1. ¹Department of Medical Genetics, University of Antwerp, Antwerp, Belgium
2. ²Laboratory of Biological Psychology, University of Leuven, Leuven, Belgium
3. ³Institut de Génétique et de Biologie Moléculaire et Cellulaire, CU de Strasbourg, France

Correspondence: Dr R Frank Kooy, Department of Medical Genetics, University of Antwerp, Universiteitsplein 1, Antwerp 2610, Belgium. Tel: +32(0) 3 820 26 30; E-mail: Frank.Kooy@ua.ac.be

Received 24 February 2006; Revised 2 May 2006; Accepted 3 May 2006; Published online 14 June 2006.

Abstract

Monozygotic twin brothers with a subtelomeric 6q deletion presented with mental retardation, microcephaly, seizures, an enlarged cisterna magna, dimpling at elbows, a high arched palate and a thin upper lip. The same subtelomeric deletion was detected in the mother of the patients, presenting with a milder phenotype. We narrowed down the breakpoint to a region of approximately 100 kb and estimated the size of the terminal deletion to be 1.2 Mb. This region contains four known and seven putative genes. Comparison of the deletion with other reported patients showed TBP was the most plausible candidate gene for the mental retardation in this syndrome. We verified that the TBP gene expression was halved in our patients using real-time PCR. Cognitive and behavioural tests performed on previously described heterozygous tbp mice suggested that TBP is potentially involved in cognitive development.