Worm Breeder's Gazette 12(2): 35 (January 1, 1992)

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.

Do Newly Formed Somatic Telomeres in Ascaris lumbricoides Exert A Position Effect on Nearby Located Genes?

Y. Huang, H. Tobler, F. Muller

Institute of Zoology, University of Fribourg, Perolles, CH-1700 Fribourg, Switzerland.

Telomeres, the ends of eukaryotic chromosomes, are essential for the stable maintenance and replication of linear chromosomes in eukaryotic cells. They are thought to occupy unique locations within the nucleus, typically being associated with the nuclear envelope. Frequently, they show heterochromatic structures. It has been demonstrated that PolII genes, if placed near the ends of chromosomes in Saccharomyces cerevisiae, undergo a position effect(1). The telomeres of the somatic chromosomes in Ascaris lumbricoides are of particular interest since they are newly formed during chromatin diminution. In the course of this process, which takes place in all presomatic cells of the early embryo of this parasitic nematode, developmentally regulated chromosomal breakage occurs within a specific, 2-3 kb long region, and is followed by the addition of many repeats of the telomeric sequence TTAGGC(2). Recently, we found a gene to be located within only 10 kb of such a de novo formed somatic telomere. Our partial sequence data indicate that it may encode a protein which contains a GTP-binding domain. The gene is expressed in oocytes and early embryonic stages but not in the intestine of adults, as shown by preliminary Northern blot experiments. Its expression pattern in cells before and after the elimination process is now analyzed in order to see whether the newly formed Ascaris somatic telomere exerts a position effect on this nearby located gene.

Literature Cited:

1) Gottschling et al., Cell 63 (1990), 751-762.

2) Muller et al., Cell 67 (1991), 815-822.