Otological problems in ichthyosis: A literature review.

BACKGROUND: Ichthyoses are a rare group of keratinization disorders characterized by scaling of the skin due to an impaired barrier function. Few studies have addressed ear involvement in patients with ichthyosis, although it is a probably underestimated aspect of the disease. OBJECTIVE: This study aims to provide an overview of the otological manifestations in ichthyosis and propose specific treatment options. METHODS: Articles were collected using PubMed, EMBASE, and Web of Science. A total of 53 articles were included in this literature review. RESULTS: The most common ear problem in patients with ichthyosis is scale accumulation in the ear canals, which can lead to conductive hearing loss and increases the risk of ear infections. Furthermore, some types of ichthyosis are associated with outer ear malformations. Lastly, sensorineural hearing loss is common in syndromic forms of ichthyosis. CONCLUSIONS: Otological problems are present in all types of ichthyoses and their treatment is challenging. The involvement of ear, nose, and throat specialists in the routine care of ichthyosis patients is essential for early identification and treatment of these manifestations. More research is needed to provide more insight into the otological problems in ichthyosis and to ameliorate treatment options.

The Abcc6a Knockout Zebrafish Model as a Novel Tool for Drug Screening for Pseudoxanthoma Elasticum.

Pseudoxanthoma elasticum (PXE) is a multisystem ectopic mineralization disorder caused by pathogenic variants in the ABCC6 gene. Though complications of the disease can be treated, PXE itself remains currently intractable. A strategy for rapid and cost-effective discovery of therapeutic drugs would be to perform chemical compound screening using zebrafish, but this approach remains to be validated for PXE. In this paper, we validate a stable CRISPR/Cas9 abcc6a knockout zebrafish model-which has spinal column hypermineralization as its primary phenotypic feature-as a model system for compound screening in ectopic mineralization. We evaluated the anti-mineralization potential of five compounds, which had (anecdotal) positive effects reported in Abcc6 knockout mice and/or PXE patients. Abcc6a knockout zebrafish larvae were treated from 3 to 10 days post-fertilization with vitamin K1, sodium thiosulfate, etidronate, alendronate or magnesium citrate and compared to matching controls. Following alizarin red S staining, alterations in notochord sheath mineralization were semiquantified and found to largely congrue with the originally reported outcomes. Our results demonstrate that the use of this abcc6a knockout zebrafish model is a validated and promising strategy for drug discovery against ectopic mineralization.

Generation and Validation of a Complete Knockout Model of abcc6a in Zebrafish.

Pseudoxanthoma elasticum is an ectopic mineralization disease due to biallelic ABCC6 mutations. As no treatment options are currently available, a reliable zebrafish model is invaluable for high throughput compound screening. However, data from previously reported knockdown and mutant zebrafish models for abcc6a, the functional orthologue of ABCC6, showed phenotypic discrepancies. To address this, we developed a complete abcc6a knockout model using Clustered Regularly Interspaced Short Palindromic Repeats/Cas9 and compared its phenotype to that of a mutant model (Sa963) and a splice junction morpholino model. Our data showed that abcc6a is not required for embryonic survival, but rather that it has an essential role in controlling mineralization. The three models developed very similar hypermineralization of spine and ribs starting embryonically and progressing in adulthood with development of scoliosis. Our results indicate a direct relation between loss of abcc6a expression and dysregulated osteogenesis. As such, our models recapitulate part of the human phenotype in which ectopic mineralization and pro-osteogenic signaling have been reported. Because of its reproducibility in three models and its ease of quantification, we consider this phenotype to be unequivocally the result of abcc6 deficiency and, as such, an excellent readout for drug screening purposes and multiplex mutagene analysis.

RT-qPCR gene expression analysis in zebrafish: Preanalytical precautions and use of expressed repetitive elements for normalization.

Gene expression analysis is increasingly important in many fields of biological research. Understanding patterns of expressed genes is assumed to provide insight into complex regulatory networks and can lead to the identification of genes relevant to specific biological processes, including disease. Among different techniques, reverse transcription quantitative polymerase chain reaction (RT-qPCR) is currently regarded as the gold standard for targeted quantification of RNA gene expression, especially because of its high sensitivity, specificity, accuracy, and precision, and also because of its practical simplicity and processing speed. However, different critical factors can influence the outcome of RT-qPCR studies, including isolation of RNA, reverse transcription to cDNA, and data analysis. These factors need to be addressed in order to obtain biologically meaningful results. In this chapter, we describe how RT-qPCR can be used in a reliable way to successfully study differential gene expression in zebrafish. Hereby, we especially focus on how expressed repetitive elements can be employed as reference targets in zebrafish RT-qPCR studies and how they can further improve the quality of the data.

Zebrafish Collagen Type I: Molecular and Biochemical Characterization of the Major Structural Protein in Bone and Skin.

Over the last years the zebrafish imposed itself as a powerful model to study skeletal diseases, but a limit to its use is the poor characterization of collagen type I, the most abundant protein in bone and skin. In tetrapods collagen type I is a trimer mainly composed of two α1 chains and one α2 chain, encoded by COL1A1 and COL1A2 genes, respectively. In contrast, in zebrafish three type I collagen genes exist, col1a1a, col1a1b and col1a2 coding for α1(I), α3(I) and α2(I) chains. During embryonic and larval development the three collagen type I genes showed a similar spatio-temporal expression pattern, indicating their co-regulation and interdependence at these stages. In both embryonic and adult tissues, the presence of the three α(I) chains was demonstrated, although in embryos α1(I) was present in two distinct glycosylated states, suggesting a developmental-specific collagen composition. Even though in adult bone, skin and scales equal amounts of α1(I), α3(I) and α2(I) chains are present, the presented data suggest a tissue-specific stoichiometry and/or post-translational modification status for collagen type I. In conclusion, this data will be useful to properly interpret results and insights gained from zebrafish models of skeletal diseases.

Swallowing dysfunction in myotonic dystrophy: a retrospective study of symptomatology and radiographic findings.

BACKGROUND: Swallowing dysfunction is a common symptom of myotonic dystrophy, but it is poorly documented in large patient series. This retrospective study was designed to investigate the presence of swallowing symptoms in a large study population and to describe a specific pattern of clinical and radiographic abnormalities. METHODS: A retrospective analysis was made of 169 files of patients with confirmed MD. Neuromuscular assessment was made by means of a standardised neurological examination; clinical swallowing symptoms were listed, and video-fluoroscopic images were analysed. RESULTS: More than half the patients reported swallowing complaints. The major symptoms were frequent choking, difficult pharyngeal transport and piecemeal deglutition. The pharyngeal phase of swallowing was most frequently compromised. This was shown radiographicaly in reduced pharyngeal peristalsis, hypopharyngeal stasis and fragmented swallowing. Aspiration was seen in half of the patients, mostly during swallowing. A typical 'hung position' of the hyoid was also seen. Different onset types of MD seem to be accompanied by comparable subjective complaints and radiographic symptoms. CONCLUSIONS: Pharyngeal transport was most affected in this patient population. Muscular weakness seems to be the major contributor to swallowing impairment in MD. Swallowing abnormalities may be present even if patients report only a few symptoms and even if the severity of the disease is not pronounced.

[Rating scales for assessing catatonia; which ones are the best?]. / Katatonie meten: welke schaal te kiezen?

BACKGROUND: Despite increasing scientific and clinical interest in catatonia, there is still no precise definition of this psychiatric disorder. AIM: To study the relevant literature and review systematically the various rating scales that have been developed for assessing catatonia in clinical practice. METHOD: Several searches were performed using Medline, the latest one in August 2010. RESULTS Seven catatonia rating scales were retrieved and studied: the Modified Rogers Scale, the Rogers Catatonia Scale, the Bush-Francis Catatonia Rating Scale (BFCRS), the Northoff Catatonia Rating Scale (NCRS), the Braunig Catatonia Scale (BCRS), the Bush-Francis Catatonia Scale- Revised version and the Kanner Scale. CONCLUSION: Several scales are suitable for assessing catatonia in clinical practice. The BFCRS, the NCRS and the BCRS are reliable scales for use in various clinical populations in which catatonia is prevalent. For routine use in clinical practice, the scale of choice is the BFCRS because it is well-founded, reliable and easy to administer.

Recessive osteogenesis imperfecta caused by LEPRE1 mutations: clinical documentation and identification of the splice form responsible for prolyl 3-hydroxylation.

BACKGROUND: Recessive forms of osteogenesis imperfecta (OI) may be caused by mutations in LEPRE1, encoding prolyl 3-hydroxylase-1 (P3H1) or in CRTAP, encoding cartilage associated protein. These proteins constitute together with cyclophilin B (CyPB) the prolyl 3-hydroxylation complex that hydroxylates the Pro986 residue in both the type I and type II collagen alpha1-chains. METHODS: We screened LEPRE1, CRTAP and PPIB (encoding CyPB) in a European/Middle Eastern cohort of 20 lethal/severe OI patients without a type I collagen mutation. RESULTS: Four novel homozygous and compound heterozygous mutations were identified in LEPRE1 in four probands. Two probands survived the neonatal period, including one patient who is the eldest reported patient (17 7/12 years) so far with P3H1 deficiency. At birth, clinical and radiologic features were hardly distinguishable from those in patients with autosomal dominant (AD) severe/lethal OI. Follow-up data reveal that the longer lived patients develop a severe osteochondrodysplasia that overlaps with, but has some distinctive features from, AD OI. A new splice site mutation was identified in two of the four probands, affecting only one of three LEPRE1 mRNA splice forms, detected in this study. The affected splice form encodes a 736 amino acid (AA) protein with a "KDEL" endoplasmic reticulum retention signal. While western blotting and immunocytochemical analysis of fibroblast cultures revealed absence of this P3H1 protein, mass spectrometry and SDS-urea-PAGE data showed severe reduction of alpha1(I)Pro986 3-hydroxylation and overmodification of type I (pro)collagen chains in skin fibroblasts of the patients. CONCLUSION: These findings suggest that the 3-hydroxylation function of P3H1 is restricted to the 736AA splice form.

Absence of arterial phenotype in mice with homozygous slc2A10 missense substitutions.

Arterial tortuosity syndrome (ATS, MIM# 208050) is a rare autosomal recessive connective tissue disease, mainly characterized by widespread arterial involvement with elongation, tortuosity, and aneurysms of the large and middle-sized arteries (Callewaert et al., 2008, Hum Mutat 29:150-158). Recently, mutations were identified in the SLC2A10 gene encoding the facilitative glucose transporter GLUT10 (Coucke et al., 2006, Nat Genet 38:452-457). It was hypothesized that loss-of-function of the transporter results in upregulation of the transforming growth factor beta (TGFbeta) signaling pathway (Coucke et al., 2006, Nat Genet 38:452-457). We anticipated that a mouse model would help to gain more insight in the complex pathophysiological mechanism of human ATS. Here, we report that two mouse models, homozygous respectively for G128E and S150F missense substitutions in glut10 do not present any of the vascular, anatomical, or immunohistological abnormalities as encountered in human ATS patients. We conclude that these mouse strains do not phenocopy human ATS and cannot help the further elucidation of pathogenetic mechanisms underlying this disease.

Arterial tortuosity syndrome: clinical and molecular findings in 12 newly identified families.

Arterial tortuosity syndrome (ATS) is a rare autosomal recessive connective tissue disease, characterized by widespread arterial involvement with elongation, tortuosity, and aneurysms of the large and middle-sized arteries. Recently, SLC2A10 mutations were identified in this condition. This gene encodes the glucose transporter GLUT10 and was previously suggested as a candidate gene for diabetes mellitus type 2. A total of 12 newly identified ATS families with 16 affected individuals were clinically and molecularly characterized. In addition, extensive cardiovascular imaging and glucose tolerance tests were performed in both patients and heterozygous carriers. All 16 patients harbor biallelic SLC2A10 mutations of which nine are novel (six missense, three truncating mutations, including a large deletion). Haplotype analysis suggests founder effects for all five recurrent mutations. Remarkably, patients were significantly older than those previously reported in the literature (P=0.04). Only one affected relative died, most likely of an unrelated cause. Although the natural history of ATS in this series was less severe than previously reported, it does indicate a risk for ischemic events. Two patients initially presented with stroke, respectively at age 8 months and 23 years. Tortuosity of the aorta or large arteries was invariably present. Two adult probands (aged 23 and 35 years) had aortic root dilation, seven patients had localized arterial stenoses, and five had long stenotic stretches of the aorta. Heterozygous carriers did not show any vascular anomalies. Glucose metabolism was normal in six patients and eight heterozygous individuals of five families. As such, overt diabetes is not related to SLC2A10 mutations associated with ATS.