Large genomic rearrangements in MECP2

Area of Science:

• Genetics
• Molecular Biology
• Neurology

Background:

• Mutations in the methyl-CpG-binding protein 2 (MECP2) gene, located at Xq28, were first identified in Rett syndrome (RTT) patients in 1999.
• While 80-90% of classic RTT cases have MECP2 coding mutations, the cause remains unknown in 10-20% of patients.
• Previous research suggested large rearrangements, specifically deletions, within MECP2 might explain some MECP2-negative RTT cases.

Purpose of the Study:

• To investigate the role of large MECP2 deletions in patients with Rett syndrome who tested negative for mutations in the coding region.
• To screen a cohort of 45 RTT patients using a specific MLPA technique to detect genomic deletions in MECP2.
• To characterize identified deletions and explore potential genotype-phenotype correlations through severity scoring and X chromosome inactivation profiling.

Main Methods:

• Utilized Multiplex Ligation-dependent Probe Amplification (MLPA) to screen 45 RTT patients for MECP2 deletions.
• Employed real-time quantitative PCR (qPCR) and long-range PCR for detailed characterization of detected genomic deletions.
• Assessed clinical severity and X chromosome inactivation patterns in patients with identified MECP2 deletions.

Main Results:

• Detected seven RTT patients with genomic deletions in the MECP2 gene among the screened cohort.
• Successfully characterized the extent and nature of these large MECP2 deletions.
• Observed a correlation between identified deletions and classic Rett syndrome presentation.

Conclusions:

• Large deletions within the MECP2 gene are a significant cause of classic Rett syndrome.
• The MLPA technique is effective in identifying MECP2 deletions in RTT patients.
• Further investigation into genotype-phenotype correlations in MECP2 deletion-positive RTT cases is warranted.