MOLECULAR ANALYSIS OF KELCH, A GENE NECESSARY FOR NURSE CELL CYTOPLASM TRANSPORT IN DROSOPHILA OOGENESIS ( KELCH GENE).
Contributors: Yale University.
Published: 1992
Number of pages: 162
Subjects: Biology, Molecular.; Biology, Cell.; Biology, Genetics.
Description: The majority of the cytoplasmic components of a Drosophila egg are synthesized in 15 nurse cells and then transported to the oocyte. Two distinct phases of nurse cell cytoplasm transport are observed in oogenesis: slow transport through the cytoplasmic bridges during the majority of oogenesis, and then rapid streaming of all remaining nurse cell cytoplasm into the oocyte at the end of oogenesis, resulting in nurse cell regression. kelch plays an essential role in cytoplasm transport since kelch mutants are defective in both the slow and fast phases of transport.

The genomic region at kelch was cloned by plasmid rescue of DNA from a P element insertion allele. About 50 kb of genomic DNA was isolated from a cosmid library. A 6 kb mRNA was identified as the kelch transcript. The transcript was most abundant in ovaries but was also found in other female tissues and males. In situ hybridization localized kelch mRNA to the nurse cells.

kelch cDNAs were isolated and sequenced. kelch has an unusual gene structure with two open reading frames (ORFs) separated by a UGA stop codon. A segment of 50 amino acids in the first open reading frame (ORF1) is repeated six times in the carboxy-half of the protein. The protein shares homology with a mouse protein, three related peptides from poxviruses, and has a motif which is also found in Drosophila tramtrack protein and a few other zinc finger proteins.

Monoclonal antibodies were made against a kelch peptide derived from ORF1. An 80 kD peptide was detected, which corresponds to the size of the predicted product of ORF1. Antibody staining of ovarian tissue showed that the protein product of ORF1 is specifically localized to the cytoplasmic bridges.

This work suggests that the gene product of kelch may be a component of the cytoplasmic bridges and that it might be involved in regulating the flow of nurse cell cytoplasm in both slow and fast phases of transport. The unusual gene structure may play a role in regulating kelch expression. The sequence conservation implies that the gene encodes an important function.
Notes: Source: Dissertation Abstracts International, Volume: 54-01, Section: B, page: 0095.

Thesis (PH.D.)--YALE UNIVERSITY, 1992.

School code: 0265.