Expansion of circulating hemocyte compartments by mutant Idh. (A) Hemocyte differentiation program in Drosophila. Prohemocytes are undifferentiated cells in Drosophila that are Wg+.⁶⁸  The lymph gland is the organ for hematopoiesis where maintenance and differentiation of prohemocytes occurs in postembryonic Drosophila. In larval circulation, prohemocytes can differentiate into crystal cells (C4+), into plasmatocytes (P1+), or under stress into lamellocytes (L1+). (B) Mutant Idh increases Wg+ hemocytes in circulation (red), compared with WT background. Most Wg+ hemocytes had relatively low hml expression, as reflected by low enhanced GFP (EGFP) signal, characteristic of prohemocytes (white arrows). Other Wg+ hemocytes strongly expressed hml, characteristic of crystal cells (gray arrow).^36,68  (C) Staining of crystal cells in larval circulation (C4+).⁵¹  Mutant Idh induces a slight increase in crystal cell composition. All C4+ cells were strongly hml+ (gray arrows). (D) Staining of lamellocytes in larval circulation (L1+). Mutant Idh induces an increase in lamellocyte composition. (E) The third instar larval lymph gland. Hemocyte precursor population or Dome+ cells are marked by GFP. Differentiated plasmatocytes of cortical zone are marked by P1,^50,73  shown in red. Mutant Idh expression under control of the lymph gland hemocyte dome-Gal4 driver is associated with a lack of differentiated cortical zone plasmatocytes (red) compared with controls. Genotypes for panels B-D: hml-Gal4, UAS-2xEGFP (control); hml-Gal4, UAS-2xEGFP; UAS-Idh-R195H (Idh mutant). Genotypes for panel E: dome-Gal4, UAS-EGFP/+ (control); dome-Gal4, UAS-EGFP/+; UAS-Idh-R195H/UAS-Idh-R195H (Idh mutant). Data are expressed as mean ± standard deviation for 3 independent groups of animals. Samples were visualized using a Nikon TE2000-E phase-contrast inverted epifluorescence microscope with a SensiCamQE camera, original magnification ×10, with MetaMorph, v6.2r6 software. Wg, Wingless.