Indispensable role of Galectin-3 in promoting quiescence of hematopoietic stem cells.

Jia, Weizhen; Kong, Lingyu; Kidoya, Hiroyasu; Naito, Hisamichi; Muramatsu, Fumitaka; Hayashi, Yumiko; Hsieh, Han-Yun; Yamakawa, Daishi et al. · Nat Commun · 2021

basic_science · Level V

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Abstract

Hematopoietic stem cells (HSCs) in adult bone marrow (BM) are usually maintained in a state of quiescence. The cellular mechanism coordinating the balance between HSC quiescence and differentiation is not fully understood. Here, we report that galactose-binding lectin-3 (galectin-3; Gal-3) is upregulated by Tie2 or Mpl activation to maintain quiescence. Conditional overexpression of Gal-3 in mouse HSCs under the transcriptional control of Tie2 or Vav1 promoters (Gal-3 Tg) causes cell cycle retardation via induction of p21. Conversely, the cell cycle of long-term repopulating HSCs (LT-HSCs) in Gal-3-deficient (Gal-3<sup>-/-</sup>) mice is accelerated, resulting in their exhaustion. Mechanistically, Gal-3 regulates p21 transcription by forming a complex with Sp1, thus blocking cell cycle entry. These results demonstrate that Gal-3 is a negative regulator of cell-cycling in HSCs and plays a crucial role in adult hematopoiesis to prevent HSC exhaustion.

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