A Complex Cortical Malformation Caused by a Mutation in the Tubulin-Encoding TUBB3 Gene.

Area of Science:

• Neurogenetics
• Developmental Neuroscience
• Molecular Biology

Background:

• Tubulinopathies are a group of rare genetic disorders characterized by congenital, non-progressive brain malformations resulting from mutations in tubulin-encoding genes.
• While mutations in several tubulin genes are known causes, mutations in the TUBB3 gene are infrequently associated with complex cortical malformations.

Observation:

• A 21-month-old boy presented with significant developmental delays, including inability to walk independently and limited speech (fewer than five words).
• Clinical examination revealed right esotropia (inward turning of the eye) and hypotonia (low muscle tone) in the lower extremities.
• Neuroimaging (MRI) demonstrated a dysmorphic brainstem, enlarged basal ganglia, a smaller right thalamus compared to the left, and disorganized cerebellar folia.

Findings:

• Genetic analysis identified a missense mutation in the TUBB3 gene in the affected child.
• This mutation is implicated as the causative factor for the observed complex brain malformations and clinical phenotype.

Implications:

• This case expands the known spectrum of clinical presentations and genetic causes of tubulinopathies, specifically highlighting the role of TUBB3 mutations.
• Understanding the impact of TUBB3 mutations is crucial for accurate diagnosis, genetic counseling, and potential future therapeutic strategies for patients with complex brain malformations.