Melanocortin-1 receptor structure and functional regulation

The melanogenic actions of the melanocortins are mediated by the melanocortin-1 receptor (MC1R). MC1R is a member of the G-protein-coupled receptors (GPCR) superfamily expressed in cutaneous and hair follicle melanocytes. Activation of MC1R by adrenocorticotrophin or alpha-melanocyte stimulating hormone is positively coupled to the cAMP signaling pathway and leads to a stimulation of melanogenesis and a switch from the synthesis of pheomelanins to the production of eumelanic pigments. The functional behavior of the MC1R agrees with emerging concepts in GPCR signaling including dimerization, coupling to more than one signaling pathway and a high agonist-independent constitutive activity accounting for inverse agonism phenomena. In addition, MC1R displays unique properties such as an unusually high number of natural variants often associated with clearly visible phenotypes and the occurrence of endogenous peptide antagonists. Therefore MC1R is an ideal model to study GPCR function. Here we review our current knowledge of MC1R structure and function, with emphasis on information gathered from the analysis of natural variants. We also discuss recent data on the regulation of MC1R function by paracrine and endocrine factors and by external stimuli such as ultraviolet light.     

Gene Expression in Tilapia Following Oral Delivery of Chitosan-Encapsulated Plasmid DNA Incorporated into Fish Feeds

DNA delivery into fish is important for transient gene expression, (e.g., DNA vaccination). Previous studies have generally focused on intramuscular injection of DNA vaccines into fish. However, this method is obviously impractical and laborious for injecting large numbers of fishes. This study reports oral delivery of a construct expressing the β-galactosidase reporter gene into fish by encapsulating the DNA in chitosan and incorporating it into fish feeds. We found that β-galactosidase expression could be observed in the stomachs, spleens, and gills of fishes fed with flakes containing the chitosan-DNA complex. These results suggest that DNA vaccines and other constructs can be easily and cheaply delivered into fishes orally by use of carriers and incorporation into fish feeds.     

Recursive partitioning models for linkage in COGA data

We have developed a recursive-partitioning (RP) algorithm for identifying phenotype and covariate groupings that interact with the evidence for linkage. This data-mining approach for detecting gene x environment interactions uses genotype and covariate data on affected relative pairs to find evidence for linkage heterogeneity across covariate-defined subgroups. We adapted a likelihood-ratio based test of linkage parameterized with relative risks to a recursive partitioning framework, including a cross-validation based deviance measurement for choosing optimal tree size and a bootstrap sampling procedure for choosing robust tree structure. ALDX2 category 5 individuals were considered affected, categories 1 and 3 unaffected, and all others unknown. We sampled non-overlapping affected relative pairs from each family; therefore, we used 144 affected pairs in the RP model. Twenty pair-level covariates were defined from smoking status, maximum drinks, ethnicity, sex, and age at onset. Using the all-pairs score in GENEHUNTER, the nonparametric linkage tests showed no regions with suggestive linkage evidence. However, using the RP model, several suggestive regions were found on chromosomes 2, 4, 6, 14, and 20, with detection of associated covariates such as sex and age at onset.     

Application of Direct Agglutination Test (DAT) and Fast Agglutination Screening Test (FAST) for sero-diagnosis of visceral leishmaniasis in endemic area of Minas Gerais,Brazil

Background  

The direct agglutination test (DAT) has proved to be a very important sero-diagnostic tool combining high levels of intrinsic validity and ease of performance. Otherwise, fast agglutination screening test (FAST) utilises only one serum dilution making the test very suitable for the screening of large populations.     

tRNA 3' end maturation in archaea has eukaryotic features: the RNase Z from Haloferax volcanii

Here, we report the first characterization and partial purification of an archaeal tRNA 3' processing activity, the RNase Z from Haloferax volcanii. The activity identified here is an endonuclease, which cleaves tRNA precursors 3' to the discriminator. Thus tRNA 3' processing in archaea resembles the eukaryotic 3' processing pathway. The archaeal RNase Z has a KCl optimum at 5mM, which is in contrast to the intracellular KCl concentration being as high as 4M KCl.The archaeal RNase Z does process 5' extended and intron-containing pretRNAs but with a much lower efficiency than 5' matured, intronless pretRNAs. At least in vitro there is thus no defined order for 5' and 3' processing and splicing. A heterologous precursor tRNA is cleaved efficiently by the archaeal RNase Z. Experiments with precursors containing mutated tRNAs revealed that removal of the anticodon arm reduces cleavage efficiency only slightly, while removal of D and T arm reduces processing effciency drastically, even down to complete inhibition. Comparison with its nuclear and mitochondrial homologs revealed that the substrate specificity of the archaeal RNase Z is narrower than that of the nuclear RNase Z but broader than that of the mitochondrial RNase Z.