Osteogenesis Imperfecta with a gross deletion including the <i>COL1A1</i> gene, induced by Alu-driven microhomology-mediated end joining.

Yamamoto, Kenichi; Nakayama, Hirofumi; Ito, Yusaku; Hattori, Masaya; Shimada, Takaaki; Ueda, Ikumi; Ishimi, Takeshi; Yamada, Chieko et al. · Bone Rep · 2026

case_report · Level V

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Abstract

Osteogenesis Imperfecta (OI) is a rare hereditary brittle bone disorder typically caused by <i>COL1A1</i> and <i>COL1A2</i> variants impairing type I collagen. However, gross deletions involving <i>COL1A1</i> are uncommon. Here, we report a family with type I OI harboring a 101-kbp deletion encompassing <i>COL1A1</i>, identified through whole genome analysis. Affected individuals presented mild phenotypes. Breakpoint analysis revealed a 5-bp microhomology-mediated end joining involving an Alu element. This report expands the understanding of genetic mechanisms underlying OI.