Adam P DeLuca, Wallace L M Alward, Jeffrey Liebmann, Robert Ritch, Kazuhide Kawase, Young H Kwon, Alan L Robin, Edwin M Stone, Todd E Scheetz, John H Fingert

Approximately 1% of normal tension glaucoma cases are caused by TANK binding kinase 1 (TBK1) gene duplications and triplications. However, the precise borders and orientation of these TBK1 gene copy number variations (CNVs) on chromosome 12 are unknown. We determined the exact borders of TBK1 CNVs and the orientation of duplicated or triplicated DNA segments in five NTG patients with different TBK1 mutations using whole genome sequencing. Tandemly duplicated chromosome segments spanning the TBK1 gene were detected in four NTG patients, each with unique borders. Four of five CNVs had borders located within interspersed repetitive DNA sequences (Alu and LINE-L1 elements), suggesting that mismatched homologous recombinations likely generated these CNVs. A fifth NTG patient had a complex rearrangement including triplication of a chromosome segment spanning the TBK1 gene. No specific mutation hot-spots for TBK1 CNVs were detected, however, interspersed repetitive sequences (i.e. Alu-elements) were identified at the borders of TBK1 CNVs, which suggests that mismatch of these elements during meiosis may be the mechanism that generated TBK1 gene dosage mutations.