Diagnostic mutational analysis of MECP2 in Korean patients with Rett syndrome

In-Joo Kim,Yeon-Joo Kim,Sang-Ook Nam,Hoon-Chul Kang,Mi-Ae Yoo,Byeong-Hee Son,Ook-Hwan Choi,Cheol-Min Kim,Heung-Dong Kim

doi:10.1038/emm.2006.15

Abstract

Rett syndrome (RTT) is an X-linked dominant neurodevelopmental disorder affecting 1 per 10,000-15,000 female births worldwide. The disease-causing gene has been identified as MECP2 (methyl-CpG-binding protein 2). In this study, we performed diagnostic mutational analysis of the MECP2 gene in RTT patients. Four exons and a putative promoter of the MECP2 gene were analyzed from the peripheral blood of 43 Korean patients with Rett syndrome by PCR-RFLP and direct sequencing. Mutations were detected in the MECP2 gene in approximately 60.5% of patients (26 cases/43 cases). The mutations consisted of 14 different types, including 9 missense mutations, 4 nonsense mutations and 1 frameshift mutation. Of these, three mutations (G161E, T311M, p385fsX409) were newly identified and were determined to be disease-causing mutations by PCR- RFLP and direct sequencing analysis. Most of the mutations were located within MBD (42.3%) and TRD (50%). T158M, R270X, and R306C mutations were identified at a high frequency. Additionally, an intronic SNP (IVS3+23C>G) was newly identified in three of the patients. IVS3+23C>G may be a disease-related and Korea-specific SNP for RTT. L100V and A201V are apparently disease-causing mutations in Korean RTT, contrary to previous studies. Disease-causing mutations and polymorphisms are important tools for diagnosing RTT in Koreans. The experimental procedures used in this study should be considered for clinical molecular biologic diagnosis.

Highlights

Rett syndrome (RTT, MIM No 312750) is an X-linked dominant neurodevelopmental disorder and is the second most common cause of mental retardation in females, following Down syndrome (Rett, 1966; dos Santos et al, 2005)
A methyl-CpG binding domain (MBD) of 85 amino acids that binds to methylated CpG islands, and a transcriptional repression domain (TRD) of 104 amino acids that interacts with the transcriptional repressor Sin3A, which recruits histone deacetylases (HDAC) (Van den Veyver and Zoghbi, 2000)
There is no clear correlation between the type and position of mutations, methyl-CpG binding protein 2 (MECP2) plays a pivotal role in the RTT phenotype (Weaving et al, 2003)

Summary

Introduction

Rett syndrome (RTT, MIM No 312750) is an X-linked dominant neurodevelopmental disorder and is the second most common cause of mental retardation in females, following Down syndrome (Rett, 1966; dos Santos et al, 2005). RTT is caused by mutations in a gene encoding the methyl-CpG binding protein 2 (MECP2, AF30876) (Amir et al, 1999). MECP2 is mapped between IRAK (interleukin-1 receptor associated kinase) and RCP (red opsin gene) loci on chromosome Xq28 (Reichwald et al, 2000). MECP2 participates in transcriptional silencing by binding to methylated DNA in nucleosomes and chromatin. It contains functional domains, a methyl-CpG binding domain (MBD) of 85 amino acids that binds to methylated CpG islands, and a transcriptional repression domain (TRD) of 104 amino acids that interacts with the transcriptional repressor Sin3A, which recruits histone deacetylases (HDAC) (Van den Veyver and Zoghbi, 2000). The function of NLS within the TRD location is to facilitate the transport of MECP2 into the nucleus

Methods

Results

Conclusion