FASCIOLA-HEPATICA - STAGE-SPECIFIC EXPRESSION OF NOVEL GENE-SEQUENCESAS IDENTIFIED BY DIFFERENTIAL DISPLAY

Differences in gene expression between adult and immature Fasciola hep atica (liver fluke) parasites isolated from the mammalian host were in vestigated using the technique of differential display. For any given primer combination used to produce these displays there were, on avera ge, 22% apparently adult-specific and 14% apparently immature-specific cDNA products able to be identified, consistent with a high degree of differential gene expression between these two parasite developmental stages. Several cDNA fragments specific to immature parasite RNA were isolated and cloned. An abundant 400- to 500-bp RNA species was ident ified on a Northern blot by hybridization to the cloned DD2 cDNA fragm ent and was determined to be expressed at levels at least 10-fold high er in immature parasites relative to adult parasites, mRNA transcripts corresponding to the remaining cDNA fragments (DD14, DD16, DISP10, an d DISP2) were apparently expressed at levels below the sensitivity lim its of Northern analysis, although differential expression of these tr anscripts was confirmed by reverse transcriptase PCR (RT-PCR). The ide ntities or functional significance of each of the five differentially expressed cDNAs identified in this study is still unclear due to the l ack of any significant sequence similarity to the entries currently he ld within sequence databases. (C) 1998 Academic Press.