Therefore, we first performed the genome-wide transgenic RNAi screen by the ubiquitous knockdown of genes with Act-Gal4 and then characterized the functions of selected genes in individual cells with cell-type-specific Gal4 (such as germ cells specific driver, Nanos (Nos)-Gal4 or CySC and early cyst-cell driver (c587-Gal4). The gene discussed is LGALS4; the disease is cyst.