A sex-linked female sterile gene in Drosophila melanogaster that is remarkable because different mutant alleles can produce quite different ovarian pathologies. One class of alleles produces ovarian tumors; hence the otu symbol. The tumors are composed of hundreds of single cells and clusters of two or three cells joined by ring canals (q.v.). These abnormalities preasumably arise from defective fusomes (q.v.). Another class of mutant alleles is characterized by germaria that either lack germ cells or contain germ cells that have undergone only one or two cell divisions. Mutants belonging to the third class can produce egg chambers, but the transport of nurse cell cytoplasm to the oocyte is inhibited. The nuclei of these abnormal nurse cells contain giant polytene chromosomes, and the largest have 8,000 times the haploid amount of DNA. Studies of the otu gene product have shown that this protein belongs to a highly conserved superfamily of cysteine proteases, many of which function to break down ubiquitin (q.v.). See cystocyte divisions, polyfusome, ubiquitin proteasome pathway.
Subjects: Genetics and Genomics.