Somatic GJA4 mutation in intracranial extra-axial cavernous hemangiomas

Objective Extra-axial cavernous hemangiomas(ECHs)are sporadic and rare intracranial occupational lesions that usually occur within the cavernous sinus.The aetiology of ECHs remains unknown.Methods Whole-exome sequencing was performed on ECH lesions from 12 patients(discovery cohort)and droplet digital polymerase-chain reaction(ddPCR)was used to confirm the identified mutation in 46 additional cases(validation cohort).Laser capture microdissection(LCM)was carried out to capture and characterise subgroups of tissue cells.Mechanistic and functional investigations were carried out in human umbilical vein endothelial cells and a newly established mouse model.Results We detected somatic GJA4 mutation(c.121G>T,p.G41C)in 5/12 patients with ECH in the discovery cohort and confirmed the finding in the validation cohort(16/46).LCM followed by ddPCR revealed that the mutation was enriched in lesional endothelium.In vitro experiments in endothelial cells demonstrated that the GJA4 mutation activated SGK-1 signalling that in turn upregulated key genes involved in cell hyperproliferation and the loss of arterial specification.Compared with wild-type littermates,mice overexpressing the GJA4 mutation developed ECH-like pathological morphological characteristics(dilated venous lumen and elevated vascular density)in the retinal superficial vascular plexus at the postnatal 3 weeks,which were reversed by an SGK1 inhibitor,EMD638683.Conclusions We identified a somatic GJA4 mutation that presents in over one-third of ECH lesions and proposed that ECHs are vascular malformations due to GJA4-induced activation of the SGK1 signalling pathway in brain endothelial cells.