Spectrum of MECP2 mutations in Rett syndrome

Area of Science:

• Genetics
• Neurodevelopmental Disorders
• Molecular Biology

Background:

• Rett syndrome is a significant X-linked dominant neurodevelopmental disorder.
• Mutations in the methyl-CpG-binding protein 2 (MECP2) gene are the primary cause in most affected females.
• Understanding the MECP2 mutational spectrum is crucial for diagnosis and research.

Purpose of the Study:

• To identify novel mutations in the MECP2 gene in individuals with Rett syndrome and related disorders.
• To further characterize the spectrum of MECP2 mutations.
• To compare mutation detection rates in classic RTT versus variant forms.

Main Methods:

• Sequencing of the MECP2 coding region in sporadic cases and families with affected females.
• Analysis of mutation types, including single nucleotide substitutions and frameshift mutations.
• Comparison of X-chromosome inactivation patterns in mutation-positive and negative samples.

Main Results:

• 18 additional MECP2 mutations were identified, including 13 C-->T transitions at CpG hotspots.
• Novel frameshift mutations (deletions, duplication/deletion rearrangement) were found in the C-terminal domain.
• The overall mutational spectrum aligns with global findings, with two-thirds truncating and one-third missense mutations.

Conclusions:

• The study expands the known spectrum of MECP2 mutations associated with Rett syndrome.
• CpG hotspots are significant sites for MECP2 mutations.
• Mutation detection rates vary, being higher in classic RTT compared to diagnostic variants.