ADAMTSL1

ADAMTSL1 (punctin) is a secreted extracellular matrix glycoprotein that functions at mechanically and developmentally critical tissue interfaces, including the myotendinous junction, condylar mesenchyme, and peripheral nerve. It adopts a hatchet-shaped structure with four thrombospondin type I repeats (TSRs) bearing O-fucose/glucose disaccharide modifications and requires C-mannosylation of Trp42 for proper folding and secretion; a dominant-negative p.Trp42Arg mutation causes intracellular retention and is associated with mandibular prognathism (PMID:11805097, PMID:28722276, PMID:30714143). The C. elegans ortholog MADD-4 acts as a secreted guidance cue that attracts axons and muscle arms through the netrin receptor UNC-40/DCC, establishing a conserved role for ADAMTSL family members as extracellular signaling ligands (PMID:22014523). ADAMTSL1 is proteolytically processed by MMP10 in fibroblast secretomes, is transcriptionally regulated by Hedgehog signaling in chondrosarcoma where it controls cell proliferation, and marks a Schwann cell subpopulation essential for large-caliber motor axon maintenance (PMID:24281761, PMID:24634412, PMID:39880678).

1. 2002 High

   Initial biochemical characterization established ADAMTSL1 as a secreted, glycosylated ECM protein with a defined domain architecture, resolving its basic identity as a TSR-containing matrix component deposited in punctate patterns outside focal contacts.

   Evidence Recombinant expression in insect and COS-1 cells; rotary shadowing EM; Edman degradation and LC-ESI-MS

   PMID:11805097

   Open questions at the time

   • No binding partners or receptors identified
   • In vivo tissue localization not established
   • Function of punctate substratum deposition unknown
2. 2009 Medium

   Identification of ADAMTSL1 TSRs as substrates for B3GLCT-mediated O-glucosylation revealed that its thrombospondin repeats carry a glucose-β1,3-fucose disaccharide, linking ADAMTSL1 post-translational modification to Peters-plus syndrome biology.

   Evidence Biochemical demonstration of O-glucosylation on purified ADAMTSL1 TSR domains

   PMID:18720094

   Open questions at the time

   • Functional consequence of O-glucosylation for ADAMTSL1 activity not tested
   • In vivo relevance of TSR glycosylation not demonstrated
3. 2011 High

   Genetic analysis of the C. elegans ortholog MADD-4 demonstrated that ADAMTSL family proteins function as secreted guidance cues acting through the DCC-family receptor UNC-40, establishing a signaling paradigm beyond a purely structural ECM role.

   Evidence Loss-of-function genetics, epistasis with unc-40/DCC, cell-autonomous rescue in C. elegans

   PMID:22014523

   Open questions at the time

   • Whether mammalian ADAMTSL1 similarly signals through DCC is untested
   • Ligand-receptor binding mechanism not defined biochemically
4. 2013 Medium

   Degradomic profiling identified ADAMTSL1 as a direct substrate of MMP10, revealing that its ECM function is regulated by proteolytic processing.

   Evidence TAILS degradomics with mass spectrometry in fibroblast secretomes

   PMID:24281761

   Open questions at the time

   • Cleavage site(s) and functional consequences of processing not characterized in detail
   • Relevance to in vivo tissue remodeling not established
5. 2014 Medium

   Placing ADAMTSL1 downstream of Hedgehog/Smoothened signaling and demonstrating its role in chondrosarcoma proliferation revealed a context-dependent growth-regulatory function for this ECM protein.

   Evidence Gene expression profiling of IPI-926-treated chondrosarcoma xenografts; functional proliferation assays

   PMID:24634412

   Open questions at the time

   • Mechanism by which ADAMTSL1 regulates proliferation unknown
   • Not clear if this is autocrine ECM signaling or structural
6. 2017 High

   Demonstrating that the p.Trp42Arg mutation disrupts C-mannosylation, causes intracellular retention, and exerts a dominant-negative effect on wild-type ADAMTSL1 secretion established that C-mannosylation is essential for proper folding and export.

   Evidence In vitro secretion assays with wild-type and mutant constructs; co-transfection experiments; cosegregation in a three-generation pedigree

   PMID:28722276

   Open questions at the time

   • Structural basis for why loss of C-mannosylation causes misfolding not determined
   • Whether dominant-negative effect operates in vivo in relevant tissues not shown
7. 2019 Medium

   Identification of ADAMTSL1 mutations in mandibular prognathism patients, combined with restricted expression in condylar mesenchyme, linked the gene to craniofacial skeletal growth, though the proposed aggrecan-cleavage mechanism remains hypothetical.

   Evidence Whole-exome sequencing in patients; in situ expression in mouse condyle

   PMID:30714143

   Open questions at the time

   • Aggrecan cleavage by ADAMTSL1 is hypothetical — no direct enzymatic or binding evidence
   • No animal model confirming craniofacial phenotype
   • Functional characterization of patient mutations not performed
8. 2022 Medium

   Single-nucleus transcriptomics identified Adamtsl1 as a marker of a Schwann cell subtype that preferentially ensheathes large-caliber motor axons, and this subtype is selectively reduced in ALS, placing ADAMTSL1 in the context of motor neuron support.

   Evidence snRNA-seq of mouse peripheral nerves; validation in SOD1-G93A ALS mice and human ALS nerve samples

   PMID:35115729

   Open questions at the time

   • ADAMTSL1 is a marker rather than a proven functional mediator of this SC subtype's activity
   • Whether ADAMTSL1 itself contributes to axon maintenance is untested
9. 2023 Medium

   Protein-level localization of ADAMTSL1 at the human myotendinous junction confirmed that it occupies a mechanically stressed ECM niche, consistent with a structural or signaling role at muscle-tendon interfaces.

   Evidence snRNA-seq, spatial transcriptomics, and immunofluorescence of human muscle-tendon samples

   PMID:36924352

   Open questions at the time

   • Functional role of ADAMTSL1 at the MTJ not tested
   • Binding partners at the MTJ unknown
10. 2025 High

    Conditional ablation of Pmp2+/Adamtsl1+ Schwann cells proved that this subtype is required for large-caliber motor axon survival, with rescue confirming the dependency, but the specific contribution of ADAMTSL1 protein within these cells remains unresolved.

    Evidence Tamoxifen-inducible Pmp2-CreERT2 diphtheria toxin ablation in mice; behavioral, electrophysiological, and ultrastructural analyses; recovery experiments

    PMID:39880678

    Open questions at the time

    • Ablation targets the entire SC subtype, not ADAMTSL1 specifically
    • Whether ADAMTSL1 secretion from these SCs mediates the axon-protective effect is unknown

• The mammalian receptor for ADAMTSL1 signaling, the functional consequences of its MMP10-mediated cleavage, and whether it directly contributes to motor axon maintenance or MTJ integrity remain unresolved.
• No mammalian receptor identified
• No ADAMTSL1-specific knockout phenotype reported in mice
• Structural basis for TSR-dependent ECM interactions undefined