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

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.

Delivery and assessment of a CRISPR/nCas9-based genome editing system on in vitro models of mucopolysaccharidoses IVA assisted by magnetite-based nanoparticles

“…After translation, GALNS undergoes post-translational modification in the endoplasmic reticulum (ER)-Golgi apparatus (GA) pathway to attach mannose motifs in the Asn204/Asn423 residues and phosphorylate them, respectively 58 , which are crucial for sorting of lysosomal proteins 59 , 60 . In this regard, structural analysis of intracellular organelles of MPS IVA fibroblasts has revealed changes in the number, length, and width on the GA but not on the ER 61 . Consequently, we hypothesized a partially impaired processing of the overexpressing GALNS enzyme in the GA after Donor AAVS1:GALNS insertion in the AAVS1 locus.…”

Sanfilippo Syndrome: Optimizing Care with a Multidisciplinary Approach

“…Sanfilippo syndrome revealed the highest dysregulation of gene expression among MPS diseases, with numbers of down-and up-regulated transcripts (relative to healthy cells) exceeding 700 in every MPS III subtype. 32 Such global changes in levels of transcripts and proteins encoded by them result in dysmorphology and dysfunctions of different cellular organelles (like nucleus, mitochondria, endoplasmic reticulum, Golgi apparatus), 33 as well as abnormalities in various cellular processes. 34 Among them, apoptosis, 35 cell activation, 36 proteasomal degradation, 37 homeostasis of different ions (especially Ca 2+ , Fe 2+ and Zn 2+ ), 38 signal transduction, 39 and cell cycle, 40 are especially strongly affected.…”

“…42 Furthermore, some of these changes in gene expression regulation could not be reversed after effective decreasing levels of stored GAGs, suggesting that these dysfunctions are either irreversible or require additional manipulations (along with abolition of the storage) to be corrected. 42 Indeed, it was demonstrated experimentally that some cellular abnormalities could not be corrected by reduction of GAG storage; these included changes in organelles, 33 and proteasomal functions. 37 Very recent investigations demonstrated that some proteins involved in the signal transduction-mediated control of gene expression, like GPER1 and OXTR receptors, form aggregates which arise as effects of their interactions with undegraded GAGs.…”

Oxidative Stress in Mucopolysaccharidoses: Pharmacological Implications

“…One of the major challenges in developing effective treatment for MPS is the fact that some severe symptoms arise from lesions of hard-to-reach tissues and organs, such as the central nervous system or the skeleton. On the other hand, the existence of additional mechanisms of MPS pathogenesis, in addition to GAG storage, which are poorly understood, has been suggested and demonstrated experimentally [ 4 , 5 , 6 , 7 , 8 , 9 , 10 ]. Describing such mechanisms could indicate not only new mechanisms of the pathogenesis of this rare disease, but also the direction to develop effective therapies in the future.…”