G protein-coupled receptors (GPCRs) are the largest and most versatile family of cell-surface receptors. They play critical roles in various cellular and physiological systems and have emerged as a leading group of therapeutic targets. Due to their structural and functional conservation across animals, much has been learned about GPCRs from studies in laboratory models. Given the extraordinary regenerative capacity of planarians and their emergence as a model for stem cell and germ cell biology, a comprehensive identification of planarian GPCRs enables functional studies on the role of this family of receptors in flatworm biology.
In this study, graduate student Amir Saberi and colleagues performed genome-enabled receptor mining to identify and categorize the complement of GPCR-encoding genes in the planarian Schmidtea mediterranea. They followed up their in silico analyses with two studies implicating planarian GPCRs in the regulation of reproductive function. First, they found the receptor component of a central neuropeptide Y signaling pathway and demonstrated its involvement in the systemic control of reproductive development. Next, they showed that a novel chemoreceptor family member (they named “ophis” after the mythological serpent guarding the Orphic Egg) is expressed in somatic cells of the planarian gonads and directs germ cell maturation via the niche. The authors predict that future studies on the hundreds of other planarian GPCRs identified in this work will not only facilitate understanding the conserved role of these receptors in various physiological pathways but also pave the way for identification of novel therapeutic targets in parasitic relatives of the planarian.
Image and description are adapted from Saberi A, Jamal A, Beets I, Schoofs L, Newmark PA (2016) GPCRs Direct Germline Development and Somatic Gonad Function in Planarians. PLoS Biol 14(5): e1002457. doi:10.1371/journal.pbio.1002457