Investigating p.Ala1035Val in NPC1: New Cellular Models for Niemann-Pick Type C Disease

Area of Science:

• Cell Biology
• Genetics
• Biochemistry

Background:

• Niemann-Pick type C (NPC) is a lysosomal storage disorder (LSD) caused by mutations in NPC1 or NPC2 genes, affecting cholesterol transport.
• The p.Ile1061Thr NPC1 variant is common in Western Europe, while p.Ala1035Val is prevalent in Portugal and globally.

Purpose of the Study:

• To investigate the cellular impact of the p.Ala1035Val NPC1 variant, particularly its interaction with the p.Ile858Val single nucleotide polymorphism (SNP).
• To compare the functional consequences of p.Ala1035Val and p.Ile1061Thr variants on NPC1 protein trafficking and lysosomal positioning.

Main Methods:

• Created variant-specific in vitro models using NPC1-deficient ARPE-19 cells expressing fluorescently-tagged NPC1 variants.
• Utilized patient-derived skin fibroblasts for cellular analysis.
• Examined lysosomal positioning and NPC1 protein trafficking pathways.

Main Results:

• Confirmed reduced lysosomal trafficking for the p.Ile1061Thr variant.
• Demonstrated impaired lysosomal trafficking for the p.Ala1035Val variant, with a more severe effect when in cis with the p.Ile858Val SNP.
• Observed similar or worse lysosomal positioning issues with p.Ala1035Val compared to p.Ile1061Thr.

Conclusions:

• The p.Ala1035Val variant significantly impacts NPC1 protein trafficking to lysosomes.
• The co-occurrence of p.Ala1035Val and p.Ile858Val in cis may exacerbate NPC disease cellular phenotypes.
• This study provides the first functional insights into the p.Ala1035Val variant, opening avenues for targeted NPC therapies.