Keratosis Follicularis Spinulosa Decalvans (KFSD) is a rare genetic disorder characterized by development of hyperkeratotic follicular papules on the scalp followed by progressive alopecia of the... Show moreKeratosis Follicularis Spinulosa Decalvans (KFSD) is a rare genetic disorder characterized by development of hyperkeratotic follicular papules on the scalp followed by progressive alopecia of the scalp, eyelashes, and eyebrows. Associated eye findings include photophobia in childhood and corneal dystrophy. Due to the genetic and clinical heterogeneity of similar disorders, a definitive diagnosis of KFSD is often challenging. Toward identification of the causative gene we reanalyzed a large Dutch KFSD family. SNP arrays (1 M) redefined the locus to a 2.9-Mb region at Xp22.12-Xp22.11. Screening of all 14 genes in the candidate region identified MBTPS2 as the candidate gene carrying a c.1523A>G (p.Asn508Ser) missense mutation. The variant was also identified in two unrelated X-linked KFSD families and cosegregated with KFSD in all families. In symptomatic female carriers, skewed X-inactivation of the normal allele matched with increased severity of symptoms. MBTPS2 is required for cleavage of sterol regulatory element-binding proteins (SREBPs). In vitro functional expression studies of the c. 1523A>G mutation showed that sterol responsiveness was reduced by half. Other missense mutations in MBTPS2 have recently been identified in patients with IFAP syndrome. We postulate that both phenotypes are in the spectrum of one genetic disorder with a partially overlapping phenotype. Hum Mutat 31:1125-1133, 2010. (C) 2010 Wiley-Liss, Inc. Show less
Antisense oligonucleotide (AON)-mediated exon skipping aimed at restoring the reading frame is a promising therapeutic approach for Duchenne muscular dystrophy that is currently tested in clinical... Show moreAntisense oligonucleotide (AON)-mediated exon skipping aimed at restoring the reading frame is a promising therapeutic approach for Duchenne muscular dystrophy that is currently tested in clinical trials. Numerous AONs have been tested in (patient-derived) cultured muscle cells and the mdx mouse model. The main outcome to measure AON efficiency is usually the exon-skipping percentage, though different groups use different methods to assess these percentages. Here, we compare a series of techniques to quantify exon skipping levels in AON-treated mdx mouse muscle. We compared densitometry of RT-PCR products on ethidium bromide-stained agarose gels, primary and nested RT-PCR followed by bioanalyzer analysis and melting curve analysis. The digital array system (Fluidigm) allows absolute quantification of skipped vs non-skipped transcripts and was used as a reference. Digital array results show that 1 ng of mdx gastrocnemius muscle-derived mRNA contains B1100 dystrophin transcripts and that 665 transcripts are sufficient to determine exon-skipping levels. Quantification using bioanalyzer or densitometric analysis of primary PCR products resulted in values close to those obtained with digital array. The use of the same technique allows comparison between different groups working on exon skipping in the mdx mouse model. Laboratory Investigation (2010) 90, 1396-1402; doi:10.1038/labinvest.2010.98; published online 10 May 2010 Show less
Vossen, R.H.A.M.; Duijn, M. van; Daha, M.R.; Dunnen, J.T. den; Roos, A. 2010
High Resolution Melting Analysis (HRMA) is a rapid and sensitive method for single nucleotide polymorphism (SNP) analysis. In the present study we present a novel HRMA assay to detect three SNPs in... Show moreHigh Resolution Melting Analysis (HRMA) is a rapid and sensitive method for single nucleotide polymorphism (SNP) analysis. In the present study we present a novel HRMA assay to detect three SNPs in close proximity of each other in the first exon of the gene encoding mannosebinding lectin (MBL), a key molecule of innate immunity. These SNPs have been selected for their known biological and clinical relevance. The three SNPs in MBL2 were simultaneously determined in sixty- nine human DNA samples using HRMA and a single non- fluorescent melting probe, without any post- PCR processing of samples. Combining analyses from amplicon melting and probe melting, we have been able to discriminate ten exon 1 MBL2 genotypes with HRMA, making it a suitable tool for MBL genotyping. A second HRMA assay is presented to detect a relevant polymorphism (Y/X SNP) in the MBL2 promoter region. In conclusion, HRMA is a closed tube assay that is easy to setup and lends itself perfectly for high throughput genotyping of MBL2 variants. The present study thereby facilitates further clinical studies into the role of MBL in inflammatory and infectious disease. (C) 2010 Wiley-Liss, Inc. Show less
Eijk, R. van; Puijenbroek, M. van; Chhatta, A.R.; Gupta, N.; Vossen, R.H.A.M.; Lips, E.H.; ... ; Wezel, T. van 2010
Kirsten RAS (KRAS) is a small GTPase that plays a key role in Ras/mitogen-activated protein kinase signaling; somatic mutations in KRAS are frequently found in many cancers. The most common KRAS... Show moreKirsten RAS (KRAS) is a small GTPase that plays a key role in Ras/mitogen-activated protein kinase signaling; somatic mutations in KRAS are frequently found in many cancers. The most common KRAS mutations result in a constitutively active protein. Accurate detection of KRAS mutations is pivotal to the molecular diagnosis of cancer and may guide proper treatment selection. Here, we describe a two-step KRAS mutation screening protocol that combines whole-genome amplification (WGA), high-resolution melting analysis (HRM) as a prescreen method for mutation carrying samples, and direct Sanger sequencing of DNA from formalin-fixed, paraffin-embedded (FFPE) tissue, from which limited amounts of DNA are available. We developed target-specific primers, thereby avoiding amplification of homologous KRAS sequences. The addition of herring sperm DNA facilitated WGA in DNA samples isolated from as few ass 100 cells. KRAS mutation screening using high-resolution melting analysis on wgaDNA from formalin-fixed, paraffin-embedded tissue is highly sensitive and specific; additionally, this method is feasible for screening of clinical specimens, as illustrated by our analysis of pancreatic cancers. Furthermore, PCR on wgaDNA does not introduce genotypic changes, as opposed to unamplified genomic DNA. This method can, after validation, be applied to virtually any potentially mutated region in the genome. (J Mol Diagn 2010, 12:27-34; DOI: 10.2353/jmoldx.2010.090028) Show less
