Exploring the transcriptome of the malaria sporozoite stage

doi:10.1073/pnas.171185198

Exploring the transcriptome of the malaria sporozoite stage

^*Michael Heidelberger Division, Department of Pathology, Kaplan Cancer Center, New York University School of Medicine, New York, NY 10016; ^‡The Institute for Genomic Research, 9712 Medical Center Drive, Rockville, MD 20850; ^§Research Computing Resource, New York University Medical Center, New York, NY 10016; ^¶Medical Entomology Section, Laboratory of Parasitic Diseases, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892-0425; ^‖Department of Biological Sciences, University of Notre Dame, Notre Dame, IN 46556; ^**Malaria Program, Naval Medical Research Center, Silver Spring, MD 20910; and ^‡‡Celera Genomics, 45 West Gude Drive, Rockville, MD 20850

Edited by Louis H. Miller, National Institutes of Health, Bethesda, MD, and approved June 19, 2001 (received for review April 13, 2001)

Abstract

Most studies of gene expression in Plasmodium have been concerned with asexual and/or sexual erythrocytic stages. Identification and cloning of genes expressed in the preerythrocytic stages lag far behind. We have constructed a high quality cDNA library of the Plasmodium sporozoite stage by using the rodent malaria parasite P. yoelii, an important model for malaria vaccine development. The technical obstacles associated with limited amounts of RNA material were overcome by PCR-amplifying the transcriptome before cloning. Contamination with mosquito RNA was negligible. Generation of 1,972 expressed sequence tags (EST) resulted in a total of 1,547 unique sequences, allowing insight into sporozoite gene expression. The circumsporozoite protein (CS) and the sporozoite surface protein 2 (SSP2) are well represented in the data set. A blastx search with all tags of the nonredundant protein database gave only 161 unique significant matches (P(N) ≤ 10⁻⁴), whereas 1,386 of the unique sequences represented novel sporozoite-expressed genes. We identified ESTs for three proteins that may be involved in host cell invasion and documented their expression in sporozoites. These data should facilitate our understanding of the preerythrocytic Plasmodium life cycle stages and the development of preerythrocytic vaccines.

Footnotes

↵ † To whom reprint requests should be addressed. E-mail: kappes01{at}popmail.med.nyu.edu.
This paper was submitted directly (Track II) to the PNAS office.
Data deposition: The EST sequences reported in this paper have been deposited in the GenBank dbEST database (accession nos. BG601070–BG603042). Complete gene sequences have been deposited in the GenBank database (accession nos. AF390551–AF390553).
Abbreviations:

CS,

circumsporozoite protein;

SSP2,

sporozoite surface protein 2;

TRAP,

thrombospondin-related anonymous protein;

EST,

expressed sequence tag;

EEF exo-erythrocytic form,

MSP-1, merozoite surface protein-1;

MyoA,

myosin A;

TSR,

thrombospondin type 1 repeat;

SPATR,

secreted protein with altered thrombospondin repeat