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A critical epithelial survival axis regulated by MCL-1 maintains thymic function in mice

Reema Jain, Julie M. Sheridan, Antonia Policheni, Melanie Heinlein, Luke C. Gandolfo, Grant Dewson, Gordon K. Smyth, Stephen N. Sansom, Nai Yang Fu, Jane E. Visvader, Georg A. Holländer, Andreas Strasser and Daniel H. D. Gray

Key Points

  • MCL-1 is essential, but BCL-2 and BCL-XL are dispensable, for TEC survival and thymic function.

  • Epidermal growth factor upregulates MCL-1 in TECs.

Publisher's Note: There is an Inside Blood Commentary on this article in this issue.

Abstract

T-cell differentiation is governed by interactions with thymic epithelial cells (TECs) and defects in this process undermine immune function and tolerance. To uncover new strategies to restore thymic function and adaptive immunity in immunodeficiency, we sought to determine the molecular mechanisms that control life and death decisions in TECs. Guided by gene expression profiling, we created mouse models that specifically deleted prosurvival genes in TECs. We found that although BCL-2 and BCL-XL were dispensable for TEC homeostasis, MCL-1 deficiency impacted on TECs as early as embryonic day 15.5, resulting in early thymic atrophy and T-cell lymphopenia, with near complete loss of thymic tissue by 2 months of age. MCL-1 was not necessary for TEC differentiation but was continually required for the survival of mature cortical and medullary TECs and the maintenance of thymic architecture. A screen of TEC trophic factors in organ cultures showed that epidermal growth factor upregulated MCL-1 via MAPK/ERK kinase activity, providing a molecular mechanism for the support of TEC survival. This signaling axis governing TEC survival and thymic function represents a new target for strategies for thymic protection and regeneration.

  • Submitted March 3, 2017.
  • Accepted September 21, 2017.
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