pipsqueak encodes a novel nuclear protein required downstream of seven-up for the development of photoreceptors R3 and R4.

Weber U, Siegel V, Mlodzik M
EMBO J. 1995 14 (24): 6247-57

PMID: 8557044 · PMCID: PMC394749

Photoreceptor induction in the Drosophila eye is mediated by activation of the Ras signal transduction cascade. Although this process is well understood, little is known about how the diversity of photoreceptor subtypes is generated. The pipsqueak (psq) gene is expressed at high levels in the R3/R4 precursors during eye development and this expression depends on seven-up (svp) gene function. Moreover, strong psq alleles are dominant suppressors of a svp-induced cone cell transformation phenotype. Although the gene was previously identified and described as a member of the maternal posterior group of genes, the strong semilethal alleles isolated here demonstrate a specific requirement for psq function downstream of svp for the development of photoreceptors R3/R4. The gene has three independent 5' ends and codes for several nuclear protein isoforms, some containing the POZ domain which has been implicated in protein-protein interactions. Interestingly, all viable alleles with a maternal posterior group phenotype cluster around one specific 5' exon, while all semilethal alleles have lesions which map to a different alternative 5' exon.

MeSH Terms (23)

Alleles Amino Acid Sequence Animals Base Sequence DNA DNA-Binding Proteins Drosophila Drosophila Proteins Exons Eye Abnormalities Eye Proteins Female Genes, Insect Male Molecular Sequence Data Mutation Nuclear Proteins Ovary Phenotype Photoreceptor Cells, Invertebrate Receptors, Steroid Sequence Homology, Amino Acid Transformation, Genetic

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