Drosophila germline stem cells (GSCs) provide accessible model systems to study stem cell behavior, including the roles of stem cell competition, niche maintenance, and niche occupancy.
A screen of aged Drosophila males has shown development of spontaneous tumors in the testis and gut; the incidence of these tumors increases with age. In the testis, loss of activity of the Drosophila gene Madm (orthologous to the human NRBP1 and NRBP2 genes) or constitutive activity of Dmel\hop (orthologous to human JAK genes) have been found to promote GSC tumor formation.
In ovaries, loss-of-function mutations of bam, which encodes a translation repressor, have been used to produce tumor-like stem cells. The role of autophagy has been studied in this system. Reduced function of Sxl or other genes involved in RNA processing of bam gives rise to the GSC tumor phenotype. Expression of bam in the cystoblast requires cell–cell communications elicited by the bone morphogenetic proteins (BMPs) from the somatic cells in the germarium; disruption of BMP signaling (FBgg00010860) results in ovarian germline tumor formation.
Drosophila adult stem cells have been found to be resistant to radiation- or chemical-induced apoptosis, thus providing a means to investigate mechanisms of resistance of stem cell tumors to various anticancer therapies. In a study using ovary germline stem cells, irradiation results in activation of a specific receptor tyrosine kinase (Dmel\Tie), which then results in upregulation of the microRNA mir-ban and the repression of apoptosis.
[updated Feb. 2022 by FlyBase; FBrf0222196]
Moderate- to high-scoring ortholog of human NRBP1 and NRBP2 (1 Drosophila to 2 human). Dmel\Madm shares 49-50% identity and 64-66% similarity with the human genes.
Moderate-scoring ortholog of human JAK1 and JAK2; low-to-moderate-scoring ortholog of human TYK2 and JAK3 (1 Drosophila to 4 human); additional lower scoring orthologs exist in humans. Dmel\hop shares 24% identity and 39-41% similarity with JAK1 and JAK2.
No gene orthologous to Dmel\bam has been identified in human.
5' seed sequence homologous to that of human MIR450B-3p (FBrf0242402).