Solving a case of allelic dropout in the GNPTAB gene: implications in the molecular diagnosis of mucolipidosis type III alpha/beta
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Maria Francisca Coutinho
Abstract
While being well known that the diagnosis of many genetic disorders relies on a combination of clinical suspicion and confirmatory genetic testing, not rarely, however, genetic testing needs much perseverance and cunning strategies to identify the causative mutation(s). Here we present a case of a thorny molecular diagnosis of mucolipidosis type III alpha/beta, which is an autosomal recessive lysosomal storage disorder, caused by a defect in the GNPTAB gene that codes for the α/β-subunits of the GlcNAc-1-phosphotransferase. We used both cDNA and gDNA analyses to characterize a mucolipidosis type III alpha/beta patient whose clinical diagnosis was already confirmed biochemically. In a first stage only one causal mutation was identified in heterozygosity, the already described missense mutation c.1196C>T(p.S399F), both at cDNA and gDNA levels. Only after conducting inhibition of nonsense-mediated mRNA decay (NMD) assays and after the utilization of another pair of primers the second mutation, the c.3503_3504delTC deletion, was identified. Our findings illustrate that allelic dropout due to the presence of polymorphisms and/or of mutations that trigger the NMD pathway can cause difficulties in current molecular diagnosis tests.
Author contributions: All the authors have accepted responsibility for the entire content of this submitted manuscript and approved submission. MFC participated in the conception and design of the study, acquisition of data, analysis and interpretation of data; article writing and in the approval of the final version of the manuscript to be published. ME participated in the acquisition of data, revision of the article for important intellectual content and in the approval of the final version of the manuscript to be published. FL participated in the acquisition of data, revision of the article critically for important intellectual content and in the approval of the final version of the manuscript to be published. LL participated in the acquisition of data, revision of the article critically for important intellectual content and in the approval of the final version of the manuscript to be published. MJP participated in the conception and design of the study; revision of the article for important intellectual content and in the approval of the final version of the manuscript to be published. SA participated in the conception and design of the study, analysis and interpretation of data, article writing and in the approval of the final version of the manuscript to be published.
Research funding: M.F. Coutinho is grantee from the FCT (SFRH/BPD/101965/2014).
Employment or leadership: None declared.
Honorarium: None declared.
Competing interests: The funding organization(s) played no role in the study design; in the collection, analysis, and interpretation of data; in the writing of the report; or in the decision to submit the report for publication.
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©2016 Walter de Gruyter GmbH, Berlin/Boston
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Articles in the same Issue
- Frontmatter
- Review
- An update on thyroid-associated ophthalmopathy in children and adolescents
- Mini Review
- Systematic review and meta-analysis of the association between mumps during childhood and risk of type 1 diabetes mellitus
- Original Articles
- Glycemic variability predicts inflammation in adolescents with type 1 diabetes
- Prevalence and risk factors for diabetic retinopathy in a hospital-based population of Australian children and adolescents with type 1 diabetes
- One month of omega-3 fatty acid supplementation improves lipid profiles, glucose levels and blood pressure in overweight schoolchildren with metabolic syndrome
- The outcome of seven patients with hereditary tyrosinemia type 1
- Increased oxidative stress parameters in children with moderate iodine deficiency
- Relationship between 25(OH)D levels and circulating lipids in African American adolescents
- Endoglin and obestatin levels, cardiometabolic risk factors and subclinical atherosclerosis in children aged 10–18 years
- Lipoprotein-associated phospholipase A2 activity and low-density lipoprotein subfractions after a 2-year treatment with atorvastatin in adolescents with type 1 diabetes
- Genetic characteristics and long-term follow-up of 11 patients with congenital hyperinsulinism followed in a single center
- Pituitary volume in children with growth hormone deficiency, idiopathic short stature and controls
- Case Reports
- A novel insulin receptor mutation in an adolescent with acanthosis nigricans and hyperandrogenism
- Primary hyperparathyroidism may masquerade as rickets-osteomalacia in vitamin D replete children
- Co-existence of phenylketonuria either with maple syrup urine disease or Sandhoff disease in two patients from Iran: emphasizing the role of consanguinity
- Severe malnutrition causing superior mesenteric artery syndrome in an adolescent with Triple A syndrome
- Solving a case of allelic dropout in the GNPTAB gene: implications in the molecular diagnosis of mucolipidosis type III alpha/beta
