Worm Breeder's Gazette 12(5): 34 (February 1, 1993)

These abstracts should not be cited in bibliographies. Material contained herein should be treated as personal communication and should be cited as such only with the consent of the author.

Gene with Early, Cell Lineage Specific Expression is Homologous to Fork Head

Ian A. Hope

Figure 1

Figure 2

Department of Pure and Applied Biology and Department of Genetics, The University of Leeds, Leeds, LS2 9JT, UK

The plasmid p UL#24 C7was identified in my initial promoter trap screen (Hope, Development, 113, 399) and consists of a 6.5kb C.elegans genomic DNA fragment cloned upstream of lacZ in Andy Fire's vector, pPD22 .11.C.elegans transformants containing this DNA express ß-galactosidase during early embryogenesis. ß-galactosidase was detected in: i. A subset of the AB Ïll lineage, descendants of ABalpa, ABalpp, ABaIaa, ABplaa, ABplpa, ABpraa and ABpIpa, from the 5th cell division in the AB cell lineage, for approximately 3 cell generations. ii. All of the D cell lineage, from the 2nd cell division in the D cell lineage until shortly after the 4th cell division. iii. Z1 and Z4 from midembryogenesis until shortly

after hatching. The gene with which lacZ has been fused in p UL#24 C7has been called pes-1 (pattern expression site).

Genomic DNA sequencing has revealed that the lacZ gene has been fused to DNA encoding part of a protein domain homologous to the DNA binding domain of the fork head family of transcription factors. Sequence 5' from the point of fusion with lacZ was determined from p UL#24 C7.Sequence 3' from the point of fusion was obtained by subcloning from the cosmid T28H11 (thanks Alan and Ratna) which contains genomic DNA flanking the insert of pU#24C7. The predicted PES1 protein shows 44% amino acid identity to fork head over a 95 residue region. Two other C.elegans genes have been described which have homology to the fork head family (WBG12.3, 37 and 12.4, 32).

[See Figure 1]

PCR, using a primer for the trans-spliced leader SL1 ,was used to examine transcripts emanating from pes-1 .There appear to be 3 sites at which transcription can initiate. Two of the transcripts would encode different proteins although both would contain the predicted DNA binding domain. The third transcript does not appear to contain a codon which would initiate translation through the fork head homologous domain, but this needs further study.

It is intriguing that there are 3 components to the ß-galactosidase expression pattem and 3 different transcripts have been detected. The possibility that a different transcript is produced in each founder cell lineage is being examined. p UL#24 C7was originally selected because the ß-galactosidase expression pattem suggested the gene tagged with lacZ was under the control of a regulatory system important in early embryogenesis. The possibility that pes-1 encodes a specific DNA binding protein means there is interest not only in how pes-1 is regulated but also in what pes-1 is regulating.

Figure 1

Figure 2