Gene Expression-Related Changes in Morphologies of Organelles and Cellular Component Organization in Mucopolysaccharidoses.

Estera Rintz,Lidia Gaffke,Grzegorz Węgrzyn,Karolina Pierzynowska,Zuzanna Cyske,Izabela Giecewicz

doi:10.3390/ijms22052766

Estera Rintz, Lidia Gaffke + Show 4 more

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https://doi.org/10.3390/ijms22052766

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Abstract

Mucopolysaccharidoses (MPS) are inherited metabolic diseases characterized by accumulation of incompletely degraded glycosaminoglycans (GAGs) in lysosomes. Although primary causes of these diseases are mutations in genes coding for enzymes involved in lysosomal GAG degradation, it was demonstrated that storage of these complex carbohydrates provokes a cascade of secondary and tertiary changes affecting cellular functions. Potentially, this might lead to appearance of cellular disorders which could not be corrected even if the primary cause of the disease is removed. In this work, we studied changes in cellular organelles in MPS fibroblasts relative to control cells. All 11 types and subtypes of MPS were included into this study to obtain a complex picture of changes in organelles in this group of diseases. Two experimental approaches were employed, transcriptomic analyses and electron microscopic assessment of morphology of organelles. We analyzed levels of transcripts of genes grouped into two terms included into the QuickGO database, ‘Cellular component organization’ (GO:0016043) and ‘Cellular anatomical entity’ (GO:0110165), to find that number of transcripts with significantly changed levels in MPS fibroblasts vs. controls ranged from 109 to 322 (depending on MPS type) in GO:0016043, and from 70 to 208 in GO:0110165. This dysregulation of expression of genes crucial for proper structures and functions of various organelles was accompanied by severe changes in morphologies of lysosomes, nuclei, mitochondria, Golgi apparatus, and endoplasmic reticulum. Interestingly, some observed changes occurred in all/most MPS types while others were specific to particular disease types/subtypes. We suggest that severe changes in organelles in MPS cells might arise from dysregulation of expression of a battery of genes involved in organelles’ structures and functions. Intriguingly, normalization of GAG levels by using recombinant human enzymes specific to different MPS types corrected morphologies of some, but not all, organelles, while it failed to improve regulation of expression of selected genes. These results might suggest reasons for inability of enzyme replacement therapy to correct all MPS symptoms, particularly if initiated at advanced stages of the disease.

Highlights

Line we found that number of transcripts with significantly changed levels in MPS fibroblasts vs. HDFa controls was relatively high, ranging from 109 to 322
Tion When (GO:0006996), endomembrane system and membrane orassessing genes grouped in theorganization child terms (GO:0010256), of cellular component organization (GO:0016043), i.e., microtubule center organization (GO:0031023), cellular ganization (GO:0061024), we foundorganizing a significant number of transcripts whose levels were component assembly (GO:0022607), vesicle tethering (GO:0099022), organelle organization (GO:0006996), endomembrane system organization (GO:0010256), and membrane organization (GO:0061024), we found a significant number of transcripts whose levels were either elevated or decreased in MPS cells in all types of the disease in almost all child terms (Figure 2)
Knowing that expression of a relatively large number of genes related to organelles is changed in MPS fibroblasts, we investigated morphology of these cellular components in fibroblasts derived from patients suffering from all know MPS types and subtypes

Summary

Introduction

Single gene defects are defined in each such disease, it appears that we are still far from understanding molecular mechanisms leading to expression of complicated symptoms due to dysfunction of just one locus, which can be exemplified by unexpected phenotypes of persons bearing known pathogenic mutations [2]. Among all LSD, 11 diseases belong to mucopolysaccharidoses (MPS) which are caused by mutations in genes coding for lysosomal enzymes required for degradation of glycosaminoglycans (GAG) [4]. Accumulation of GAGs in lysosomes is the primary cause of MPS, and due to continuous production of these compounds and their impaired degradation, these diseases are progressive and severe, with expected average life span between one and two decades [4]. Despite incredible progress of molecular genetic studies and extensive medical investigations, only a few therapeutic options are available for MPS patients while none of them being able solve all, or even most, clinical problems [5,6]

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