We have used long-range PCR to identify mutations in the duplicated part of the PKD1 gene. By means of a PKD1-specific primer in intron 1, an approximately 13.6-kb PCR product that includes exons 2-15 of the PKD1 gene has been used to search for mutations, by direct sequence analysis. This region contains the majority of the predicted extracellular domains of the PKD1-gene product, polycystin, including the 16 novel PKD domains that have similarity to immunoglobulin-like domains found in many cell-adhesion molecules and cell-surface receptors. Direct sequence analysis of exons encoding all the 16 PKD domains was performed on PCR products from a group of 24 unrelated patients with autosomal dominant polycystic kidney disease (ADPKD [MIM 173900]). Seven novel mutations were found in a screening of 42% of the PKD1-coding region in each patient, representing a 29% detection rate; these mutations included two deletions (one of 3 kb and the other of 28 bp), one single-base insertion, and four nucleotide substitutions (one splice site, one nonsense, and two missense). Five of these mutations would be predicted to cause a prematurely truncated protein. Two coding and 18 silent polymorphisms were also found. When, for the PKD1 gene, this method is coupled with existing mutation-detection methods, virtually the whole of this large, complex gene can now be screened for mutations.

A b s t r a c t :When designing learning materials, great emphasis is put on creating a 'definitive re s o u rce' -but this focus can often lead to the production of inflexible content which f o l l ows a fixed pedagogy and fails to cater to individual learning styles and teaching situations. If this is recognised, tools can be produced that allow the teacher to customise generic components to provide a tailored learning experience support i n g d i f f e rent teaching approaches and scenarios and addressing a wider range of learning styles. This paper will relate these ideas to the use of online simulations in science and engineering education. In support of this, the educational benefits of simulations are outlined, followed by a re v i ew of re s e a rch into factors influencing their effective use.The complex nature of these factors leads to the conclusion that the notion of a ' d e f i n i t i ve' simulation interface is a myth. Simulation users must be empowe red by tools allowing them to take control of the design process. The range of changes which could be facilitated by giving teachers the tools to alter simulation visualisations are discussed and demonstrated with examples of simulations and online learning materials produced using a suite of tools for creating and customising educational simulations, Je L S I M .Keywords: Ja va, e-Learning, simulations, education. Interactive Demonstration:Ja va applet based simulations are linked as examples from this paper for which yo u will need a Ja va -a w a re web brow s e r. The tools used to create the simulations are f reely available from the JeLSIM (Ja va eLearning SIMulations) website. C o m m e n t a r i e s :

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Deficiency in the DNA end-processing enzyme, tyrosyl-DNA phosphodiesterase 1 (TDP1), causes progressive neurodegeneration in humans. Here, we generated a tdp1 knockout zebrafish and confirmed the lack of TDP1 activity. In adulthood, homozygotes exhibit hypersensitivity to topoisomerase 1 (Top1) poisons and a very mild locomotion defect. Unexpectedly, embryonic tdp1−/− zebrafish were not hypersensitive to Top1 poisons and did not exhibit increased Top1-DNA breaks. This is in contrast to the hypersensitivity of Tdp1-deficient vertebrate models reported to date. Tdp1 is dispensable in the zebrafish embryo with transcript levels down-regulated in response to Top1-DNA damage. In contrast, apex2 and ercc4 (xpf) transcripts were up-regulated. These findings identify the tdp1−/− zebrafish embryo as the first vertebrate model that does not require Tdp1 to protect from Top1-DNA damage and identify apex2 and ercc4 (xpf) as putative players fulfilling this role. It highlights the requirement of distinct DNA repair factors across the life span of vertebrates.