Mutations in the lysosomal enzyme-targeting pathway and persistent stuttering

Area of Science:

• Genetics
• Neurodevelopmental Disorders
• Molecular Biology

Background:

• Stuttering is a speech disorder with unknown etiology, characterized by disruptions in speech flow.
• Genetic factors are suspected contributors to stuttering, with prior research linking it to chromosome 12.
• Nonsyndromic stuttering affects speech fluency without other apparent developmental issues.

Purpose of the Study:

• To investigate the genetic underpinnings of nonsyndromic stuttering.
• To analyze the chromosome 12q23.3 genomic region for mutations associated with stuttering.
• To identify specific genes involved in the etiology of stuttering.

Main Methods:

• Analysis of the chromosome 12q23.3 genomic region in consanguineous Pakistani families with stuttering.
• Genomic analysis of unrelated case and control subjects from Pakistan and North America.
• Mutation screening in candidate genes involved in lysosomal metabolism.

Main Results:

• A missense mutation in the GNPTAB gene (encoding GlcNAc-phosphotransferase) was associated with stuttering in Pakistani families.
• Mutations in GNPTAB, GNPTG (gamma subunit of GNPT), and NAGPA (uncovering enzyme) were identified in stuttering individuals but not in controls.
• These genes are crucial for generating the mannose-6-phosphate signal, essential for lysosomal enzyme targeting.

Conclusions:

• Genetic variations in genes regulating lysosomal metabolism are associated with susceptibility to nonsyndromic stuttering.
• Mutations in GNPTAB, GNPTG, and NAGPA provide new insights into the molecular mechanisms of stuttering.
• This research highlights the role of lysosomal pathways in speech disorders.