776V Poster - 12. Physiology, metabolism and aging
Wednesday April 06, 4:00 PM - 7:00 PM

Authors:
Luis Sullivan ¹; Robert Scott ¹; Rosario Vicidomini ²; Mihaela Serpe ²; Benjamin White ¹

Affiliations:
1) Laboratory of Molecular Biology, National Institute of Mental Health, NIH, Bethesda, MD 20892, USA; 2) Section on Cellular Communication, National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892, USA

Keywords:
n. hormonal control; c. hormones

An evolutionarily ancient hormonal signaling system consisting of two glycoprotein hormone-like subunits, gpa2 and gpb5, and their leucine-rich repeat containing G-protein coupled receptor, called Lgr1 in Drosophila, are found throughout bilaterian genomes from flies to humans. The function of this conserved hormonal system remains obscure, but has been best characterized in the mosquito and the fruit fly, where Lgr1 is strongly expressed in the hindgut and has been implicated in maintenance of hydromineral balance. Using the Trojan exon method to create an Lgr1-specific Gal4 driver, we have confirmed robust expression of Lgr1 in both larval and adult hindgut, as well as in numerous other structures that support chloride transport such as the stellate cells of the Malpighian tubules and larval anal papillae. Interestingly, expression in the larval hindgut is limited to a ventral compartment, whereas in adult hindgut it is expressed throughout the hindgut epithelium. Using scRNAseq analysis combined with gene-specific Trojan Gal4 driver lines, we find that the larval epithelium is compartmentalized into ventral and dorsal cell-types conforming to those that express Delta and engrailed in the embryonic hindgut. Ventral cells express several genes implicated in ion transport and antidiuresis, while dorsal cells selectively express receptors for two known diuretic hormones, Dh44 and Leucokinin (Lk). These gene expression patterns suggest that half of the larval hindgut may promote water uptake from the hemolymph while the other may promote ion retrieval from the hindgut into the hemolymph. We speculate that this division of labor allows the larva to survive in its quasi-aqueous environment, permitting it to shed absorbed water, but retain ions. Consistent with this, hindgut compartmentalization is lost in the adult hindgut, together with Lk receptor expression, suggesting a purely antidiuretic function in the adult, which has a terrestrial lifestyle in which water retention is paramount.