Innexin Gap Junctions

Genetic screens for innexin interacting loci

Image comparing the morphology of a wild type fly with an Inx2(dominant)+interacting deficiency fly

Figure legend: Image showing some of the developmental phenotypes that were observed during a screen to identify loci that genetically interact with a dominant Inx2 mutant. Left panels: wild type Drosophila have straight, flat, wing blades (arrow) and a regular array of ommatidia in their compound eyes. Right panels: A double heterozygote mutant fly carrying a dominant Inx2 mutation and a deletion that uncovers an interacting locus. The wings are often malformed (arrow, this is an extreme example) and the arrangement of ommatidia is irregular. Flies carrying only the Inx2Dominant mutation alone do not exhibit these phenotypes.

Scanning electron microscopy images of a wild type eye and a double mutant of Innexin2 with an interactor loci

Figure legend: Scanning electron microscopy images of a wild type Drosophila eye (left) and a heterozygote carrying an Inx2TA181 allele and a deficiency uncovering a genetically interacting locus (right). All tissues at the surface of the mutant compound eye, ommatidia and inter-ommatidial bristles, are disrupted. Close-up images of the eye phenotype can be seen here. The club-shaped arista of the Inx2Dominant mutant can be seen in the image on the right.

Enhancer/suppressor screens (St. Johnston 2002) based on heterozygous mutant animals, such as the one employed to retrieve loci that genetically interact with Inx2Dominant alleles (shown above), provide a rapid way of identifying genes whose protein products are likely to participate in processes that overlap with, or are functionally related to, the biological process that is disrupted by the Inx2dominant mutant gap junction protein. However, genetic studies utilising homozygous mutant animals are generally more convincing and provide far more detailed information (for example, Lechner et al. 2007).

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