Highly efficient transgenesis with miniMos in Caenorhabditis briggsae.

Caenorhabditis briggsae as a companion species for Caenorhabditis elegans has played an increasingly important role in study of evolution of development and genome and gene regulation. Aided by the isolation of its sister spices, it has recently been established as a model for speciation study. To take full advantage of the species for comparative study, an effective transgenesis method especially those with single-copy insertion is important for functional comparison. Here, we improved a transposon-based transgenesis methodology that had been originally developed in C. elegans but worked marginally in C. briggsae. By incorporation of a heat shock step, the transgenesis efficiency in C. briggsae with a single-copy insertion is comparable to that in C. elegans. We used the method to generate 54 independent insertions mostly consisting of a mCherry tag over the C. briggsae genome. We demonstrated the use of the tags in identifying interacting loci responsible for hybrid male sterility between C. briggsae and Caenorhabditis nigoni when combined with the GFP tags we generated previously. Finally, we demonstrated that C. briggsae tolerates the C. elegans toxin, PEEL-1, but not SUP-35, making the latter a potential negative selection marker against extrachromosomal array.

Genomic architecture of 5S rDNA cluster and its variations within and between species.

BACKGROUND: Ribosomal DNAs (rDNAs) are arranged in purely tandem repeats, preventing them from being reliably assembled onto chromosomes during generation of genome assembly. The uncertainty of rDNA genomic structure presents a significant barrier for studying their function and evolution. RESULTS: Here we generate ultra-long Oxford Nanopore Technologies (ONT) and short NGS reads to delineate the architecture and variation of the 5S rDNA cluster in the different strains of C. elegans and C. briggsae. We classify the individual rDNA's repeating units into 25 types based on the unique sequence variations in each unit of C. elegans (N2). We next perform assembly of the cluster by taking advantage of the long reads that carry these units, which led to an assembly of 5S rDNA cluster consisting of up to 167 consecutive 5S rDNA units in the N2 strain. The ordering and copy number of various rDNA units are consistent with the separation time between strains. Surprisingly, we observed a drastically reduced level of variation in the unit composition in the 5S rDNA cluster in the C. elegans CB4856 and C. briggsae AF16 strains than in the C. elegans N2 strain, suggesting that N2, a widely used reference strain, is likely to be defective in maintaining the 5S rDNA cluster stability compared with other wild isolates of C. elegans or C. briggsae. CONCLUSIONS: The results demonstrate that Nanopore DNA sequencing reads are capable of generating assembly of highly repetitive sequences, and rDNA units are highly dynamic both within and between population(s) of the same species in terms of sequence and copy number. The detailed structure and variation of the 5S rDNA units within the rDNA cluster pave the way for functional and evolutionary studies.

Comprehension by older people of medication information with or without supplementary pharmaceutical pictograms.

This study examined the benefits of pharmaceutical pictograms for improving comprehension of medication information for older people. Fifty Hong Kong Chinese older people completed a medical information comprehension task for five drugs. Participants in the control group were presented with text labels while those in the experimental group were given the text labels plus supplementary pharmaceutical pictograms, and then all reported their understanding of the medication information conveyed. Lower educated older people had poorer understanding of medication information. The addition of pharmaceutical pictograms significantly improved the comprehension of medication information for older people. The majority of older people tested with pictograms favored adding pictograms to text and thought the pictograms were useful for conveying medical information rather than using written text alone. The findings suggested that pharmaceutical and health care professionals should include pharmaceutical pictograms on labels to better convey instructions on medication to older people.