Browsing by Author "Bergmann, C."

Branchio-oto-renal (BOR) syndrome is an autosomal dominantly inherited developmental disorder, which is characterized by anomalies of the ears, the branchial arches and the kidneys. It is caused by mutations in the genes EYA1, SIX1 and SIX5. Genomic rearrangements of chromosome 8 affecting the EYA1 gene have also been described. Owing to this fact, methods for the identification of abnormal copy numbers such as multiplex ligation-dependent probe amplification (MLPA) have been introduced as routine laboratory techniques for molecular diagnostics of BOR syndrome. The advantages of these techniques are clear compared to standard cytogenetic and array approaches as well as Southern blot. MLPA detects deletions or duplications of a part or the entire gene of interest, but not balanced structural aberrations such as inversions and translocations. Consequently, disruption of a gene by a genomic rearrangement may escape detection by a molecular genetic analysis, although this gene interruption results in haploinsufficiency and, therefore, causes the disease. In a patient with clinical features of BOR syndrome, such as hearing loss, preauricular fistulas and facial dysmorphisms, but no renal anomalies, neither sequencing of the 3 genes linked to BOR syndrome nor array comparative genomic hybridization and MLPA were able to uncover a causative mutation. By routine cytogenetic analysis, we finally identified a pericentric inversion of chromosome 8 in the affected female. High-resolution multicolor banding confirmed the chromosome 8 inversion and narrowed down the karyotype to 46,XX,inv(8)(p22q13). By applying fluorescence in situ hybridization, we narrowed down both breakpoints on chromosome 8 and found the EYA1 gene in q13.3 to be directly disrupted. We conclude that standard karyotyping should not be neglected in the genetic diagnostics of BOR syndrome or other Mendelian disorders, particularly when molecular testing failed to detect any causative alteration in patients with a convincing phenotype. (C) 2013 S. Karger AG, Basel

In order to investigate the low-temperature electronic properties of the heavy-fermion metal CeNi2Ge2, single crystals were grown using the floating zone technique. Previous investigations on polycrystals of CeNi7Ge2 have revealed that the low-temperature properties, i.e., non-Fermi liquid (NFL) behavior and incipient superconductivity, are strongly sample dependent, possibly due to a slight variation of the Ni and Ge content. We prepared polycrystalline feed rods of slightly off-stoichiometric composition by induction or arc-melting methods and grew single crystals using a four-mirror optical furnace under high-purity argon atmosphere. As a result, large single crystals of few centimeter size have been obtained. Annealed pieces were investigated by measurements of the temperature dependence of the electrical resistivity rho(T). A clear correlation between the starting composition and the obtained resistivity ratio (RR2K) was found with the highest ratio for a nominal starting composition of Ce0.98Ni2.025Ge1.975 (RR2K = 29). The temperature dependence of the electrical resistivity is similar as reported previously and displays NFL behavior below 1 K. (C) 2010 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim