Functional Analysis of Complex Structural and Splice-Altering Variants in the ARSB Gene Towards the Personalized...

Area of Science:

• Genetics
• Molecular Biology
• Biochemistry

Background:

• Mucopolysaccharidosis Type VI (MPS VI) is a genetic disorder caused by variants in the ARSB gene, leading to lysosomal dysfunction.
• Standard genetic testing may fail to detect complex variants underlying MPS VI.
• Identifying causative variants is crucial for diagnosis and therapeutic development.

Purpose of the Study:

• To investigate the genetic basis of MPS VI in patients with unexplained clinical presentations.
• To identify complex structural variants in the ARSB gene missed by routine sequencing.
• To explore potential therapeutic strategies targeting aberrant splicing.

Main Methods:

• Whole genome sequencing and RNA analysis were employed to identify causative variants.
• Minigene-based cellular models were utilized to study variant effects on splicing.
• Antisense molecule strategies (modified U7 snRNAs and circular RNAs) were tested for therapeutic potential.

Main Results:

• Three MPS VI patients had complex ARSB variants, including a large intronic insertion and an intragenic deletion, missed by Sanger sequencing.
• A deep intronic variant activating a pseudoexon and an exon 2 deletion were identified.
• Antisense molecules effectively blocked pseudoexons, increasing wild-type ARSB mRNA levels by approximately twofold.

Conclusions:

• Complex structural variants and deep intronic mutations can cause MPS VI and evade standard genetic detection.
• Targeting pseudoexon activation with antisense oligonucleotides shows promise for MPS VI therapy.
• This approach could restore functional ARSB mRNA levels in patients with specific genetic defects.