Runx1/Cbfβ2 Complexes Are Required for Lymphoid Tissue Inducer Cell Differentiation at Two Developmental Stages

Abstract

Hematopoietic lymphoid tissue inducer (LTi) cells are essential for the development of secondary lymphoid tissues including lymph nodes and Peyer’s patches. Two transcription factors, the helix-loop-helix inhibitor Id2 and the retinoic acid-related orphan receptor γt (Rorγt), have been shown to be crucial for LTi cell development. However, it remains unclear how the specification of multipotent hematopoietic progenitor cells toward the LTi lineage is programmed. In this study, we report impaired lymphoid tissue organogenesis in mice in which the function of Runx1/Cbfβ transcription factor complexes was attenuated by the loss of either the distal promoter-derived Runx1 or Cbfβ2 variant protein. We found that LTi progenitors in fetal liver, defined previously as a lineage marker-negative α4β7 integrin (α4β7)+ IL-7R α-chain (IL-7Rα)+ population, can be subdivided into Rorγt-expressing IL-7Rαhigh cells and nonexpressing IL-7Rαmid cells. Whereas Id2 and Rorγt are required to direct α4β7+IL-7Rαmid cells to become α4β7+IL-7Rαhigh cells, Runx1/Cbfβ2 complexes are necessary for the emergence of α4β7+IL-7Rαmid cells. In addition, the loss of Cbfβ2, but not P1-Runx1, resulted in an inefficient upregulation of Rorγt in residual α4β7+IL-7Rα+ LTi cells at anlagen. Our results thus revealed that Runx1/Cbfβ2 complexes regulate the differentiation of LTi cells at two stages: an early specification of hematopoietic progenitors toward the LTi lineage and a subsequent activation of Rorγt expression at anlagen.

Critical role of P1-Runx1 in mouse basophil development

“…In addition to these granulocytes, numbers of monocytes (Gr-1 low Siglec-F Ϫ ), NK cells (NK1.1 ϩ CD3 Ϫ ), total T cells (CD3 ϩ ), B cells (B220 ϩ ), and dendritic cells (CD11c ϩ ) were not significantly different in Runx1 P1N/P1N mice compared with WT mice in either the BM or spleen (Figure 2A-B). As we reported previously, 40 NKT cells (NK1.1 ϩ CD3 ϩ ) were reduced in both the BM and spleen (Figure 2A-B). These data indicate that, among granulocyte populations, basophils are uniquely deficient in Runx1 P1N/P1N mice.…”

“…34 We had demonstrated previously a requirement for P1-Runx1 in lymphoid tissue inducer cell differentiation, 40 and found that Runx1 P1N/P1N mice have severe reductions in NKT cells, mild T-cell deficits, and an increase in Lin Ϫ c-Kit ϩ Sca-1 ϩ HSCs. 40 However, there have been no previous reports describing the myeloid cell compartment in these mice. When we analyzed myeloid cells in Runx1 P1N/P1N mice, we found that they have a severe reduction in basophils.…”

Characteristics of innate lymphoid cells (ILCs) and their role in immunological disorders (an update)

“…It has been demonstrated that Notch signaling helps to maximize the efficiency of LTi cell differentiation [41]. Likewise, LTi cell differentiation needs to some transcriptions factors such as Runx1 and Tox [68,69]. Furthermore, aryl hydrocarbon receptor (AhR) signals are required for the maintenance and expansion of postnatal emerging of ILC3 subset [47].…”

Cbfb2 Isoform Dominates More Potent Cbfb1 and Is Required for Skeletal Development

“…(10,19,21) In brief, with the splice signal for Cbfb1 located inside of exon 5, the GTG was mutated to CTC, and with the splice signal for Cbfb2 at the 3' terminus of exon 5, GTTAG was mutated to AATTC. Cbfb fl/fl/Cre mice were generated by using Cbfb fl/fl mice and Dermo1 Cre knock-in mice, in which Cre is expressed in mesenchymal cells giving rise to both chondrocyte and osteoblast lineages.…”

“…(17,18) Cbfb1 and Cbfb2 are formed by alternative splicing using donor splice sites located inside exon 5 and at the 3' terminus of exon 5, respectively, and an acceptor splice site located at the 5' terminus of exon 6. (18) Although Cbfb2 is required for the differentiation of lymphoid tissue inducer cells and the development of mucosa-associated lymphoid tissue, (19,20) the functions of the two isoforms in skeletal development are completely unknown. In this study, we examined the skeletal development of mice lacking the Cbfb1 isoform (Cbfb1 -/-) and mice lacking the Cbfb2 isoform (Cbfb2 -/-).…”