MXRA7

MXRA7 is a cytoplasmic protein that acts as a broad negative regulator of hematopoietic and immune cell differentiation while supporting survival programs in leukemic and normal cells (PMID:35680791, PMID:38735126). In leukemia models it promotes cell survival: overexpression in SHI-1 cells blunts drug-induced apoptosis through upregulation of BCL-2 (PMID:35680791), and its knockdown in NB4 acute promyelocytic leukemia cells lowers PML-RARα while restoring PML and RARα to potentiate ATRA-induced differentiation (PMID:37419299). As a brake on myeloid maturation, MXRA7 knockdown in THP-1 monocytes accelerates monocyte-to-macrophage differentiation and skews toward an inflammatory M1 state with elevated TNF-α, IL-1β, and IL-6, coupled to induction of VCAM-1 and ICAM-1 and activation of NF-κB (p52/p100) and MAPK signaling (PMID:38735126). In the megakaryocyte lineage MXRA7 conversely supports differentiation, as its loss in mice reduces megakaryocyte numbers, platelet counts, and proplatelet formation through diminished GATA-1/FOG-1 expression and ERK/MAPK signaling (PMID:37546710). Consistent with an anti-inflammatory role in tissue, MXRA7-deficient mice develop exacerbated imiquimod-induced psoriasis with heightened IL-17/IL-22/IL-23 and keratinocyte proliferation (PMID:29781547). Beyond these lineage and inflammatory phenotypes, no direct biochemical activity or binding partner for MXRA7 has been defined in the available corpus.

1. 2011 Low

   An initial functional handle suggested MXRA7 (as alias PS1TP1) could influence gene expression, framing it as a regulator with downstream transcriptional consequences.

   Evidence Suppression subtractive hybridization of PS1TP1-transfected HepG2 cells identifying putative downstream targets

   PMID:21977585

   Open questions at the time

   • SSH is a screening method with no functional validation of individual targets
   • No demonstration of direct DNA binding or transcriptional activity
   • Single lab, no replication
2. 2018 Medium

   The first in vivo loss-of-function model established MXRA7 as a negative modulator of inflammatory tissue pathology, moving it from screen candidate to physiological regulator.

   Evidence MXRA7 knockout mice in an imiquimod psoriasis model with cytokine RT-PCR and keratinocyte proliferation assays

   PMID:29781547

   Open questions at the time

   • Cell type responsible for the phenotype not resolved (keratinocyte-intrinsic vs immune)
   • No molecular mechanism linking MXRA7 to IL-17/IL-22/IL-23 induction
   • No biochemical activity defined
3. 2022 Medium

   MXRA7 was tied to a survival program in leukemia, explaining how it could restrain apoptosis.

   Evidence Confocal localization plus Western blot for BCL-2 and Annexin V/7-AAD apoptosis assays in stable MXRA7-overexpressing SHI-1 cells

   PMID:35680791

   Open questions at the time

   • Mechanism connecting MXRA7 to BCL-2 expression unknown
   • No rescue or mutagenesis to establish causality
   • Single cell line
4. 2023 Medium

   Knockdown studies positioned MXRA7 as a brake on differentiation and a stabilizer of the PML-RARα oncoprotein, linking it to ATRA responsiveness in APL.

   Evidence shRNA knockdown in NB4 cells with Western blots for PML-RARα/PML/RARα plus expression profiling and a NOD-SCID xenograft

   PMID:37419299

   Open questions at the time

   • Whether MXRA7 physically interacts with or directly stabilizes PML-RARα is unknown
   • Mechanism of the accompanying transcriptional changes (C/EBPβ/δ, KDM5A, etc.) not defined
5. 2023 Low

   Parallel work in B-ALL extended the pro-proliferative/anti-apoptotic role of MXRA7 to another leukemia context.

   Evidence shRNA knockdown in REH cells with proliferation, cell-cycle, apoptosis assays and caspase-3/-9 Western blots

   PMID:36765476

   Open questions at the time

   • No pathway reconstitution beyond caspase detection
   • Single paper, single lab
   • Upstream mechanism for cell-cycle arrest unknown
6. 2023 Medium

   A knockout mouse revealed a lineage-specific positive role, showing MXRA7 is required for megakaryopoiesis and platelet production via GATA-1/FOG-1 and ERK/MAPK signaling.

   Evidence MXRA7 knockout mice with bone marrow/spleen histology, platelet assays, GATA-1/FOG-1/ERK/β-tubulin Western blots, and MEG-01 knockdown

   PMID:37546710

   Open questions at the time

   • How MXRA7 connects to GATA-1/FOG-1 expression mechanistically is unknown
   • Direct molecular partners in megakaryocytes unidentified
7. 2024 Medium

   RNA-seq plus pathway dissection clarified that MXRA7 suppresses monocyte-to-macrophage differentiation and M1 polarization through adhesion molecules and NF-κB/MAPK signaling.

   Evidence shRNA knockdown in THP-1 cells with flow cytometry, cytokine ELISA, RNA sequencing, adhesion assays, and Western blots for NF-κB/MAPK

   PMID:38735126

   Open questions at the time

   • Direct molecular target of MXRA7 upstream of NF-κB/MAPK not identified
   • No demonstration of direct binding to any signaling component
8. 2026 Low

   Single-cell profiling extended MXRA7 function to bone marrow aging, implicating it in macrophage population dynamics and chemokine signaling.

   Evidence scRNA-seq of young/aged wild-type vs MXRA7-knockout bone marrow with ligand-receptor interaction analysis

   PMID:42220555

   Open questions at the time

   • scRNA-seq associations are correlative without functional validation
   • Ccl24-Ccr3 axis link inferred, not experimentally tested
   • Mechanism by which MXRA7 alters macrophage populations unknown

• The fundamental biochemical activity of MXRA7 remains undefined: no enzymatic function, direct binding partner, or structural mechanism has been established to explain its consistent regulatory effects across lineages.
• No defined molecular activity
• No validated direct physical partner
• No structural model linking MXRA7 to NF-κB/MAPK/ERK or PML-RARα