Chitin synthase in the filarial parasite, Brugia malayi

Fragments of putative chitin synthase (chs) genes from two filarial species (Brugia malayi and Dirofilaria immitis) were amplified by PCR using degene rate primers. The full genomic and cDNA sequences were obtained for the B. malayi chs gene (Bm-chs-1); the predicted amino acid sequence is highly sim ilar, over a large region, to two CHS sequences of the nematode Caenorhabdi tis elegans and also to two insect CHS sequences. Bm-chs-1 is abundantly tr anscribed in B. malayi adult females, independent of their fertilization st atus, but is also expressed in males and microfilariae. Oocytes and early e mbryos contain large amounts of Bm-chs-1 transcript by in situ hybridizatio n, but later stage embryos within the maternal uterus show little or no Bm- chs-1 transcript. No specific hybridization could be demonstrated in matern al somatic tissues. Polyclonal antibodies were raised against a peptide exp ressed from a recombinant cDNA fragment of Bm-chs-1; immunostaining detecte d CHS protein in oocytes and early to midstage embryos. These studies chara cterize a gene that is likely to be essential to oogenesis and embryonic de velopment in a parasitic nematode. Because chitin synthesis and eggshell fo rmation begin after fertilization, the presence of CHS protein in early ooc ytes suggests that the enzyme must be activated as a result of fertilizatio n. These studies also demonstrate that chitin synthesis may not be restrict ed to eggshell formation in nematodes, as the Bm-chs-1 gene is transcribed in life cycle stages other than adult females. (C) 2000 Elsevier Science B. V. All rights reserved.