Lunatic, Manic, and Radical Fringe Each Promote T and B Cell Development

Abstract

Lunatic, Manic and Radical Fringe (LFNG, MFNG and RFNG) are N-acetylglucosaminyltransferases that modify Notch receptors and regulate Notch signaling. Loss of LFNG affects thymic T cell development and LFNG and MFNG are required for marginal zone (MZ) B cell development. However, roles for MFNG and RFNG in T cell development, RFNG in B cell development, or Fringes in T and B cell activation, are not identified. Here we show that Lfng/Mfng/Rfng triple knockout (Fng tKO) mice exhibited reduced binding of DLL4 Notch ligand to CD4/CD8 double-negative (DN) T cell progenitors, and reduced expression of NOTCH1 targets Deltex1 and CD25. Fng tKO mice had reduced frequencies of DN1/cKit+ and DN2 T cell progenitors and CD4+CD8+ double positive (DP) T cell precursors, but increased frequencies of CD4+ and CD8+ single positive (SP) T cells in thymus. In spleen, Fng tKO mice had reduced frequencies of CD4+, CD8+, central memory T cells and marginal zone (MZ) B cells, and an increased frequency of effector memory T cells, neutrophils, follicular (Fo) and MZ P B cells. The Fng tKO phenotype was cell-autonomous and largely rescued in mice expressing one allele of a single Fng gene. Stimulation of Fng tKO splenocytes with anti-CD3/CD28 beads or lipopolysaccharide gave reduced proliferation compared to controls, and the generation of activated T cells by concanavalin A or L-PHA was also reduced in Fng tKO mice. Therefore, each Fringe contributes to T and B cell development, and Fringe is required for optimal in vitro stimulation of T and B cells.

Fine-tuning of Notch signaling sets the boundary of the organ of Corti and establishes sensory cell fates

“…Although Fringe genes are often expressed in overlapping patterns, no obvious synergy has been reported in the brain, axial skeleton, limbs or cranial nerves for mutants in multiple family members (Moran et al, 2009). However, an interaction between Lfng, Rfng and Mfng has been observed in the maturation of marginal zone B cell precursors (Tan et al, 2009; Song et al, 2016), suggesting that in at least some cases, the combined effects of these three enzymes on Notch signaling in either cis or trans cannot be achieved by either alone.…”

What Have We Learned from Glycosyltransferase Knockouts in Mice?

“…Mice null for Mfng are viable but compound heterozygotes with Jag1 exhibit bile duct defects [92], and MFNG is required for optimal production of marginal zone B cells [93]. Mice null for Rfng have mild defects in T and B cell production [94], and compound Rfng/Jag1 heterozygotes have defective bile ducts [92]. In the Fuc-O-TSP pathway (Fig.…”

Deciphering the Fringe-Mediated Notch Code: Identification of Activating and Inhibiting Sites Allowing Discrimination between Ligands

“…Elimination of Mfng or Rfng in mice has no obvious developmental phenotype (Moran et al, 2009) but both have been implicated in a variety of Notch-dependent processes such as bile duct remodeling (D'Amato et al, 2016; Ryan et al, 2008). All three Fringes cooperate to modulate Notch activity during both B and T cell differentiation (Song et al, 2016) and have been linked to breast cancer (Xu et al, 2012; Zhang et al, 2015). …”