Affinage

MDFI

MyoD family inhibitor · UniProt Q99750

Length
246 aa
Mass
25.0 kDa
Annotated
2026-04-28
31 papers in source corpus 18 papers cited in narrative 19 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

MDFI (I-mfa) is a cysteine-rich transcriptional repressor that functions broadly as a cytoplasmic sequestration factor for multiple classes of transcription factors and as a modulator of calcium-dependent signaling in muscle and kidney. MDFI binds and inhibits bHLH myogenic regulatory factors (MyoD family), TCF/LEF transcription factors, and Zic proteins by blocking their nuclear import and DNA binding, thereby regulating myogenesis and Wnt/β-catenin signaling; β-catenin competes with MRFs for MDFI binding, and canonical Wnt signaling relieves MDFI-mediated repression to initiate myogenic differentiation (PMID:9799236, PMID:11238923, PMID:16301527, PMID:17090604). Beyond transcription factor sequestration, MDFI interacts with cyclin T1/T2 (P-TEFb subunits) and viral transactivators to repress HIV-1 and HTLV-1 promoter activity (PMID:17289077, PMID:26469549), promotes fast-to-slow muscle fiber transformation through CaMKK2/AMPK-dependent calcium signaling (PMID:37307704), and suppresses mesangial cell contractility by reducing TRPC1 channel abundance to regulate glomerular filtration rate (PMID:39446484). MDFI is also required for placental trophoblast giant cell differentiation and megakaryocyte lineage commitment, with knockout mice exhibiting embryonic lethality (placental) and thrombocytopenia, respectively (PMID:9799236, PMID:37267696).

Mechanistic history

Synthesis pass · year-by-year structured walk · 13 steps
  1. 1998 High

    Establishing MDFI as a selective inhibitor of bHLH myogenic factors and a required developmental gene resolved how myogenic transcription factors are held inactive in the cytoplasm and revealed an essential role in trophoblast differentiation.

    Evidence Targeted gene deletion in mice (embryonic lethality with placental defects), nuclear import assays, transcriptional reporters, and gain-of-function in trophoblast stem cells

    PMID:9799236

    Open questions at the time
    • Mechanism by which MDFI blocks nuclear import not structurally defined
    • Selectivity determinants among bHLH proteins not mapped at residue level
    • Whether MDFI loss-of-function placental phenotype is solely due to Mash2 inhibition unclear
  2. 2001 High

    Demonstrating that MDFI inhibits TCF3/β-catenin-dependent transcription and Wnt target genes in Xenopus expanded its role from a myogenic repressor to a Wnt signaling modulator.

    Evidence Ectopic expression in Xenopus embryos with dorsal axis and Wnt target gene readouts, DNA-binding assays

    PMID:11238923

    Open questions at the time
    • Whether MDFI acts on TCF/LEF in mammalian Wnt contexts not yet tested
    • Relative contribution of bHLH vs. TCF inhibition to embryonic phenotype unknown
  3. 2002 High

    Identifying MDFI as an interactor of the Axin destruction complex and a direct LEF-1 binding partner established it as a multi-node regulator within canonical Wnt signaling and JNK pathways.

    Evidence Reciprocal co-immunoprecipitation, TCF/LEF reporter assays, Axin-mediated β-catenin and JNK readouts

    PMID:12192039

    Open questions at the time
    • Whether MDFI modulates Axin complex stability or only signaling output not resolved
    • Stoichiometry and competition between MDFI–Axin and MDFI–LEF interactions unknown
  4. 2004 Medium

    Finding that MDFI binds Zic family zinc-finger proteins and blocks their nuclear import generalized its mechanism of cytoplasmic sequestration beyond bHLH and HMG-box factors.

    Evidence Yeast two-hybrid, co-immunoprecipitation, nuclear localization and reporter assays

    PMID:15207726

    Open questions at the time
    • Single-lab observation not independently replicated
    • In vivo relevance for Zic-dependent processes (e.g., neural crest) not tested
  5. 2005 High

    Showing that β-catenin directly binds MDFI and competes with MRFs for MDFI binding revealed how Wnt signaling derepresses myogenic transcription factors to initiate myogenesis.

    Evidence Co-immunoprecipitation, siRNA knockdown, and myogenic differentiation in P19 cells

    PMID:16301527

    Open questions at the time
    • Binding site on β-catenin for MDFI not structurally mapped
    • Whether this competition operates in adult muscle stem cells in vivo not established
  6. 2006 High

    Epistasis experiments demonstrated that canonical Wnt signaling relieves MDFI-mediated suppression of LEF-1 by elevating β-catenin, integrating MDFI into a coherent Wnt-to-myogenesis relay.

    Evidence siRNA knockdown mimicking Wnt treatment, dominant-negative LEF-1 rescue, competition co-immunoprecipitation in P19 cells

    PMID:17090604

    Open questions at the time
    • Whether MDFI–LEF-1 interaction is regulated by post-translational modifications unknown
  7. 2007 High

    Identifying P-TEFb (cyclin T1/T2) as MDFI partners and showing MDFI inhibits HIV-1 Tat/P-TEFb-dependent transcription extended MDFI function to transcription elongation control and viral gene regulation.

    Evidence Yeast two-hybrid, in vitro binding, co-immunoprecipitation, phosphorylation assays, HIV-1 promoter reporters

    PMID:17289077

    Open questions at the time
    • Physiological significance of MDFI–P-TEFb interaction in non-viral contexts unknown
    • Whether MDFI regulates global Pol II elongation not tested
  8. 2011 Medium

    Demonstrating that MDFI binds and represses SERTA domain proteins and affects Fbxw7 mRNA levels expanded the repertoire of MDFI targets to cell cycle regulators.

    Evidence Co-immunoprecipitation, transcriptional reporters, qRT-PCR in cell lines

    PMID:21664411

    Open questions at the time
    • Single-lab study
    • Mechanism linking MDFI–SEI interaction to Fbxw7 mRNA regulation not defined
    • In vivo cell cycle consequences not tested
  9. 2015 Medium

    Showing MDFI directly binds HTLV-1 Tax and represses Tax-dependent HTLV-1 LTR and NF-κB transcription broadened its antiviral repressive capacity beyond HIV-1.

    Evidence In vitro binding, co-immunoprecipitation, reporters in COS-1, Jurkat, and HTLV-1-infected T cells

    PMID:26469549

    Open questions at the time
    • Single-lab finding
    • Whether MDFI affects HTLV-1 viral replication or latency in vivo unknown
  10. 2021 Medium

    Demonstrating that MDFI overexpression drives fast-to-slow muscle fiber transformation via MyoD/CaMK2b and downstream metabolic gene induction established MDFI as a fiber-type specification factor.

    Evidence CRISPR/Cas9-mediated overexpression in C2C12, RNA-seq, qRT-PCR, Western blot

    PMID:33553177

    Open questions at the time
    • In vivo fiber-type switching not demonstrated
    • Mechanism connecting MDFI to CaMK2b activation not resolved
  11. 2023 Medium

    Identifying that MDFI elevates intracellular calcium via IP3R/RYR channels and activates CaMKK2/AMPK signaling provided a mechanistic pathway for MDFI-driven slow-fiber transformation and mitochondrial biogenesis.

    Evidence Overexpression/knockdown in C2C12 with pharmacological IP3R and RYR inhibitors, Western blot, immunofluorescence

    PMID:37307704

    Open questions at the time
    • How MDFI increases ER calcium release mechanistically unresolved
    • Not replicated in primary muscle fibers or in vivo
  12. 2023 Medium

    Showing that MDFI knockout mice have reduced platelets and impaired megakaryocyte progenitors, with altered JNK/ERK signaling, revealed a non-muscle developmental role for MDFI in hematopoietic lineage commitment.

    Evidence Knockout mouse bone marrow analysis, shRNA knockdown and overexpression in K562 cells, flow cytometry, phospho-kinase Western blot

    PMID:37267696

    Open questions at the time
    • Whether MDFI acts via bHLH sequestration or an independent pathway in megakaryopoiesis not determined
    • Conditional KO not performed to exclude non-cell-autonomous effects
  13. 2024 High

    Establishing that MDFI suppresses mesangial cell contractility by reducing TRPC1 channel abundance and calcium entry defined a kidney-specific function regulating glomerular filtration rate.

    Evidence I-mfa KO mice with transdermal GFR measurement, siRNA nanoparticle delivery to mesangial cells, scRNA-seq, calcium imaging, TRPC1 inhibitor rescue

    PMID:39446484

    Open questions at the time
    • Mechanism by which MDFI reduces TRPC1 protein levels (transcriptional vs. post-translational) not resolved
    • Whether MDFI regulates other TRP channels in kidney not explored

Open questions

Synthesis pass · forward-looking unresolved questions
  • Key open questions include: (1) how MDFI's I-mfa domain structurally engages its diverse transcription factor and channel targets, (2) whether the cryo-EM-resolved PIEZO channel interaction operates in vivo to tune mechanosensation, (3) what post-translational modifications regulate MDFI partner selectivity, and (4) whether MDFI's numerous binding activities are coordinated or context-exclusive in specific tissues.
  • No high-resolution structure of MDFI alone or in complex with transcription factors
  • In vivo validation of PIEZO channel modulation pending peer review
  • Tissue-specific regulation of MDFI activity largely uncharacterized

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0098772 molecular function regulator activity 9 GO:0140110 transcription regulator activity 5
Localization
GO:0005829 cytosol 3
Pathway
R-HSA-162582 Signal Transduction 5 R-HSA-1266738 Developmental Biology 2 R-HSA-397014 Muscle contraction 2
Partners
AXIN1CCNT1CTNNB1JMJD1ALEF1MYOD1TRPC1ZIC1

Evidence

Reading pass · 19 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1998 I-mfa (MDFI) binds to MyoD family bHLH transcription factors, inhibits their transcriptional activity, and blocks their nuclear import and DNA binding. I-mfa also interacts with the bHLH protein Mash2 and inhibits its transcriptional activity, but does not interfere with Hand1 activity, demonstrating selectivity among bHLH proteins. Cell culture overexpression, nuclear import assays, transcriptional reporter assays, targeted gene deletion in mice with placental and skeletal phenotypes The EMBO journal High 9799236
1998 I-mfa is required for placental trophoblast giant cell differentiation; targeted deletion causes embryonic lethality with placental defects, and overexpression in Rcho-1 trophoblast stem cells induces differentiation into giant cells. Targeted gene deletion in mice, overexpression in rat trophoblast stem cells, in situ hybridization The EMBO journal High 9799236
2001 I-mfa inhibits the activity and DNA binding of the HMG box transcription factor Tcf3 (XTcf3), and ectopic expression of I-mfa in Xenopus embryos inhibited dorsal axis specification and Tcf3/beta-catenin-regulated gene expression (siamois, Xnr3), placing I-mfa as a regulator of both Wnt signaling and bHLH proteins. Ectopic expression in Xenopus embryos, transcriptional reporter assays, DNA-binding assays Molecular and cellular biology High 11238923
2002 I-mfa interacts in vivo with the Axin complex through its C-terminal I-mfa domain, inhibiting Axin-mediated downregulation of cytosolic beta-catenin. I-mfa also directly interacts with LEF and inhibits beta-catenin/TCF-reporter constructs. Both I-mfa and HIC decrease Axin-mediated JNK activation. Co-immunoprecipitation, transcriptional reporter assays, dominant-negative domain experiments Molecular and cellular biology High 12192039
2004 I-mfa physically interacts with the amino-terminal domain of Zic family proteins (Zic1-3) and inhibits their nuclear import in cultured cells, thereby inhibiting Zic-mediated transcriptional activation. Yeast two-hybrid screen, co-immunoprecipitation, nuclear localization assays, transcriptional reporter assays in cultured cells Biochemical and biophysical research communications Medium 15207726
2005 Beta-catenin directly interacts with I-mfa (MDFI), and this interaction (enhanced by Wnt3a) attenuates I-mfa binding to myogenic regulatory factors (MRFs), relieving I-mfa-mediated transcriptional suppression and cytosolic sequestration of MRFs to initiate myogenesis in P19 cells. Co-immunoprecipitation, siRNA knockdown, transcriptional reporter assays, P19 cell myogenic differentiation model Proceedings of the National Academy of Sciences of the United States of America High 16301527
2006 I-mfa suppresses myogenesis by inhibiting TCF/LEF-1, and canonical Wnt signaling relieves I-mfa-mediated suppression of LEF-1 by elevating beta-catenin levels which compete with LEF-1 for I-mfa binding; knockdown of endogenous I-mfa mimics canonical Wnt treatment in P19 cells. siRNA knockdown, co-immunoprecipitation competition assays, transcriptional reporter assays, dominant-negative LEF-1 rescue Journal of cell science High 17090604
2007 I-mfa interacts with cyclin T1 and cyclin T2 (P-TEFb subunits) through its I-mfa domain at two binding sites (the histidine-rich regulatory domain and a lysine/arginine-rich motif); I-mfa can serve as a P-TEFb substrate and inhibits Tat- and P-TEFb-dependent transcription from the HIV-1 promoter in a cell-type specific manner. Yeast two-hybrid, co-immunoprecipitation, in vitro binding assays, transcriptional reporter assays, phosphorylation assays Journal of molecular biology High 17289077
2011 I-mfa interacts with SERTA domain proteins (SEI-1, SEI-2, SEI-3, SERTAD3, SERTAD4) through its I-mfa domain in vivo, affects intracellular localization of I-mfa, and represses the intrinsic transcriptional activities of SEI-1, SEI-2, and SERTAD3; I-mfa also decreases the SEI-1·DP-1 complex and endogenous Fbxw7 mRNA levels. Co-immunoprecipitation, transcriptional reporter assays, Western blot, qRT-PCR Biochimie Medium 21664411
2015 I-mfa (MDFI) directly interacts in vitro and in vivo with HTLV-1 Tax protein through its I-mfa domain, and represses Tax-dependent transactivation of HTLV-1 LTR and NF-κB reporter constructs. In vitro binding assays, co-immunoprecipitation, transcriptional reporter assays in COS-1, Jurkat, and HTLV-1-infected T cells Virology Medium 26469549
2018 MDFI promotes pig muscle satellite cell (PSC) proliferation and inhibits PSC differentiation in vitro; miR-27b targets the MDFI 3'UTR directly (validated by dual-luciferase reporter assay) and promotes PSC myogenesis by suppressing MDFI expression. In vivo, interfering with MDFI expression promotes mouse muscle regeneration after injury. Dual-luciferase reporter assay, siRNA/miRNA transfection, EdU staining, qRT-PCR, Western blot, H&E staining in vivo Cellular physiology and biochemistry Medium 29734192
2020 MDFI interacts with the histone demethylase JMJD1A in colorectal cancer cells; MDFI stimulates and MDFIC inhibits growth of HCT116 cells. JMJD1A influences transcription of several genes also regulated by MDFI or MDFIC. Co-immunoprecipitation, cell growth assays, gene expression analysis Scientific reports Medium 32457453
2021 MDFI overexpression in C2C12 cells promotes myoblast differentiation by upregulating MyoD, Myogenin, and Myosin expression, and promotes fast-to-slow-twitch muscle fiber transformation via a pathway involving MyoD, CaMK2b, and downstream metabolic genes (Pgc1a, Pdk4, Cs, Cox4, etc.). CRISPR/Cas9-mediated MDFI overexpression, RNA-seq, qRT-PCR, Western blot, immunofluorescence Frontiers in cell and developmental biology Medium 33553177
2023 MDFI promotes fast-to-slow muscle fiber type transformation by activating the calcium signaling pathway: elevated MDFI stimulates CaMKK2 and AMPK phosphorylation, promotes mitochondrial biogenesis and aerobic metabolism, increases intracellular calcium via IP3R and RYR channels from the ER, driving conversion of C2C12 cells from fast glycolytic to slow oxidative type. Lipofection-based OE/knockdown in C2C12, immunofluorescence, qPCR, Western blot, pharmacological channel inhibition (IP3R and RYR inhibitors) Biochemical and biophysical research communications Medium 37307704
2023 I-MFA (MDFI) plays a cell-intrinsic role in megakaryocyte lineage commitment and terminal differentiation: I-MFA knockout mice show reduced platelets, reduced MK/erythrocyte progenitors, and increased myeloid progenitors; shRNA knockdown of I-MFA in K562 cells reduces PMA-induced MK differentiation with prolonged phospho-JNK and phospho-ERK signaling, while I-MFA overexpression promotes MK differentiation. Knockout mouse analysis (bone marrow, blood counts), shRNA knockdown in K562 cells, overexpression, flow cytometry, phospho-kinase Western blot Blood cells, molecules & diseases Medium 37267696
2024 I-mfa (MDFI) promotes glomerular filtration rate by suppressing contractile function of mesangial cells through decreasing TRPC1 channel protein abundance, thereby reducing angiotensin II-stimulated calcium entry and cell contraction. Knockdown of I-mfa in mesangial cells decreases GFR, and I-mfa KO mice show significantly lower GFR with increased TRPC1 protein. I-mfa KO mice with transdermal GFR measurement, mesangial cell-targeted siRNA nanoparticle delivery, single-cell RNA sequencing, Western blot, Ca2+ imaging, contractility assay, TRPC1 inhibitor (Pico145) pharmacology Journal of the American Society of Nephrology High 39446484
2024 MDFI directly interacts with LAMB3 and ITGB4 in colorectal cancer cells (validated by co-immunoprecipitation), upregulates the AKT signaling pathway through this interaction, enhances CRC cell proliferation, and reduces sensitivity to oxaliplatin and fluorouracil. Co-immunoprecipitation, lentiviral overexpression, shRNA knockdown, colony formation assay, CCK8 assay, single-cell RNA sequencing data analysis Cancer biology & therapy Medium 38375821
2024 miR-128 directly targets MDFI (validated by luciferase assay), reduces MDFI expression, promotes cardiomyocyte apoptosis and attenuates proliferation; MDFI upregulation inhibits Wnt1 and beta-catenin expression, while miR-128 elevation upregulates these, placing MDFI as a negative regulator of the Wnt1/beta-catenin pathway in cardiomyocytes. Luciferase reporter assay, qPCR, Western blot, MTT assay, transwell assay, echocardiography, histology Journal of cellular and molecular medicine Medium 39046458
2025 MDFI (and MDFIC) physically bind to PIEZO1 and PIEZO2 channels through a conserved binding pocket in the pore modules of PIEZO1/2, mediated by the post-translationally modified distal C-termini of MyoD-family inhibitor proteins. MDFI regulates endogenous PIEZO channel currents in non-sensory cell types, altering mechanosensitivity and inactivation kinetics, converting PIEZO channels into high-threshold slowly inactivating mechanoreceptors. Cryo-EM structural determination, electrophysiology (patch clamp), co-immunoprecipitation/pulldown, overexpression in multiple cell types bioRxivpreprint High bio_10.1101_2025.10.26.684595

Source papers

Stage 0 corpus · 31 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
1998 Requirement of the mouse I-mfa gene for placental development and skeletal patterning. The EMBO journal 97 9799236
2002 I-mfa domain proteins interact with Axin and affect its regulation of the Wnt and c-Jun N-terminal kinase signaling pathways. Molecular and cellular biology 60 12192039
2000 Molecular cloning of a novel human I-mfa domain-containing protein that differently regulates human T-cell leukemia virus type I and HIV-1 expression. The Journal of biological chemistry 55 10671520
2001 Inhibition of Tcf3 binding by I-mfa domain proteins. Molecular and cellular biology 52 11238923
2005 Beta-catenin regulates myogenesis by relieving I-mfa-mediated suppression of myogenic regulatory factors in P19 cells. Proceedings of the National Academy of Sciences of the United States of America 50 16301527
2017 DNA methylation of CMTM3, SSTR2, and MDFI genes in colorectal cancer. Gene 42 28782576
2004 Myogenic repressor I-mfa interferes with the function of Zic family proteins. Biochemical and biophysical research communications 42 15207726
2003 The human I-mfa domain-containing protein, HIC, interacts with cyclin T1 and modulates P-TEFb-dependent transcription. Molecular and cellular biology 41 12944466
2018 MiR-27b Promotes Muscle Development by Inhibiting MDFI Expression. Cellular physiology and biochemistry : international journal of experimental cellular physiology, biochemistry, and pharmacology 36 29734192
2010 Human I-mfa domain proteins specifically interact with KSHV LANA and affect its regulation of Wnt signaling-dependent transcription. Biochemical and biophysical research communications 24 20417616
2021 Mdfi Promotes C2C12 Cell Differentiation and Positively Modulates Fast-to-Slow-Twitch Muscle Fiber Transformation. Frontiers in cell and developmental biology 23 33553177
2020 Opposite Roles of the JMJD1A Interaction Partners MDFI and MDFIC in Colorectal Cancer. Scientific reports 23 32457453
2005 Direct interaction of the human I-mfa domain-containing protein, HIC, with HIV-1 Tat results in cytoplasmic sequestration and control of Tat activity. Proceedings of the National Academy of Sciences of the United States of America 23 16260749
2011 I-mfa domain proteins specifically interact with SERTA domain proteins and repress their transactivating functions. Biochimie 21 21664411
2007 Developmental regulators containing the I-mfa domain interact with T cyclins and Tat and modulate transcription. Journal of molecular biology 18 17289077
2019 MiR-501-3p Forms a Feedback Loop with FOS, MDFI, and MyoD to Regulate C2C12 Myogenesis. Cells 15 31212688
2000 Sequence requirement for the nucleolar localization of human I-mfa domain-containing protein (HIC p40). European journal of cell biology 15 11139147
2015 I-mfa domain proteins specifically interact with HTLV-1 Tax and repress its transactivating functions. Virology 14 26469549
2006 Beta-catenin relieves I-mfa-mediated suppression of LEF-1 in mammalian cells. Journal of cell science 13 17090604
2023 MDFI regulates fast-to-slow muscle fiber type transformation via the calcium signaling pathway. Biochemical and biophysical research communications 11 37307704
2022 ACAN, MDFI, and CHST1 as Candidate Genes in Gastric Cancer: A Comprehensive Insilco Analysis. Asian Pacific journal of cancer prevention : APJCP 11 35225482
2024 MDFI promotes the proliferation and tolerance to chemotherapy of colorectal cancer cells by binding ITGB4/LAMB3 to activate the AKT signaling pathway. Cancer biology & therapy 10 38375821
2001 Vitamin D(3) enhances the expression of I-mfa, an inhibitor of the MyoD family, in osteoblasts. Biochimica et biophysica acta 10 11389974
2022 Inhibition of MDFI attenuates proliferation and glycolysis of Helicobacter pylori-infected gastric cancer cells by inhibiting Wnt/β-catenin pathway. Cell biology international 8 36116024
2021 Putative MicroRNA-mRNA Networks Upon Mdfi Overexpression in C2C12 Cell Differentiation and Muscle Fiber Type Transformation. Frontiers in molecular biosciences 6 34738011
2018 Hypermethylation of MDFI promoter with NSCLC is specific for females, non-smokers and people younger than 65. Oncology letters 5 29805634
2009 The complex regulation of HIC (Human I-mfa domain containing protein) expression. PloS one 3 19582149
2024 The role of miR-128 and MDFI in cardiac hypertrophy and heart failure: Mechanistic. Journal of cellular and molecular medicine 2 39046458
2023 The inhibitor of MyoD Family A (I-MFA) regulates megakaryocyte lineage commitment and terminal differentiation. Blood cells, molecules & diseases 2 37267696
2024 I-mfa, Mesangial Cell TRPC1 Channel, and Regulation of GFR. Journal of the American Society of Nephrology : JASN 1 39446484
2016 Effect of Genetic Variations within the I-mfa Gene on the Growth Traits of Chinese Cattle. Animal biotechnology 1 27565872