Molecular markers to characterize the hermaphroditic reproductive system of the planarian Schmidtea mediterranea

To identify genes expressed differentially between these strains, we performed microarray analyses and identified >800 genes that were upregulated in the sexual planarian. From these, we characterized 24 genes by fluorescent in situ hybridization (FISH), revealing their expression in male germ cells or accessory reproductive organs. To identify additional markers of the planarian reproductive system, we also used immuno- and fluorescent lectin staining, identifying several antibodies and lectins that labeled structures associated with reproductive organs.Collectively, these cell-type specific markers will enable future efforts to characterize genes that are important for reproductive development in the planarian.While the planarian has re-emerged as an animal model for studying regeneration and stem cell biology [1-5], recent studies of Schmidtea mediterranea have also contributed to understanding germ cell biology and sexual development [6-9]. Two modes of specifying germ cells have evolved among animals, involving either localized determinants or inductive signaling [10-12]. Sexual planarians have a reproductive system that can be regenerated de novo from stem cells after amputation [9,13], suggesting that they specify their germline inductively like mammals and many basal metazoans [10,14,15].S. mediterranea is a powerful model for understanding germ cell development due, in part, to the existence of distinct sexual and asexual strains that allow identification and characterization of genes involved in the different modes of reproduction. The reproductive system of the hermaphrodite consists of the male and female gonads, as well as accessory reproductive organs [7]. Numerous testes are distributed dorsolaterally along the animal, and a pair of ovaries is situated more ventrally at the posterior region of the cephalic ganglia (brain). Ciliated oviducts and sperm ducts running along the nerve cords lead to the copulatory apparatus, comprised of the gonopore (gn),