Egypt. J. Exp. Biol. (Zool.), 11(1): 37 – 42 (2015) © The Egyptian Society of Experimental Biology ISSN: 2090 - 0511 On Line ISSN: 2090 - 0503 http://www.egyseb.org RESEARCH ARTICLE Samar E. El-Kholy Wesam S. Meshrif TEMPORAL AND SPATIAL EXPRESSION PATTERNS OF SAPR IN THE FRUIT FLY DROSOPHILA MELANOGASTER (DIPTERA: DROSOPHILIDAE) ABSTRACT: Temporal and spatial expression patterns of saposin-related protein receptor (SapR) were determined in Drosophila melanogaster using GAL4/UAS system. The first step was to generate Drosophila line expressing SapR conjugated with GAL4. Then, the resulting line was crossed to UAS-GFP line. The GFP expression pattern in the first generation was monitored and analyzed in details. The results revealed that SapR was expressed in salivary glands, trachea, Malpighian tubule and CNS of larvae, compound eyes, oenocytes and the base of tactile sensillae of adults. GFP was also detected in intestine of both larval and adult stages. KEY WORDS: Drosophila , GAL4/UAS system, temporal and spatial expression patterns, immunohistochemistry, SapR CORRESPONDENCE: Samar E. El-Kholy Zoology Department, Faculty of Science, Tanta University, Tanta, Egypt E-mail: samar_elkholy@science.tanta.edu.eg Wesam S. Meshrif Zoology Department, Faculty of Science, Tanta University, Tanta, Egypt ARTICLE CODE: 04.01.15 INTRODUCTION: Saposins are activator heat-stable glycoproteins that promote the function of certain lysosomal hydrolases required for sphingolipid degradation. In humans, there are 4 saposins encoded by the prosaposin gene. Prosaposin is synthesized in the endoplasmic reticulum (ER), where it gets folded by UDP-glucose:glycoprotein glucosyl- transferase 1 (UGT1, also known as UGGT). This process promotes interaction with the ER-associated, lectin-like chaperones calreticulin and calnexin (Pearse et al ., 2010). Following successful folding, prosaposin advances through the secretory pathway into the Golgi apparatus, where it is being subjected to further glycosylation. There are two glycosylation sites on the saposin A domain, whereas, each of the other saposin domains has only one site (Morimoto et al ., 1989; O’Brien and Kishimoto, 1991). Therefore, prosaposin has a total of five oligosaccharide chains. The composition of the glycans on each domain is not homogeneous (Yamashita et al ., 1990; Ito et al ., 1993). The reason for the different glycosylation of each saposin domain is not known, but may be due to sequence variation around the glycosylation sites in each domain (Ito et al ., 1993). Mutations affecting any of these saposins lead to different neurodegenerative LSDs, as does the deficiency of prosaposin (a lack of all 4 saposins) due to lysosomal storage disorders (Harzer et al., 1989; Kretz et al., 1990; Rafi et al., 1990; Schnabel et al. , 1991; Zhang et al. , 1991). Dysfunctions in this gene have been causally implicated in several severe human diseases, most notably Gaucher disease, Tay-Sachs disease and metachromatic leukodystrophy (Morimoto et al ., 1990). To elucidate the molecular mechanisms involved in saposin functions, the expression pattern of saposin-related protein receptor should be studied in a simple model organism such as Drosophila melanogaster . The main attributes of Drosophila are: rapid generation time, ease of culturing and low maintenance costs. For these reasons, Drosophila represents the