Affinage

SPECC1L

Cytospin-A · UniProt Q69YQ0

Length
1117 aa
Mass
124.5 kDa
Annotated
2026-04-28
32 papers in source corpus 13 papers cited in narrative 13 extracted findings

Mechanistic narrative

Synthesis pass · prose summary of the discoveries below

SPECC1L is a cytoskeletal scaffolding protein that crosslinks filamentous actin and microtubule networks through its calponin homology and coiled-coil domains, coordinating actomyosin organization, cell adhesion, and collective cell migration during embryonic tissue fusion events (PMID:21703590, PMID:34302166). Its second coiled-coil domain (CCD2) is essential for microtubule association and intracellular trafficking; disease-associated mutations in CCD2 act as gain-of-function alleles that disrupt actomyosin dynamics and cause craniofacial malformations including cleft palate and frontonasal dysplasia (PMID:34302166, PMID:31943082, PMID:41657552). SPECC1L directly binds the MYPT1/PP1β myosin phosphatase complex and distributes it between cytoskeletal networks, while modulating PI3K-AKT signaling to regulate adherens junction remodeling and cranial neural crest cell delamination and movement (PMID:36634848, PMID:26787558, PMID:33446878). SPECC1L also controls primary cilia length through F-actin regulation, with its loss leading to shortened cilia and elevated Hedgehog signaling in cranial mesenchyme (PMID:41657552).

Mechanistic history

Synthesis pass · year-by-year structured walk · 10 steps
  1. 2011 High

    The initial characterization established that SPECC1L associates with both actin and microtubule networks and is required for cytoskeletal reorganization, cell adhesion, and migration — defining it as a cytoskeletal scaffolding protein relevant to morphogenesis.

    Evidence Immunofluorescence colocalization and siRNA knockdown in mammalian cells, Drosophila morpholino knockdown, zebrafish knockdown

    PMID:21703590

    Open questions at the time
    • Direct binding to actin vs. microtubules not biochemically resolved
    • Mechanism of cytoskeletal crosslinking unknown
    • Relevant signaling pathways downstream not identified
  2. 2014 Medium

    Zebrafish studies demonstrated that SPECC1L is specifically required for cranial neural crest cell convergence and integration during facial morphogenesis, linking its cytoskeletal function to craniofacial development.

    Evidence Morpholino knockdown with lineage tracing in zebrafish

    PMID:25357034

    Open questions at the time
    • Morpholino-based, not genetic mutant
    • Molecular mechanism of CNCC convergence failure not defined
  3. 2016 High

    A key signaling axis was identified: SPECC1L deficiency stabilizes adherens junctions through reduced PI3K-AKT signaling, and pathway activation rescues the defect — establishing PI3K-AKT as the mediator of SPECC1L's role in junction remodeling and neural crest delamination.

    Evidence siRNA knockdown, immunostaining, electron microscopy, PI3K-AKT inhibition/activation rescue in mammalian cells and mouse embryos

    PMID:26787558

    Open questions at the time
    • How SPECC1L activates PI3K-AKT mechanistically is unknown
    • Whether PI3K-AKT mediates all SPECC1L functions or only AJ regulation unclear
  4. 2020 High

    Genetic epistasis in mice placed SPECC1L downstream of the transcription factor IRF6 in palatogenesis and showed that disease mutations cluster in CCD2 and calponin homology domains, disrupting microtubule association — connecting human disease variants to a specific molecular defect.

    Evidence Mouse compound heterozygous models, genetic epistasis with Irf6, patient cohort sequencing

    PMID:31943082

    Open questions at the time
    • Direct transcriptional regulation of Specc1l by IRF6 not shown
    • Why CCD2 mutations specifically impair microtubule binding not structurally resolved
  5. 2021 High

    CCD2 was established as the critical microtubule-association domain: its in-frame deletion causes perinuclear protein accumulation and ectopic peripheral actomyosin bundles, acting as a gain-of-function perturbation distinct from complete loss — explaining why patient CCD2 variants produce dominant phenotypes.

    Evidence Mouse knock-in models (null vs. CCD2 deletion alleles), immunofluorescence, live-cell imaging

    PMID:34302166

    Open questions at the time
    • No structural model of CCD2-microtubule interaction
    • Gain-of-function mechanism (dominant-negative vs. neomorphic) not distinguished
  6. 2021 High

    SPECC1L was shown to regulate collective cell movement, not just individual cell migration: deficient palatal mesenchyme cells lose coordinated movement during wound repair, and PI3K-AKT activation restores both speed and directionality.

    Evidence Live-imaging wound-repair assay with primary mouse embryonic palatal mesenchyme cells, PI3K-AKT rescue

    PMID:33446878

    Open questions at the time
    • Whether collective migration defect is cell-autonomous or involves paracrine signaling not resolved
    • In vivo relevance for palate closure not directly tested
  7. 2023 High

    The direct biochemical mechanism was advanced by identifying MYPT1/PP1β myosin phosphatase complex as a physical partner: SPECC1L binds MYPT1 directly and distributes the phosphatase between actin and microtubule networks, providing a molecular basis for actomyosin regulation.

    Evidence Reciprocal co-immunoprecipitation, BioID proximity biotinylation, direct binding assay

    PMID:36634848

    Open questions at the time
    • Whether SPECC1L modulates MYPT1/PP1β phosphatase activity or only localization is unknown
    • Substrate specificity of the SPECC1L-MYPT1 complex not defined
  8. 2023 Medium

    An unexpected role in meiotic spindle assembly was identified: SPECC1L knockdown in oocytes produces abnormal spindles, misaligned chromosomes, and reduced developmental competence, extending its cytoskeletal function to cell division.

    Evidence siRNA knockdown in mouse oocytes, immunofluorescence, live-cell imaging, developmental competence assays

    PMID:37698179

    Open questions at the time
    • Single lab, not independently replicated
    • Whether spindle role involves the same MYPT1/actin-microtubule crosslinking mechanism is untested
  9. 2025 Medium

    SPECC1L was linked to primary cilia regulation: its loss elevates F-actin, shortens cilia, and increases Hedgehog signaling via GLI1 in cranial mesenchyme. Genetic interaction with the IFT-A component Thm1 demonstrates convergence on cilia-mediated craniofacial patterning.

    Evidence Conditional knockout (Wnt1-Cre2), F-actin depolymerization rescue, cilia length measurement, GLI1 immunostaining, compound heterozygote genetic epistasis

    PMID:41278885 PMID:41657552

    Open questions at the time
    • Cilia findings partly from preprint, awaiting peer review
    • Whether cilia shortening is a direct F-actin effect or involves additional SPECC1L-dependent mechanisms unknown
    • Relationship between AJ/PI3K-AKT axis and cilia regulation not established
  10. 2025 Medium

    Conservation of SPECC1L function in focal adhesion dynamics was demonstrated in Drosophila: the ortholog Spdi associates with NMII and actin, and disease-analogous point mutations increase focal adhesion turnover beyond depletion alone, supporting a conserved gain-of-function mechanism for patient variants.

    Evidence RNAi knockdown and disease-analog point mutations in Drosophila, live-cell imaging of focal adhesions (preprint)

    PMID:40236004

    Open questions at the time
    • Preprint, not peer-reviewed
    • Whether Drosophila Spdi also regulates cilia or PI3K-AKT not tested
    • Microtubule association was not observed for Spdi, raising questions about conservation of the MT-crosslinking function

Open questions

Synthesis pass · forward-looking unresolved questions
  • How SPECC1L mechanistically activates PI3K-AKT signaling, whether its MYPT1-distribution function is the primary effector of actomyosin regulation in vivo, and the structural basis of CCD2-mediated microtubule binding remain open questions.
  • No structural model of SPECC1L or its CCD2-microtubule interface
  • Mechanism linking SPECC1L to PI3K-AKT activation unknown
  • In vivo contribution of MYPT1/PP1β regulation vs. direct actin-MT crosslinking not dissected

Mechanism profile

Synthesis pass · controlled-vocabulary classification · explore literature graph →
Molecular activity
GO:0008092 cytoskeletal protein binding 4 GO:0060090 molecular adaptor activity 2
Localization
GO:0005856 cytoskeleton 4 GO:0005829 cytosol 2
Pathway
R-HSA-1266738 Developmental Biology 3 R-HSA-162582 Signal Transduction 2
Partners
IRF6MYH10MYH9MYPT1PPP1CBTHM1
Complex memberships
MYPT1/PP1β myosin phosphatase complex

Evidence

Reading pass · 13 per-paper findings extracted from the source corpus
Year Finding Method Journal Conf PMIDs
2011 SPECC1L colocalizes with both tubulin and actin in mammalian cells, and its deficiency results in defective actin-cytoskeleton reorganization, as well as abnormal cell adhesion and migration. Knockdown in Drosophila phenocopies integrin signaling pathway mutants with cell-migration and adhesion defects. Immunofluorescence colocalization, siRNA knockdown in mammalian cells, Drosophila morpholino knockdown, zebrafish knockdown American journal of human genetics High 21703590
2016 SPECC1L deficiency results in increased adherens junction (AJ) stability, with elevated β-catenin and E-cadherin staining and apico-basal diffusion of AJs, impairing cranial neural crest cell (CNCC) delamination. This AJ defect is mediated through reduced PI3K-AKT signaling, as moderate PI3K-AKT inhibition in wildtype cells recapitulates AJ alterations, and AJ changes from SPECC1L knockdown are rescued by PI3K-AKT pathway activation. siRNA knockdown, electron microscopy, immunostaining of AJ components, mouse knockout model, PI3K-AKT inhibition/activation assays, rescue experiments Scientific reports High 26787558
2020 SPECC1L functions downstream of IRF6 in palatogenesis. SPECC1L mutations cluster in the second coiled-coil and calponin homology domains and severely affect SPECC1L association with microtubules. Specc1l compound heterozygous mouse embryos exhibit palate elevation delay with transient oral epithelial adhesions, periderm layer abnormalities, and ectopic apical expression of adherens junction markers, consistent with acting downstream of Irf6 (SPECC1L expression is drastically reduced in Irf6 mutant palatal shelves). Mouse genetic models (gene-trap and truncation alleles), immunostaining, genetic epistasis with Irf6, sequencing of patient cohorts Human molecular genetics High 31943082
2021 The second coiled-coil domain (CCD2) of SPECC1L mediates microtubule association and correct intracellular trafficking. In-frame deletion of CCD2 causes perinuclear accumulation of mutant SPECC1L-ΔCCD2 protein with diminished microtubule overlap and abnormally increased actin and non-muscle myosin II bundles dislocated to the cell periphery. CCD2 perturbation in full-length SPECC1L context is gain-of-function, disrupting actomyosin cytoskeletal organization and tissue fusion dynamics. Mouse knock-in models (null and CCD2 in-frame deletion alleles), immunofluorescence colocalization, live-cell imaging, embryo phenotyping Human molecular genetics High 34302166
2021 SPECC1L-deficient primary mouse embryonic palatal mesenchyme (MEPM) cells show reduced cell speed and defective coordinated (collective) cell movement during wound repair. PI3K-AKT pathway activation rescues both cell speed and guidance defects in SPECC1L-deficient MEPM cells, demonstrating that SPECC1L regulates collective cell movement through PI3K-AKT signaling. Live-imaging wound-repair assay with primary MEPM cells, open-field 2D culture, PI3K-AKT pathway activation rescue Scientific reports High 33446878
2023 SPECC1L directly binds MYPT1 and exists in a stable complex with MYPT1/PP1β (myosin phosphatase complex) in cells. SPECC1L can regulate the distribution of the MYPT1/PP1β complex between the microtubule and filamentous actin networks. Coimmunoprecipitation, proximity biotinylation assays (BioID), interactome comparison, direct binding assay The Journal of biological chemistry High 36634848
2023 SPECC1L associates with non-muscle myosin II (NMII), filamentous actin, microtubules, and adherens junction membrane components. Its CCD2 domain is required for microtubule association and proper intracellular trafficking. Perturbation of CCD2 leads to abnormal actomyosin organization, affecting tissue movement and fusion events during embryogenesis. Review/synthesis of mouse models, immunofluorescence, Co-IP, interactome data from multiple studies Biochemical Society transactions Medium 37345651
2023 SPECC1L is required for proper bipolar spindle assembly during mouse oocyte meiosis. Knockdown of Specc1l in oocytes results in abnormal spindle morphology, misaligned chromosomes, reduced polar body extrusion, and decreased blastocyst formation rate. SPECC1L localizes to the cytoplasm and germinal vesicle in oocytes but does not colocalize with chromatin at MII stage. siRNA knockdown in mouse oocytes, immunofluorescence, live-cell imaging, developmental competence assays Reproduction (Cambridge, England) Medium 37698179
2025 SPECC1L loss leads to elevated filamentous actin (F-actin) and shortened primary cilia; depolymerizing F-actin in Specc1l mutant cells restored cilia lengths, establishing an inverse relationship between SPECC1L-regulated F-actin and cilia length. A genetic interaction between Specc1l and Thm1 (an IFT-A protein) was identified: compound heterozygotes show higher penetrance of cleft palate than Specc1l heterozygotes alone. Mouse genetics (compound heterozygotes), F-actin depolymerization rescue, cilia length measurement, genetic epistasis bioRxivpreprint Medium 41278885
2025 In cranial neural crest cell (CNCC)-specific Specc1l knockout mice (Wnt1-Cre2), loss of SPECC1L in CNCCs leads to shortened primary cilia and increased Hedgehog (Hh) signaling (elevated GLI1 immunostaining) in cranial mesenchyme at E13.5 and in E9.5 facial prominences, resulting in frontonasal dysplasia features (shortened skulls, reduced frontal bone, nasal and midface defects). Conditional knockout (Cre-lox), GLI1 immunostaining, cilia length measurement, craniofacial morphometry Frontiers in physiology Medium 41657552
2025 The Drosophila SPECC1L homolog Split discs (Spdi) co-localizes with non-muscle myosin II (NMII) and actin (not microtubules). RNAi depletion of Spdi increases focal adhesion dynamics, and conserved point mutations analogous to human disease variants further increase focal adhesion dynamics above depletion alone, suggesting SPECC1L regulates focal adhesion dynamics through NMII association. RNAi knockdown, immunofluorescence, live-cell imaging of focal adhesions, disease-analog point mutations in Drosophila bioRxivpreprint Medium 40236004
2014 In zebrafish, specc1lb is expressed in epithelia juxtaposed to chondrocytes. Knockdown of specc1lb results in bilateral clefts between frontonasal and maxillary equivalent structures; lineage tracing showed cranial neural crest cells contributing to the frontonasal prominence failed to integrate with maxillary prominence populations, and mandibular cells failed to converge, establishing SPECC1L function in CNCC integration and convergence. Morpholino knockdown, lineage tracing, immunohistochemistry, RT-PCR, TUNEL assay in zebrafish Plastic and reconstructive surgery Medium 25357034
2020 SPECC1L-NTRK2 fusion (identified in pediatric cancer) promotes cytokine-independent cell survival and proliferation when expressed in cells, and transformed cells are sensitive to TRK inhibitor treatment, demonstrating oncogenic gain-of-function of the SPECC1L-NTRK2 fusion. Cloning of fusion from patient sample, enforced expression in cells, cytokine-independent growth assay, TRK inhibitor sensitivity assay Cold Spring Harbor molecular case studies Medium 33144287

Source papers

Stage 0 corpus · 32 papers · ranked by NIH iCite citations
Year Title Journal Citations PMID
2011 Deficiency of the cytoskeletal protein SPECC1L leads to oblique facial clefting. American journal of human genetics 75 21703590
2016 SPECC1L deficiency results in increased adherens junction stability and reduced cranial neural crest cell delamination. Scientific reports 43 26787558
2014 Mutations in SPECC1L, encoding sperm antigen with calponin homology and coiled-coil domains 1-like, are found in some cases of autosomal dominant Opitz G/BBB syndrome. Journal of medical genetics 39 25412741
2015 Expanding the SPECC1L mutation phenotypic spectrum to include Teebi hypertelorism syndrome. American journal of medical genetics. Part A 32 26111080
2018 Phenotypic spectrum associated with SPECC1L pathogenic variants: new families and critical review of the nosology of Teebi, Opitz GBBB, and Baraitser-Winter syndromes. European journal of medical genetics 30 30472488
2020 SPECC1L regulates palate development downstream of IRF6. Human molecular genetics 23 31943082
2014 Functional analysis of SPECC1L in craniofacial development and oblique facial cleft pathogenesis. Plastic and reconstructive surgery 22 25357034
2021 In-frame deletion of SPECC1L microtubule association domain results in gain-of-function phenotypes affecting embryonic tissue movement and fusion events. Human molecular genetics 15 34302166
2021 SPECC1L-deficient primary mouse embryonic palatal mesenchyme cells show speed and directionality defects. Scientific reports 12 33446878
2023 SPECC1L binds the myosin phosphatase complex MYPT1/PP1β and can regulate its distribution between microtubules and filamentous actin. The Journal of biological chemistry 11 36634848
2023 SPECC1L: a cytoskeletal protein that regulates embryonic tissue dynamics. Biochemical Society transactions 11 37345651
2020 A novel SPECC1L mutation causing Teebi hypertelorism syndrome: Expanding phenotypic and genetic spectrum. European journal of medical genetics 10 31953237
2020 Congenital diaphragmatic hernia as a prominent feature of a SPECC1L-related syndrome. American journal of medical genetics. Part A 8 32954677
2020 Recurrent SPECC1L-NTRK fusions in pediatric sarcoma and brain tumors. Cold Spring Harbor molecular case studies 7 33144287
2022 BCL6-SPECC1L: A Novel Fusion Gene in Nasopharyngeal Carcinoma. Technology in cancer research & treatment 5 36412101
2024 Changes in expression of VGF, SPECC1L, HLA-DRA and RANBP3L act with APOE E4 to alter risk for late onset Alzheimer's disease. Scientific reports 3 38942763
2021 A novel p.Pro871Leu missense mutation in SPECC1L gene causing craniosynostosis in a patient. Orthodontics & craniofacial research 3 33527670
2025 First Report of SPECC1L::ALK Fusion in Medullary Thyroid Carcinoma with Remarkable Response to Alectinib. Thyroid : official journal of the American Thyroid Association 2 40376737
2025 Oral Undifferentiated Pleomorphic Sarcoma: A Novel SPECC1L::TERT Gene Fusion and a Comprehensive Literature Review. Genes 2 40725486
2025 Genetic interaction of Specc1l and Thm1 reveals cytoskeletal-ciliary crosstalk. bioRxiv : the preprint server for biology 2 41278885
2024 NTRK-rearranged spindle cell tumor with SPECC1L-NTRK3 fusion in the thoracic spine: a case report. Journal of cancer research and clinical oncology 2 39661164
2023 Specc1l deficiency leads to abnormal oocyte meiosis and reduced blastocyst development in mouse. Reproduction (Cambridge, England) 2 37698179
2022 SPECC1L Mutations Are Not Common in Sporadic Cases of Opitz G/BBB Syndrome. Genes 2 35205294
2025 Disruption of SPECC1L translation initiation by intragenic deletion: novel pathogenic mechanism in Teebi-hypertelorism syndrome. NPJ genomic medicine 1 41120295
2023 Efficacy and safety of iruplinalkib (WX‑0593) on non‑small cell lung cancer with SPECC1L‑ALK fusion: A case report. Experimental and therapeutic medicine 1 38234623
2026 Loss of SPECC1L in cranial neural crest cells results in increased hedgehog signaling and frontonasal dysplasia. Frontiers in physiology 0 41657552
2025 The Drosophila SPECC1L homolog, Split Discs, co-localizes with non-muscle myosin II and regulates focal adhesion dynamics. bioRxiv : the preprint server for biology 0 40236004
2025 Case Report: Dual resistance to dasatinib/olverembatinib in accelerated-phase cml: identification of a novel SPECC1L-inserted e8a2 BCR::ABL1 transcript and ABL1 V379I mutation. Frontiers in oncology 0 41211450
2025 Loss of SPECC1L in cranial neural crest cells results in increased hedgehog signaling and frontonasal dysplasia. bioRxiv : the preprint server for biology 0 41332626
2024 Clinical and Molecular Traits of a Novel SPECC1L-ALK Fusion in a Patient with Advanced Non-Small Cell Lung Cancer. Journal of personalized medicine 0 39063924
2023 [Identification of a child with Teebi hypertelorism syndrome 1 due to variant of SPECC1L gene]. Zhonghua yi xue yi chuan xue za zhi = Zhonghua yixue yichuanxue zazhi = Chinese journal of medical genetics 0 37532501
2023 The Human Brainome: changes in expression of VGF, SPECC1L, HLA-DRA and RANBP3L act with APOE E4 to alter risk for late onset Alzheimer's disease. Research square 0 38168398