Representation of an immune responsive gene family encoding fibrinogen-related proteins in the freshwater mollusc Biomphalaria glabrata, an intermediate host for Schistosoma mansoni.
Fibrinogen-related proteins (FREPs) are found in the hemolymph of the freshwater snail Biomphalaria glabrata, are up-regulated following exposure to digenetic trematode parasites, and bind to trematode larval surfaces, suggestive of a role in internal defense. Southern blot and degenerate-polymerase chain reaction (PCR) analyses were undertaken to better understand the diversity of the FREP-encoding gene family. Probes corresponding to the N-terminal IgSF domains of specific FREP gene subfamilies (FREPs 2, 3, 4, 7, 12 and 13) revealed between 1 to 8 loci per subfamily on Southern blots. Probes representing the relatively conserved C-terminal fibrinogen domain of FREPs bound many sequences in Southern blots of genomic DNA from B. glabrata, and from two related gastropod species, Biomphalaria pfeifferi and Helisoma trivolvis. Using degenerate-PCR, we obtained 42 unique fibrinogen-encoding sequences from 180 clones derived from a single individual of the M-line strain of B. glabrata, further supporting the notion of their abundant representation in the B. glabrata genome. The fibrinogen-encoding sequences of FREPs encoding one or two IgSF domains tended to separate into distinct clades, but bootstrap support for this separation was low. A novel category of fibrinogen-encoding sequence was also revealed. This study provides the approximate number of gene copies in several FREP subfamilies, confirms the existence of a diverse FREP gene family, reports additional unusual sequences encoding fibrinogen-like molecules, and provides further justification to explore the functional roles of FREPs in both B. glabrata and B. pfeifferi, both important intermediate hosts of the human pathogen, Schistosoma mansoni.
Department of Biology, University of New Mexico, Albuquerque, NM 87131, USA.
Si-Ming
SM
Zhang
Eric S
ES
Loker
D000595:Amino Acid Sequence; D000818:Animals; D001700:Biomphalaria / Q000235:genetics* / Q000276:immunology / Q000469:parasitology; D015152:Blotting, Northern; D015139:Blotting, Southern; D004247:DNA / Q000737:chemistry / Q000235:genetics / Q000302:isolation & purification; D020869:Gene Expression Profiling; D014644:Genetic Variation; D007136:Immunoglobulins / Q000235:genetics*; D008969:Molecular Sequence Data; D005810:Multigene Family / Q000235:genetics*; D010802:Phylogeny; D012550:Schistosoma mansoni / Q000254:growth & development; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity
D007136:Immunoglobulins; C445540:fibrinogen-related protein 7, Biomphalaria glabrata; D004247:DNA