Component of nuclear coiled bodies, also known as Cajal bodies or CBs, which are involved in the modification and assembly of nucleoplasmic snRNPs (PubMed:19846657). Required for Cajal body formation (PubMed:19158395, PubMed:19846657). Detected in the CBs of cells from a number of different larval and adult tissues. In stage 8-9 oocytes detected only in the single CB of the germinal vesicle. Also detected in the histone locus bodies (HLBs) of late stage nurse cells, and low expression in the HLBs of large polytene or polyploid nuclei within the salivary glands, fat bodies and Malpighian tubule cells. In germline stem cells and cystocytes (where CBs are not evident), expressed throughout the nucleoplasm. During interphase localized to foci scattered throughout the nucleoplasm. During metaphase (in meiotic and mitotic cells) these foci localize to the centromere regions on the metaphase plate. At anaphase, no longer detected as foci and is instead detected throughout the spindle. When the nucleus reforms, it localizes to multiple nuclear foci and throughout the nucleoplasm. Very low expression and not detected at the protein level. Relatively higher levels of expression in the cytoplasm of follicle cells that have no expression of Isoform D in their CBs. In egg chambers expressed in the follicle cells, nurse cells and oocyte. Expressed in the larval brain, salivary glands, fat bodies and in the somatic hub cells at the tip of the testis. Expressed in the spermatogonia and spermatocytes, and in the adult ejaculatory duct (at protein level). Expressed in the adult Malpighian tubules. Viable and fertile with no obvious phenotype (PubMed:19158395). Loss of Cajal bodies (CBs) in the nurse cells, spermatocytes, ejaculatory ducts (PubMed:19158395). Loss of CBs in the adult Malpighian tubule cells (PubMed:19158395, PubMed:19846657). Histone locus bodies (HLBs) in the same cell types are present and not affected (PubMed:19158395). In stage 8-9 oocytes, the single CB present in the germinal vesicle is unaffected (PubMed:19158395). Belongs to the coilin family.