May be involved in JAK/STAT signaling. Isoform D is required for the proper arrangement of niche cells and is autonomously required for proper niche cell size, isoform C negatively regulates the adhesive properties of the niche. The germline stem cell (GSC) niche in ovaries is made up of two somatic cell types: 8-9 cells in a single-filed array make up the terminal filament (TF), and a tight cluster of 5 or 6 cap cells (CpC). Regulating the size and adhesive properties of the CpCs is an important component of the mechanism that controls their capacity to support stem cells, isoform C and isoform D are important factors in mediating this regulation. In contrast, isoform C acts as a positive regulator of cell adhesion in follicle cell epithelium. Distribution varies depending on cell type and developmental stage. At late embryogenesis expression is enriched in the nuclei of follicle cells and germline cells and at the nurse cell membranes. In pupal ovaries, expression is seen in niche cells at the cell periphery. In adult ovaries expression is in the nuclei and cytoplasm of the CpCs and TF cells of the niche. Expressed in the GSCs and in dividing cysts. Expression is reduced in the germline as individual egg chambers are formed. Isoform C is expressed in all somatic and germline cells of the ovary. Isoform D is expressed in the GSC niche. Lack of isoform D causes an increase in niche cell size and abnormal terminal filament organization. This in turn increases niche capacity by increasing the potential contact surface between CpCs and stem cells. Lack of isoform C causes defects in the organization of the follicle cell layer and defects in dorsal appendage morphogenesis. Belongs to the RANBP9/10 family. Intron retention. Intron retention.