Deleterious fibronectin type III-related gene variants may induce a spinal extradural arachnoid cyst: an exome sequencing study of identical twin cases.

Purpose: Despite numerous studies, the etiology of spinal extradural arachnoid cyst (SEDAC), a lesion associated with neurological symptoms, remains unknown. In this genomic twin study, we investigated the genetic etiology of SEDACs.
Methods: The subjects were identical twins who developed notably similar SEDACs at the same vertebral level. Accordingly, we performed whole-exome sequencing analyses of genomic material from the twins and their parents using a next-generation sequencer. Additionally, we determined their detailed family history and analyzed the family pedigree.
Results: The pedigree analysis suggested the potential presence of SEDACs in certain family members, indicating a genetic disease. Sequenced data were analyzed and filtered using a purpose-built algorithm, leading to the identification of 155 novel single-nucleotide polymorphisms (SNPs), of which 118 encoded missense or nonsense variants. A functional analysis of the proteins encoded by these SNP alleles revealed strong enrichment for the fibronectin type III (FN3) protein domain (q = 0.00576). Specifically, the data indicated that a missense variant affecting the FN3 protein domain of fibronectin 1 (FN1, p.P969S) can be the causal mutation underlying the SEDACs.
Conclusion: The data suggest that deleterious mutations in fibronectin-related genes may cause SEDACs. In particular, it was suspected that a variant of FN1 may be the cause of the SEDACs in the twin cases studied herein. Detailed studies with a larger number of cases are needed.