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Open Access Research article

Developmentally regulated expression, alternative splicing and distinct sub-groupings in members of the Schistosoma mansoni venom allergen-like (SmVAL) gene family

Iain W Chalmers1*, Andrew J McArdle1, Richard MR Coulson2, Marissa A Wagner1, Ralf Schmid3, Hirohisa Hirai4 and Karl F Hoffmann15*

Author Affiliations

1 Department of Pathology, University of Cambridge, Tennis Court Road, Cambridge, CB2 1QP, UK

2 Microarray Group, The European Bioinformatics Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge CB10 1SD, UK

3 Department of Biochemistry, University of Leicester, Lancaster Road, Leicester LE1 9HN, UK

4 Primate Research Institute, Kyoto University, Inuyama, Aichi 484-8506, Japan

5 Institute of Biological Sciences, The University of Wales, Aberystwyth, Ceredigion, SY23 3DA, UK

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BMC Genomics 2008, 9:89  doi:10.1186/1471-2164-9-89

Published: 23 February 2008

Abstract

Background

The

    S
perm-
    c
oating
    p
rotein/
    T
px-1/
    A
g5/
    P
R-1/
    S
c7 (SCP/TAPS) domain is found across phyla and is a major structural feature of insect allergens, mammalian sperm proteins and parasitic nematode secreted molecules. Proteins containing this domain are implicated in diverse biological activities and may be important for chronic host/parasite interactions.

Results

We report the first description of an SCP/TAPS gene family (

    S
chistosoma
    m
ansoni
    v
enom
    a
llergen-
    l
ike (SmVALs)) in the medically important Platyhelminthes (class Trematoda) and describe individual members' phylogenetic relationships, genomic organization and life cycle expression profiles. Twenty-eight SmVALs with complete SCP/TAPS domains were identified and comparison of their predicted protein features and gene structures indicated the presence of two distinct sub-families (group 1 & group 2). Phylogenetic analysis demonstrated that this group 1/group 2 split is zoologically widespread as it exists across the metazoan sub-kingdom. Chromosomal localisation and PCR analysis, coupled to inspection of the current S. mansoni genomic assembly, revealed that many of the SmVAL genes are spatially linked throughout the genome. Quantitative lifecycle expression profiling demonstrated distinct SmVAL expression patterns, including transcripts specifically associated with lifestages involved in definitive host invasion, transcripts restricted to lifestages involved in the invasion of the intermediate host and transcripts ubiquitously expressed. Analysis of SmVAL6 transcript diversity demonstrated statistically significant, developmentally regulated, alternative splicing.

Conclusion

Our results highlight the existence of two distinct SCP/TAPS protein types within the Platyhelminthes and across taxa. The extensive lifecycle expression analysis indicates several SmVAL transcripts are upregulated in infective stages of the parasite, suggesting that these particular protein products may be linked to the establishment of chronic host/parasite interactions.