Modeling cartilage pathology in mucopolysaccharidosis VI using iPSCs reveals early dysregulation of chondrogenic and metabolic gene expression.

Mucopolysaccharidosis type VI (MPS VI) is a metabolic disorder caused by disease-associated variants in the Arylsulfatase B (ARSB) gene, resulting in ARSB enzyme deficiency, lysosomal glycosaminoglycan accumulation, and cartilage and bone pathology. The molecular response to MPS VI that results in cartilage pathology in human patients is largely unknown. Here, we generated a disease model to study the early stages of cartilage pathology in MPS VI. We generated iPSCs from four patients and isogenic controls by inserting the ARSB cDNA in the AAVS1 safe harbor locus using CRISPR/Cas9. Using an optimized chondrogenic differentiation protocol, we found Periodic acid-Schiff positive inclusions in hiPSC-derived chondrogenic cells with MPS VI. Genome-wide mRNA expression analysis showed that hiPSC-derived chondrogenic cells with MPS VI downregulated expression of genes involved in TGF-ß/BMP signalling, and upregulated expression of inhibitors of the Wnt/ß-catenin signalling pathway. Expression of genes involved in apoptosis and growth was upregulated, while expression of genes involved in glycosaminoglycan metabolism was dysregulated in hiPSC-derived chondrogenic cells with MPS VI. These results suggest that human ARSB deficiency in MPS VI causes changes in the transcriptional program underlying the early stages of chondrogenic differentiation and metabolism.

Intrafamilial oocyte donation in classic galactosemia: ethical and societal aspects.

Classic galactosemia is a rare inherited disorder of galactose metabolism. Primary ovarian insufficiency (POI) with subfertility affects > 80% of female patients and is an important concern for patients and their parents. Healthcare providers are often consulted for subfertility treatment possibilities. An option brought up by the families is intrafamilial oocyte donation (mother-to-daughter or sister-to-sister). In addition to POI, galactosemia patients can also present varying cognitive and neurological impairments, which may not be fully clear at the time when mother-to-daughter oocyte donation is considered. Ethical and societal aspects arise when exploring this option. This study aimed to provide guidance in aspects to consider based on the views of different groups involved in the oocyte donation process. A qualitative study using in-depth semi-structured interviews with > 50 participants (patients, family members, and healthcare providers) was conducted. From these interviews, themes of concern emerged, which are illustrated and reviewed: (1) family relations, (2) medical impact, (3) patients' cognitive level, (4) agreements to be made in advance and organization of counseling, (5) disclosure to the child, and (6) need for follow-up. We conclude that discussing and carrying out intrafamilial oocyte donation in galactosemia patients requires carefully addressing these themes. This study adds value to the already existing recommendations on intrafamilial oocyte donation in general, since it highlights important additional aspects from the perspectives of patients and their families.

Severe tracheal and bronchial collapse in adults with type II mucopolysaccharidosis.

BACKGROUND: Mucopolysaccharidosis type II (MPSII) patients frequently suffer from dyspnoea caused by restrictive airway disease due to skeletal abnormalities as well as glycosaminoglycans (GAG) accumulation at different levels of the airway, including the trachea. In this study we describe the extent of the tracheal and bronchial narrowing, the changes in airway diameter during respiration and the effects of these obstructions on respiratory function in adult MPSII patients. METHODS: Five adult MPSII patients (mean age 40 years) were included. Pulmonary function tests and in- and expiratory chest CT scans were obtained. Cross-sectional areas of trachea and main bronchi were measured at end-inspiration and -expiration and percentage collapse was calculated. RESULTS: There was diffuse narrowing of the entire intra-thoracic trachea and main bronchi and severe expiratory collapse of the trachea in all patients. At 1 cm above the aortic arch the median % collapse of the trachea was 68 (range 60 to 77%), at the level of the aortic arch 64 (range 21-93%), for the main bronchi this was 58 (range 26-66%) on the left and 44 (range 9-76%) on the right side. The pulmonary function tests showed that this airway collapse results in obstructive airway disease in all patients, which was severe (forced expiratory volume <50% of predicted) in four out of five patients. CONCLUSION: In adult MPS II patients, central airways diameters are strikingly reduced and upon expiration there is extensive collapse of the trachea and main bronchi. This central airways obstruction explains the severe respiratory symptoms in MPSII patients.

Bone, joint and tooth development in mucopolysaccharidoses: relevance to therapeutic options.

The mucopolysaccharidoses (MPS) are prominent among the lysosomal storage diseases. The intra-lysosomal accumulation of glycosaminoglycans (GAGs) in this group of diseases, which are caused by several different enzyme deficiencies, induces a cascade of responses that affect cellular functions and maintenance of the extra-cellular matrix. Against the background of normal tissue-specific processes, this review summarizes and discusses the histological and biochemical abnormalities reported in the bones, joints, teeth and extracellular matrix of MPS patients and animal models. With an eye to the possibilities and limitations of reversing the pathological changes in the various tissues, we address therapeutic challenges, and present a model in which the cascade of pathologic events is depicted in terms of primary and secondary events.

[Diagnostic image (395). A girl with failure to thrive and abdominal distension]. / Diagnose in beeld (395). Een meisje met groeivertraging en een bolle buik.

A 1.5-year-old girl presented with a failure to thrive caused by coeliac disease.

Genes differentially expressed in medulloblastoma and fetal brain.

Serial analysis of gene expression (SAGE) was used to identify genes that might be involved in the development or growth of medulloblastoma, a childhood brain tumor. Sequence tags from medulloblastoma (10229) and fetal brain (10692) were determined. The distributions of sequence tags in each population were compared, and for each sequence tag, pairwise chi2 test statistics were calculated. Northern blot was used to confirm some of the results obtained by SAGE. For 16 tags, the chi2 test statistic was associated with a P value < 10(-4). Among those transcripts with a higher expression in medulloblastoma were the genes for ZIC1 protein and the OTX2 gene, both of which are expressed in the cerebellar germinal layers. The high expression of these two genes strongly supports the hypothesis that medulloblastoma arises from the germinal layer of the cerebellum. This analysis shows that SAGE can be used as a rapid differential screening procedure.

Molecular cloning of human MUC3 cDNA reveals a novel 59 amino acid tandem repeat region.

The human MUC3 gene is highly expressed in small intestine and gallbladder. Thus far only 646 basepairs of its cDNA encoding 17 amino acid repeats have been cloned. In order to further clone the human MUC3 cDNA, a human small intestinal cDNA library was constructed and screened with a cDNA probe encompassing the 17 amino acid tandem repeat region of human MUC3. In two subsequent screenings of the library resulting positive clones were used as probes. In total, 27 partial MUC3 cDNA clones were isolated and sequenced that define a semi-unique region and a novel 177 nucleotide tandem repeat region, located upstream of the region encoding the 17 amino acid tandem repeats. The 177 nucleotide repeat region is at least 5 kb in length and encodes 59 amino acid repetitive peptides with a consensus sequence of VSTTPVASSEASTLSTTPVDTSTPVTTSTQASSSPTTAEGTSMPTSTPSEGSTPLTSMP, that is notably different from the 17 amino acid repeat of MUC3 or any other known mucin repeat.

The human intestinal cell lines Caco-2 and LS174T as models to study cell-type specific mucin expression.

Mucin expression was studied during proliferation and differentiation of the enterocyte-like Caco-2 and goblet cell-like LS174T cell lines. Caco-2 cells express mRNAs of MUC1, MUC3, MUC4 and MUC5A/C whereas MUC2 and MUC6 mRNAs are virtually absent. Furthermore, MUC3 mRNA is expressed in a differentiation dependent manner, as is the case for enterocytes. Concomitantly MUC3 protein precursor (approximately 550 kDa) was detected in Caco-2 cells. In LS174T cells mucin mRNAs of MUC1, MUC2 and MUC6 are constitutively expressed at high levels, whereas MUC3, MUC4 and MUC5A/C mRNAs are present at low levels. At the protein level LS174T cells express the goblet cell specific mucin protein precursors MUC2, MUC5A/C and MUC6 with apparent molecular masses of about 600 kDa, 470/500 kDa and 400 kDa respectively. MUC3 protein is not detectable. Furthermore, human gallbladder mucin protein (approximately 470 kDa precursor), of which the gene has not yet been identified, is expressed in LS174T cells. In addition, synthesis and secretion of the goblet cell specific mature MUC2, MUC5A/C and human gallbladder mucin was demonstrated in LS174T cells. It is concluded that Caco-2 and LS174T cell lines provide excellent in vitro models to elucidate the cell-type specific mechanisms responsible for mucin expression.