Copy Number Variant Analysis in CHM to Detect Duplications Underlying Choroideremia

Abstract

Purpose: To investigate the possibility of duplications or deletions within the CHM gene as a cause of choroideremia (CHM).

Materials and Methods: Eight males and one female subject were identified in whom clinical features were consistent with a clinical diagnosis of CHM. In all cases, sequencing of the coding region and adjacent intronic splice sites did not identify a mutation. In some cases, supplemental immunoblot analysis of protein from peripheral blood leukocytes with anti-REP-1 antibody confirmed absence of Rab escort protein-1, REP-1. A multiplex ligation-dependent probe amplification assay (MLPA) for the CHM gene was developed to test for deletions and duplications within the CHM gene.

Results: A duplication of exons 3–8 of the CHM gene (NM_000390.2) was identified in one case.

Discussion: While likely an uncommon event, duplication within the CHM gene could be considered as an explanation for CHM cases in which no mutation is found by sequence analysis.

• Choroideremia
• duplication
• MLPA
• REP-1
• synthetic probes

Acknowledgments

We would like to thank the following clinicians for forwarding samples on their patients: Dr J. E. Bourgeois, Dr Marilyn Ekins, Dr John Heckenlively, Dr Samuel Jacobson, Dr Lee Jampol, Dr Daryl Kurz, Dr Richard A. Lewis, and Dr Richard Weleber.