Research note Molecular characterisation of the actin gene of the ®larial parasite Wuchereria bancrofti p J.K. Casinader Saverimuttu, E.H. Karunanayake *, N.V. Chandrasekharan, S.M.T. Jayasena Department of Biochemistry and Molecular Biology, Faculty of Medicine, University of Colombo, Colombo 8, Sri Lanka Received 20 September 1999; received in revised form 16 November 1999; accepted 16 November 1999 Abstract Wuchereria bancrofti is the major cause of lymphatic ®lariasis in humans. Although it is responsible for this immensely morbid and debilitating disease, very little is known of the basic molecular biology of this parasite, and there is a vast lack of knowledge on its gene organisation. In this study, the actin gene of W. bancrofti has been characterised by sequencing a clone isolated from a genomic DNA library of this parasite. The 5 0 ¯anking region had a potential TATA box and a putative mRNA initiation site. The gene had ®ve exons encoding 376 amino acids, and four introns ranging in size from 109 to 190 bp. The 3 0 ¯anking region had a potential polyadenylation signal with the sequence ATTAAA which is a common natural variant of the conventional sequence AATAAA. The gene was AT-rich, with a GC content of 37.2%. Southern blot analysis of W. bancrofti genomic DNA indicated that the gene is possibly found as a single copy. The actin amino acid sequence of W. bancrofti showed a high degree of homology to the actin of many organisms of dierent taxonomic groups, but the highest homology was observed with the free-living nematode Plectus acuminatus. This suggests that P. acuminatus may bear a close evolutionary relationship to W. bancrofti. # 2000 Australian Society for Parasitology Inc. Published by Elsevier Science. All rights reserved. Keywords: Actin; Filariasis; Wuchereria bancrofti An estimated 128 million people worldwide are cur- rently infected or diseased with lymphatic ®larial species, of which Wuchereria bancrofti is responsible for approximately 115 million [1]. Although W. ban- crofti is the major causative organism, very little is known about the molecular biology, biochemistry and immune mechanisms of this parasite. Research has been impeded by the paucity of parasite material as W. bancrofti cannot be maintained in laboratory ani- mals, unlike its closely related counterpart Brugia malayi [2]. Although ®lariasis has been identi®ed as one of six infectious diseases which are currently con- sidered to be ``eradicable'' or ``potentially eradicable'' [3], the lack of knowledge on the basic molecular biology and immune mechanisms of this parasite has retarded progress in designing eective therapeutic and preventive measures necessary for its eradication [4]. Actin is a ubiquitous protein, which is highly con- served in evolution among eukaryotes [5, 6]. Although, in a majority of organisms, it is present as a multi- gene family [7], there are several lower eukaryotic organisms in which it is found as a single copy ([8, 9]; Chandrasekharan NV. Cloning and characterization of repetitive deoxyribonucleic acid sequences from Diro®laria repens and the gene for actin from Setaria digitata. PhD thesis, University of Colombo, 1994). The products of the multi-gene family are represented by multiple isoforms of actin which fall into two main classes, namely, cytoplasmic actin and muscle International Journal for Parasitology 30 (2000) 119±124 0020-7519/00/$20.00 # 2000 Australian Society for Parasitology Inc. Published by Elsevier Science Ltd. All rights reserved. PII: S0020-7519(99)00176-9 www.elsevier.nl/locate/ijpara p Note: Nucleotide sequence data reported in this paper are avail- able in the GenBank 2 database under the accession number AF184961. * Corresponding author. Tel.: +94-1-697485; fax: +94-1-689181. E-mail address: erick@eureka.lk (E. H. Karunanayake).