Monday, September 24, 2007

Finding co-dependent genes in fission yeast

A method for the rapid and large-scale generation of double mutants in a popular yeast strain to determine which genes are functionally dependent on each other is published online this week in Nature Methods.

Yeast is a simple unicellular organism but it comes in many different species that are only very distantly related on an evolutionary scale. The two main species used for research are budding and fission yeast – the former being very popular with geneticists for ease of handling, the latter being of interest because it is more closely related to higher eukaryotes.

Yeast, being a single cell organism, is ideal for the screening of genes that together are essential for survival of the cell. These interaction screens are done in yeast cells with a haploid genome - consisting of only one set of chromosomes – where each cell has mutations in two genes. If the combination of the two genes is required the yeast will die. By generating all possible combinations of gene pairs, a map of genetic interaction can be drawn.

These screens are already widely used in budding yeast, but the difficulty in generating haploid double mutants in fission yeast have prevented their application in this species. Nevan Krogan and colleagues now present a strategy to target genes of interest in fission yeast and select for haploid double-mutant cells. By investigating the pairs of all genes linked to a certain biological process they can draw a comprehensive map of the genes involved in this process.

Comparing the genetic maps in both of these yeast species will shed light on biological pathways that were conserved or diverged during evolution.

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