Association of common DNA sequence variants at 33 genetic loci with blood lipids in individuals of African ancestry from Jamaica

The relevance of loci associated with blood lipids recently identified in European populations in individuals of African ancestry is unknown. We tested association between lipid traits and 36 previously described single-nucleotide polymorphisms (SNPs) in 1,466 individuals of African ancestry from Spanish Town, Jamaica. For the same allele and effect direction as observed in individuals of European ancestry, SNPs at three loci (1p13, 2p21, and 19p13) showed statistically significant association (p < 0.05) with LDL, two loci (11q12 and 20q13) showed association with HDL cholesterol, and two loci (11q12 and 2p24) showed association with triglycerides. The most significant association was between a SNP at 1p13 and LDL cholesterol (p = 4.6 × 10(-8)). This SNP is in a linkage disequilibrium region containing four genes (CELSR2, PSRC1, MYBPHL, and SORT1) and was recently shown to relate to risk for myocardial infarction. Overall, the results of this study suggest that much of the genetic variation which influences blood lipids is shared across ethnic groups.

Long-term management of bilateral metastases of renal cell carcinoma to the choroid plexus

BACKGROUND

Metastatic tumors to the brain presenting exclusively in the choroid plexus are exceedingly rare. These events are frequently associated with renal cell carcinoma (RCC), of which all reported cases have been solitary lesions.

METHODS

The authors present the unusual case of a patient with metastatic RCC who developed bilateral tumors of the choroid plexus. These tumors, one of which was confirmed to be metastatic RCC by histologic analysis, were treated over a 5-year period with a combination of interventions, including surgical resection, stereotactic radiosurgery, and chemotherapy, in conjunction with continual radiological monitoring.

FINDINGS

Follow-up over a 5-year period demonstrated good control of the patient's intracranial disease and very little neurologic sequelae.

INTERPRETATION

This strategy was successful in keeping the patient in good health with minimal neurological symptoms, despite the bilateral nature of the disease and its generally poor prognosis.

Paraneoplastic neurologic disease antigens: RNA-binding proteins and signaling proteins in neuronal degeneration

Studies of the disorders known as paraneoplastic neurologic degenerations exemplify the successful application of modern molecular biological techniques to diseases, yielding, even for these extremely rare disorders, wide-ranging insight into basic neurobiology, tumor immunity, and autoimmune neurologic disease. Immune responses to paraneoplastic neurologic degeneration antigens, also called onconeural antigens, have been exploited to clone and characterize a number of neuron-specific proteins, including several RNA-binding proteins and new kinds of signaling molecules. The biology and functions of these proteins are reviewed, and a model in which their functions are related to the pathogenesis of autoimmune neurologic disease is discussed.

The tetranucleotide UCAY directs the specific recognition of RNA by the Nova K-homology 3 domain

The Nova family of proteins are target antigens in the autoimmune disorder paraneoplastic opsoclonus-myoclonus ataxia and contain K-homology (KH)-type RNA binding domains. The Nova-1 protein has recently been shown to regulate alternative splicing of the alpha2 glycine receptor subunit pre-mRNA by binding to an intronic element containing repeats of the tetranucleotide UCAU. Here, we have used selection-amplification to demonstrate that the KH3 domain of Nova recognizes a single UCAY element in the context of a 20-base hairpin RNA; the UCAY tetranucleotide is optimally presented as a loop element of the hairpin scaffold and requires protein residues C-terminal to the previously defined KH domain. These results suggest that KH domains in general recognize tetranucleotide motifs and that biological RNA targets of KH domains may use either RNA secondary structure or repeated sequence elements to achieve high affinity and specificity of protein binding.

Sequence-specific RNA binding by a Nova KH domain: implications for paraneoplastic disease and the fragile X syndrome

The structure of a Nova protein K homology (KH) domain recognizing single-stranded RNA has been determined at 2.4 A resolution. Mammalian Nova antigens (1 and 2) constitute an important family of regulators of RNA metabolism in neurons, first identified using sera from cancer patients with the autoimmune disorder paraneoplastic opsoclonus-myoclonus ataxia (POMA). The structure of the third KH domain (KH3) of Nova-2 bound to a stem loop RNA resembles a molecular vise, with 5'-Ura-Cyt-Ade-Cyt-3' pinioned between an invariant Gly-X-X-Gly motif and the variable loop. Tetranucleotide recognition is supported by an aliphatic alpha helix/beta sheet RNA-binding platform, which mimics 5'-Ura-Gua-3' by making Watson-Crick-like hydrogen bonds with 5'-Cyt-Ade-3'. Sequence conservation suggests that fragile X mental retardation results from perturbation of RNA binding by the FMR1 protein.

Crystal structures of Nova-1 and Nova-2 K-homology RNA-binding domains

BACKGROUND

Nova-1 and Nova-2 are related neuronal proteins that were initially cloned using antisera obtained from patients with the autoimmune neurological disease paraneoplastic opsoclonus-myoclonus ataxia (POMA). Both of these disease gene products contain three RNA-binding motifs known as K-homology or KH domains, and their RNA ligands have been identified via binding-site selection experiments. The KH motif structure has been determined previously using NMR spectroscopy, but not using X-ray crystallography. Many proteins contain more than one KH domain, yet there is no published structural information regarding the behavior of such multimers.

RESULTS

We have obtained the first X-ray crystallographic structures of KH-domain-containing proteins. Structures of the third KH domains (KH3) of Nova-1 and Nova-2 were determined by multiple isomorphous replacement and molecular replacement at 2.6 A and 2.0 A, respectively. These highly similar RNA-binding motifs form a compact protease-resistant domain resembling an open-faced sandwich, consisting of a three-stranded antiparallel beta sheet topped by three alpha helices. In both Nova crystals, the lattice is composed of symmetric tetramers of KH3 domains that are created by two dimer interfaces.

CONCLUSIONS

The crystal structures of both Nova KH3 domains are similar to the previously determined NMR structures. The most significant differences among the KH domains involve changes in the positioning of one or more of the alpha helices with respect to the betasheet, particularly in the NMR structure of the KH1 domain of the Fragile X disease protein FMR-1. Loop regions in the KH domains are clearly visible in the crystal structure, unlike the NMR structures, revealing the conformation of the invariant Gly-X-X-Gly segment that is thought to participate in RNA-binding and of the variable region. The tetrameric arrangements of the Nova KH3 domains provide insights into how KH domains may interact with each other in proteins containing multiple KH motifs.

Insulin-stimulated phosphatidylcholine hydrolysis, diacylglycerol/protein kinase C signalling, and hexose transport in pertussis toxin-treated BC3H-1 myocytes

Pertussis toxin was used to block insulin-stimulated phosphatidylinositol (PI)-glycan hydrolysis, consequent de novo synthesis of phosphatidic acid (PA) and the diacylglycerol (DAG) production that results from these two related processes in BC3H-1 myocytes. In contrast, pertussis toxin pretreatment did not inhibit insulin-stimulated hydrolysis of phosphatidylcholine (PC) which was found to be at least partly due to activation of a phospholipase D. Moreover, pertussis toxin-insensitive PC hydrolysis was accompanied by rapid biphasic increases in DAG and translocative activation of protein kinase C (PKC). Insulin-stimulated glucose transport was also insensitive to pertussis toxin pretreatment. Our findings suggest that insulin-stimulated PC hydrolysis pays an important role in DAG/PKC signalling during insulin action.

Preferential activation of microsomal diacylglycerol/protein kinase C signaling during glucose treatment (De Novo phospholipid synthesis) of rat adipocytes

Glucose has been reported to increase the de novo synthesis of diacylglycerol (DAG) and translocate and activate protein kinase C (PKC) in rat adipocytes. Presently, we examined the major subcellular site of PKC translocation/activation in response to glucose-induced DAG. Glucose rapidly increased DAG content and PKC enzyme activity in microsomes, but not in plasma membranes or other membranes, during a 30-min treatment of rat adipocytes. This glucose-induced increase in microsomal DAG was attended by increases in immunoreactive PKC alpha, beta, and epsilon. Glucose-induced activation of DAG/PKC signaling in microsomes was not associated with a change in the translocation of Glut-4 transporters from microsomes to the plasma membrane, a biological response that is known to be stimulated by agonists, e.g., phorbol esters, which increase DAG/PKC signaling in plasma membranes, as well as in microsomes. In conclusion, an increase in de novo phospholipid synthesis, as occurs during glucose treatment of rat adipocytes, primarily activates DAG/PKC signaling in microsomes; moreover, this signaling response and biological consequences thereof may differ from those of agonists that primarily stimulate DAG/PKC signaling in the plasma membrane.