A molecular analysis of the tissue polarity gene prickle and associated transcripts in Drosophila melanogaster.

Green, Clare Patricia (1999). A molecular analysis of the tissue polarity gene prickle and associated transcripts in Drosophila melanogaster. PhD thesis The Open University.

DOI: https://doi.org/10.21954/ou.ro.0000ff4c

Abstract

The distinct patterns of bristles and hairs on the surface of an adult Drosophila indicate a planar polarity and reflect the polarity of the underlying structures. Many of the planar polarity genes have been analysed molecularly and found to encode a diverse group of proteins. In this thesis, I describe the molecular characterisation of prickle.

Three classes of mutation are found at the prickle locus; prickle (pk^pk), spiny- legs (pk^sple) and prickle-spiny-legs (pk^pk-sple). Three transcripts were identified and sequenced. The 4.2 kb pk transcript has seven exons that span 70 kb. The other two transcripts, sple and pkM, share six exons with pk and have alternatively spliced 5' ends.

The GAL4-UAS system was used to demonstrate rescue of the prickle and spiny-legs phenotypes with the pk and sple transcripts, respectively. Overexpression of the UAS[pk⁺] construct also resulted in a phenotype resembling loss-of-function pk^sple and vice versa.

The transcripts encode novel proteins with three LIM or UM-like motifs in the shared exons. LIM domains are cysteine rich sequences known to be involved in protein- protein interactions. A novel domain, named the PET domain, was also identified in these proteins just upstream of the LLM motifs. Database searches found the PET domain conserved in a small group of proteins. A Drosophila homologue, espinas (esn), was also identified and sequenced.

A cluster of transcripts was found in the region of the 5' exon of the pk transcript. These were sequenced and shown to have homology to serine proteinase inhibitors or serpins. The most distal of the three was shown to rescue the necrotic phenotype.

The possible roles of prickle in planar polarity signalling are discussed and it is suggested that the prickle proteins may be involved in the formation of multiprotein complexes.