Rapid detection of SMARCB1 sequence variation using high resolution melting

Background : Rhabdoid tumors are rare cancers of early childhood arising in the kidney, central nervous system and other organs. The majority are caused by somatic inactivating mutations or deletions affecting the tumor suppressor locus SMARCB1 [OMIM 601607]. Germ-line SMARCB1 inactivation has been reported in association with rhabdoid tumor, epitheloid sarcoma and familial schwannomatosis, underscoring the importance of accurate mutation screening to ascertain recurrence and transmission risks. We describe a rapid and sensitive diagnostic screening method, using high resolution melting (HRM), for detecting sequence variations in SMARCB1. Methods : Amplicons, encompassing the nine coding exons of SMARCB1, flanking splice site sequences and the 5\u27 and 3\u27 UTR, were screened by both HRM and direct DNA sequencing to establish the reliability of HRM as a primary mutation screening tool. Reaction conditions were optimized with commercially available HRM mixes. Results : The false negative rate for detecting sequence variants by HRM in our sample series was zero. Nine amplicons out of a total of 140 (6.4%) showed variant melt profiles that were subsequently shown to be false positive. Overall nine distinct pathogenic SMARCB1 mutations were identified in a total of 19 possible rhabdoid tumors. Two tumors had two distinct mutations and two harbored SMARCB1 deletion. Other mutations were nonsense or frame-shifts. The detection sensitivity of the HRM screening method was influenced by both sequence context and specific nucleotide change and varied from 1: 4 to 1:1000 (variant to wild-type DNA). A novel method involving digital HRM, followed by re-sequencing, was used to confirm mutations in tumor specimens containing associated normal tissue. Conclusions : This is the first report describing SMARCB1 mutation screening using HRM. HRM is a rapid, sensitive and inexpensive screening technology that is likely to be widely adopted in diagnostic laboratories to facilitate whole gene mutation screening

Characterization of a t(8;13)(p11;q11-12) in an atypical myeloproliferative disorder

Fourteen cases of an atypical myeloproliferative disorder associated with consistent translocations involving 8p11-12 have previously been described. A t(8;13)(p11;q11-12) was the most common, but variant t(8;9)(p11- 12;q32-34) and t(6;8)(q27;p12) were also reported. Here we have used a series of yeast artificial chromosomes (YACs) derived from the 8p11 and 13q11-12 regions to analyse one of the t(8;13) cases by fluorescence in situ hybridization (FISH). YACs flanking the 13q11-12 breakpoint and spanning the 8p11 breakpoint have been isolated. These YACs will facilitate characterization of the genes involved in this rearrangement

Gastrointestinal polyps in McCune Albright syndrome

Background: McCune Albright syndrome (MAS), a disorder caused by somatic activating mutations in the GNAS gene, usually presents with cutaneous, skeletal, and endocrine manifestations. While focal lesions involving multiple tissues have been identified in MAS, almost nothing is known about gastrointestinal lesions in this disease. Methods: Two MAS patients with perioral freckling, resembling Peutz–Jeghers syndrome (PJS), and two MAS patients without similar pigmentation underwent gastrointestinal endoscopy to establish if they had coexisting hamartomatous polyposis. Three of 4 subjects had documented GNAS mutations in peripheral blood. Genetic testing for STK11 and PRKAR1A genes was performed to exclude presence of coexistent PJS and Carney complex. Genetic testing of biopsy material was also performed. Results: Hamartomatous gastrointestinal polyps with histological features similar to those in PJS were observed in all 4 subjects, only in the stomach and/or upper duodenum. Activating GNAS mutations were found in the polyps or adjacent mucosa in 3 of 4 subjects. One patient each had mutation only in the blood or tissue, while 2 patients had both. No subject harboured any detectable PRKARIA or STK11 mutation as determined by direct DNA sequencing and copy number variation analysis. Conclusions: These findings confirm that gastrointestinal polyps are a common manifestation of MAS, indicate an overlap between MAS and PJS, and point towards a putative interaction between the GNAS and STK11 genes in the pathogenesis of these two disorders. The findings suggest a need for routine gastrointestinal endoscopy in patients with MAS, to establish the true incidence of polyps in these patients

Severe Generalized Epidermolysis Bullosa Simplex in Two Hong Kong Children due to De Novo Variants in KRT14 and KRT5

We report two Hong Kong children with severe generalized epidermolysis bullosa simplex (EBS), the most severe form of EBS, without a family history of EBS. EBS is a rare genodermatosis usually inherited in an autosomal dominant fashion although rare autosomal recessive cases have been reported. Genetic studies in these patients showed that the first case was due to a novel de novo heterozygous variant, c.377T>G (NM_000526.5 (c.377T>G, p.Leu126Arg)) in the KRT14 gene and the second case was due to a rare de novo heterozygous variant c.527A>G (NM_000424.4, c.527A>G, p.Asn176Ser) in the KRT5 gene. To our knowledge, the c.377T>G variant in the KRT14 gene has not been previously reported, and the c.527A>G variant in the KRT5 gene is a rare cause of severe generalized EBS. In severe generalized EBS, infants exhibit severe symptoms at the onset; however, they tend to improve with time. A precise genetic diagnosis in these two cases aided in counseling the families concerning the prognosis in their affected children and the recurrence risk for future pregnancies

Pluronic L-81 ameliorates diabetic symptoms in db/db mice through transcriptional regulation of microsomal triglyceride transfer protein

AIM: To test whether oral L-81 treatment could improve the condition of mice with diabetes and to investigate how L-81 regulates microsomal triglyceride transfer protein (MTP) activity in the liver

Heterozygous tx mice have an increased sensitivity to copper loading: implications for Wilson\u27s Disease carriers

Wilson\u27s disease carriers constitute 1% of the human population. It is unknown whether Wilsons disease carriers are at increased susceptibility to copper overload when exposed to chronically high levels of ingested copper. This study investigated the effect of chronic excess copper in drinking water on the heterozygous form of the Wilson&rsquo;s disease mouse model &ndash; the toxic milk (tx) mouse. Mice were provided with drinking water containing 300 mg/l copper for 4&ndash;7, 8&ndash;11, 12&ndash;15 or 16&ndash;20 months. At the completion of the study liver, spleen, kidney and brain tissue were analyzed by atomic absorption spectroscopy to determine copper concentration. Plasma ceruloplasmin oxidase activity and liver histology were also assessed. Chronic copper loading resulted in significantly increased liver copper in both tx heterozygous and tx homozygous mice, while wild type mice were resistant to the effects of copper loading. Copper loading effects were greatest in tx homozygous mice, with increased extrahepatic copper deposition in spleen and kidney &ndash; an effect absent in heterozygote and wild type mice. Although liver histology in homozygous mice was markedly abnormal, no histological differences were noted between heterozygous and wild type mice with copper loading. Tx heterozygous mice have a reduced ability to excrete excess copper, indicating that half of the normal liver Atp7b copper transporter activity is insufficient to deal with large copper intakes. Our results suggest that Wilsons disease carriers in the human population may be at increased risk of copper loading if chronically exposed to elevated copper in food or drinking water.<br /