syndromes associated with the alteration of this gene have been described, focusing in this case on retinal vasculopathy with cerebral leukodystrophy (RVCL). We present the case of a 44-year-old female patient with a familial history of cerebral pseudotumors. At the time of diagnosis, the patient presented weakness in the lower limbs and dysesthesias of the right body at the beginning of the clinical picture, without visual alterations or retinal changes at fundus examination. A cranial magnetic resonance imaging (MRI) study showed a pseudotumoral lesion at the inferior frontal gyrus with a report of a choline peak in spectroscopy, ring enhancement in contrasted T1 sequence, and apparent central necrosis. A molecular study shows a mutation in c2136G>A, c.799dup, and c.5312A>G related to genes expressing PDE6A, TREX1, and VCAN proteins, respectively, mutations that have not been previously reported.

Retinal Vasculopathy with Cerebral Leukoencephalopathy and Systemic manifestations (RVCL-S): An update on basic science and clinical perspectives

Retinal vasculopathy with cerebral leukoencephalopathy and systemic manifestations (RVCL-S) is a rare, underrecognized, systemic small vessel disease caused by heterozygous C-terminal truncating TREX1 mutations. The disease is characterized by vascular retinopathy, focal neurological complaints, cognitive decline and a wide range of systemic manifestations, including Raynaud's phenomenon, anemia and liver and kidney disease. Eventually, RVCL-S leads to premature death. The underlying pathological finding in RVCL-S is a nonatherosclerotic, amyloid-negative angiopathy involving small arteries and capillaries. However, the exact mechanisms by which the truncated TREX1 protein causes angiopathy remains unknown. Timely recognition of this disease is important to slow down and treat complications of the disorder, but also to prevent unnecessary (invasive) diagnostic or therapeutic procedures. As we move forward, translational research combining basic science advances and clinical findings as well as studies focusing on natural history following RVCL-S patients at different disease stages, will be critical to help elucidate RVCL-S pathophysiology. These studies will also provide the tools to identify appropriate biomarkers and therapeutic agent options for RVCL-S patients.

Novel de novo TREX1 mutation in a patient with retinal vasculopathy with cerebral leukoencephalopathy and systemic manifestations mimicking demyelinating disease

Retinal vasculopathy with cerebral leukoencephalopathy and systemic manifestations (RVCL-S) is a rare fatal autosomal dominant vasculopathy associated with mutations in the TREX1 gene. Only one de novo case has been reported in the literature. We report the long-term clinical, radiological, and pathological presentation of a patient with a de novo and novel mutation in this gene. Description of the clinical, genetic, imaging and pathologic characteristics is important to better characterize RVCL-S and prevent unnecessary interventions. RVCL-S should be considered in patients with tumefactive brain lesions unresponsive to immunotherapy.

Monogenic Causes of Apparently Idiopathic Perinatal Intracranial Hemorrhage

OBJECTIVE

Perinatal intracranial hemorrhage (pICH) is a rare event that occurs during the fetal/neonatal period with potentially devastating neurological outcome. However, the etiology of pICH is frequently hard to depict. We investigated the role of rare genetic variations in unexplained cases of pICH.

METHODS

We performed whole-exome sequencing (WES) in fetuses and term neonates with otherwise unexplained pICH and their parents. Variant causality was determined according to the American College of Medical Genetics and Genomics (ACMG) criteria, consistency between suggested genes and phenotypes, and mode of inheritance.

RESULTS

Twenty-six probands (25 families) were included in the study (9 with a prenatal diagnosis and 17 with a postnatal diagnosis). Intraventricular hemorrhage (IVH) was the most common type of hemorrhage (n = 16, 62%), followed by subpial (n = 4, 15%), subdural (n = 4, 15%), and parenchymal (n = 2, 8%) hemorrhage. Causative/likely causative variants were found in 4 subjects from 3 of the 25 families (12%) involving genes related to the brain microenvironment (COL4A1, COL4A2, and TREX-1). Additionally, potentially causative variants were detected in genes related to coagulation (GP1BA, F11, Von Willebrand factor [VWF], FGA, and F7; n = 4, 16%). A potential candidate gene for phenotypic expansion related to microtubular function (DNAH5) was identified in 1 case (4%). Fifty-five percent of the variants were inherited from an asymptomatic parent. Overall, these findings showed a monogenic cause for pICH in 12% to 32% of the families.

INTERPRETATION

Our findings reveal a clinically significant diagnostic yield of WES in apparently idiopathic pICH and support the use of WES in the evaluation of these cases. ANN NEUROL 2021;89:813-822.

Astrocyte-Oligodendrocyte-Microglia Crosstalk in Astrocytopathies

Defective astrocyte function due to a genetic mutation can have major consequences for microglia and oligodendrocyte physiology, which in turn affects the white matter integrity of the brain. This review addresses the current knowledge on shared and unique pathophysiological mechanisms of astrocytopathies, including vanishing white matter, Alexander disease, megalencephalic leukoencephalopathy with subcortical cysts, Aicardi-Goutières syndrome, and oculodentodigital dysplasia. The mechanisms of disease include protein accumulation, unbalanced secretion of extracellular matrix proteins, pro- and anti-inflammatory molecules, cytokines and chemokines by astrocytes, as well as an altered gap junctional network and a changed ionic and nutrient homeostasis. Interestingly, the extent to which astrogliosis and microgliosis are present in these astrocytopathies is highly variable. An improved understanding of astrocyte-microglia-oligodendrocyte crosstalk might ultimately lead to the identification of druggable targets for these, currently untreatable, severe conditions.

Lesion evolution and neurodegeneration in RVCL-S: A monogenic microvasculopathy

Objective

To characterize lesion evolution and neurodegeneration in retinal vasculopathy with cerebral leukoencephalopathy and systemic manifestations (RVCL-S) using multimodal MRI.

Methods

We prospectively performed MRI and cognitive testing in RVCL-S and healthy control cohorts. Gray and white matter volume and disruption of white matter microstructure were quantified. Asymmetric spin echo acquisition permitted voxel-wise oxygen extraction fraction (OEF) calculation as an in vivo marker of microvascular ischemia. The RVCL-S cohort was included in a longitudinal analysis of lesion subtypes in which hyperintense lesions on fluid-attenuated inversion recovery (FLAIR), T1-postgadolinium, and diffusion-weighted imaging were delineated and quantified volumetrically.

Results

Twenty individuals with RVCL-S and 26 controls were enrolled. White matter volume and microstructure declined faster in those with RVCL–S compared to controls. White matter atrophy in RVCL-S was highly linear (ρ = −0.908, p < 0.0001). Normalized OEF was elevated in RVCL-S and increased with disease duration. Multiple cognitive domains, specifically those measuring working memory and processing speed, were impaired in RVCL-S. Lesion volumes, regardless of subtype, progressed/regressed with high variability as a function of age, while FLAIR lesion burden increased near time to death (p < 0.001).

Conclusion

RVCL-S is a monogenic microvasculopathy affecting predominantly the white matter with regard to atrophy and cognitive impairment. White matter volumes in RVCL-S declined linearly, providing a potential metric against which to test the efficacy of future therapies. Progressive elevation of white matter OEF suggests that microvascular ischemia may underlie neurodegeneration in RVCL-S.

Oncolytic Adenovirus Expressing ST13 Increases Antitumor Effect of Tumor Necrosis Factor-Related Apoptosis-Inducing Ligand Against Pancreatic Ductal Adenocarcinoma

Oncolytic adenoviruses (OAds) are promising agents for cancer therapy, representing a novel therapeutic strategy for pancreatic ductal adenocarcinoma (PDAC). However, there are challenges associated with the successful use of an OAd alone, involving the security of the viral vector and screening of an effective antitumor gene. In the present study, a novel OAd CD55-ST13-tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) was constructed in which the dual therapeutic genes ST13 and TRAIL were inserted, featuring the carcinoembryonic antigen (CEA) as a promoter to control E1A and deletion of the 55 kDa E1B gene. ST13, known as a colorectal cancer suppressor gene, exhibited lower expression in PDAC than in tumor-adjacent tissues and was associated with poor prognosis in PDAC patients. In vitro studies demonstrated that CD55-ST13-TRAIL was effective in promoting the expression of ST13 and TRAIL in CEA-positive pancreatic cancer cells. Moreover, CD55-ST13-TRAIL exhibited a synergistic effect toward tumor cell death compared with CD55-ST13 alone or CD55-TRAIL alone, and inhibited tumor cell proliferation and induced cell apoptosis dependent on caspase pathways in PDAC cells. Furthermore, xenograft experiments in a mouse model indicated that CD55-ST13-TRAIL significantly inhibited tumor growth and improved the survival of animals with xenografts. The findings demonstrate that oncolytic virotherapy under the control of the promoter CEA enables safe and efficient treatment of PDAC, and suggest that it represents a promising candidate for the treatment of metastatic diseases.

Aggravated brain injury after neonatal hypoxic ischemia in microglia-depleted mice

Background

Neuroinflammation plays an important role in neonatal hypoxic-ischemic encephalopathy (HIE). Although microglia are largely responsible for injury-induced inflammatory response, they play beneficial roles in both normal and disease states. However, the effects of microglial depletion on neonatal HIE remain unclear.

Methods

Tamoxifen was administered to Cx3cr1^CreER/+Rosa26^DTA/+ (microglia-depleted model) and Cx3cr1^CreER/+Rosa26^DTA/− (control) mice at P8 and P9 to assess the effect of microglial depletion. The density of microglia was quantified using Iba-1 staining. Moreover, the proportion of resident microglia after the HI insult was analyzed using flow cytometric analysis. At P10, the HI insult was conducted using the Rice-Vannucci procedure at P10. The infarct size and apoptotic cells were analyzed at P13. Cytokine analyses were performed using quantitative polymerase chain reaction and enzyme-linked immunosorbent assay (ELISA) at P13.

Results

At P10, tamoxifen administration induced > 99% microglial depletion in DTA⁺ mice. Following HI insult, there was persisted microglial depletion over 97% at P13. Compared to male DTA⁻ mice, male DTA⁺ mice exhibited significantly larger infarct volumes; however, there were no significant differences among females. Moreover, compared to male DTA⁻ mice, male DTA⁺ mice had a significantly higher density of TUNEL⁺ cells in the caudoputamen, cerebral cortex, and thalamus. Moreover, compared to female DTA⁻ mice, female DTA⁺ mice showed a significantly greater number of TUNEL⁺ cells in the hippocampus and thalamus. Compared to DTA⁻ mice, ELISA revealed significantly lower IL-10 and TGF-β levels in both male and female DTA⁺ mice under both normal conditions and after HI (more pronounced).

Conclusion

We established a microglial depletion model that aggravated neuronal damage and apoptosis after the HI insult, which was predominantly observed in males.