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Two-step PCR procedures are an efficient and well established way to generate amplicon libraries for NGS sequencing. However, there is a high risk of cross-contamination by carry-over of amplicons from first to second amplification rounds, potentially leading to severe misinterpretation of results. Here we describe a new method able to prevent and/or to identify carry-over contaminations by introducing the K-box, a series of three synergistically acting short sequence elements. Our K-boxes are composed of (i) K1 sequences for suppression of contaminations, (ii) K2 sequences for detection of possible residual contaminations and (iii) S sequences acting as separators to avoid amplification bias. In order to demonstrate the effectiveness of our method we analyzed two-step PCR NGS libraries derived from a multiplex PCR system for detection of T-cell receptor beta gene rearrangements. We used this system since it is of high clinical relevance and may be affected by very low amounts of contaminations. Spike-in contaminations are effectively blocked by the K-box even at high rates as demonstrated by ultra-deep sequencing of the amplicons. Thus, we recommend implementation of the K-box in two-step PCR-based NGS systems for research and diagnostic applications demanding high sensitivity and accuracy., (© The Author(s) 2015. Published by Oxford University Press on behalf of Nucleic Acids Research.)

The human X chromosome has a unique biology that was shaped by its evolution as the sex chromosome shared by males and females. We have determined 99.3% of the euchromatic sequence of the X chromosome. Our analysis illustrates the autosomal origin of the mammalian sex chromosomes, the stepwise process that led to the progressive loss of recombination between X and Y, and the extent of subsequent degradation of the Y chromosome. LINE1 repeat elements cover one-third of the X chromosome, with a distribution that is consistent with their proposed role as way stations in the process of X-chromosome inactivation. We found 1,098 genes in the sequence, of which 99 encode proteins expressed in testis and in various tumour types. A disproportionately high number of mendelian diseases are documented for the X chromosome. Of this number, 168 have been explained by mutations in 113 X-linked genes, which in many cases were characterized with the aid of the DNA sequence.

GOblet is a comprehensive web server application providing the annotation of anonymous sequence data with Gene Ontology (GO) terms. It uses a variety of different protein databases (human, murines, invertebrates, plants, sp-trembl) and their respective GO mappings. The user selects the appropriate database and alignment threshold and thereafter submits single or multiple nucleotide or protein sequences. Results are shown in different ways, e.g. as survey statistics for the main GO categories for all sequences or as detailed results for each single sequence that has been submitted. In its newest version, GOblet allows the batch submission of sequences and provides an improved display of results with the aid of Java applets. All output data, together with the Java applet, are packed to a downloadable archive for local installation and analysis. GOblet can be accessed freely at http://goblet.molgen.mpg.de.

Gene Ontology (GO) is the most widely accepted attempt to construct a unified and structured vocabulary for the description of genes and their products in any organism. Annotation by GO terms is performed in most of the current genome projects, which besides generality has the advantage of being very convenient for computer based classification methods. However, direct use of GO in small sequencing projects is not easy, especially for species not commonly represented in public databases. We present a software package (GOblet), which performs annotation based on GO terms for anonymous cDNA or protein sequences. It uses the species independent GO structure and vocabulary together with a series of protein databases collected from various sites, to perform a detailed GO annotation by sequence similarity searches. The sensitivity and the reference protein sets can be selected by the user. GOblet runs automatically and is available as a public service on our web server. The paper also addresses the reliability of automated GO annotations by using a reference set of more than 6000 human proteins. The GOblet server is accessible at http://goblet.molgen.mpg.de.