The original sequencing and annotation of the Caenorhabditis elegans genome along with recent advances in sequencing technology provide an exceptional opportunity for the genomic analysis of wild-type and mutant strains. Using the Illumina Genome Analyzer, we sequenced the entire genome of Rec-1, a strain that alters the distribution of meiotic crossovers without changing the overall frequency. Rec-1 was derived from ethylmethane sulfonate (EMS)-treated strains, one of which had a high level of transposable element mobility. Sequencing of this strain provides an opportunity to examine the consequences on the genome of altering the distribution of meiotic recombination events.
Colorectal cancers are one of the most prevalent tumour types worldwide and, despite the emergence of targeted and biologic therapies, have among the highest mortality rates. The Personalized OncoGenomics (POG) program at BC Cancer performs whole genome and transcriptome analysis (WGTA) to identify specific alterations in an individual’s cancer that may be most effectively targeted. Informed using WGTA, a patient with advanced mismatch repair-deficient colorectal cancer was treated with the antihypertensive drug irbesartan and experienced a profound and durable response. We describe the subsequent relapse of this patient and potential mechanisms of response using WGTA and multiplex immunohistochemistry (m-IHC) profiling of biopsies before and after treatment from the same metastatic site of the L3 spine. We did not observe marked differences in the genomic landscape before and after treatment. Analyses revealed an increase in immune signalling and infiltrating immune cells, particularly CD8+ T cells, in the relapsed tumour. These results indicate that the observed anti-tumour response to irbesartan may have been due to an activated immune response. Determining whether there may be other cancer contexts in which irbesartan may be similarly valuable will require additional studies.
Suppressor screens are an invaluable method for identifying novel genetic interactions between genes in the model organism Caenorhabditis elegans. However, traditionally this approach has suffered from the laborious and protracted process of mapping mutations at the molecular level. Using a mutagen known to generate small deletions, coupled with oligoarray comparative genomic hybridization (aCGH), we have identified mutations in two genes that suppress the lethality associated with a mutation of the essential receptor tyrosine kinase rol-3. First, we find that deletion of the Bicaudal-C ortholog, bcc-1, suppresses rol-3–associated lethality. Second, we identify several duplications that also suppress rol-3–associated lethality. We establish that overexpression of srap-1, a single gene present in these duplications, mediates the suppression. This study demonstrates the suitability of deletion-biased mutagenesis screening in combination with aCGH characterization for the rapid identification of novel suppressor mutations. In addition to detecting small deletions, this approach is suitable for identifying copy number suppressor mutations, a class of suppressor not easily characterized using alternative approaches.