During the early development of the parasitic nematode, Ascaris suum , larva are bathed in perivitelline fluid (PF) within the eggshell. However, little is known about the secretion of the PF. A cDNA coding for one of the major PF proteins (As-
p18) was cloned, sequenced and functionally expressed. Analysis of the predicted amino acid sequence of As-
p18 indicated that As-
p18 exhibited most identity to a family of putative C. elegans fatty acid binding proteins arranged in tandem on X chromosome. A similar gene cluster was also identified in C.briggsae although it also contained two psuedogenes. The potential C. elegans As-
p18 homologues (LBP-1, LBP-2 and LBP-3) contained putative secretory peptides and predicted structural characteristics, in common with As-
p18 and in contrast to all other LBPs identified. To characterize the synthesis and presumably the secretion of the LBPs, a vector was constructed fusing the individual promoter regions of
lbp-1,
lbp-2 and
lbp-3 to sequence coding for a nuclear localization signal and GFP. These individual GFP fusion constructs and a plasmid marker pRF4(
rol-6 ) were cotransfected into the gonads of hermaphroditic C. elegans . The expression of the
lbp-1 fusion construct was localized to nuclei of
hyp-7 cells during early embryogenesis, i.e., the comma and three -fold stages of early C. elegans development. This pattern of
lbp-1 expression is completely consistent with the results obtained from Northern and immunoblots of As-
p18 in A. suum and suggest that As-
p18 is secreted by hypodermal cells into the perivitelline fluid prior to the formation of the cuticle. In contrast,
lbp-2 and
lbp-3 exhibited different expression patterns, i.e.,
lbp-2 was expressed in muscle, later in development and
lbp-3 exhibited a expression pattern which appeared to be a composite of
lbp-1 and
lbp-2 . These results suggested that As-
p18 might also be secreted from somatic muscle latter in development and this hypothesis was confirmed by 2D gel analysis of perientiric fluid isolated from adult A. suum . These studies are continuing with the intention of identifying the promoter elements responsible for the stage and tissue-specific expression of the lbps .