Sequencing of neuroblastoma identifies chromothripsis and defects in neuritogenesis genes

Neuroblastoma is a childhood tumour of the peripheral sympathetic nervous system. The pathogenesis has for a long time been quite enigmatic, as only very few gene defects were identified in this often lethal tumour. Frequently detected gene alterations are limited to MYCN amplification (20%) and ALK activations (7%). Here we present a whole-genome sequence analysis of 87 neuroblastoma of all stages. Few recurrent amino-acid-changing mutations were found. In contrast, analysis of structural defects identified a local shredding of chromosomes, known as chromothripsis, in 18% of high-stage neuroblastoma. These tumours are associated with a poor outcome. Structural alterations recurrently affected ODZ3, PTPRD and CSMD1, which are involved in neuronal growth cone stabilization. In addition, ATRX, TIAM1 and a series of regulators of the Rac/Rho pathway were mutated, further implicating defects in neuritogenesis in neuroblastoma. Most tumours with defects in these genes were aggressive high-stage neuroblastomas, but did not carry MYCN amplifications. The genomic landscape of neuroblastoma therefore reveals two novel molecular defects, chromothripsis and neuritogenesis gene alterations, which frequently occur in high-risk tumours.     

Infantile-onset symptomatic epilepsy syndrome caused by a homozygous loss-of-function mutation of GM3 synthase

We identified an autosomal recessive infantile-onset symptomatic epilepsy syndrome associated with developmental stagnation and blindness. Assuming a founder effect in a large Old Order Amish pedigree, we carried out a genome-wide screen for linkage and identified a single region of homozygosity on chromosome 2p12-p11.2 spanning 5.1 cM (maximum lod score of 6.84). We sequenced genes in the region and identified a nonsense mutation in SIAT9, which is predicted to result in the premature termination of the GM3 synthase enzyme (also called lactosylceramide alpha-2,3 sialyltransferase). GM3 synthase is a member of the sialyltransferase family and catalyzes the initial step in the biosynthesis of most complex gangliosides from lactosylceramide. Biochemical analysis of plasma glycosphingolipids confirmed that affected individuals lack GM3 synthase activity, as marked by a complete lack of GM3 ganglioside and its biosynthetic derivatives and an increase in lactosylceramide and its alternative derivatives. Although the relationship between defects in ganglioside catabolism and a range of lysosomal storage diseases is well documented, this is the first report, to our knowledge, of a disruption of ganglioside biosynthesis associated with human disease.     

The taxonomic identity of Anthidium fasciatellum Friese, 1917 (Hymenoptera: Apoidea: Anthidiini)

Anthidium fasciatellum, described in 1917 by Heinrich Friese on the basis of a single female, has long been regarded as a synonym of Trachusa laticeps (Morawitz, 1873). Examination of a new series of specimens from Turkey shows that the two taxa overlap in many characters, but both males and females are clearly distinct in some features of the colour pattern and in the fine structure of the mandibles. None of nine morphometric characters of the head examined alone allowed the two species to be distinguished, but in a multivariate discriminant analysis the combination of these parameters revealed conspicuous differences, especially in the shape of the head; 96.2% of all specimens could be classified correctly with the help of these metric parameters. Anthidium fasciatellum Friese, 1917 should be regarded as a valid species: Trachusa fasciatellum (Friese, 1917), comb. nov. While T. laticeps has an almost circum-Mediterranean distribution, it is replaced in the eastern Mediterranean by T. fasciatellum, which is endemic to Turkey and probably to some eastern Aegean islands of Greece. Archianthidium laticeps ssp. anatolicum Mavromoustakis, 1939, is placed as a synonym of Trachusa fasciatellum (syn. nov.).

www.zoobank.org/urn:lsid:zoobank.org:pub:755E60D9-E2D6-4956-B4D1-619DAA73EBD9     

Evidence for essential catalytic determinants for human erythrocyte pyrimidine 5′-nucleotidase

Human erythrocyte pyrimidine 5′-nucleotidase, PN-I, catalyzes the dephosphorylation of pyrimidine nucleoside monophosphates. The enzyme also possesses phosphotransferase activity, transferring phosphate groups between pyrimidine nucleoside monophosphates and various pyrimidine nucleosides. Deficiency of the enzyme activity is associated with a hemolytic anemia. PN-I cDNA has been expressed in Escherichia coli, yielding a fully active recombinant enzyme, which was purified to homogeneity and extensively characterized. Multiple sequence alignment of PN-I and homologues proteins revealed the existence of conserved regions, whose importance in catalysis was examined by performing experiments designed to intercept covalent intermediates as strongly suggested by our previous kinetic studies. Furthermore, a functional analysis of the enzyme was carried out through site-directed mutagenesis designed on the basis of the sequence of the identified conserved regions as well as mutations observed in PN-I-deficient patients.Received 25 March 2005; received after revision 3 May 2005; accepted 13 May 2005     

Baker's yeast cytidine deaminase: Substrate and inhibitor specificity,and a hypothesis on metabolic and regulatory significance

Riassunio La citidina deaminasi, parzialmente purificata da lievito di pane, è capace di deaminare sia la citidina che la deossicitidina. I valori delleK _m per ambedue i 2 substrati sono 25×10^–5 M e 9.1×10^–5 M rispettivamente. Inoltre l'enzima è inibito da numerosi nucleosidi monofosfati, difosfati e trifosfati. È molto significativa il tipo di inibizione allosterica esercitata dal dTTP. Si riporta una ipotesi sul ruolo metabolico della citidina deaminasi.     

Presence of a specific uridine 5'-monophosphate pyrophosphorylase in baker's yeast.

Uridine 5'-monophosphate pyrophosphorylase was found to be present in baker's yeast. The enzyme preparation, purified about 30-fold, shows a strict specificity toward uracil and requires Mg++ for its activity.     

Tas1r3, encoding a new candidate taste receptor, is allelic to the sweet responsiveness locus Sac

The ability to taste the sweetness of carbohydrate-rich foodstuffs has a critical role in the nutritional status of humans. Although several components of bitter transduction pathways have been identified, the receptors and other sweet transduction elements remain unknown. The Sac locus in mouse, mapped to the distal end of chromosome 4 (refs. 7-9), is the major determinant of differences between sweet-sensitive and -insensitive strains of mice in their responsiveness to saccharin, sucrose and other sweeteners. To identify the human Sac locus, we searched for candidate genes within a region of approximately one million base pairs of the sequenced human genome syntenous to the region of Sac in mouse. From this search, we identified a likely candidate: T1R3, a previously unknown G protein-coupled receptor (GPCR) and the only GPCR in this region. Mouse Tas1r3 (encoding T1r3) maps to within 20,000 bp of the marker closest to Sac (ref. 9) and, like human TAS1R3, is expressed selectively in taste receptor cells. By comparing the sequence of Tas1r3 from several independently derived strains of mice, we identified a specific polymorphism that assorts between taster and non-taster strains. According to models of its structure, T1r3 from non-tasters is predicted to have an extra amino-terminal glycosylation site that, if used, would interfere with dimerization.     

Mutations in the profilin 1 gene cause familial amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a late-onset neurodegenerative disorder resulting from motor neuron death. Approximately 10% of cases are familial (FALS), typically with a dominant inheritance mode. Despite numerous advances in recent years, nearly 50% of FALS cases have unknown genetic aetiology. Here we show that mutations within the profilin 1 (PFN1) gene can cause FALS. PFN1 is crucial for the conversion of monomeric (G)-actin to filamentous (F)-actin. Exome sequencing of two large ALS families showed different mutations within the PFN1 gene. Further sequence analysis identified 4 mutations in 7 out of 274 FALS cases. Cells expressing PFN1 mutants contain ubiquitinated, insoluble aggregates that in many cases contain the ALS-associated protein TDP-43. PFN1 mutants also display decreased bound actin levels and can inhibit axon outgrowth. Furthermore, primary motor neurons expressing mutant PFN1 display smaller growth cones with a reduced F/G-actin ratio. These observations further document that cytoskeletal pathway alterations contribute to ALS pathogenesis.