A new polymorphism of arylsulfatase A within the coding region

Area of Science:

• Genetics
• Biochemistry
• Neurology

Background:

• Metachromatic leukodystrophy (MLD) is a rare genetic disorder affecting the nervous system.
• Arylsulfatase A (ASA) gene mutations are the primary cause of MLD and ASA pseudodeficiency.
• Accurate genetic diagnosis requires complete characterization of both ASA alleles.

Purpose of the Study:

• To determine the complete genotype of a patient with juvenile MLD.
• To investigate the role of a newly identified ASA variant (L/P76) in MLD.
• To assess the clinical significance of the L/P76 substitution in relation to ASA activity and MLD.

Main Methods:

• Gene sequencing of the arylsulfatase A (ASA) gene to identify mutations.
• Analysis of patient DNA and DNA from MLD-unrelated controls.
• Assay of leukocyte ASA activity and measurement of urinary sulfatide excretion.

Main Results:

• A patient with juvenile MLD was found to have the 459 + 1G-->A mutation and a novel T-to-C transition (L/P76) in the ASA gene.
• The L/P76 variant was present in 18 out of 20 MLD-unrelated controls, indicating it is a common polymorphism.
• The L/P76 variant did not affect leukocyte ASA activity or urinary sulfatide levels, suggesting it is not pathogenic for MLD or pseudodeficiency.

Conclusions:

• The leucine 76 to proline substitution (L/P76) in the ASA gene represents a common polymorphism, not associated with MLD or ASA pseudodeficiency.
• Despite its lack of pathogenicity, the L/P76 variant's frequency and location may be important for genetic studies requiring allelic differentiation within families.
• Further research is needed to fully elucidate the genotype of the index case with juvenile MLD.