The large Maf factor Traffic Jam controls gonad morphogenesis in Drosophila

Abstract

Interactions between somatic and germline cells are critical for the normal development of egg and sperm. Here we show that the gene traffic jam (tj) produces a soma-specific factor that controls gonad morphogenesis and is required for female and male fertility. tj encodes the only large Maf factor in Drosophila melanogaster, an orthologue of the atypical basic Leu zipper transcription factors c-Maf and MafB/Kreisler in vertebrates. Expression of tj occurs in somatic gonadal cells that are in direct contact with germline cells throughout development. In tj mutant gonads, somatic cells fail to inter-mingle and properly envelop germline cells, causing an early block in germ cell differentiation. In addition, tj mutant somatic cells show an increase in the level of expression for several adhesion molecules. We propose that tj is a critical modulator of the adhesive properties of somatic cells, facilitating germline-soma interactions that are essential for germ cell differentiation.

Retinoic acid induces Sertoli cell paracrine signals for spermatogonia differentiation but cell autonomously drives spermatocyte meiosis

“…This motif is unlikely to recruit RARA/RXR heterodimers because RARA acts in SC through a noncanonical pathway, independently of RXR (9). Control of Mafb expression by RA-activated RARA in SC seems particularly relevant to spermatogonia differentiation because the MAFB transcription factor often instructs cell lineage commitment (27) and because its Drosophila ortholog Traffic Jam is required, in somatic cells of the fly gonad for GC differentiation (28). The involvement of MAFB in the RA-dependent differentiation of spermatogonia is, however, not testable through a genetic approach in the mouse as null mutants are not viable (29,30), conditional alleles of Mafb are not available, and mice bearing the chemically induced Kr mutation (31) are deficient in MAFB only in the hindbrain region (32).…”

discs large regulates somatic cyst cell survival and expansion in Drosophila testis

“…As mutations in tj encoding the Drosophila Maf transcription factor primarily prevent somatic cells to intermingle between germ cells [26], the occurrence in dlg testes of numerous Tj-positive cells mixed with germ cells indicates that dlg inactivation has no effect on this process. The eya gene encodes a transcriptional activator, which in combination with Sine oculis (So), forms dlg function in formation of Drosophila testis 1146 npg a transcription complex required for early eye specification [34].…”

“…In the dlg mutant testes, the SSCs and early SCCs survived as indicated by the positive Tj staining, whereas the late SCCs died, as revealed by the positive caspase-3 staining and the absence of Eya-staining. The critical period of dlg function takes place between the time of tj inactivation in somatic cells surrounding SCs [26] and that of eya activation in somatic cells wrapping spermatocyte cysts [27]. The shift between tj and eya expression coincides with a marked change in Dlg distribution.…”

“…As gonad development requires a coordinated somagermline interaction ensuing renewal and differentiation of germline and SSCs, we first studied the distribution of known nuclear markers of somatic cell differentiation, including Traffic-jam (Tj) [26] and Eyes absent (Eya) [27]. In wt testes, Tj is produced in early SCCs and in elongated SCCs wrapping 2-, 4-, 8-cell cysts ( Figure 1B), whereas Eya is present in SCCs enclosing larger cysts ( Figure 2A) [28].…”

Somatic gonadal cells: The supporting cast for the germline

“…Sex determination, GSC niche formation (Sheng et al, 2009b;Wawersik et al, 2005) talin/rhea Actin binding SGPs Hub anchoring (Brown et al, 2002) three rows (thr) Unknown SGP cluster adhesion (Weyers et al, 2011) traffic jam (tj) MAF family transcription factor SGPs Ensheathment (Kawashima et al, 2003;Li et al, 2003) transformer (tra) Transcription factor Female SGPs Sex determination (Marsh and Wieschaus, 1978) transformer (tra2) Transcription factor SGPs Sex determination (Schupbach, 1982) unpaired (upd)…”