Cancer incidence and spectrum among children with genetically confirmed Beckwith-Wiedemann spectrum in Germany: a retrospective cohort study.

BACKGROUND: Beckwith-Wiedemann syndrome (BWS) is a cancer predisposition syndrome caused by defects on chromosome 11p15.5. The quantitative cancer risks in BWS patients depend on the underlying (epi)genotype but have not yet been assessed in a population-based manner. METHODS: We identified a group of 321 individuals with a molecularly confirmed diagnosis of BWS and analysed the cancer incidence up to age 15 years and cancer spectrum by matching their data with the German Childhood Cancer Registry. RESULTS: We observed 13 cases of cancer in the entire BWS cohort vs 0.4 expected. This corresponds to a 33-fold increased risk (standardised incidence ratio (SIR) = 32.6; 95% confidence interval = 17.3-55.7). The specific cancers included hepatoblastoma (n = 6); nephroblastoma (n = 4); astrocytoma (n = 1); neuroblastoma (n = 1) and adrenocortical carcinoma (n = 1). The cancer SIR was highest in patients with a paternal uniparental disomy of 11p15.5 (UPDpat). A high cancer risk remained when cases of cancer diagnosed prior to the BWS diagnosis were excluded. CONCLUSIONS: This study confirms an increased cancer risk in children with BWS. Our findings suggest that the highest cancer risk is associated with UPDpat. We were unable to confirm an excessive cancer risk in patients with IC1 gain of methylation (IC1-GOM) and this finding requires further investigation.

The Caveolin-3 G56S sequence variant of unknown significance: Muscle biopsy findings and functional cell biological analysis.

PURPOSE: In the era of next-generation sequencing, we are increasingly confronted with sequence variants of unknown significance. This phenomenon is also known for variations in Caveolin-3 and can complicate the molecular diagnosis of the disease. Here, we aimed to study the ambiguous character of the G56S Caveolin-3 variant. EXPERIMENTAL DESIGN: A comprehensive approach combining genetic and morphological studies of muscle derived from carriers of the G56S Caveolin-3 variant were carried out and linked to biochemical assays (including phosphoblot studies and proteome profiling) and morphological investigations of cultured myoblasts. RESULTS: Muscles showed moderate chronic myopathic changes in all carriers of the variant. Myogenic RCMH cells expressing the G56S Caveolin-3 protein presented irregular Caveolin-3 deposits within the Golgi in addition to a regular localization of the protein to the plasma membrane. This result was associated with abnormal findings on the ultra-structural level. Phosphoblot studies revealed that G56S affects EGFR-signaling. Proteomic profiling demonstrated alterations in levels of physiologically relevant proteins which are indicative for antagonization of G56S Caveolin-3 expression. Remarkably, some proteomic alterations were enhanced by osmotic/mechanical stress. CONCLUSIONS AND CLINICAL RELEVANCE: Our studies suggest that G56S might influence the manifestation of myopathic changes upon the presence of additional cellular stress burden. Results of our studies moreover improve the current understanding of (genetic) causes of myopathic disorders classified as caveolinopathies.

Complementation of non-tumorigenicity of HPV18-positive cervical carcinoma cells involves differential mRNA expression of cellular genes including potential tumor suppressor genes on chromosome 11q13.

The fusion between human tumorigenic cells and normal human diploid fibroblasts results in non-tumorigenic hybrid cells, suggesting a dominant role for tumor suppressor genes in the generated hybrid cells. After long-term cultivation in vitro, tumorigenic segregants may arise. The loss of tumor suppressor genes on chromosome 11q13 has been postulated to be involved in the induction of the tumorigenic phenotype of human papillomavirus (HPV)18-positive cervical carcinoma cells and their derived tumorigenic hybrid cells after subcutaneous injection in immunocompromised mice. The aim of this study was the identification of novel cellular genes that may contribute to the suppression of the tumorigenic phenotype of non-tumorigenic hybrid cells in vivo. We used cDNA microarray technology to identify differentially expressed cellular genes in tumorigenic HPV18-positive hybrid and parental HeLa cells compared to non-tumorigenic HPV18-positive hybrid cells. We detected several as yet unknown cellular genes that play a role in cell differentiation, cell cycle progression, cell-cell communication, metastasis formation, angiogenesis, antigen presentation, and immune response. Apart from the known differentially expressed genes on 11q13 (e.g., phosphofurin acidic cluster sorting protein 1 (PACS1) and FOS ligand 1 (FOSL1 or Fra-1)), we detected novel differentially expressed cellular genes located within the tumor suppressor gene region (e.g., EGF-containing fibulin-like extracellular matrix protein 2 (EFEMP2) and leucine rich repeat containing 32 (LRRC32) (also known as glycoprotein-A repetitions predominant (GARP)) that may have potential tumor suppressor functions in this model system of non-tumorigenic and tumorigenic HeLa x fibroblast hybrid cells.

Gain-of-function mutations in TRPM4 cause autosomal dominant isolated cardiac conduction disease.

BACKGROUND: Isolated cardiac conduction block is a relatively common condition in young and elderly populations. Genetic predisposing factors have long been suspected because of numerous familial case reports. Deciphering genetic predisposing factors of conduction blocks may give a hint at stratifying conduction block carriers in a more efficient way. METHODS AND RESULTS: One Lebanese family and 2 French families with autosomal dominant isolated cardiac conduction blocks were used for linkage analysis. A maximum combined multipoint lod score of 10.5 was obtained on a genomic interval including more than 300 genes. After screening 12 genes of this interval for mutation, we found a heterozygous missense mutation of the TRPM4 gene in each family (p.Arg164Trp, p.Ala432Thr, and p.Gly844Asp). This gene encodes the TRPM4 channel, a calcium-activated nonselective cation channel of the transient receptor potential melastatin (TRPM) ion channel family. All 3 mutations result in an increased current density. This gain of function is due to an elevated TRPM4 channel density at the cell surface secondary to impaired endocytosis and deregulation of Small Ubiquitin MOdifier conjugation (SUMOylation). Furthermore, we showed by immunohistochemistry that TRPM4 channel signal level is higher in atrial cardiomyocytes than in common ventricular cells, but is highest in Purkinje fibers. Small bundles of highly TRPM4-positive cells were found in the subendocardium and in rare intramural bundles. CONCLUSIONS: the TRPM4 gene is a causative gene in isolated cardiac conduction disease with mutations resulting in a gain of function and TRPM4 channel being highly expressed in cardiac Purkinje fibers.

Impaired endocytosis of the ion channel TRPM4 is associated with human progressive familial heart block type I.

Progressive familial heart block type I (PFHBI) is a progressive cardiac bundle branch disease in the His-Purkinje system that exhibits autosomal-dominant inheritance. In 3 branches of a large South African Afrikaner pedigree with an autosomal-dominant form of PFHBI, we identified the mutation c.19G-->A in the transient receptor potential cation channel, subfamily M, member 4 gene (TRPM4) at chromosomal locus 19q13.3. This mutation predicted the amino acid substitution p.E7K in the TRPM4 amino terminus. TRPM4 encodes a Ca2+-activated nonselective cation (CAN) channel that belongs to the transient receptor potential melastatin ion channel family. Quantitative analysis of TRPM4 mRNA content in human cardiac tissue showed the highest expression level in Purkinje fibers. Cellular expression studies showed that the c.19G-->A missense mutation attenuated deSUMOylation of the TRPM4 channel. The resulting constitutive SUMOylation of the mutant TRPM4 channel impaired endocytosis and led to elevated TRPM4 channel density at the cell surface. Our data therefore revealed a gain-of-function mechanism underlying this type of familial heart block.