Molecular & Biochemical Parasitology 144 (2005) 114–118 Short communication Differentially expressed sequences from a cestode parasite reveals conserved developmental genes in platyhelminthes  Cristiano V. Bizarro b , M´ ario H. Bengtson c , Felipe K. Ricachenevsky b , Arnaldo Zaha a,b , Mari C. Sogayar c , Henrique B. Ferreira a,b,∗ a Departamento de Biologia Molecular e Biotecnologia, Universidade Federal do Rio Grande do Sul, Caixa Postal 15005, Porto Alegre, 91501-970, RS, Brazil b Centro de Biotecnologia, Universidade Federal do Rio Grande do Sul, Caixa Postal 15005, Porto Alegre, 91501-970, RS, Brazil c Instituto de Qu´ ımica, Universidade de S˜ ao Paulo, S˜ ao Paulo, SP, Brazil Received 15 February 2005; accepted 1 July 2005 Available online 18 August 2005 Keywords: Mesocestoides corti; Eucestoda; Tetrathyridia; Gene expression; Cestode strobilation Cestodes are the etiological agents of major parasitic dis- eases both in humans and in domesticated animals [1,2]. Despite the considerable attention received by some disease- causing cestode species, such as Echinococcus spp., and Taenia spp., little is known about the molecular biology of the developmental transition from larval forms into adult par- asites. In the light of the recently proposed metazoan phylo- genies, platyhelminthes have a much more derived condition than previously thought, being placed within the lophotroco- zoan branch [3,4]. In this context, inclusion of data from the currently neglected cestode strobilation phenomena would offer a more complete picture on the extent of evolution- ary conservation of developmental mechanisms in bilaterian metazoans. As a first step toward this aim, we are using Mesocestoides corti as a model organism to study the development of the cestode strobilar stage. The research potential of M. corti has already been recognized [5–7]. We have improved culture conditions that induce larvae (tetrathyridia) to differentiate into strobilated worms [8] and are currently conducting a Abbreviations: RDA, representational difference analysis; RT-PCR, reverse transcription polymerase chain reaction  Note: Nucleotide sequence data reported in this paper are available in the GenBank TM , EMBL and DDBJ databases under the acession numbers CX863392–CX865174. ∗ Corresponding author. Tel.: +55 51 3316 60 70; fax: +55 51 3316 7309. E-mail address: henrique@cbiot.ufrgs.br (H.B. Ferreira). morphological and histological analysis of M. corti in vitro strobilation (unpublished observations). Here, we have adapted the cDNA representational dif- ference analysis technique [9], which enables the isola- tion of genes with an altered expression between tissues or cell samples, to isolate differentially expressed sequences between tetrathyridia and strobilated forms obtained from in vitro cultures. First strand cDNA was synthesized using the SMART TM PCR cDNA Synthesis kit (Clontech Inc.) with 200U of superscript II RNAse H - (Invitro- gen Life Technologies) and the PCR primer (5 ′ -AAGCA- GTGGTAACAACGCAGAGT-3 ′ ), which allowed us to start the libraries with only 1 g of total RNA. The amplified cDNAs were digested with Sau3AI and then subjected to cDNA RDA as previously described [10]. In the Forward library, cDNAs from segmented worms were used as tester and cDNAs from tetrathyridia as drivers. In the Reverse library, tetrathyridia cDNAs were used as tester and cDNAs from segmented worms as drivers. M. corti RDA-subtracted cDNA libraries were constructed after two rounds of subtrac- tion, using a driver:tester ratio of 100:1 and 800:1 in the first and second rounds, respectively. As a first approach to verify the efficiency of cDNA subtraction in both libraries, we used the second differen- tial products (DP2) from both the Forward and the Reverse cDNA fragment pools as probes against the SMART cDNA synthesis products of tetrathyridia and segmented worms (Fig. S1—Supplemental Material) The DP2 Reverse probe 0166-6851/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.molbiopara.2005.07.002