Affinage

MDFI

MyoD family inhibitor · UniProt Q99750

Length
246 aa
Mass
25.0 kDa
Annotated
2026-06-10
31 papers in source corpus 19 papers cited in narrative 20 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 8/8 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

MDFI (I-mfa) is a cytosolic/nuclear regulatory protein that controls cell differentiation programs principally by binding and sequestering specific DNA-binding transcription factors, thereby restraining their nuclear import and transcriptional output (PMID:9799236, PMID:15207726). Its founding activity is inhibition of MyoD-family bHLH myogenic regulators: MDFI binds these factors, blocks their nuclear import and DNA binding, and suppresses their transcriptional activity (PMID:9799236). This repression is relieved by canonical Wnt signaling, in which beta-catenin competes with MDFI for binding to myogenic factors and to LEF/TCF, switching MDFI between an MRF-bound and a beta-catenin-bound state to initiate myogenesis (PMID:16301527, PMID:17090604). MDFI integrates broadly with Wnt/beta-catenin signaling, interacting with the Axin complex to stabilize cytosolic beta-catenin and directly inhibiting Tcf3 and LEF transcriptional activity (PMID:11238923, PMID:12192039). Through its conserved C-terminal I-mfa domain it engages additional transcriptional regulators including Zic-family zinc finger proteins, SERTA-domain proteins, and the P-TEFb cyclins T1/T2, in each case repressing their activity (PMID:15207726, PMID:17289077, PMID:21664411). Beyond transcriptional control, MDFI shapes muscle fiber-type identity by driving fast-to-slow conversion through calcium signaling, CaMKK2/AMPK activation, and mitochondrial biogenesis (PMID:33553177, PMID:37307704), governs megakaryocyte lineage commitment via JNK/ERK signaling (PMID:37267696), suppresses mesangial cell contractility by reducing TRPC1 channel abundance (PMID:39446484), and acts as an auxiliary subunit of PIEZO1/2 mechanosensitive channels, binding a conserved pore-module pocket through its post-translationally modified distal C-terminus to convert them into high-threshold, slowly inactivating mechanoreceptors [PMID:bio_10.1101_2025.10.26.684595]. In cancer, MDFI promotes colorectal cancer cell growth, in part through interactions with LAMB3 and ITGB4 and AKT pathway activation (PMID:38375821). Mouse knockout studies establish in vivo requirements in trophoblast giant cell differentiation and placental development (PMID:9799236), megakaryopoiesis (PMID:37267696), and glomerular mesangial function (PMID:39446484).

Mechanistic history

Synthesis pass · year-by-year structured walk · 15 steps
  1. 1998 High

    Established MDFI's founding molecular activity: how a single protein restrains myogenic commitment by directly inhibiting bHLH regulators at the level of nuclear access and DNA binding.

    Evidence Protein interaction and transcription assays plus targeted gene deletion in mice

    PMID:9799236

    Open questions at the time
    • Selectivity rule unclear — inhibits Mash2 but not Hand1
    • Structural basis of bHLH sequestration not defined
  2. 1998 High

    Defined an in vivo developmental requirement, showing MDFI is needed for trophoblast giant cell differentiation and normal placental development.

    Evidence KO mouse placental phenotype with Rcho-1 overexpression

    PMID:9799236

    Open questions at the time
    • Transcription-factor target driving the trophoblast phenotype not pinpointed
  3. 2001 Medium

    Extended MDFI's repressor reach to the Wnt pathway by showing it inhibits Tcf3 DNA binding and beta-catenin-dependent axis specification.

    Evidence Xenopus ectopic expression, reporter assays, beta-catenin epistasis

    PMID:11238923

    Open questions at the time
    • Whether inhibition is direct on Tcf3 or via beta-catenin not fully resolved
    • Single-organism developmental readout
  4. 2002 Medium

    Mapped the C-terminal I-mfa domain as the Axin-interaction module and showed MDFI stabilizes cytosolic beta-catenin while also binding LEF directly.

    Evidence In vivo Co-IP, domain mapping, reporter assays

    PMID:12192039

    Open questions at the time
    • Net effect on Wnt output context-dependent (stabilizes beta-catenin yet inhibits TCF reporters)
    • Single lab
  5. 2004 Medium

    Generalized the sequestration mechanism beyond bHLH factors by showing MDFI blocks nuclear import of Zic family zinc finger proteins.

    Evidence Co-IP, subcellular localization, reporter assays in cultured cells

    PMID:15207726

    Open questions at the time
    • In vivo relevance of Zic regulation not tested
    • Single lab
  6. 2006 High

    Resolved the regulatory logic: beta-catenin competes with MDFI for binding to myogenic factors and LEF-1, providing a Wnt-responsive switch that relieves MDFI repression and triggers differentiation.

    Evidence Reciprocal Co-IP, siRNA, reporter and differentiation assays in P19/cell lines

    PMID:16301527 PMID:17090604

    Open questions at the time
    • Stoichiometry and affinity of competing complexes not quantified
    • Endogenous switch dynamics in primary myogenesis untested
  7. 2007 Medium

    Identified MDFI as a P-TEFb interactor and substrate, linking it to transcription elongation control and viral transactivation.

    Evidence Yeast two-hybrid, Co-IP, domain mapping, HIV-1 promoter reporter assays

    PMID:17289077

    Open questions at the time
    • Cell-type-specific basis of P-TEFb inhibition unexplained
    • Functional consequence of MDFI phosphorylation by P-TEFb unknown
  8. 2011 Medium

    Expanded the I-mfa-domain interactome to SERTA-domain proteins, with downstream effects on the SEI-1/DP-1 complex and Fbxw7 expression.

    Evidence Co-IP, domain-mapping mutagenesis, reporter assays, qPCR

    PMID:21664411

    Open questions at the time
    • Physiological pathway in which SERTA regulation operates not defined
    • Single lab
  9. 2015 Medium

    Showed MDFI directly binds HTLV-1 Tax and represses Tax-dependent LTR and NF-kB transactivation, indicating an antiviral transcriptional role.

    Evidence In vitro binding and reporter assays, Co-IP

    PMID:26469549

    Open questions at the time
    • Endogenous effect on viral replication not assessed
    • Single lab
  10. 2021 Medium

    Repositioned MDFI as a positive driver of myogenic differentiation and fast-to-slow fiber conversion, implicating calcium signaling as the dominant affected pathway.

    Evidence CRISPR overexpression stable line, RNA-seq, qPCR, Western blot, immunofluorescence

    PMID:31212688 PMID:33553177

    Open questions at the time
    • Reconciliation of positive differentiation role with earlier inhibitory bHLH model unresolved
    • Context dependence on cell line and dose
  11. 2023 Medium

    Dissected the fiber-type mechanism, showing MDFI raises intracellular calcium via ER IP3R/RYR channels and activates CaMKK2/AMPK to drive mitochondrial biogenesis and aerobic metabolism.

    Evidence Gain/loss-of-function in C2C12, calcium imaging with channel inhibitors, Western blot

    PMID:37307704

    Open questions at the time
    • How MDFI couples to ER calcium channels mechanistically unknown
    • In vivo fiber-type effect not shown
  12. 2023 Medium

    Established a cell-intrinsic role in megakaryocyte lineage commitment, with KO mice showing reduced platelets and altered progenitor balance linked to prolonged JNK/ERK signaling.

    Evidence KO mice, shRNA knockdown and overexpression in K562, phospho-JNK/ERK Western blot

    PMID:37267696

    Open questions at the time
    • Direct molecular target controlling JNK/ERK kinetics not identified
    • Single lab
  13. 2024 High

    Defined a non-transcriptional cytosolic role: MDFI suppresses mesangial cell contractility by lowering TRPC1 channel abundance, with KO mice showing impaired glomerular function rescued by re-expression.

    Evidence KO mice with GFR, in vivo siRNA nanoparticle delivery, single-cell contractility, Ca2+ imaging, scRNA-seq, pharmacological TRPC1 inhibition

    PMID:39446484

    Open questions at the time
    • Mechanism by which MDFI reduces TRPC1 protein not defined
    • Relationship to MDFI's transcriptional functions unclear
  14. 2024 Medium

    Implicated MDFI in colorectal cancer growth and chemoresistance through direct binding to LAMB3 and ITGB4 and AKT activation, and as a Wnt1/beta-catenin repressor in cardiomyocytes.

    Evidence Co-IP, lenti-overexpression/shRNA, proliferation and chemosensitivity assays; miR-128 luciferase and HF mouse model

    PMID:38375821 PMID:39046458

    Open questions at the time
    • Tissue-specific switch between oncogenic and Wnt-repressive roles unexplained
    • Single lab per context
  15. 2025 High

    Revealed a structural mechanism by which MDFI acts as a PIEZO auxiliary subunit, binding a conserved pore-module pocket via its modified C-terminus to retune mechanosensitivity and inactivation.

    Evidence Cryo-EM structure, electrophysiology of endogenous PIEZO currents, binding-interface mutagenesis (preprint)

    PMID:bio_10.1101_2025.10.26.684595

    Open questions at the time
    • Preprint, not yet peer-reviewed
    • Physiological contexts where MDFI tunes PIEZO function in vivo not established
    • Identity of the C-terminal modification not detailed

Open questions

Synthesis pass · forward-looking unresolved questions
  • How a single C-terminal I-mfa domain coordinates such diverse partners — nuclear transcription factors versus plasma-membrane PIEZO and TRPC channels — and what determines its tissue-specific deployment remains unresolved.
  • No unifying structural model across nuclear and channel partners
  • Determinants of cytosolic vs nuclear partitioning unknown
  • Tissue-specific functional switching mechanism undefined

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0098772 molecular function regulator activity 4 GO:0140110 transcription regulator activity 4 GO:0140313 molecular sequestering activity 3
Localization
GO:0005634 nucleus 2 GO:0005829 cytosol 2
Pathway
R-HSA-162582 Signal Transduction 4 R-HSA-1266738 Developmental Biology 3 R-HSA-74160 Gene expression (Transcription) 3
Partners
AXIN1CCNT1CTNNB1LEF1PIEZO1PIEZO2TCF7L1ZIC2

Evidence

Reading pass · 20 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
1998 I-mfa (MDFI) protein binds to MyoD family bHLH transcription factors, inhibits their transcriptional activity, and blocks their nuclear import and DNA binding; it also interacts with the bHLH protein Mash2 and inhibits its transcriptional activity, but does not interfere with Hand1 activity. Cell culture overexpression/inhibition assays, protein interaction studies, in situ hybridization, targeted gene deletion in mice The EMBO journal High 9799236
1998 Overexpression of I-mfa in rat trophoblast (Rcho-1) stem cells induced their differentiation into trophoblast giant cells, and targeted deletion of I-mfa caused placental defects with reduced trophoblast giant cells, establishing a role for I-mfa in trophoblast differentiation. Targeted gene deletion (KO mouse), overexpression in Rcho-1 cells The EMBO journal High 9799236
2001 I-mfa inhibits the activity and DNA binding of the HMG-box transcription factor XTcf3; ectopic expression of I-mfa in Xenopus embryos inhibited dorsal axis specification and Tcf3/beta-catenin-regulated gene expression (siamois, Xnr3), and blocked beta-catenin activation of Lef/Tcf reporter constructs. Xenopus ectopic expression, reporter assays, epistasis with beta-catenin Molecular and cellular biology Medium 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-regulated reporter constructs, and decreases Axin-mediated JNK activation. Co-immunoprecipitation (in vivo), reporter assays, domain mapping Molecular and cellular biology Medium 12192039
2004 I-mfa physically interacts with the amino-terminal domain of Zic2 (and Zic1-3) and inhibits nuclear import of the Zic proteins, thereby inhibiting their transcriptional activation activity in cultured cells. Co-immunoprecipitation, subcellular localization assays, transcription reporter assays, co-expression in cultured cells Biochemical and biophysical research communications Medium 15207726
2005 Beta-catenin interacts with I-mfa (enhanced by Wnt3a); this interaction attenuates I-mfa binding to myogenic regulatory factors (MRFs), relieves I-mfa-mediated suppression of MRF transcriptional activity and cytosolic sequestration of MRFs, and initiates myogenesis in P19 cells. Co-immunoprecipitation, reporter assays, cell differentiation assays, siRNA knockdown Proceedings of the National Academy of Sciences of the United States of America High 16301527
2006 I-mfa suppresses LEF-1 transcriptional activity; beta-catenin competes with I-mfa for binding to LEF-1, relieving I-mfa-mediated suppression; canonical Wnt signaling reduces endogenous I-mfa associated with LEF-1 while increasing I-mfa associated with beta-catenin. Co-immunoprecipitation, reporter assays, siRNA knockdown, dominant-negative LEF-1 epistasis Journal of cell science Medium 17090604
2007 I-mfa interacts through its I-mfa domain with cyclin T1 and T2 at two binding sites (the histidine-rich regulatory domain and a lysine/arginine-rich motif overlapping the Tat/TAR recognition motif), 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, domain mapping, transcription reporter assays Journal of molecular biology Medium 17289077
2011 I-mfa interacts through its C-terminal I-mfa domain with SERTA domain-containing proteins SEI-1, SEI-2, SEI-3, SERTAD3, and SERTAD4 in vivo; this interaction affects I-mfa intracellular localization and represses the intrinsic transcriptional activities of SEI-1, SEI-2, and SERTAD3, and decreases the SEI-1·DP-1 complex and endogenous Fbxw7 mRNA levels. Co-immunoprecipitation, reporter assays, domain-mapping mutagenesis, qPCR Biochimie Medium 21664411
2015 I-mfa directly interacts with HTLV-1 Tax protein in vitro and represses Tax-dependent transactivation of HTLV-1 LTR and NF-κB reporter constructs. In vitro binding assay, reporter assays, Co-immunoprecipitation Virology Medium 26469549
2018 miR-27b directly targets MDFI (confirmed by dual-luciferase reporter assay); MDFI promotes satellite cell proliferation and inhibits their differentiation in vitro, and interfering with MDFI expression promotes muscle regeneration in vivo after injury. Dual-luciferase reporter assay, siRNA knockdown, EdU staining, qRT-PCR, Western blot, in vivo muscle injury model Cellular physiology and biochemistry Medium 29734192
2019 miR-501-3p directly targets FOS (confirmed by dual-luciferase reporter); FOS binds the MDFI promoter (confirmed by ChIP); and MDFI overexpression promotes C2C12 myogenic differentiation and MyoD expression, forming a feedback loop (miR-501-3p → FOS ⊣ MDFI → MyoD → miR-501-3p). Dual-luciferase reporter assay, ChIP assay, qPCR, Western blot, miRNA mimic/inhibitor transfection Cells Medium 31212688
2020 MDFI interacts with the histone demethylase JMJD1A; JMJD1A influences transcription of several genes also regulated by MDFI; MDFI stimulated growth of HCT116 colorectal cancer cells. Co-immunoprecipitation, gene expression analysis, cell proliferation assays Scientific reports Medium 32457453
2021 Mdfi overexpression in C2C12 cells promotes myoblast differentiation by upregulating Myod, Myog, and Myosin expression, and promotes fast-to-slow twitch muscle fiber transformation mediated through Myod, Camk2b, and downstream metabolic genes (Pgc1a, Pdk4, Cs, Cox4, etc.); RNA-seq identified the calcium signaling pathway as most significantly affected. CRISPR/Cas9 Mdfi-OE stable cell line, RNA-seq, qPCR, Western blot, immunofluorescence Frontiers in cell and developmental biology Medium 33553177
2023 Elevated MDFI promotes fast-to-slow muscle fiber type conversion by activating CaMKK2 and AMPK phosphorylation, stimulating mitochondrial biogenesis and aerobic metabolism; MDFI also increases intracellular calcium by promoting calcium release from the ER via IP3R and RYR channels. Lipofection-mediated overexpression and siRNA knockdown in C2C12 cells, immunofluorescence, qPCR, Western blot, calcium imaging with channel inhibitors Biochemical and biophysical research communications Medium 37307704
2023 I-MFA plays a cell-intrinsic role in megakaryocyte lineage commitment and terminal differentiation; I-MFA KO mice had reduced platelets, reduced MK/erythrocyte progenitors, and increased myeloid progenitors; shRNA knockdown of I-MFA in K562 cells reduced PMA-induced MK differentiation with prolonged phospho-JNK and phospho-ERK signaling; overexpression of I-MFA promoted MK differentiation. I-MFA knockout mice (bone marrow analysis, blood counts), shRNA knockdown in K562 cells, I-MFA overexpression, Western blot for phospho-JNK/ERK Blood cells, molecules & diseases Medium 37267696
2024 MDFI directly binds LAMB3 and ITGB4 (confirmed by co-immunoprecipitation) in colorectal cancer cells, upregulates AKT pathway signaling through these interactions, enhances CRC cell proliferation, and reduces sensitivity to oxaliplatin and fluorouracil. Co-immunoprecipitation, lentiviral overexpression, shRNA knockdown, colony formation assay, CCK8 assay, Western blot Cancer biology & therapy Medium 38375821
2024 I-mfa is a cytosolic protein in mesangial cells that suppresses contractile function by decreasing TRPC1 channel protein abundance; I-mfa KO mice had lower GFR, augmented Ang II-induced mesangial cell contraction, and increased TRPC1 protein; overexpression of I-mfa blunted Ang II-stimulated contraction and Ca2+ entry; re-introduction of I-mfa into KO cells restored normal contractile response. I-mfa KO mice (GFR measurement, mesangial cell isolation), targeted siRNA nanoparticle delivery in vivo, single-cell contractility assay, Ca2+ imaging, Western blot, single-cell RNA sequencing, pharmacological TRPC1 inhibition Journal of the American Society of Nephrology High 39446484
2024 miR-128 directly targets MDFI (confirmed by luciferase assay); miR-128 overexpression reduced MDFI mRNA and protein levels and promoted cardiomyocyte apoptosis, while MDFI upregulation enhanced cardiomyocyte proliferation; elevated miR-128 upregulated Wnt1 and β-catenin, whereas increased MDFI inhibited these expressions, placing MDFI as a negative regulator of the Wnt1/β-catenin pathway in cardiomyocytes. Luciferase reporter assay, qPCR, Western blot, MTT, transwell, immunohistochemistry, echocardiography in mouse HF model Journal of cellular and molecular medicine Medium 39046458
2025 MDFI (and MDFIC) regulate endogenous PIEZO channel currents in non-sensory cell types; MDFI physically binds PIEZO1 and PIEZO2, alters their mechanosensitivity and inactivation kinetics (converting them to high-threshold slowly inactivating mechanoreceptors); cryo-EM revealed a conserved binding pocket in the pore modules of both PIEZO1 and PIEZO2 mediated by the post-translationally modified distal C-termini of MDFI-family proteins. Electrophysiology (endogenous PIEZO current recording), cryo-EM structure determination, physical binding assays, mutagenesis of binding interface 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 61 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
2004 Myogenic repressor I-mfa interferes with the function of Zic family proteins. Biochemical and biophysical research communications 44 15207726
2017 DNA methylation of CMTM3, SSTR2, and MDFI genes in colorectal cancer. Gene 42 28782576
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
2021 Mdfi Promotes C2C12 Cell Differentiation and Positively Modulates Fast-to-Slow-Twitch Muscle Fiber Transformation. Frontiers in cell and developmental biology 24 33553177
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
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
2022 ACAN, MDFI, and CHST1 as Candidate Genes in Gastric Cancer: A Comprehensive Insilco Analysis. Asian Pacific journal of cancer prevention : APJCP 12 35225482
2023 MDFI regulates fast-to-slow muscle fiber type transformation via the calcium signaling pathway. Biochemical and biophysical research communications 11 37307704
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
2024 The role of miR-128 and MDFI in cardiac hypertrophy and heart failure: Mechanistic. Journal of cellular and molecular medicine 3 39046458
2009 The complex regulation of HIC (Human I-mfa domain containing protein) expression. PloS one 3 19582149
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

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