title: Genetic basis for developmental homeostasis of germline stem cell niche number: a network of Tramtrack-Group nuclear BTB factors.
abstract: The potential to produce new cells during adult life depends on the number of stem cell niches and the capacity of stem cells to divide, and is therefore under the control of programs ensuring developmental homeostasis. However, it remains generally unknown how the number of stem cell niches is controlled. In the insect ovary, each germline stem cell (GSC) niche is embedded in a functional unit called an ovariole. The number of ovarioles, and thus the number of GSC niches, varies widely among species. In Drosophila, morphogenesis of ovarioles starts in larvae with the formation of terminal filaments (TFs), each made of 8-10 cells that pile up and sort in stacks. TFs constitute organizers of individual germline stem cell niches during larval and early pupal development. In the Drosophila melanogaster subgroup, the number of ovarioles varies interspecifically from 8 to 20. Here we show that pipsqueak, Trithorax-like, batman and the bric-à-brac (bab) locus, all encoding nuclear BTB/POZ factors of the Tramtrack Group, are involved in limiting the number of ovarioles in D. melanogaster. At least two different processes are differentially perturbed by reducing the function of these genes. We found that when the bab dose is reduced, sorting of TF cells into TFs was affected such that each TF contains fewer cells and more TFs are formed. In contrast, psq mutants exhibited a greater number of TF cells per ovary, with a normal number of cells per TF, thereby leading to formation of more TFs per ovary than in the wild type. Our results indicate that two parallel genetic pathways under the control of a network of nuclear BTB factors are combined in order to negatively control the number of germline stem cell niches.
authors.affiliation: Centre de Génétique Moléculaire, Unité Propre de Recherche 3404 du Centre National de la Recherche Scientifique, Gif-sur-Yvette, France.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Bartoletti
authors.forename: Thomas
authors.initials: T
authors.lastname: Rubin
authors.forename: Fabienne
authors.initials: F
authors.lastname: Chalvet
authors.forename: Sophie
authors.initials: S
authors.lastname: Netter
authors.forename: Nicolas
authors.initials: N
authors.lastname: Dos Santos
authors.forename: Emilie
authors.initials: E
authors.lastname: Poisot
authors.forename: Mélanie
authors.initials: M
authors.lastname: Paces-Fessy
authors.forename: Delphine
authors.initials: D
authors.lastname: Cumenal
authors.forename: Frédérique
authors.initials: F
authors.lastname: Peronnet
authors.forename: Anne-Marie
authors.initials: AM
authors.lastname: Pret
authors.forename: Laurent
authors.initials: L
authors.lastname: Théodore
mesh_terms: D000818:Animals; D004268:DNA-Binding Proteins / Q000235:genetics / Q000378:metabolism; D029721:Drosophila Proteins / Q000235:genetics / Q000378:metabolism; D004331:Drosophila melanogaster / Q000235:genetics / Q000254:growth & development; D005260:Female; D018628:Gene Dosage / Q000235:genetics; D018507:Gene Expression Regulation, Developmental; D005854:Germ Cells / Q000166:cytology / Q000254:growth & development; D006706:Homeostasis / Q000235:genetics / Q000502:physiology; D009024:Morphogenesis; D009687:Nuclear Proteins / Q000235:genetics / Q000378:metabolism; D010053:Ovary / Q000166:cytology / Q000254:growth & development; D055153:Stem Cell Niche / Q000235:genetics* / Q000502:physiology; D014157:Transcription Factors / Q000235:genetics / Q000378:metabolism
chemical_list: C093752:Bric-a-brac protein 1, Drosophila; D004268:DNA-Binding Proteins; D029721:Drosophila Proteins; D009687:Nuclear Proteins; D014157:Transcription Factors; C063460:Trl protein, Drosophila; C471547:lolal protein, Drosophila; C097735:psq protein, Drosophila