Screening for Partial Deletions in the CREBBP Gene in Rubinstein–Taybi Syndrome Patients Using Multiplex PCR/Liquid Chromatography

Abstract

Rubinstein–Taybi syndrome (RTS, MIM 180849) is a multiple malformation syndrome characterized by growth retardation, developmental delay, and dysmorphic features, including down-slanting palpebral fissures, a beaked nose, broad thumbs, and halluces. Mutations in the gene encoding the CREB-binding protein gene (CREBBP, also known as CBP) on chromosome 16p13.3 were identified in 1995. Recently, we developed a mutation analysis protocol using denaturing high-performance liquid chromatography (DHPLC) and identified heterozygous CREBBP mutations in 12 of 21 RTS patients. To test whether exonic deletions represent a common pathogenic mechanism, we assessed the copy number of all the coding exons using a recently developed method, the multiplex PCR/liquid chromatography assay (MP/LC). By using MP/LC, we performed screening for CREBBP exonic deletions among 25 RTS patients in whom no point mutations or small insertions/ deletions were identified by DHPLC screening. We identified four classic RTS patients with deletions encompassing multiple exons (14–16, 5–31, 1–16, and 4–26). We conclude that large deletions including several exons are a relatively frequent cause of RTS, and that MP/LC is an effective method for detecting these deletions.