Journal Article

The landscape of submicroscopic structural variants at the OPN1LW/OPN1MW gene cluster on Xq28 underlying blue cone monochromacy

Andreasson, Sten, Cideciyan, Artur V., Zrenner, Eberhart, Birch, David, Traboulsi, Elias I., Kellner, Ulrich, Rosenberg, Thomas, Wissinger, Bernd, Buena-Atienza, Elena, Baumann, Britta, Mora, Jaume Català, Stingl, Katarina, Lorenz, Birgit, Kohl, Susanne, Bocquet, Beatrice, Manfredini, Emanuela, Zarate, Yuri A., Gardner, Jessica C., Branham, Kari E., Vincent, Andrea L., Jacobson, Samuel G., Meunier, Isabelle, Rüther, Klaus, Preising, Markus N., Audo, Isabelle, Hardcastle, Alison J., Dollfus, Hélène, Martorell, Loreto, Ravesh, Zeinab, Michaelides, Michel, Vijzelaar, Raymon

2022

Overview

Blue cone monochromacy (BCM) is an X-linked retinal disorder characterized by low vision, photoaversion, and poor color discrimination. BCM is due to the lack of long-wavelength-sensitive and middle-wavelength-sensitive cone photoreceptor function and caused by mutations in the OPN1LW/OPN1MW gene cluster on Xq28. Here, we investigated the prevalence and the landscape of submicroscopic structural variants (SVs) at single-base resolution in BCM patients. We found that about onethird (n = 73) of the 213 molecularly confirmed BCM families carry an SV, most commonly deletions restricted to the OPN1LW/OPN1MW gene cluster. The structure and precise breakpoints of the SVs were resolved in all but one of the 73 families. Twenty-two families—all from the United States—showed the same SV, and we confirmed a common ancestry of this mutation. In total, 42 distinct SVs were identified, including 40 previously unreported SVs, thereby quadrupling the number of precisely mapped SVs underlying BCM. Notably, there was no “region of overlap” among these SVs. However, 90% of SVs encompass the upstream locus control region, an essential enhancer element. Its minimal functional extent based on deletion mapping in patients was refined to 358 bp. Breakpoint analyses suggest diverse mechanisms underlying SV formation as well as in one case the gene conversionbased exchange of a 142-bp deletion between opsin genes. Using parsimonious assumptions, we reconstructed the composition and copy number of the OPN1LW/OPN1MW gene cluster prior to the mutation event and found evidence that large gene arrays may be predisposed to the occurrence of SVs at this locus.

• Publisher: National Academy of Sciences
• Subject: Basic Medicine / Biological Sciences / Breakpoints / Color vision / Color Vision Defects - genetics / Copy number / Gene conversion / Gene Deletion / Genetics / Humans / Life Sciences / Medical and Health Sciences / Medical Genetics and Genomics (including Gene Therapy) / Medicin och hälsovetenskap / Medicinsk genetik och genomik (Här ingår: Genterapi) / Medicinska och farmaceutiska grundvetenskaper / Multigene Family - genetics / Mutation / Retinal Cone Photoreceptor Cells / Rod Opsins - genetics / Wavelength