Genetic basis of galactosemia

Area of Science:

• Biochemistry
• Genetics
• Metabolic Disorders

Background:

• Classic galactosemia is an inherited metabolic disorder.
• It is caused by a deficiency in the enzyme galactose-1-phosphate uridyltransferase (GALT).
• Clinical presentation of galactosemia is highly variable among patients.

Purpose of the Study:

• To investigate the molecular basis of classic galactosemia.
• To correlate identified mutations with enzyme deficiency and clinical variability.
• To understand the impact of mutations on GALT enzyme function.

Main Methods:

• Identification and characterization of mutations in the GALT gene.
• Analysis of GALT protein expression (CRM) in patients.
• Correlation of mutation types with clinical phenotypes.

Main Results:

• Nine missense, three splicing mutations, three polymorphisms, and one silent substitution in GALT identified.
• Most disease-causing mutations are rare; Q188R is the most common (25% frequency).
• Mutations fall into CRM+ missense (most common), CRM- missense, and splicing categories.
• Eight of nine missense mutations are in conserved domains, suggesting functional importance.
• Protein polymorphisms affect variable amino acids, likely without functional impact.

Conclusions:

• Galactosemia exhibits significant molecular heterogeneity.
• This heterogeneity likely contributes to the observed clinical variability.
• Understanding mutation impact is crucial for diagnosing and managing galactosemia.