MAP3K1 Integrates Genetic and Environmental Signals in Eyelid Morphogenesis.

Developmental disorders often arise from complex interactions between genetic variation and environmental factors, yet the molecular mechanisms underlying gene-gene (G × G) and gene-environment (G × E) interactions remain poorly understood. Mouse embryonic eyelid closure provides a genetically tractable in vivo model for investigating these mechanisms. Eyelid closure requires coordinated epithelial migration and cytoskeletal remodeling orchestrated by interconnected signaling pathways. Among these pathways, MAP3K1 functions as a critical signaling hub that integrates inputs from S1PR-RHOA-ROCK and other upstream regulators to activate JNK and promote eyelid closure. Genetic studies show that multiple components within the GPCR-RHOA-ROCK-MAP3K1-JNK network cooperate to maintain developmental robustness. Reducing the activity of pathway components dose-dependently impairs eyelid closure and produces the characteristic eye-open-at-birth (EOB) phenotype. Environmental factors also converge on this network. Although exposure to dioxin does not impair eyelid closure in wild-type embryos, it induces EOB in embryos harboring otherwise phenotypically silent mutations in the MAP3K1 network, such as Map3k1+/-, Jnk1-/- and S1pr2-/-. These findings identify the MAP3K1 pathway as a point of convergence of genetic and environmental signals and establish embryonic eyelid closure as a powerful model for elucidating molecular mechanisms underlying developmental robustness, susceptibility and resilience.