Oculodentodigital dysplasia, or ODDD, is an ultra-rare autosomal dominant disorder caused by germline variants in GJA1. Patients typically show a pleiotropic constellation of features affecting the eyes, teeth, digits, and sometimes the central nervous system, with severity varying dramatically even within the same family. Connexin 43 is the most ubiquitously expressed connexin in the human body, forming gap junction channels that allow direct cytoplasmic exchange between adjacent cells. But the protein’s long C-terminal tail also does channel-independent work, physically associating with signaling partners such as β-catenin and various kinases. It is this second, scaffolding role that the new research places at the center of the disease mechanism.

The team, led by researchers at Peking Union Medical College Hospital and Children’s Hospital of Soochow University, recruited two families with classic ODDD presentations. Proband 1, a young girl, displayed short palpebral fissures, hypoplastic alae nasi, sparse hair, bilateral syndactyly of the fourth and fifth fingers, and dental anomalies including microdontia and enamel hypoplasia. Her affected younger brother carried the same craniofacial and hand phenotype, while their mother showed only mild bilateral brachydactyly of the fifth fingers—a striking example of intra-familial variability. Proband 2 presented similar features along with syndactyly of the toes, and whole-genome sequencing revealed his variant arose de novo, absent from both clinically healthy parents. Sanger sequencing confirmed heterozygous missense variants, c.253G>C in Family 1 and c.605G>A in Family 2, both segregating perfectly with disease status.

What makes the study unusual is its reliance on primary patient-derived cells rather than engineered model systems. The researchers cultured skin fibroblasts from both patients and mesenchymal stromal cells, or MSCs, harvested from discarded surgical bone and skin tissue collected during syndactyly release and corrective osteotomy procedures. Controls came from age- and sex-matched pediatric patients undergoing hand trauma surgery at the same anatomical site, with whole-genome sequencing used to exclude any pathogenic variants in known disease genes. Flow cytometry confirmed the MSC identity, with cells positive for CD90, CD105, and CD73 and negative for CD45, meeting the International Society for Cellular Therapy minimal criteria.

RNA sequencing on patient fibroblasts and MSCs revealed a transcriptional landscape split cleanly in two. Downregulated gene sets were dominated by Wnt signaling, extracellular matrix–receptor interaction, osteoblast differentiation, DNA replication, and cell cycle regulation. Upregulated sets lit up with inflammatory response genes, cytokine-mediated signaling, JAK-STAT signaling, tumor necrosis factor response, and ECM structural constituents. The team then validated these patterns at the protein level using RT-qPCR, Western blotting, immunofluorescence, and ELISA. In both fibroblasts and MSCs, mRNA levels of canonical Wnt targets—AXIN2, CCND1, PCNA, and c-MYC—fell sharply. Protein levels of Cx43, β-catenin, and IκBα dropped in parallel, while the ratio of phosphorylated p65 to total p65 rose, a signature of NF-κB pathway activation.

The inflammatory profile that emerged is the study’s most surprising finding. Interleukin-6 expression and secretion surged in patient cells, yet CXCL8—better known as IL-8—was paradoxically and significantly reduced, despite NF-κB being switched on. Interferon-stimulated genes MX1 and IFIT1 were simultaneously elevated. The researchers traced this uncoupling to c-MYC, the Wnt-dependent transcription factor whose loss appears to lift normal repression on MMP3 while simultaneously starving CXCL8 of a required activator. MMP3, or stromelysin-1, is a matrix metalloproteinase that degrades components of the extracellular matrix, and its abnormal upregulation points to excessive ECM remodeling—a process that could plausibly underlie the tissue fusion seen in syndactyly, though the authors caution that this connection remains speculative and requires in vivo validation.

Functional assays confirmed the molecular story has real cellular consequences. Transwell migration assays showed patient fibroblasts and MSCs crossed basement membranes at markedly reduced rates, while EdU incorporation revealed suppressed proliferation. These defects align with the coordinated downregulation of CCND1, PCNA, and c-MYC, key regulators of the G1/S cell cycle transition, suggesting GJA1 deficiency stalls cells before they enter DNA synthesis. Differentiation assays added another layer: patient MSCs showed compromised osteogenic capacity, with reduced alkaline phosphatase activity and diminished Alizarin Red S mineralization, alongside aberrantly enhanced adipogenic potential measured by Oil Red O staining. This lineage shift mirrors the classical biology of Wnt signaling, which normally maintains MSC stemness, promotes bone formation, and suppresses fat cell differentiation—offering a cellular explanation for the bone hypoplasia seen in ODDD patients.

To establish causality rather than mere correlation, the team ran bidirectional genetic interventions. Knocking down GJA1 with siRNA in normal control cells, reducing expression to roughly the level seen in patient cells, faithfully reproduced the entire patient phenotype: Wnt suppression, the IL-6-high/CXCL8-low inflammatory bias, elevated MMP3, impaired migration, and skewed differentiation. Conversely, overexpressing wild-type connexin 43 in patient cells substantially reversed these defects, restoring IκBα levels, reducing p65 phosphorylation, suppressing MMP3, and rescuing migration. A second round of experiments isolated c-MYC’s role directly: silencing c-MYC in normal MSCs reproduced the CXCL8 collapse and MMP3 surge, while overexpressing c-MYC in patient MSCs rescued both, establishing c-MYC as a necessary and sufficient regulator of these two genes downstream of the GJA1/Wnt axis.

Pharmacological experiments then mapped the hierarchy of the pathway. Treating patient cells with CHIR99021, a selective GSK-3β inhibitor that activates canonical Wnt signaling, restored c-MYC expression, corrected the CXCL8 deficit, suppressed MMP3, reduced IL-6 secretion, and improved both migration and osteogenic differentiation. In contrast, a neutralizing antibody against IL-6 acted only on downstream readouts: it dampened the interferon response but failed to restore c-MYC, could not rescue CXCL8, and left MMP3 overexpression untouched. The combination of both agents produced the strongest overall rescue, simultaneously targeting the core upstream defect and the downstream inflammatory overactivation. The comparison makes a clear translational argument: blocking a single cytokine treats symptoms, but reactivating the Wnt/c-MYC axis addresses the disease’s root signaling failure.

The authors are candid about the study’s limits. Fibroblasts came from only two patients and MSCs from one, so transcriptomic findings are explicitly framed as exploratory, and technical replicates from a single donor cannot substitute for independent biological replicates. The researchers also could not perform promoter-reporter or chromatin immunoprecipitation experiments to demonstrate direct c-MYC binding at the CXCL8 or MMP3 promoters, again because of the scarcity of pediatric patient cells. Connexin 43’s broad expression in heart, brain, and skin means long-term neurological and cardiac follow-up of the two families is warranted, even though neither child currently shows overt deficits in those systems. Still, the work delivers a coherent new pathogenic framework for ODDD—one in which a broken gap junction protein silently rewires Wnt, NF-κB, and matrix remodeling all at once—and it nominates Wnt activation, rather than isolated cytokine blockade, as the therapeutic strategy most worth pursuing in this rare and poorly understood disorder.

Subject of Research: Molecular mechanisms of GJA1-related oculodentodigital dysplasia in patient-derived fibroblasts and mesenchymal stromal cells

Article Title: GJA1 dysfunction suppresses Wnt/c-MYC signaling and promotes inflammatory imbalance and MMP3-associated ECM remodeling in fibroblasts and mesenchymal stromal cells from patients with ODDD

Article References: Tao, S., Zhao, B., Wang, X., Shen, X., & Zhao, X. (2026). GJA1 dysfunction suppresses Wnt/c-MYC signaling and promotes inflammatory imbalance and MMP3-associated ECM remodeling in fibroblasts and mesenchymal stromal cells from patients with ODDD. Frontiers in Cell and Developmental Biology, 14, Article 1959966. https://doi.org/10.3389/fcell.2026.1959966

Image Credits: AI Generated

DOI: 10.3389/fcell.2026.1959966

Keywords: oculodentodigital dysplasia, GJA1, connexin 43, Wnt signaling, c-MYC, NF-κB, MMP3, mesenchymal stromal cells, fibroblasts, rare disease, osteogenic differentiation, CHIR99021