β-catenin is a known transcriptional coregulator that interacts with transcription factors in the Tcf/Lef family and others to modulate gene expression (Cadigan, 2012; Mosimann et al., 2009). β-catenin protein is regulated through post-translational modifications. Phosphorylation at a cluster of Ser/Thr residues in its N-terminus results in proteasome-mediated degradation of β-catenin (Cadigan, 2012; Mosimann et al., 2009). Activation of several signaling pathways such as Wnt and prostaglandin E2 leads to inactivation of the kinases that are responsible for β-catenin phosphorylation and therefore accumulation of β-catenin protein (Goessling et al., 2011; Klaus and Birchmeier, 2008). Due to its strong impact on transcription, the activity of β-catenin is tightly controlled, with aberrant β-catenin activation frequently associated with malignant transformation and various cancers (Clevers and Nusse, 2012). In the hematopoietic system, modest activation of β-catenin has been shown to have beneficial effects, such as extending survival of thymocytes (Xie et al., 2005) and regulatory T cells (Ding et al., 2008), promoting expansion of memory CD8⁺ T cells (Gattinoni et al., 2009; Zhao et al., 2010). However, excessive β-catenin activation, through deletion of exon 3 of Ctnnb1 gene (which encodes the Ser/Thr cluster in β-catenin protein), has detrimental effects on the function of hematopoietic stem cells (HSCs) (Kirstetter et al., 2006; Scheller et al., 2006), blocks thymocyte maturation and promotes thymocyte transformation (Guo et al., 2007b).

Whereas it is clear that β-catenin activation bears strong biological effects on blood cells, the requirement for β-catenin has been controversial. During thymocyte maturation, for example, genetic deletion of exons 3–6 of the Ctnnb1 gene caused modest developmental blocks and modest reduction in thymic cellularity (Xu et al., 2003). In other reports, however, no thymocyte maturation defects were observed when Ctnnb1 exons 2–6 were inducibly deleted with Mx1-Cre (Cobas et al., 2004), or in chimeric mice reconstituted with fetal liver cells lacking β-catenin and its homologue, γ-catenin (Jeannet et al., 2008; Koch et al., 2008). Additionally, mature CD8⁺ T cells in these β-catenin-targeted models showed intact response to viral infections (Driessens et al., 2010; Prlic and Bevan, 2011). On the other hand, among the Tcf/Lef family transcription factors (TFs) that interact with β-catenin, Tcf1 and Lef1 are expressed in T lineage cells (Staal et al., 2008; Xue and Zhao, 2012). Null mutations of Tcf1 alone or together with Lef1 show more profound T cell developmental blocks and more severe decrease in thymic cellularity (Germar et al., 2011; Okamura et al., 1998; Verbeek et al., 1995; Weber et al., 2011; Yu et al., 2012b). Recent studies also revealed multifaceted roles of Tcf1 in mature T cell responses including differentiation of follicular helper T cells (Choi et al., 2015; Raghu et al., 2019; Wu et al., 2015; Xu et al., 2015). These discrepancies have posed a major challenge in the past two decades as to the true requirements for β-catenin and its connection with Tcf/Lef TFs in hematopoietic cells.

One notable observation is that both Ctnnb1-targeted strains used in previous studies retain a truncated protein in hematopoietic cells (Jeannet et al., 2008). The Ctnnb1 gene has 15 exons, deletion of exons 2–6 or exons 3–6 in both models (Brault et al., 2001; Huelsken et al., 2000) may have allowed in-frame translation from downstream exons, giving rise to an N-terminally truncated β-catenin protein of 40–50 kDa. Because the N-terminus of β-catenin contains phosphorylation sites for ubiquitin-dependent degradation, an N-terminally truncated form of β-catenin protein has longer half-life, and its ectopic expression has been shown to stimulate proliferation and apoptosis of intestinal crypts (Wong et al., 1998). In addition, a C-terminally truncated β-catenin is a naturally occurring β-catenin paralog in planarians, and acts as a negative regulator of full-length β-catenin during planarian eye photoreceptor specification (Su et al., 2017). Therefore, the presence of the truncated β-catenin protein in previously β-catenin-targeted models may functionally compensate for loss of full-length β-catenin, underlying the lack of severe defects in T cell development or mature T cell responses. On the other hand, the truncated β-catenin protein may function as a dominant negative, and this possibility then raises questions on observed requirements for β-catenin using the existing β-catenin-targeted models. For example, β-catenin is considered essential for self-renewal of leukemic stem cells (LSCs) in both chronic and acute myeloid leukemia (CML and AML, respectively) (Hu et al., 2009; Wang et al., 2010; Yeung et al., 2010; Zhao et al., 2007). This work aims to address these long-standing questions.

We previously obtained the Ctnnb1 exons 2–6 floxed model (Brault et al., 2001). We aimed to ablate β-catenin protein in all hematopoietic cells using Vav-Cre, but found accumulation of a truncated form of β-catenin protein of approximately 40 kDa in bone marrow (BM) cells (Figure 1—figure supplement 1), consistent with a previous report (Jeannet et al., 2008). To achieve complete ablation of β-catenin protein, we re-targeted the Ctnnb1 gene locus by inserting LoxP sites into introns 1 and 14, respectively (Figure 1A) so that a Cre recombinase removes 13 of a total of 15 Ctnnb1 exons. The resulting Ctnnb1-floxed mice were crossed with a strain that expresses Cre recombinase and estrogen receptor fusion protein (Cre-ER^T2) in the ubiquitously expressed Rosa26 locus (Guo et al., 2007a). We maintained a single Rosa26^Cre-ERT2 allele in all mice used in this study (referred to as CreER⁺ for simplicity), so as to avoid dose-dependent effects by tamoxifen and/or Cre. Lineage-negative BM cells and peripheral T cells from CreER⁺Ctnnb1^fl/fl mice were cultured in vitro with tamoxifen or its carrier solvent, DMSO, and immunoblotting validated effective ablation of β-catenin protein without generating truncated form(s) (Figure 1B). A band of 50 kDa was detected in both tamoxifen- and DMSO-treated T cells, which was considered non-specific because its size was larger than the truncated β-catenin protein resulting from translation from downstream exons (compare with Figure 1—figure supplement 1). These analyses validate that the new targeting strategy can generate a true β-catenin null mutation.

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Source files, containing original data for Figure 1E,F and G, to document thymic cellularity (E), frequency of thymocyte subsets at different developmental stages (F, G).

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When the whole mice were treated with tamoxifen in vivo for four consecutive days, however, CreER⁺Ctnnb1^fl/fl mice exhibited morbidity within 10 days, while CreER⁺Ctnnb1^+/+ mice remained healthy (Figure 1—figure supplement 2), indicating ablating β-catenin in multiple organs may have severely compromised vital functions. To specifically address the function of β-catenin in hematopoietic cells, we transplanted BM cells from CD45.2⁺ CreER⁺Ctnnb1^+/+ (WT) or CreER⁺Ctnnb1^fl/fl mice into irradiated CD45.1⁺ recipients (Figure 1C). After ≥6 weeks when the BM chimeras were stably established, treatment of the recipients with the same tamoxifen regimen did not cause lethality (not shown). Effective ablation of β-catenin was observed in sorted CD45.2⁺CreER⁺Ctnnb1^fl/fl thymocytes, splenic T cells, and total BM cells (Figure 1D). We further determined the efficacy of deleting floxed exons in genomic DNAs, where the PCR products from F1 and R1 primers were detected from the WT Ctnnb1 allele (Figure 1A), but were barely detectable in sorted CD45.2⁺ BM cells from tamoxifen-treated CreER⁺Ctnnb1^fl/fl recipients (Figure 1—figure supplement 3A). On the other hand, PCR products from the F1 and R2 primer combination were only detected after the intervening exons were deleted (Figure 1—figure supplement 3A). Effective deletion of Ctnnb1 transcripts was also validated by RT-PCR using primer 13F (complementary to the deleted exon 13) in combination with primer 15R (complementary to undeleted exon 15) (Figure 1—figure supplement 3B). These characterizations further validated that null mutation of β-catenin is achieved in vivo in all hematopoietic cells in the BM chimeras.

To directly address the functional redundancy between β-catenin and its homologue γ-catenin (encoded by Jup), we crossed the Jup^fl/fl strain (Demireva et al., 2011) with CreER⁺Ctnnb1^fl/fl mice to produce CreER⁺Ctnnb1^fl/flJup^fl/fl mice and generated BM chimeras as in Figure 1C. Excision of the floxed Jup exons 3–5 after tamoxifen treatment was validated in genomic DNAs from sorted CD45.2⁺ BM cells with similar strategy as above (Figure 1—figure supplement 4A). The PCR products from Jup F1 and R1 primers detected from the WT Jup allele in WT cells were greatly diminished in tamoxifen-treated CreER⁺Ctnnb1^fl/flJup^fl/fl cells, while PCR products from Jup F1 and R2 primer combination were only detected in the latter (Figure 1—figure supplement 4B). On the mRNA level, Jup transcripts were only one fiftieth as abundant as Ctnnb1 transcripts in WT cells, but both Jup and Ctnnb1 transcripts were effectively deleted in tamoxifen-treated CreER⁺Ctnnb1^fl/flJup^fl/fl BM cells (Figure 1—figure supplement 4C). Consistent with low Jup transcript abundance, detection of γ-catenin protein in WT or targeted BM cells proved to be challenging; however, γ-catenin protein was readily detectable in WT hepatocytes and was greatly diminished in hepatocytes in tamoxifen-treated CreER⁺Ctnnb1^fl/flJup^fl/fl mice (non-BM chimeras, Figure 1—figure supplement 4D). These analyses validated effective ablation of γ-catenin in our experimental system.

Following tamoxifen-induced target gene deletion in the chimeras, total thymic cellularity was similar in WT chimeras and those lacking β-catenin alone or both β-catenin and γ-catenin (Figure 1E). Thymocyte maturation follows sequential stages from CD4^–CD8^–double negative (DN) to CD4⁺CD8⁺double positive (DP) followed by further differentiation to CD4⁺ or CD8⁺ single positive cells. Each thymic subset was detected at similar frequency among all genotypes examined (Figure 1F). By intracellular staining of Ki67, DN and DP cells exhibited more active proliferation than CD4⁺ and CD8⁺ thymocytes, and each subset showed similar frequency of Ki67⁺ cells among all genotypes (Figure 1—figure supplement 5A). Detection of active Caspase-3/7 revealed that DN thymocytes showed modestly increased susceptibility to apoptosis than thymocytes in later stages, and each subset showed similar frequency of Caspase-3/7⁺ cells among all genotypes (Figure 1—figure supplement 5B). In addition, subfractionating the DN thymocytes based on CD25 and CD44 expression showed that distribution of DN1-4 subsets was similar among all genotypes (Figure 1G). A cohort of CreER⁺ WT and CreER⁺Ctnnb1^fl/flJup^fl/fl BM chimeras (n = 5 each) was monitored for 16 weeks after tamoxifen treatment, and none of these mice showed signs of malignant transformation of thymocytes or other hematopoietic lineage cells. These analyses showed that complete loss of β-catenin or both β- and γ-catenin did not detectably cause T cell developmental blocks, or alterations in thymocyte proliferative capacity or survival.

In response to acute viral infections, antigen-specific mature CD4⁺ and CD8⁺ T cells mount protective immune responses by clonal expansion and differentiation into functional effector cells. To test the requirements for β-catenin and γ-catenin in mature T cell responses, we infected tamoxifen-treated BM chimera with lymphocytic choriomeningitis virus Armstrong strain (LCMV-Arm) to elicit acute viral infection. Activated CD4⁺ T cells predominantly differentiate into CXCR5^–SLAM^hi T helper 1 (T_H1) and CXCR5⁺SLAM^loT follicular helper (T_FH) lineage cells (Crotty, 2014). T_FH cells depend on Tcf1 and Lef1 for Bcl6 induction and further differentiation (Choi et al., 2015; Wu et al., 2015; Xu et al., 2015); in contrast, deletion of β-catenin alone or in combination with γ-catenin did not affect the frequency of T_H1 or T_FH cells at the peak response (i.e., 8 days post-infection, dpi) (Figure 2A). In addition, Bcl6-expressing germinal center (GC)-T_FH cells were detected at similar frequency among all genotypes (Figure 2B), suggesting that β-catenin and γ-catenin are not essential for T_FH cell differentiation. Whereas T_FH cells maintain Tcf1 expression similar to naïve CD4⁺ T cells (Gullicksrud et al., 2017), fully differentiated cytotoxic effector CD8⁺T cells downregulate Tcf1 (Gullicksrud et al., 2017; Zhao et al., 2010). Consistent with this Tcf1 expression pattern, loss of Tcf1 has little impact on differentiation of effector CD8⁺T cells (Shan et al., 2017; Zhou et al., 2010). Not surprisingly, deletion of β-catenin alone or both β/γ-catenin did not detectably affect generation of antigen-specific effector CD8⁺T cells, identified as IFN-γ-producing cells upon stimulation with peptides derived from the LCMV glycoprotein (GP) 33 epitope (Figure 2C). The GP33-specfic effector CD8⁺T cells showed similar capacity of producing TNF-α and similar expression of granzyme B among all genotypes (Figure 2C,D), suggesting that β-catenin and γ-catenin are dispensable for CD8⁺ T cells to differentiate into functional cytotoxic T cells.

Figure 2

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Source files, containing original data for Figure 2A–F, to document frequency of antigen-specific Tfh cells (A, B) and CD8 T cells (C), expression of Granzyme B in CD8 T cells (D) at the effector response phase, and the frequency of antigen-specific Tfh cells (E) and CD8 T cells (F) at the memory phase.

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After the peak responses that resolve acute infections, a fraction of antigen-specific T cells persists as memory T cells (Martin and Badovinac, 2014). Tcf1 is expressed in long and short isoforms with the former having the capacity of interacting with β-catenin through its N-terminal domain (Staal et al., 2008; Xue and Zhao, 2012). Previously we ablated the Tcf1 long isoform, which led to profound reduction of memory T_H1 and T_FH cells (Gullicksrud et al., 2017). Tcf1 is also required for memory CD8⁺ T cells (Jeannet et al., 2010; Zhou et al., 2010). To determine if β-catenin and γ-catenin are required for memory T cells, we analyzed the infected BM chimeras at ≥40 dpi. During 15–16 and 30–31 dpi, we added two rounds of tamoxifen treatment to the LCMV-infected BM chimeras, so as to prevent rebound of undeleted cells and ensure persistent deletion of β/γ-catenin proteins. CXCR5⁺ memory T_FH cells were detected at similar frequency in WT and β/γ-catenin-null BM chimeras (Figure 2E). GP33-specific memory CD8⁺ T cells were not diminished in β/γ-catenin-null BM chimeras and preserved similar capacity of producing TNF-α (Figure 2F). Collectively, loss of β-catenin and γ-catenin did not detectably affect T cell responses at either effector or memory phase.

β-catenin ablation using previously Ctnnb1-targeted models did not show potent impact on maintenance of HSCs (Ruiz-Herguido et al., 2012; Zhao et al., 2007). Consistent with these observations, null mutation of β-catenin alone or both β/γ-catenin did not affect BM cellularity (Figure 3A), or the frequency of Lin^–Sca1⁺c-Kit⁺ (LSK) cells, in which HSCs were enriched (Figure 3B). HSCs with long-term repopulation capacity, as marked by CD150⁺CD48^– phenotype, were detected at similar frequency among all genotypes (Figure 3B), suggesting that loss of β/γ-catenin did not perturb HSC homeostasis.

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Source files, containing original data for Figure 3A,B and F, to document BM cellularity (A), and frequency of LSKs and Slam HSCs in BM cells (B), and leukemia burden in peripheral blood of AML receipt mice (F).

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Unlike HSCs, AML LSCs have been reported to critically depend on β-catenin using the MLL-AF9 or MLL-ENL mouse models (Wang et al., 2010; Yeung et al., 2010). To reappraise this requirement with our new animal model, we used the same MLL-AF9 AML model by retroviral delivery of the fusion protein (co-expressed with GFP) into Lin^– BM cells from tamoxifen-treated CreER⁺ WT or CreER⁺Ctnnb1^fl/fl BM chimeras (Figure 3C). The MLL-AF9-GFP-infected Lin^– BM cells were then transplanted into CD45.1⁺ primary (1^o) recipients (Figure 3C). Because tamoxifen-mediated target gene ablation may not achieve 100% deletion efficiency in all cells, rare non-deleted cells could have growth advantage over β-catenin-deficient cells, especially in long-term studies such as LSC serial transplantation. To eliminate potential outgrowth of the rare non-deleted cells, we took the approach of recurring tamoxifen treatments at a standardized interval. Our optimizing experiments found that following the initial 4 doses of tamoxifen administration, 3 doses of tamoxifen delivery at 4 week intervals sustained elimination of β-catenin protein in Ctnnb1-targeted cells with minimal impact on hematopoietic cellularity. The efficacy of this regimen was validated by immunoblotting for β-catenin in CD45.2⁺GFP⁺Mac1⁺ AML cells in the BM of 1^o recipients (Figure 3D). The 1^o recipients in both groups showed similar rate of survival (Figure 3E), suggesting that β-catenin null mutation did not affect the onset of AML.

To specifically investigate self-renewal of AML LSCs, we sort-purified CD45.2⁺GFP⁺Lin^–Mac1^loc-Kit^hi Sca1^loCD16/CD32^hi cells as AML LSCs from the 1^o recipients (see Figure 3—figure supplement 1 for gating strategy), followed by transplantation into secondary (2^o) recipients (Figure 3C). Both WT and β-catenin-deficient AML LSCs showed similar capacity of propagating AML as determined by longitudinal tracking of CD45.2⁺Mac1⁺ GFP⁺ AML leukemia burden in peripheral blood cells (PBCs, Figure 3F), and by the survival rate of 2^o recipients (Figure 3E). In an independent experiment, 2^o recipients of β/γ-catenin-deficient AML LSCs showed similar survival as those of WT or β-catenin-deficient LSCs (Figure 3—figure supplement 2). These data collectively argue against an essential role of β-catenin for AML LSCs.

To further substantiate the unexpected lack of impact on AML LSCs by null mutation of β/γ-catenin, we extended our AML studies to determine a requirement for Tcf/Lef family TFs that interact with β-catenin. There are four members in the Tcf/Lef family: Tcf1, Lef1, Tcf3 and Tcf4 (encoded by Tcf7, Lef1, Tcf7l1, and Tcf7l2, respectively). To fully address functional redundancy among Tcf/Lef family TFs, we used Tcf7l1-targeted murine embryonic stem (ES) cells generated by the International Knockout Mouse Consortium (Figure 4A) to produce Tcf7l1^fl/fl mouse strain. By crossing with CreER and Tcf7l2^fl/fl (Angus-Hill et al., 2011) strains, we generated CreER⁺Tcf7l1^fl/flTcf7l2^fl/fl (CreER⁺Tcf3/4-dKO) mice. This line was further crossed with our established CreER⁺Tcf7^fl/flLef1^fl/fl (CreER⁺Tcf1/Lef1-dKO) mice (Yu et al., 2016) to generate CreER⁺Tcf7^fl/flLef1^fl/flTcf7l1^fl/flTcf7l2^fl/fl mice (called CreER⁺Tcf-qKO herein). Following treatment with the same tamoxifen regimen as above, the CreER⁺Tcf-qKO mice did not exhibit early lethality, and Tcf1 and Lef1 proteins were ablated in thymocytes of CreER⁺Tcf1/Lef1-dKO mice as determined by intracellular staining (Figure 4B). While ablation of Tcf4 protein was also effective in thymocytes as determined by immunoblotting (Figure 4B), Tcf3 protein was not reliably detected in thymocytes or BM cells (not shown), likely due to its expression in very low abundance (see Figure 4C). It should be noted that deletion efficacy for Tcf3 protein was independently verified in mouse embryonic fibroblasts in a recent report using the same ES clone (Mašek et al., 2016). We further verified with quantitative RT-PCR that the targeted exon in Tcf7l1 transcripts was as effectively deleted as that in Tcf7l2 transcripts, in spite of the low abundance (Figure 4C). Tamoxifen treatment resulted in >90% reduction in thymic cellularity in CreER⁺Tcf1/Lef1-dKO and CreER⁺Tcf-qKO mice, but did not detectably affect CreER⁺Tcf3/4-dKO thymocyte numbers (Figure 4D). Consistent with a requirement for Tcf1 for DP thymocyte survival (Ioannidis et al., 2001), tamoxifen-treated CreER⁺Tcf1/Lef1-dKO and CreER⁺Tcf-qKO mice showed profound reduction in DP thymocyte frequency, with concomitant relative increase in CD4⁺ and CD8⁺ single positive thymocyte frequency (Figure 4E). Within the DN compartment, CreER⁺Tcf1/Lef1-dKO and CreER⁺Tcf-qKO mice both showed DN1 accumulation and apparent loss of DN2 thymocytes (Figure 4F), in line with a key function of Tcf1 in specification of early thymic progenitors to T cell lineage (Germar et al., 2011; Weber et al., 2011). In all these critical aspects, CreER⁺Tcf3/4-dKO mice exhibited little or modest changes; furthermore, the defects observed in CreER⁺Tcf1/Lef1-dKO mice were not detectably more exacerbated in CreER⁺Tcf-qKO mice with additional deletion of Tcf3 and Tcf4. Taken together, these observations suggest that Tcf3 and Tcf4 are not essential for thymopoiesis and further validate critical function of Tcf1 and Lef1 among the Tcf/Lef family in T cell development.

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Source files, containing original data for Figure 4D–H, to document thymic cellularity (D), frequency of thymocyte subsets at different developmental stages (E, F), and leukemia burden in peripheral blood of AML receipt mice (G).

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Given the demonstrated efficacy of ablating Tcf/Lef factors in hematopoietic cells, we extended our studies to investigate their requirement in AML LSCs. We used Lin^– BM cells from tamoxifen-treated CreER⁺ WT or CreER⁺Tcf-qKO mice directly for the AML studies, without establishing BM chimeras. The 1^o recipients of MLL-AF9-infected Tcf-qKO BM cells showed similar survival rate as those of WT BM cells (Figure 4G), indicating ablation of all four Tcf/Lef TFs did not affect AML onset. In addition, WT and Tcf-qKO AML LSCs isolated from the 1^o recipients showed similar capacity of propagating AML leukemic cells in PBCs in 2^o recipients (Figure 4H), resulting in similar survival rate of the 2^o recipients (Figure 4G). Collectively, our data do not support an essential requirement for Tcf/Lef and β-catenin proteins in AML LSCs. It is of note that the lack of impact on AML LSCs by ablating Tcf/Lef TFs or β-catenin was not due to technical issues, because we have used the same protocol to demonstrate that 1) constitutive activation of non-canonical NF-κB pathway (Xiu et al., 2018) or 2) genetic ablation of Groucho/TLE corepressors (to be described elsewhere) impairs AML LSC self-renewal.

By use of the newly established β-catenin null mutation, this study clarifies on a long-standing controversy and provides more conclusive evidence indicating that β-catenin and γ-catenin are not essential for thymocyte development, T cell responses to viral infection at either effector or memory phase. This is in stark contrast to the versatile functions described for Tcf1 and Lef1 in T lineage cells (Raghu et al., 2019). We previously showed that deletion of the N-terminal domain in Tcf1, which abrogates interaction with β-catenin, does reduce thymic cellularity and compromise T_FH cell differentiation at effector and memory phases (Gullicksrud et al., 2017; Xu et al., 2017). Given the apparent lack of impact upon β/γ-catenin deletion, Tcf1 may engage coactivators other than β-catenin to exert those biological functions. Indeed, we recently reported that Tcf1 interacts with a Ser21-phosphorylated form of Ezh2 to cooperatively induce Bcl6 and Icos during T_FH cell differentiation in response to acute viral infection (Li et al., 2018). It may thus be fruitful to search for novel Tcf1 partners in developing thymocytes and antigen-responding mature T cells (Steinke and Xue, 2014).

It is surprising that ablation of neither β-catenin nor Tcf/Lef TFs affected LSC self-renewal in the AML mouse model. The reported requirements for β-catenin using previously Ctnnb1-targeted mouse strains may be likely ascribed to unwanted effects by the truncated β-catenin protein. Although genetic alterations in Wnt-β-catenin pathway components are not among the primary driver mutations of AML (Papaemmanuil et al., 2016; Tyner et al., 2018), frequent translocation products including MLL-AF9 result in elevated β-catenin accumulation (Lane et al., 2011; Müller-Tidow et al., 2004). Our data do not refute the facts that aberrant activation of β-catenin has pathological effects, and there is no denial of therapeutic values in inhibiting Wnt-β-catenin pathway for debulking AML blasts. The findings in this study nonetheless caution that for the purpose of eradicating AML LSCs, targeting β-catenin may not be as effective as previously hoped.

Source data files provided. Mouse strain will be made available to other investigators on request.

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Author details

1. Xin Zhao

   Center for Discovery and Innovation, Hackensack University Medical Center, Nutley, United States

   Contribution

   Conceptualization, Data curation, Formal analysis, Supervision, Validation, Investigation, Writing - original draft, Writing - review and editing

   Contributed equally with

   Peng Shao

   Competing interests

   No competing interests declared

2. Peng Shao

   Department of Microbiology and Immunology, Carver College of Medicine, University of Iowa, Iowa City, United States

   Contribution

   Data curation, Formal analysis, Validation, Investigation

   Contributed equally with

   Xin Zhao

   Competing interests

   No competing interests declared

3. Kexin Gai

   Center for Discovery and Innovation, Hackensack University Medical Center, Nutley, United States

   Contribution

   Data curation, Formal analysis, Investigation

   Competing interests

   No competing interests declared

4. Fengyin Li

   Hefei National Laboratory for Physical Sciences at Microscale, the CAS Key Laboratory of Innate Immunity and Chronic Disease, School of Basic Medical Sciences, Division of Life Sciences and Medicine, University of Science and Technology of China, Hefei, China

   Contribution

   Data curation, Formal analysis, Investigation

   Competing interests

   No competing interests declared

5. Qiang Shan

   Center for Discovery and Innovation, Hackensack University Medical Center, Nutley, United States

   Contribution

   Data curation, Formal analysis, Investigation

   Competing interests

   No competing interests declared

6. Hai-Hui Xue

   1. Center for Discovery and Innovation, Hackensack University Medical Center, Nutley, United States
   2. New Jersey Veterans Affairs Health Care System, East Orange, United States

   Contribution

   Conceptualization, Supervision, Funding acquisition, Writing - original draft, Project administration, Writing - review and editing

   For correspondence

   haihui.xue@hmh-cdi.org

   Competing interests

   No competing interests declared

   "This ORCID iD identifies the author of this article:" 0000-0002-9163-7669

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