title: Deletion of the bis gene results in a marked increase in the production of corticosterone that is associated with thymic atrophy in mice.
abstract: Bis (Bag3) is known to be involved in cell survival, migration, the regulating of chaperones, and protein quality control. We reported recently on the production of bis gene-deleted mice, which show early lethality within 3 wk after birth with a phenotype showing severe malnutrition and shrinkage of the thymus. In this report, we provide evidence to show that an intrinsic problem of adrenal gland is the the primary cause for the severe atrophy of the thymus in bis(-/-) mice. The bis(-/-) mice show significantly higher levels of corticosterone, but CRH and ACTH levels were considerably lower than those of wild littermates. The transcription of steroidogenic enzymes was increased in the adrenal glands of bis(-/-) mice, accompanied by an increase in the thickness of the zona reticularis. An analysis of thymus tissue from bis(-/-) mice revealed that the severe atrophy of the thymus is due to the specific loss of immature double-positive (CD4(+)CD8(+)) cortical thymocytes by apoptosis, as evidenced by immunohistochemical examination and flow cytometric analysis, which were restored by injection of an inhibitor of glucocorticoid synthesis. In vitro cultures of thymocytes with increasing doses of dexamethasone exhibited a similar degree of apoptosis between wild and bis(-/-) thymocytes. The corticosterone levels from fasted wild littermates were one-half those of bis(-/-) mice, although serum glucose levels were similar. Thus, the deletion of the bis gene resulted in the intrinsic defect in the adrenal gland, leading to a marked increase in glucocorticoid levels, probably upon starvation stress, which accounts for the massive apoptosis of the thymus.
authors.affiliation: Department of Biochemistry, College of Medicine, The Catholic University of Korea, Seoul, South Korea.
authors.forename: Dong-Ye
authors.initials: DY
authors.lastname: Youn
authors.forename: Jung-Sook
authors.initials: JS
authors.lastname: Yoon
authors.forename: Yong Kwan
authors.initials: YK
authors.lastname: Kim
authors.forename: Chung Eun
authors.initials: CE
authors.lastname: Yeum
authors.forename: Seong-Beom
authors.initials: SB
authors.lastname: Lee
authors.forename: Ho-Joong
authors.initials: HJ
authors.lastname: Youn
authors.forename: Yoshihide
authors.initials: Y
authors.lastname: Tsujimoto
authors.forename: Jeong-Hwa
authors.initials: JH
authors.lastname: Lee
mesh_terms: D048868:Adaptor Proteins, Signal Transducing; D000311:Adrenal Glands / Q000378:metabolism / Q000473:pathology; D000818:Animals; D051017:Apoptosis Regulatory Proteins; D001284:Atrophy / Q000235:genetics; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D003345:Corticosterone / Q000378:metabolism*; D017353:Gene Deletion; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009929:Organ Size / Q000235:genetics; D010641:Phenotype; D013217:Starvation / Q000378:metabolism / Q000473:pathology; D013950:Thymus Gland / Q000378:metabolism / Q000473:pathology*; D015854:Up-Regulation / Q000235:genetics
chemical_list: D048868:Adaptor Proteins, Signal Transducing; D051017:Apoptosis Regulatory Proteins; C498806:Bag3 protein, mouse; D002352:Carrier Proteins; D003345:Corticosterone