Affinage

MBNL2

Muscleblind-like protein 2 · UniProt Q5VZF2

Length
373 aa
Mass
40.5 kDa
Annotated
2026-06-10
25 papers in source corpus 15 papers cited in narrative 15 extracted findings
Cross-family judge vs UniProt: Affinage preferred faithfulness: 6/6 claims corpus-supported (100%)

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

MBNL2 is an RNA-binding protein that controls developmental RNA processing programs by regulating alternative splicing and mRNA stability across muscle, heart, and brain (PMID:18213585, PMID:35567413, PMID:35606145). As a splicing regulator it is required for correct alternative splicing of the muscle chloride channel Clcn1 in vivo, and loss of MBNL2 produces myotonia (PMID:18213585); together with MBNL1 it acts as an enhancer of Tau exon 2 inclusion through intronic cis-regulatory elements, and the two paralogs cooperate to reverse repeat-induced mis-splicing (PMID:24440524). Beyond splicing, MBNL2 directly binds target transcripts to control their stability, stabilizing p21 (CDKN1A) mRNA in a p53-independent manner to drive DNA-damage-induced senescence (PMID:33466733) and binding the Ccr2 3'-UTR in sensory neurons to limit Ccr2 transcript stability (PMID:41967179). MBNL2 abundance and nuclear localization are set post-translationally: calpain-2 translocates to the nucleus under excitotoxic/calcium-dysregulated conditions and degrades nuclear MBNL2, reverting RNA processing to a fetal pattern (PMID:35606145), while alternative splicing of MBNL2's own exon 6 (controlling nuclear translocation) and exon 9 (which removes a PEST degron and stabilizes the protein) is governed by MBNL1, providing a compensatory autoregulatory circuit (PMID:36617982). In myotonic dystrophy, expanded CUG/CCUG repeat transcripts sequester MBNL2 into nuclear RNA foci, producing widespread spliceopathy (PMID:11929853, PMID:35567413) and, in the developing cortex, impairing migration and differentiation of late-born neurons through MBNL2 dysfunction in outer radial glial progenitors (PMID:41644016). MBNL2 also restrains cancer cell migration and invasion by suppressing the PI3K/AKT-driven EMT program (PMID:31320607, PMID:34659561).

Mechanistic history

Synthesis pass · year-by-year structured walk · 9 steps
  1. 2002 Medium

    Established that MBNL2 is physically captured by pathogenic repeat RNA, providing the first molecular link between MBNL2 and myotonic dystrophy.

    Evidence GFP-fusion co-localization with CUG/CCUG foci in DM1 and DM2 patient cells

    PMID:11929853

    Open questions at the time
    • Did not define downstream splicing targets affected by sequestration
    • Tagged overexpression rather than endogenous protein
  2. 2008 Medium

    Showed MBNL2 has a non-redundant in vivo splicing function, connecting its loss to a concrete muscle phenotype.

    Evidence Mbnl2 knockout mice with EMG myotonia and RT-PCR of Clcn1 splicing

    PMID:18213585

    Open questions at the time
    • Single splicing target characterized
    • Did not address brain or cardiac roles
  3. 2014 Medium

    Defined how MBNL1 and MBNL2 cooperate on a neuronal splicing target, clarifying the basis of repeat-induced Tau mis-splicing.

    Evidence Tau minigene splicing assays, EMSA binding, MBNL1/2 over/knockdown

    PMID:24440524

    Open questions at the time
    • Direct binding shown for MBNL1; MBNL2 contribution inferred from functional cooperation
    • Cell-line minigene context only
  4. 2019 Medium

    Linked MBNL2's own isoform balance and subcellular distribution to disease, and revealed a splicing-independent anti-metastatic role.

    Evidence Isogenic CRISPR DM1 myoblasts with fractionation and isoform analysis; cancer cell over/knockdown with migration and xenograft assays

    PMID:31116797 PMID:31320607

    Open questions at the time
    • Mechanism linking MBNL2 to AKT/EMT not resolved at molecular level
    • Whether mis-spliced MBNL2 isoforms are functionally distinct untested
  5. 2021 Medium

    Identified MBNL2 as a stabilizer of p21 mRNA and a node in the DNA damage response, and showed miR-182 suppresses MBNL2 to engage PI3K/AKT-EMT.

    Evidence MBNL2 knockdown with transcriptomics, p21/pChk1 readouts and p21 epistasis; miR-182 luciferase targeting and MBNL2 rescue

    PMID:33466733 PMID:34659561

    Open questions at the time
    • Direct MBNL2 binding to p21 mRNA not shown
    • Connection between p21 stabilization and EMT roles unintegrated
  6. 2022 High

    Defined a post-translational switch — nuclear calpain-2 degradation of MBNL2 — that converts adult to fetal RNA processing, and extended MBNL2 loss to lethal cardiac phenotypes.

    Evidence Neuronal excitotoxicity models with calpain-2 KD/inhibition, fractionation and splicing assays across DM1/AD mouse models; Myh6-Cre Mbnl1/2 double KO with ECG and RNA-seq

    PMID:35567413 PMID:35606145

    Open questions at the time
    • Calpain-2 cleavage site on MBNL2 not mapped
    • Cardiac phenotype requires combined Mbnl1/Mbnl2 loss, isolating MBNL2 contribution unresolved
  7. 2023 High

    Revealed an MBNL1-controlled autoregulatory circuit in which MBNL2 exon 6 and exon 9 splicing tune nuclear localization and PEST-dependent proteasomal stability.

    Evidence Mbnl1 KO mice with RT-PCR, fractionation, proteasome inhibition and stability assays, validated in DM1 model

    PMID:36617982

    Open questions at the time
    • Functional consequences of compensatory MBNL2 upregulation in disease not quantified
    • Direct MBNL1 binding to Mbnl2 pre-mRNA not detailed
  8. 2024 Low

    Expanded MBNL2 function to muscle MTOC reprogramming and to cardiac fibrosis regulation through protein interaction and SUMOylation pathways.

    Evidence Mbnl2 siRNA in differentiating C2C12 with AKAP6β/Pcnt readouts; piRNA profiling with RIP/pulldown; MBNL2 over/inhibition in fibroblasts with SUMO1-KLF4 co-IP

    PMID:38974966 PMID:39122223 PMID:39996710

    Open questions at the time
    • Cardiac fibrosis mechanisms rest on Co-IP/pulldown without reconstitution
    • Whether MBNL2 directly regulates AKAP6β transcript vs splicing not resolved
    • SUMOylation effect inferred from pathway markers
  9. 2026 Medium

    Demonstrated direct MBNL2 control of Ccr2 mRNA stability in sensory neurons and a progenitor-stage role in cortical development under repeat-expansion conditions.

    Evidence DRG neuron MBNL2 knockdown/rescue with RIP and mRNA stability assays and behavioral pain models; CDM hiPSC forebrain organoids with CRISPR-corrected isogenic controls

    PMID:41644016 PMID:41967179

    Open questions at the time
    • Whether MBNL2 acts on Ccr2 via the same RNA-binding mode used for splicing untested
    • oRG-specific MBNL2 targets driving migration defects not identified

Open questions

Synthesis pass · forward-looking unresolved questions
  • The full target set MBNL2 regulates and how its distinct splicing versus mRNA-stability activities are partitioned across tissues remain unresolved.
  • No transcriptome-wide MBNL2 binding map integrating splicing and stability roles
  • Structural basis of MBNL2 RNA recognition not addressed in this corpus
  • Causal MBNL2-specific contribution to human DM phenotypes vs MBNL1 not isolated

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0003723 RNA binding 4 GO:0140110 transcription regulator activity 2
Localization
GO:0005634 nucleus 4 GO:0005829 cytosol 2
Pathway
R-HSA-8953854 Metabolism of RNA 4 R-HSA-1643685 Disease 3
Partners
CDKN1AMBNL1

Evidence

Reading pass · 15 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2002 GFP-tagged MBNL2 (MBLL) co-localizes with nuclear foci of expanded CUG/CCUG repeat transcripts in DM1 and DM2 cells, indicating direct sequestration of MBNL2 in repeat RNA foci. GFP-fusion protein co-localization by fluorescence microscopy in DM1 and DM2 patient cells Human molecular genetics Medium 11929853
2008 Loss of MBNL2 in mice causes myotonia and defective mRNA splicing of the chloride channel (Clcn1) in skeletal muscle, demonstrating that MBNL2 is required for correct Clcn1 alternative splicing in vivo. Mbnl2 knockout mouse model; electromyography for myotonia; RT-PCR for Clcn1 splicing Developmental dynamics Medium 18213585
2014 MBNL1 and MBNL2 both act as enhancers of Tau exon 2 inclusion; an intronic region 250 nt downstream of exon 2 contains cis-regulatory enhancers that directly bind MBNL1, and both MBNL1 and MBNL2 must interact together to fully reverse Tau exon 2 mis-splicing induced by long CUG repeats. Tau minigene splicing assays in cell culture; EMSAs/binding assays to identify cis-regulatory elements; overexpression and knockdown of MBNL1/MBNL2 Biochimica et biophysica acta Medium 24440524
2019 In DM1 cells with (CTG)2600 repeat, MBNL2 exons 5 and 8 show disproportionate inclusion, causing a reduced quantity and imbalanced collection of MBNL2 splice variants that accumulate in both cytoplasm and nucleus, contributing to skeletal muscle pathology starting at the myoblast stage. Isogenic CRISPR/Cas9-edited DM1 myoblast cell lines; RT-PCR isoform analysis; subcellular fractionation; Western blotting PloS one Medium 31116797
2019 MBNL2 overexpression inhibits breast and lung cancer cell migration and metastasis by suppressing the pAKT/EMT pathway; MBNL2 knockdown partially eliminates the anti-metastatic effect of neobractatin. MBNL2 overexpression and knockdown in cancer cell lines; migration/invasion assays; in vivo xenograft model; Western blotting for pAKT/EMT markers Cell death & disease Medium 31320607
2021 MBNL2 stabilizes p21 (CDKN1A) mRNA and protein in a p53-independent manner; MBNL2 depletion increases Chk1 S345 phosphorylation and DNA damage signaling, inhibits DNA damage-induced senescence, and promotes apoptosis after DNA damage through a p21-dependent mechanism. MBNL2 knockdown in cancer cell lines; transcriptome analysis; qRT-PCR and Western blotting for p21 and pChk1; flow cytometry for senescence/apoptosis; epistasis with p21 rescue International journal of molecular sciences Medium 33466733
2021 miR-182 directly targets and suppresses MBNL2 expression; this leads to activation of PI3K/AKT-mediated EMT and promotes cancer cell migration and invasion; re-introduction of MBNL2 reverses the pro-metastatic effect of miR-182. miR-182 overexpression and MBNL2 re-introduction in cancer cell lines; migration/invasion assays; luciferase reporter assay for miR-182 targeting of MBNL2; Western blotting for AKT/EMT markers Journal of Cancer Medium 34659561
2022 Neurodegenerative conditions (NMDA excitotoxicity, dysregulated calcium homeostasis) trigger nuclear translocation of calpain-2, which degrades MBNL2 in the nucleus; this degradation reverses MBNL2-regulated RNA processing to a fetal/developmental pattern; knockdown or inhibition of calpain-2 nuclear translocation prevents MBNL2 degradation and maintains adult RNA processing patterns. Neuronal culture excitotoxicity models; calpain-2 knockdown/inhibition; subcellular fractionation; Western blotting; splicing assays; DM1 and AD mouse models (EpA960/CaMKII-Cre, APP/PS1, THY-Tau22) The Journal of neuroscience High 35606145
2022 Cardiac-specific double knockout of Mbnl1 and Mbnl2 (via Myh6-Cre) in mice causes spontaneous lethal cardiac arrhythmias, recapitulates DM heart spliceopathy by RNA sequencing, and leads to ~6-fold increase in Calsequestrin 1 and 50% reduction of EGF protein in cardiomyocytes. Myh6-Cre conditional double KO mice; ECG/telemetry; RNA sequencing; immunoblotting Human molecular genetics Medium 35567413
2023 Loss of MBNL1 increases inclusion of Mbnl2 exon 6 and exon 9; exon 6 inclusion promotes MBNL2 nuclear translocation; exon 9 inclusion shifts the reading frame to an alternative C-terminus lacking a PEST domain that otherwise targets MBNL2 for proteasomal degradation, resulting in compensatory upregulation of MBNL2 protein. Mbnl1 KO mice; RT-PCR for exon inclusion; nuclear/cytoplasmic fractionation; proteasome inhibitor experiments; protein stability assays; DM1 mouse model validation Nucleic acids research High 36617982
2024 MBNL2 is required for nuclear envelope MTOC (NE-MTOC) formation in skeletal muscle cells; Mbnl2 depletion reduces expression of AKAP6β and affects Pericentrin (Pcnt) isoform expression, thereby impairing the developmental switch from centrosomal to NE-localized MTOC. siRNA knockdown of Mbnl2 in differentiating C2C12 myoblasts; longitudinal co-immunofluorescence staining; Western blotting for AKAP6β and Pcnt isoforms Cells Medium 39996710
2024 MBNL2 interacts with p21 (CDKN1A) and the piRNA CFAPIR competitively binds MBNL2 to modulate the TGF-β1/SMAD3 signaling pathway and cardiac fibrosis. Arraystar PiRNA profiling; RNA-protein immunoprecipitation; pulldown assays; Western blotting for TGF-β1/SMAD3 pathway markers; in vivo and in vitro cardiac fibrosis models Biochimica et biophysica acta. Molecular basis of disease Low 39122223
2024 MBNL2 promotes aging-related cardiac fibrosis by orchestrating SUMOylation of KLF4; MBNL2 inhibition increases SUMO1 binding to KLF4 by reducing SENP1-mediated deSUMOylation, and the TGF-β1/SMAD3 pathway mediates the pro-fibrotic effect of MBNL2 overexpression. MBNL2 overexpression and inhibition in senescent cardiac fibroblasts and aged mouse hearts; SUMO1-KLF4 co-IP; SENP1 expression analysis; Western blotting for TGF-β1/SMAD3 iScience Low 38974966
2026 MBNL2 binds the 3'-UTR of Ccr2 mRNA in dorsal root ganglion (DRG) neurons; paclitaxel-induced downregulation of MBNL2 reduces this binding, enhancing Ccr2 mRNA stability and increasing CCR2 protein expression, thereby contributing to chemotherapy-induced neuropathic pain. DRG neuron MBNL2 knockdown and rescue; RNA immunoprecipitation for MBNL2-Ccr2 3'UTR binding; mRNA stability assay; behavioral pain assays in mice Neurotherapeutics Medium 41967179
2026 MBNL2 is expressed in outer radial glial (oRG) cells during corticogenesis; dysfunction of MBNL2 (due to CTG-expanded DMPK transcript sequestration) in these progenitors impairs neuronal migration and differentiation of late-born cortical neurons, as demonstrated in CDM patient hiPSC-derived forebrain organoids with CRISPR-corrected controls. CDM patient hiPSC-derived forebrain organoids; CRISPR/Cas9 excision of CTG repeats as isogenic control; immunostaining for oRG markers and cortical neuron markers; MBNL2 expression analysis Neurobiology of disease Medium 41644016

Source papers

Stage 0 corpus · 25 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2002 Three proteins, MBNL, MBLL and MBXL, co-localize in vivo with nuclear foci of expanded-repeat transcripts in DM1 and DM2 cells. Human molecular genetics 375 11929853
2003 Developmental expression of mouse muscleblind genes Mbnl1, Mbnl2 and Mbnl3. Gene expression patterns : GEP 107 12915312
2008 Muscleblind-like 2 (Mbnl2) -deficient mice as a model for myotonic dystrophy. Developmental dynamics : an official publication of the American Association of Anatomists 51 18213585
2019 The natural compound neobractatin inhibits tumor metastasis by upregulating the RNA-binding-protein MBNL2. Cell death & disease 36 31320607
2014 Tau exon 2 responsive elements deregulated in myotonic dystrophy type I are proximal to exon 2 and synergistically regulated by MBNL1 and MBNL2. Biochimica et biophysica acta 27 24440524
2019 Methylphenidate Attenuates the Cognitive and Mood Alterations Observed in Mbnl2 Knockout Mice and Reduces Microglia Overexpression. Cerebral cortex (New York, N.Y. : 1991) 26 30060068
2021 MBNL2 Regulates DNA Damage Response via Stabilizing p21. International journal of molecular sciences 21 33466733
2019 (CTG)n repeat-mediated dysregulation of MBNL1 and MBNL2 expression during myogenesis in DM1 occurs already at the myoblast stage. PloS one 20 31116797
2023 Alternative splicing mediates the compensatory upregulation of MBNL2 upon MBNL1 loss-of-function. Nucleic acids research 19 36617982
2016 Paradoxical overexpression of MBNL2 in hepatocellular carcinoma inhibits tumor growth and invasion. Oncotarget 19 27564110
2021 RNA-binding Protein MBNL2 regulates Cancer Cell Metastasis through MiR-182-MBNL2-AKT Pathway. Journal of Cancer 18 34659561
2022 Mice lacking MBNL1 and MBNL2 exhibit sudden cardiac death and molecular signatures recapitulating myotonic dystrophy. Human molecular genetics 16 35567413
2021 Mbnl1 and Mbnl2 regulate brain structural integrity in mice. Communications biology 16 34848815
2020 SNPs in SNCA, MCCC1, DLG2, GBF1 and MBNL2 are associated with Parkinson's disease in southern Chinese population. Journal of cellular and molecular medicine 15 32652860
2022 Calpain-2 Mediates MBNL2 Degradation and a Developmental RNA Processing Program in Neurodegeneration. The Journal of neuroscience : the official journal of the Society for Neuroscience 13 35606145
2020 Protective effects of mirtazapine in mice lacking the Mbnl2 gene in forebrain glutamatergic neurons: Relevance for myotonic dystrophy 1. Neuropharmacology 11 32171677
2024 PiRNA CFAPIR inhibits cardiac fibrosis by regulating the muscleblind-like protein MBNL2. Biochimica et biophysica acta. Molecular basis of disease 7 39122223
2024 Studying the Effect of MBNL1 and MBNL2 Loss in Skeletal Muscle Regeneration. International journal of molecular sciences 6 38473933
2024 MBNL2 promotes aging-related cardiac fibrosis via inhibited SUMOylation of Krüppel-like factor4. iScience 6 38974966
2023 Mbnl2 loss alters novel context processing and impairs object recognition memory. iScience 5 37216102
2025 NE-MTOC Formation in Skeletal Muscle Is Mbnl2-Dependent and Occurs in a Sequential and Gradual Manner. Cells 1 39996710
2025 MBNL2 enhances cisplatin resistance by regulating apoptosis in ovarian cancer cells. BMB reports 1 40176605
2026 MBNL2 dysfunction in outer radial glial cells is associated with disrupted corticogenesis in congenital myotonic dystrophy. Neurobiology of disease 0 41644016
2026 RNA-binding protein MBNL2 mitigates neuropathic pain after chemotherapy through destabilizing CCR2 expression in primary sensory neurons. Neurotherapeutics : the journal of the American Society for Experimental NeuroTherapeutics 0 41967179
2025 Primary pulmonary spindle cell sarcoma with novel MBNL2::NUTM1 fusion and associated langerhans cell hyperplasia. Pathology, research and practice 0 40819508

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