TRAF7 mutations stabilize K/NRAS and hyperactivate MAPK signaling to cause CAFDADD neurodevelopmental defects.

The MAPK-ERK1/2 pathway plays a crucial role in neurodevelopment during embryogenesis, and the hyperactivation of this signaling cascade serves as a pathological hallmark for various neurodevelopmental disorders. Germline variants in TRAF7, encoding a RING-type E3 ubiquitin ligase, are genetically associated with cardiac, facial, and digital anomalies with developmental delay (CAFDADD) syndrome; however, the downstream substrates of TRAF7 and the precise mechanism driving neurodevelopmental defects remain enigmatic. Here, we established a Traf7R654Q/+ knock-in mouse model and patient-specific induced pluripotent stem cell (iPSC)-derived human cortical organoids (hCOs) carrying the recurrent TRAF7R655Q mutation. Heterozygous Traf7R654Q/+ mice exhibited remarkable growth retardation, skeletal abnormalities, and neurobehavioral deficits, whereas mutant hCOs displayed early cortical neurogenesis defects, characterized by premature neural differentiation and a depleted progenitor pool. Mechanistically, biochemical analyses revealed that TRAF7 interacts with KRAS and NRAS to promote their polyubiquitination and subsequent proteasomal degradation, maintaining physiological homeostatic control over the downstream MAPK cascade. CAFDADD-associated TRAF7 variants exert a dominant-negative effect, disrupting WT protein function and causing the posttranslational accumulation of KRAS and NRAS, which fundamentally drives constitutive MAPK-ERK1/2 pathway hyperactivation. Notably, pharmacological inhibition of MEK1/2 with selumetinib suppressed ERK1/2 hyperactivation, partially mitigated aberrant neuroepithelial morphology and neural differentiation in TRAF7R655Q/+ hCOs, and improved brain-to-body weight ratios in Traf7R654Q/+ mice. Together, our findings identify TRAF7 as a critical posttranslational regulator of RAS proteostasis during development and uncover a pivotal mechanistic link between impaired RAS ubiquitination and CAFDADD pathogenesis, providing preliminary clinical-front evidence for targeting the MAPK pathway to manage ongoing developmental deficits in TRAF7-associated disorders.