Abstract
FoxN1 is cell-autonomously expressed in skin and thymic epithelial cells (TECs), essential for their development. Inborn mutation of FoxN1 results in hair follicle and TEC development failure, whereas insufficient postnatal FoxN1 expression induces thymic atrophy, resulting in declined T lymphopoiesis. Although upregulating FoxN1 expression in the aged FoxN1-declined thymus rejuvenates T lymphopoiesis, whether its over- and ectopic-expression in early life is beneficial for T lymphopoiesis is unknown. Using our newly generated Rosa26-STOPflox–FoxN1 mice, in which over- and ectopic-expression of FoxN1 can be induced by various promoter-driven Cre-mediated deletions of the roadblock STOPflox in early life, we found that K14Cre-mediated inborn FoxN1 overexpression induced neonatal lethality, exhibited abnormal permeability in the skin and abnormal nursing. Ubiquitous deletion of the STOPflox mediated by progressive uCreERT leakage in juvenile mice affected thymus and bone marrow normality, resulting in an increased ratio of medullary/cortical TECs, along with declined T and B lymphopoiesis. Although the K5CreERT-mediated FoxN1 overexpression mice had a normal lifespan, induction of K5CreERT activation in juveniles adversely influenced total thymoycte development and produced ichthyosis-like skin. Therefore, FoxN1 has temporal and tissue-specific activity. Over- and ectopic-expression of FoxN1 in early life adversely influence immature TEC, T and B cell, and skin epithelial development.
Highlights
FoxN1 overexpression induced neonatal lethality, exhibited abnormal permeability in the skin and abnormal nursing
We found that FoxN1 over- and ectopic-expression in early life stages adversely affected the development of the skin, thymus and T cells, as well as B cells, whereas K5CreERT-mediated FoxN1 overexpression in adult mice did not cause any observable defects, and can probably be expected to attenuate age-related thymic involution as reported.[14,15]
We found that newborn mice with both Rosa26-STOPflox–FoxN1 and K14Cre transgenes had strong FoxN1 and GFP expression (Supplementary Figures S1B and C) in the skin and thymus.[1]
Summary
FoxN1 overexpression induced neonatal lethality, exhibited abnormal permeability in the skin and abnormal nursing. We found that FoxN1 over- and ectopic-expression (or nonprominent location expression) in early life stages adversely affected the development of the skin, thymus and T cells, as well as B cells, whereas K5CreERT-mediated FoxN1 overexpression in adult mice did not cause any observable defects, and can probably be expected to attenuate age-related thymic involution as reported.[14,15] FoxN1 exhibits both temporal and tissue-specific activity.
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