Genotype-phenotype correspondence in Sanfilippo syndrome type B

Area of Science:

• Genetics
• Biochemistry
• Rare Diseases

Background:

• Sanfilippo syndrome type B (mucopolysaccharidosis type IIIB) is caused by defects in the alpha-N-acetylglucosaminidase (NAGLU) gene.
• The number of described mutations in the NAGLU gene has been limited, hindering comprehensive genetic analysis.

Purpose of the Study:

• To develop and apply a rapid, automated sequencing method for identifying mutations in the entire coding region of the NAGLU gene.
• To significantly expand the catalog of known NAGLU mutations associated with Sanfilippo syndrome type B.

Main Methods:

• An automated sequencing procedure was employed to analyze the complete coding region and exon-intron boundaries of the NAGLU gene.
• Eight families affected by Sanfilippo syndrome type B were studied, with all 16 alleles analyzed.

Main Results:

• The study identified mutations in all 16 alleles from the eight families, more than doubling the previously published NAGLU mutations.
• Eight novel mutations were described, including five missense, two nonsense, and one insertion mutation.
• A specific mutation at codon R674 was found to be prevalent (36% of point mutations), potentially indicating a common or ancient mutation.

Conclusions:

• The developed automated sequencing method is effective for rapid and comprehensive identification of NAGLU mutations.
• The findings expand the known mutational landscape of Sanfilippo syndrome type B, providing crucial data for genotype-phenotype correlations.
• Understanding these mutations is vital for evaluating future therapeutic strategies, such as gene therapy.