Deletion of B-cell translocation gene 2 (BTG2) alters the responses of glial cells in white matter to chronic cerebral hypoperfusion

Kaoru Suzuki,Hidekazu Tomimoto,Akio Fukumori,Miho Yamamoto,Yoshitaka Tashiro,Mitsuru Shinohara,Ghupurjan Gheni,Naoyuki Sato,Tomoji Mashimo,Akihiko Shindo,Yoshihiro Uno

doi:10.1186/s12974-021-02135-w

Abstract

BackgroundSubcortical ischemic vascular dementia, one of the major subtypes of vascular dementia, is characterized by lacunar infarcts and white matter lesions caused by chronic cerebral hypoperfusion. In this study, we used a mouse model of bilateral common carotid artery stenosis (BCAS) to investigate the role of B-cell translocation gene 2 (BTG2), an antiproliferation gene, in the white matter glial response to chronic cerebral hypoperfusion.MethodsBtg2−/− mice and littermate wild-type control mice underwent BCAS or sham operation. Behavior phenotypes were assessed by open-field test and Morris water maze test. Brain tissues were analyzed for the degree of white matter lesions and glial changes. To further confirm the effects of Btg2 deletion on proliferation of glial cells in vitro, BrdU incorporation was investigated in mixed glial cells derived from wild-type and Btg2−/− mice.ResultsRelative to wild-type mice with or without BCAS, BCAS-treated Btg2−/− mice exhibited elevated spontaneous locomotor activity and poorer spatial learning ability. Although the severities of white matter lesions did not significantly differ between wild-type and Btg2−/− mice after BCAS, the immunoreactivities of GFAP, a marker of astrocytes, and Mac2, a marker of activated microglia and macrophages, in the white matter of the optic tract were higher in BCAS-treated Btg2−/− mice than in BCAS-treated wild-type mice. The expression level of Gfap was also significantly elevated in BCAS-treated Btg2−/− mice. In vitro analysis showed that BrdU incorporation in mixed glial cells in response to inflammatory stimulation associated with cerebral hypoperfusion was higher in Btg2−/− mice than in wild-type mice.ConclusionBTG2 negatively regulates glial cell proliferation in response to cerebral hypoperfusion, resulting in behavioral changes.

Highlights

Subcortical ischemic vascular dementia, one of the major subtypes of vascular dementia, is characterized by lacunar infarcts and white matter lesions caused by chronic cerebral hypoperfusion
Because B-cell translocation gene 2 (BTG2) belongs to the BTG/TOB family, we asked whether the expression of other members of the BTG/TOB family was upregulated by a compensatory mechanism in Btg2−/− mice
Expression levels of other members of the BTG/TOB family were not upregulated in Btg2−/− mice (Fig. 2), suggesting deletion of Btg2 is not compensated by upregulation of other family members

Summary

Introduction

Subcortical ischemic vascular dementia, one of the major subtypes of vascular dementia, is characterized by lacunar infarcts and white matter lesions caused by chronic cerebral hypoperfusion. We used a mouse model of bilateral common carotid artery stenosis (BCAS) to investigate the role of B-cell translocation gene 2 (BTG2), an antiproliferation gene, in the white matter glial response to chronic cerebral hypoperfusion. Brain inflammation, defined by glial activation, has attracted a great deal of attention in stroke research [7,8,9,10] In this regard, proliferation of glial cells, including astrocytes, is observed after ischemic injury in animal models [11,12,13]. The roles of BTG2 in chronic cerebral hypoperfusion remain unclear To answer this question, in this study, we generated Btg2−/− mice, performed BCAS surgery, and analyzed locomotor activity, cognitive behavior, white matter lesions, and glial cells in the white matter

Results

Discussion

Conclusion