# Establishment of a Human iPSC Line from Mucolipidosis Type II That Expresses the Key Markers of the Disease

## TL;DR

Scientists created a new human cell line for Mucolipidosis type II, a rare fatal disease, which can help study its causes and treatments.

## Contribution

A novel iPSC line for Mucolipidosis type II was established, carrying the most frequent disease-causing mutation.

## Key findings

- The iPSC line expresses pluripotency markers and maintains a normal karyotype.
- ML II iPSCs show key disease hallmarks like reduced M6P-dependent hydrolase activity and cholesterol accumulation.
- The iPSCs can differentiate into three germ layers, making them a versatile disease model.

## Abstract

Mucolipidosis type II (ML II) is a rare and fatal disease of acid hydrolase trafficking. It is caused by pathogenic variants in the GNPTAB gene, leading to the absence of GlcNAc-1-phosphotransferase activity, an enzyme that catalyzes the first step in the formation of the mannose 6-phosphate (M6P) tag, essential for the trafficking of most lysosomal hydrolases. Without M6P, these do not reach the lysosome, which accumulates undegraded substrates. The lack of samples and adequate disease models limits the investigation into the pathophysiological mechanisms of the disease and potential therapies. Here, we report the generation and characterization of an ML II induced pluripotent stem cell (iPSC) line carrying the most frequent ML II pathogenic variant [NM_024312.5(GNPTAB):c.3503_3504del (p.Leu1168fs)]. Skin fibroblasts were successfully reprogrammed into iPSCs that express pluripotency markers, maintain a normal karyotype, and can differentiate into the three germ layers. Furthermore, ML II iPSCs showed a phenotype comparable to that of the somatic cells that originated them in terms of key ML II hallmarks: lower enzymatic activity of M6P-dependent hydrolases inside the cells but higher in conditioned media, and no differences in an M6P-independent hydrolase and accumulation of free cholesterol. Thus, ML II iPSCs constitute a novel model for ML II disease, with the inherent iPSC potential to become a valuable model for future studies on the pathogenic mechanisms and testing potential therapeutic approaches.