Characterization of a Lamellocyte Transcriptional Enhancer Located within the misshapen Gene of Drosophila melanogaster

Abstract

Drosophila has emerged as an excellent model system in which to study cellular and genetic aspects of hematopoiesis. Under normal developmental conditions and in wild-type genetic backgrounds, Drosophila possesses two types of blood cells, crystal cells and plasmatocytes. Upon infestation by a parasitic wasp or in certain altered genetic backgrounds, a third hemocyte class called the lamellocyte becomes apparent. Herein we describe the characterization of a novel transcriptional regulatory module, a lamellocyte-active enhancer of the misshapen gene. This transcriptional control sequence appears to be inactive in all cell types of the wild-type larva, including crystal cells and plasmatocytes. However, in lamellocytes induced by wasp infestation or by particular genetic conditions, the enhancer is activated and it directs reporter GFP or DsRed expression exclusively in lamellocytes. The lamellocyte control region was delimited to a 140-bp intronic sequence that contains an essential DNA recognition element for the AP-1 transcription factor. Additionally, mutation of the kayak gene encoding the dFos subunit of AP-1 led to a strong suppression of lamellocyte production in tumorous larvae. As misshapen encodes a protein kinase within the Jun N-terminal kinase signaling pathway that functions to form an active AP-1 complex, the lamellocyte-active enhancer likely serves as a transcriptional target within a genetic auto-regulatory circuit that promotes the production of lamellocytes in immune-challenged or genetically- compromised animals.

Serpent, Suppressor of Hairless and U-shaped are crucial regulators of hedgehog niche expression and prohemocyte maintenance during Drosophila larval hematopoiesis

“…Transgenic lines harboring hh DNA-GFP reporter fusions were generated as described previously (Rubin and Spradling, 1982;Tokusumi et al, 2009b). Briefly, we amplified hh genomic DNA fragments from a BAC clone using PrimeStar DNA polymerase (Takara-Millus), followed by DNA subcloning into the P-element vector pH Stinger (Barolo et al, 2000).…”

“…Crystal cells make up the minor class, being involved in wound healing and large foreign body encapsulation. Together, they number ~700 cells by the end of embryogenesis and persist into larval stages, when they undergo multiple rounds of mitosis, generating 6000-8000 hemocytes by the end of larval development Tokusumi et al, 2009b). A subpopulation of these cells will take up residence as sessile hemocytes in subepidermal locations within larvae, where they can be rapidly converted into lamellocytes, a third hemocyte type that is produced in response to wasp infestation (Markus et al, 2009;Honti et al, 2010).…”

“…By contrast, the third lymph gland domain -the cortical zone -solely contains differentiating and mature hemocytes, such as plasmatocytes and crystal cells. Upon wasp parasitization, or in certain altered genetic backgrounds, lamellocytes will also appear in the cortical zone as a third type of differentiated hemocyte (Lanot et al, 2001;Sorrentino et al, 2002;Sorrentino et al, 2007;Gao et al, 2009;Markus et al, 2009;Tokusumi et al, 2009b).…”

Germ line differentiation factor Bag of Marbles is a regulator of hematopoietic progenitor maintenance during Drosophila hematopoiesis

“…, UAS-mir-7 and mir-7 enhancer-GFP (Li and Carthew, 2005;Li, X. et al, 2009) (R. Carthew); and eaterGal4, hhF4f-GFP and MSNF9mo-mCherry (Tokusumi et al, 2009a;Tokusumi et al, 2009b;Tokusumi et al, 2010).…”

The Avoided Target: The Ceratitis capitata Cellular Encapsulation Response

“…Lamellocytes are large, flat adhesive cells that will leave the lymph gland (thus causing the lymph gland to disperse [27]), enter the hemocoel, and adhere to the wasp egg [26]. A sufficient number of lamellocytes will form a multilayered cellular capsule around the wasp egg [28] (this response is evocative of the behavior of mammalian eosinophils). Crystal cells can also be part of the capsule, and will rupture and release proPO which will then be proteolytically activated, and catalyze the formation of melanin.…”