DCDC2 is associated with reading disability and modulates neuronal development in the brain

Area of Science:

• Genetics
• Neuroscience
• Developmental Biology

Background:

• The DYX2 locus on chromosome 6p22 is the most consistently identified genetic region associated with reading disability (RD).
• Previous studies have implicated this region in the genetic underpinnings of dyslexia.

Purpose of the Study:

• To identify the specific genetic variants within the DYX2 locus responsible for reading disability.
• To investigate the functional role of the DCDC2 gene in neuronal development and its potential link to reading traits.

Main Methods:

• Fine-mapping of the DYX2 locus using single nucleotide polymorphism (SNP) markers.
• Identification and characterization of a large polymorphic deletion in intron 2 of the DCDC2 gene.
• Analysis of allele frequencies and their association with reading traits.
• Reverse transcription polymerase chain reaction (RT-PCR) to determine DCDC2 expression in brain regions.
• RNA interference (RNAi) studies to assess the impact of DCDC2 down-regulation on neuronal migration.

Main Results:

• A large polymorphic deletion containing tandem repeats of putative transcription factor binding sites was identified in intron 2 of DCDC2.
• Alleles of this repeat were found to be in significant linkage disequilibrium with multiple reading traits.
• DCDC2 gene expression was detected in brain regions critical for fluent reading.
• Down-regulation of DCDC2 via RNA interference led to alterations in neuronal migration.

Conclusions:

• The identified DCDC2 deletion and its functional impact on neuronal migration provide strong evidence for DCDC2 as a candidate gene for reading disability.
• These findings integrate genetic, functional, and neuroimaging data, offering a comprehensive understanding of the molecular basis of dyslexia.
• The study highlights the role of DCDC2 in neurodevelopmental processes essential for reading acquisition.