ITGA7

ITGA7 encodes a laminin-binding integrin alpha subunit that localizes to the skeletal muscle sarcolemma, where it functions as a laminin receptor linking the extracellular matrix to the internal actin cytoskeleton; its systemic overexpression in a severe muscular dystrophy mouse model extends longevity, reduces kyphosis, and protects against contraction-induced force loss (PMID:26076707). The gene is developmentally regulated during myogenesis and produces multiple cytoplasmic (alpha7A/B) and extracellular (X1/X2) splice variants encoded across at least 27 exons (PMID:7607681, PMID:10403775). Alternative splicing of the mutually exclusive X1/X2 isoforms is controlled by the RNA-binding protein QKI, and this isoform choice governs polarized localization of ITGA7 and dystrophin proteins, asymmetric muscle stem cell division, and maintenance of the myogenic progenitor population (PMID:35165120); at the sarcolemma ITGA7 co-localizes at the nanoscale with dystroglycan, consistent with a shared role in coupling cytoskeleton to matrix (PMID:37509580). ITGA7 expression is directly activated by FOXC1 binding to its promoter and repressed through an ATF1/miR-214-5p axis (PMID:29884889, PMID:35568813). Mechanistically, ITGA7 binds CKAP4 to block the CKAP4–PI3K p85alpha interaction, thereby restraining PI3K/AKT/NF-kB signaling; loss of ITGA7 releases CKAP4 to activate p85alpha, driving NF-kB nuclear translocation and transcription of pro-invasive targets including MMP9, SETD7, and ADAM15 in colorectal cancer (PMID:38885843). ITGA7 also acts as an upstream activator of PI3K-AKT signaling in non-muscle contexts such as granulosa cells and osteogenic stem cells (PMID:35415300, PMID:36901882).

1. 1995 Medium

   Established ITGA7 as a single-copy gene whose expression is developmentally regulated during skeletal muscle formation, framing it as a myogenesis-associated integrin.

   Evidence Southern blotting, in situ hybridization, and phylogenetic analysis in rat and human genomes

   PMID:7607681

   Open questions at the time

   • Did not define isoform function
   • No protein-level localization or ligand confirmed
2. 1999 Medium

   Resolved the exon/intron architecture and catalogued the cytoplasmic (alpha7A/B) and extracellular (X1/X2) splice variants, defining the structural repertoire later shown to be functionally important.

   Evidence Genomic sequencing of exon boundaries, RT-PCR, radiation hybrid mapping

   PMID:10403775

   Open questions at the time

   • Functional distinction between isoforms not established
   • Regulators of splicing unknown at this stage
3. 2015 High

   Demonstrated in vivo that ITGA7 acts as a sarcolemmal laminin receptor coupling matrix to cytoskeleton, with therapeutic restoration of muscle force in a dystrophy model.

   Evidence AAV-mediated systemic ITGA7 overexpression in mdx/utrn(-/-) mice with force measurement and immunohistochemistry

   PMID:26076707

   Open questions at the time

   • Molecular partners at the sarcolemma not enumerated
   • Signaling consequences downstream of ITGA7 not addressed
4. 2018 High

   Identified FOXC1 as a direct transcriptional activator of ITGA7 and placed ITGA7 downstream of FOXC1 in driving cancer invasion, extending ITGA7 biology beyond muscle.

   Evidence ChIP, reporter assays, genetic epistasis, and in vivo lung metastasis model in colorectal cancer

   PMID:29884889

   Open questions at the time

   • Molecular effector of ITGA7-driven invasion not yet defined
   • Whether muscle isoforms apply to cancer context unclear
5. 2018 Low

   Indicated a tumor-suppressive role of ITGA7 in breast cancer via repression of EMT-associated markers, an apparent contrast to its pro-invasive role elsewhere.

   Evidence siRNA knockdown with migration/invasion assays and Western blot in breast cancer lines

   PMID:29760566

   Open questions at the time

   • No mechanistic rescue
   • Direction of effect conflicts with colorectal findings, unresolved by context
6. 2020 Low

   Reinforced an EMT-suppressing role of ITGA7 in thyroid carcinoma, supporting a context-dependent tumor-suppressive function.

   Evidence siRNA knockdown with proliferation/invasion assays and EMT marker Western blots in papillary thyroid cell lines

   PMID:31942970

   Open questions at the time

   • No mechanistic rescue
   • Upstream and downstream pathway not connected
7. 2021 Low

   Linked ITGA7 loss to dopaminergic cell apoptosis and alpha-synuclein accumulation, introducing a possible neuronal role.

   Evidence siRNA knockdown in SH-SY5Y cells with Western blot for TH, alpha-synuclein, and apoptotic markers

   PMID:34884422

   Open questions at the time

   • Single readout without pathway rescue
   • Mechanism connecting ITGA7 to alpha-synuclein unknown
8. 2022 High

   Showed that QKI-controlled X1/X2 splicing of Itga7 governs protein polarity, asymmetric muscle stem cell division, and progenitor maintenance, giving functional meaning to the long-known isoform diversity.

   Evidence Conditional QKI knockout mouse, transcriptomics, antisense splice-switching, and imaging of protein polarity

   PMID:35165120

   Open questions at the time

   • Distinct ligand or signaling properties of X1 vs X2 not defined
   • How polarized ITGA7 directs the spindle/division apparatus unresolved
9. 2022 Medium

   Defined an ATF1/miR-214-5p axis that directly represses ITGA7 to promote osteoclastogenesis, identifying a transcriptional/post-transcriptional repression arm.

   Evidence ChIP, luciferase reporter, siRNA epistasis, TRAP staining, and OVX mouse model

   PMID:35568813

   Open questions at the time

   • Downstream signaling of derepressed ITGA7 in osteoclasts not detailed
10. 2022 Medium

    Connected ITGA7 to PI3K-AKT activation in bone marrow stem cells responding to nanohydroxyapatite, implicating it in matrix-sensing osteogenic signaling.

    Evidence hBMSC culture with nHAP, ITGA7 siRNA knockdown, PI3K-AKT activity assays, and ectopic osteogenesis in mice

    PMID:35415300

    Open questions at the time

    • Direct ITGA7-PI3K coupling not biochemically resolved here
    • Mechanism distinguishing fixed vs free nHAP effects unclear
11. 2022 Low

    Extended the ITGA7/alpha-synuclein relationship to muscle cells, supporting a conserved suppression of alpha-synuclein accumulation.

    Evidence siRNA knockdown in C2C12 cells with immunofluorescence and Western blot

    PMID:35628462

    Open questions at the time

    • Single readout, no mechanistic follow-up
    • Causal pathway to alpha-synuclein unknown
12. 2023 Low

    Established ITGA7 as an upstream activator of PI3K-AKT supporting proliferation and survival in granulosa cells, generalizing its pro-survival signaling role.

    Evidence siRNA knockdown with PI3K-AKT Western blots, apoptosis flow cytometry, and proliferation assays in porcine granulosa cells

    PMID:36901882

    Open questions at the time

    • No direct binding or reconstitution
    • Effector linking ITGA7 to PI3K not identified in this system
13. 2023 Medium

    Provided nanoscale spatial evidence that ITGA7 and dystroglycan co-localize at the sarcolemma, supporting parallel matrix-cytoskeleton linkage roles.

    Evidence FPALM super-resolution microscopy with confocal validation in intact zebrafish muscle fibers

    PMID:37509580

    Open questions at the time

    • Physical interaction between ITGA7 and dystroglycan not demonstrated
    • Functional consequence of distinct nanoscale distributions unclear
14. 2024 Medium

    Defined the molecular mechanism by which ITGA7 restrains pro-invasive signaling: binding CKAP4 to block CKAP4-PI3K p85alpha interaction and suppress NF-kB-driven transcription of MMP9, SETD7, and ADAM15.

    Evidence Co-immunoprecipitation, nuclear/cytoplasmic fractionation, RNA-seq, rescue assays, and promoter methylation analysis in colorectal cancer cells

    PMID:38885843

    Open questions at the time

    • CoIP from single lab without reciprocal structural validation
    • Reconciliation with FOXC1-driven pro-invasive role not fully integrated
15. 2024 Low

    Implicated ITGA7 in maintaining stromal stem cell identity, where its loss drives cancer-associated fibroblast conversion and a pro-metastatic secretome.

    Evidence siRNA knockdown in primary omental ADSCs with morphology, biomarker, and conditioned-medium migration assays

    PMID:38174862

    Open questions at the time

    • No mechanistic pathway identified
    • Secreted factors driving cancer cell invasion not defined

• It remains unresolved how ITGA7 produces opposite effects across contexts — acting as a PI3K-AKT activator and pro-invasive effector in some tissues while suppressing PI3K/AKT/NF-kB and EMT in others.
• No unifying model reconciling activating vs suppressing roles
• Isoform-specific signaling differences not mapped to cancer/stem cell phenotypes
• No structural model of the ITGA7-CKAP4 interface