Performance and precision of double digestion RAD (ddRAD) genotyping in large multiplexed datasets of marine fish species.

The development of Genotyping-By-Sequencing (GBS) technologies enables cost-effective analysis of large numbers of Single Nucleotide Polymorphisms (SNPs), especially in "non-model" species. Nevertheless, as such technologies enter a mature phase, biases and errors inherent to GBS are becoming evident. Here, we evaluated the performance of double digest Restriction enzyme Associated DNA (ddRAD) sequencing in SNP genotyping studies including high number of samples. Datasets of sequence data were generated from three marine teleost species (>5500 samples, >2.5 × 1012 bases in total), using a standardized protocol. A common bioinformatics pipeline based on STACKS was established, with and without the use of a reference genome. We performed analyses throughout the production and analysis of ddRAD data in order to explore (i) the loss of information due to heterogeneous raw read number across samples; (ii) the discrepancy between expected and observed tag length and coverage; (iii) the performances of reference based vs. de novo approaches; (iv) the sources of potential genotyping errors of the library preparation/bioinformatics protocol, by comparing technical replicates. Our results showed use of a reference genome and a posteriori genotype correction improved genotyping precision. Individual read coverage was a key variable for reproducibility; variance in sequencing depth between loci in the same individual was also identified as an important factor and found to correlate to tag length. A comparison of downstream analysis carried out with ddRAD vs single SNP allele specific assay genotypes provided information about the levels of genotyping imprecision that can have a significant impact on allele frequency estimations and population assignment. The results and insights presented here will help to select and improve approaches to the analysis of large datasets based on RAD-like methodologies.

Microbial dynamics during shelf-life of industrial Ricotta cheese and identification of a Bacillus strain as a cause of a pink discolouration.

Dairy products are perishable and have to be preserved from spoilage during the food chain to achieve the desired shelf-life. Ricotta is a typical Italian soft dairy food produced by heat coagulation of whey proteins and is considered to be a light and healthy product. The shelf-life of Ricotta could be extended, as required by the international food trade market; however, heat resistant microflora causes spoilage and poses issues regarding the safety of the product. Next-generation sequencing (NGS) applied to the Ricotta samples defined the composition of the microbial community in-depth during the shelf-life. The analysis demonstrated the predominance of spore-forming bacteria throughout the shelf-life, mostly belonging to Bacillus, Paenibacillus and Clostridium genera. A strain involved in spoilage and causing a pink discolouration of Ricotta was isolated and characterised as Bacillus mycoides/weihenstephanensis. This is the first report of a food discolouration caused by a toxigenic strain belonging to the Bacillus cereus group that resulted the predominant strain in the community of the defective ricotta. These results suggest that the processing of raw materials to eliminate spores and residual microflora could be essential for improving the quality and the safety of the product and to extend the shelf-life of industrial Ricotta.

Life at depth: Photobacterium profundum genome sequence and expression analysis.

Deep-sea life requires adaptation to high pressure, an extreme yet common condition given that oceans cover 70% of Earth's surface and have an average depth of 3800 meters. Survival at such depths requires specific adaptation but, compared with other extreme conditions, high pressure has received little attention. Recently, Photobacterium profundum strain SS9 has been adopted as a model for piezophily. Here we report its genome sequence (6.4 megabase pairs) and transcriptome analysis. The results provide a first glimpse into the molecular basis for life in the largest portion of the biosphere, revealing high metabolic versatility.

Gene expression profiles of epithelial cells microscopically isolated from a breast-invasive ductal carcinoma and a nodal metastasis.

Expression profiles of breast carcinomas are difficult to interpret when they are obtained from tissue in toto, which may contain a large proportion of non-cancer cells. To avoid this problem, we microscopically isolated cells from a primary invasive ductal carcinoma of the breast and from an axillary node harboring a metastatic breast carcinoma, to obtain pure populations of carcinoma cells ( approximately 500) and used them for serial analysis of gene expression. The expression profiles generated from both populations of cells were compared with the profile of a disease-free mammary epithelium. We showed that the expression profiles obtained are exclusive of carcinoma cells with no contribution of non-epithelial cells. From a total of 16,939 unique tags analyzed, we detected 559 statistically significant changes in gene expression; some of these genes have not been previously associated with breast cancer. We observed that many of the down-regulated genes are the same in both cancers, whereas the up-regulated genes are completely different, suggesting that the down-regulation of a set of genes may be the basic mechanism of cancer formation, while the up-regulation may characterize and possibly control the state of evolution of individual cancers. The results obtained may help in characterizing the neoplastic process of breast cancer.

Do the four clades of the mtDNA haplogroup L2 evolve at different rates?

Forty-seven mtDNAs collected in the Dominican Republic and belonging to the African-specific haplogroup L2 were studied by high-resolution RFLP and control-region sequence analyses. Four sets of diagnostic markers that subdivide L2 into four clades (L2a-L2d) were identified, and a survey of published African data sets appears to indicate that these clades encompass all L2 mtDNAs and harbor very different geographic/ethnic distributions. One mtDNA from each of the four clades was completely sequenced by means of a new sequencing protocol that minimizes time and expense. The phylogeny of the L2 complete sequences showed that the two mtDNAs from L2b and L2d seem disproportionately derived, compared with those from L2a and L2c. This result is not consistent with a simple model of neutral evolution with a uniform molecular clock. The pattern of nonsynonymous versus synonymous substitutions hints at a role for selection in the evolution of human mtDNA. Regardless of whether selection is shaping the evolution of modern human mtDNAs, the population screening of L2 mtDNAs for the mutations identified by our complete sequence study should allow the identification of marker motifs of younger age with more restricted geographic distributions, thus providing new clues about African prehistory and the origin and relationships of African ethnic groups.

Immediate early genes induced by H-Ras in thyroid cells.

Expression of oncogenic v-H-Ras in the thyroid cell line FRTL-5 (FRTL-5(Ras)) results in uncontrolled proliferation, loss of thyroid-specific gene expression and tumorigenicity. Concomitant expression of constitutively activated MEK and Rac, two major H-Ras downstream effectors, in FRTL-5 (FRTL-5(MEK/Rac)) recapitulates H-Ras effects on proliferation and morphology. In contrast to FRTL-5(Ras), however, FRTL-5(MEK/Rac) cells remain differentiated and are not tumorigenic. To find H-Ras induced genes potentially responsible for tumorigenicity and loss of differentiation, we have used subtractive suppression hybridization (SSH), a PCR-based cDNA subtraction technique, between de-differentiated and tumorigenic FRTL-5(Ras) cells and differentiated and non-tumorigenic FRTL-5(MEK/Rac) cells. We examined 800 of the cDNA clones obtained after subtraction and verified their levels of expression in the two cell lines by reverse northern, identifying 337 H-Ras induced genes. By sequence analysis, we clustered 57 different genes. Among these, 39 were known genes (involved in diverse signal transduction processes regulating mitogenic activity, cell survival, cytoskeletal reorganization, stress response and invasion) while the remaining 18 clones were novel genes. Among the 57 H-Ras specific clones, we identified those genes whose expression is induced early by H-Ras. We suggest that these immediate-early genes may play a crucial role in H-Ras-mediated transformation in thyroid epithelial cells.

Characterization of 16 novel human genes showing high similarity to yeast sequences.

The entire set of open reading frames (ORFs) of Saccharomyces cerevisiae has been used to perform systematic similarity searches against nucleic acid and protein databases: with the aim of identifying interesting homologies between yeast and mammalian genes. Many similarities were detected: mostly with known genes. However: several yeast ORFs were only found to match human partial sequence tags: indicating the presence of human transcripts still uncharacterized that have a homologous counterpart in yeast. About 30 such transcripts were further studied and named HUSSY (human sequence similar to yeast). The 16 most interesting are presented in this paper along with their sequencing and mapping data. As expected: most of these genes seem to be involved in basic metabolic and cellular functions (lipoic acid biosynthesis: ribulose-5-phosphate-3-epimerase: glycosyl transferase: beta-transducin: serine-threonine-kinase: ABC proteins: cation transporters). Genes related to RNA maturation were also found (homologues to DIM1: ROK1-RNA-elicase and NFS1). Furthermore: five novel human genes were detected (HUSSY-03: HUSSY-22: HUSSY-23: HUSSY-27: HUSSY-29) that appear to be homologous to yeast genes whose function is still undetermined. More information on this work can be obtained at the website http://grup.bio.unipd.it/hussy

Sequence and analysis of chromosome 3 of the plant Arabidopsis thaliana.

Arabidopsis thaliana is an important model system for plant biologists. In 1996 an international collaboration (the Arabidopsis Genome Initiative) was formed to sequence the whole genome of Arabidopsis and in 1999 the sequence of the first two chromosomes was reported. The sequence of the last three chromosomes and an analysis of the whole genome are reported in this issue. Here we present the sequence of chromosome 3, organized into four sequence segments (contigs). The two largest (13.5 and 9.2 Mb) correspond to the top (long) and the bottom (short) arms of chromosome 3, and the two small contigs are located in the genetically defined centromere. This chromosome encodes 5,220 of the roughly 25,500 predicted protein-coding genes in the genome. About 20% of the predicted proteins have significant homology to proteins in eukaryotic genomes for which the complete sequence is available, pointing to important conserved cellular functions among eukaryotes.

A comprehensive, high-resolution genomic transcript map of human skeletal muscle.

We present the Human Muscle Gene Map (HMGM), the first comprehensive and updated high-resolution expression map of human skeletal muscle. The 1078 entries of the map were obtained by merging data retrieved from UniGene with the RH mapping information on 46 novel muscle transcripts, which showed no similarity to any known sequence. In the map, distances are expressed in megabase pairs. About one-quarter of the map entries represents putative novel genes. Genes known to be specifically expressed in muscle account for <4% of the total. The genomic distribution of the map entries confirmed the previous finding that muscle genes are selectively concentrated in chromosomes 17, 19, and X. Five chromosomal regions are suspected to have a significant excess of muscle genes. Present data support the hypothesis that the biochemical and functional properties of differentiated muscle cells may result from the transcription of a very limited number of muscle-specific genes along with the activity of a large number of genes, shared with other tissues, but showing different levels of expression in muscle. [The sequence data described in this paper have been submitted to the EMBL data library under accession nos. F23198-F23242.]