Molecular cloning and characterization of two eye-specific genes of Drosophila melanogaster

Lin Chen, Purdue University

Abstract

The visual system of Drosophila melanogaster has become a major subject of investigations in neurobiology. A growing body of evidence suggests that proteins important to the physiological processes in the eye are often encoded by eye-specifically or eye-preferentially expressed genes. A pool of eye-specific clones was generated by subtractive and differential library screening. Two novel Drosophila eye-specific genes, DES72E-I and DES72E-II, located at 72E1-2 of the third chromosome were isolated from analysis of these clones. Transcribed from the DES72E-I gene is a single eye-specific transcript of 0.9 kb, which encodes a novel transmembrane protein of 191 amino acids. This transcript is expressed only in the distal layer of the retina and only in the adult stage during development. The DES72E-II gene has at least two transcripts. Both transcripts encode the same novel secretory protein of 99 amino acids. The DES72E-II gene is expressed in the distal layer of the retina and ocellus, and in the secondary pigment cell region of the retina. One of the DES72E-II transcripts, the 0.4 kb eye-specific transcript, is first expressed in the pupal stage during development. The expression pattern suggests that these two genes could play a role in the generation of the pseudocone and/or lens in the compound eye and ocellus, and may indirectly regulate the function of photoreceptors through their action on the secondary pigment cells. The drepA (delay in repolarization) mutation, which is contained in the third chromosome balancer, TM6, has been mapped between 72E1-2 and 73A3-4. The eye-specific gene DES72E-II, which is likely to be expressed in the secondary pigment cells, was localized within this map position of the drepA mutant. Northern hybridization shows that the amount of the 0.4 kb eye-specific transcript of DES72E-II gene is reduced dramatically in the drepA mutant. Therefore, drepA may be the mutant corresponding to the DES72E-II gene. A defect in this gene could affect the K$\sp{+}$ uptake into the pigment cell and thus cause a delay in repolarization of photoreceptor response.

Degree

Ph.D.

Advisors

Pak, Purdue University.

Subject Area

Molecular biology|Neurology

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