Rus Florentina

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University of Szeged

Volume 48(1-4):77, 2004Acta Biologica Szegediensishttp://www.sci.u-szeged.hu/ABSDISSERTATION SUMMARYInstitute of Genetics, Biological Research Center, Hungarian Academy of Sciences, Szeged, HungaryExpression and a novel function of fi lamin-240 in lamellocyte development in DrosophilaFlorentina RusSupervisor: István AndóE-mail: inarus2001@yahoo.com77Drosophila has a very effective innate immune system with striking similarities to innate immunity in vertebrates. Cel-lular immune defense in Drosophila is mediated by three different classes of hemocytes: the plasmatocytes, the lamel-locytes and the crystal cells. Lamellocytes represent a unique population of hemocytes, both in terms of morphology and function. The lamellocytes are large, flat, adherent cells, involved in encapsulation and neutralization of intruders or of abnormally developed tissues, too large to be engulfed by plasmatocytes. These cells are nonphagocytic and their cytoplasmic constituents are relatively sparse. Very few lamellocytes are observed in wild-type Oregon-R larvae. Parasitization by the Hymenopteran wasp, Leptopilinia bou-lardi, initiates the rapid differentiation of lamellocytes, which subsequently adhere to and surround the egg capsule. This capsule subsequently melanizes, locally generating cytotoxic compounds and creating a barrier. Bacterial challenge does not induce lamellocyte differentiation, but this can be induced artifi cially by objects placed in the larval haemocel that are too large to be phagocytated (Evans et al. 2003). They develop from small (8-10 μm), round stem cells and become large (40-50 μm) fl attened cells capable of binding and encapsulating large foreign particles. The development of lamellocytes from stem cells to effector cells involves two major steps: fi rst, the differentiation of small stem cells to the immediate precur-sors of the fully differentiated large cells. This step requires cell division and is terminated by the expression of the L1 antigen. Second, the terminal differentiation of the immediate precursors to the large fl attened cells. This process does not require cell division but is characterized by the expression of L4 and L6 antigens and the most characteristic morphological changes. In this work we studied the role of a lamellocyte antigen in lamellocyte development, which turned out to be a unique, actin-binding component of the cytoskeleton in lamellocytes.By screening Drosophila cDNA expression libraries with an antibody reacting preferentially with lamellocytes, positive clones were obtained and 5 DNA fragments were isolated. The analysis of the generated sequences showed that these correspond to 8 exons of cheerio gene, which encodes fi lamin, a protein that organizes fi lamentous actin in networks and stress fi bers and also anchors various transmembrane proteins to the active cytoskeleton. All of our isolated cDNA sequences contain a so-called filamin-folding domain, a consensus motif profi le, generated from the 25 existing fi lamin domain sequences. Filamin exists in two isoforms in Drosophila, as a result of alternative splicing. The longest form, fi lamin-240, contains an N-terminal actin-binding domain and so far it has been known to be specifi c for the ring canals in the ovaries. Our studies revealed that this isoform is expressed in lamel-locytes too, and is possibly involved in the organisation in the actin-network during the terminal stage of lamellocyte devel-opment. To get further insight into the role of fi lamin-240 in lamellocyte development, we studied the possible effect of the lack of this protein in the cher1/cher1 loss of- function type mutant stock. The results show that the lack of the isoform results in abnormal number and proportion of developing lamellocytes, suggesting that fi lamin-240 is involved in the regulation of lamellocyte differentiation, perhaps as an orga-nizer of the rearrangement of the cytoskeleton.References Andó I, Laurinyecz B, Nagy I, Márkus R, Rus F, Váczi B, Zsámboki J, Fehér L, Gateff E, Hultmark D, Kurucz É (2003) Our archaic heritage: the innate immunity. The cellular immunity of Drosophila. Magy Im-munol 2:39-45.Evans CJ, Hartenstein V, Banerjee U (2003) Thicker than blood. Conserved mechanisms in Drosophila and vertebrate hematopoiesis. Dev Cell 5:673-690.

Expression and a novel function of filamin-240 in lamellocyte development in Drosophila

http://acta.bibl.u-szeged.hu/22649/1/4877.pdf

Expression and a novel function of filamin-240 in lamellocyte development in Drosophila

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