Table 1.

Localization and function of genes that are expressed in GSCs or their niche

Function*
Expression
PathwayFemalesMalesGene/proteinFemalesMales
TGF-β signaling pathway GSC maintenance and rate of division Cyst development (limiting mitosis/promoting meiosis) or gonialblast differentiation dpp/gbb dpp- Cap, IS cells, by ISH (Xie and Spradling, 2000). Not detected by enhancer trap(Forbes et al., 1996a). gbb- IS or early follicle cells or both, by RT-PCR(Song et al., 2004). dpp- Not detected by enhancer trap(Matunis et al., 1997). No ISH data. gbb-SSCs, by ISH(Shivdasani and Ingham, 2003). Hub cells and SSCs/somatic cyst cells, by RT-PCR(Kawase et al., 2004). 
 Possible later role in cyst development Possible role in GSC survival/maintenance tkv, med, mad, pnt GSCs, inferred by genetic requirement for maintenance(Xie and Spradling, 1998). GSCs, inferred by genetic requirement for maintenance(Kawase et al., 2004). 
   Phosphorylated Mad Strong expression in GSCs. Weaker in dividing cysts, by Ab staining(Gilboa et al., 2003; Kai and Spradling, 2003). GSCs, by Ab staining (Kawase et al.,2004). 
   pnt. shn GSCs, inferred by genetic requirement for maintenance(Xie and Spradling, 1998; Xie and Spradling, 2000). Cyst cells, inferred by genetic requirement for germ line cyst differentiation(Matunis et al., 1997). 
JAK/STAT signaling pathway FC differentiation, BC migration GSC, and possibly SSC maintenance upd Polar cells, possibly cap cells, by ISH(Silver and Montell, 2001). Hub cells, by ISH (Kiger et al.,2001; Tulina and Matunis,2001). 
 Possible minor or indirect role in GSC maintenance  stat92E Cap cells, by ISH (Silver and Montell,2001). GSCs, inferred by genetic requirement for maintenance(Kiger et al., 2001; Tulina and Matunis, 2001). 
Piwi GSC maintenance, rate of division GSC maintenance piwi TF, by ISH (Cox et al., 1998). Early germ cells, at anterior tip, by ISH(Schulz et al., 2002). 
(PPD family protein)   Piwi TF, Cap, IS, GSCs, dividing cysts, by Ab staining of a tagged piwitransgene (Cox et al., 2000).  
Yb (novel) GSC maintenance, cyst differentiation, follicle cell patterning Males fertile Yb TF, by ISH (King and Lin,1999). Expressed in males, by western blot (King and Lin, 1999). 
Hh signaling pathway Major function — SSC maintenance No function in GSC maintenance Hh TF, Cap cells, by Ab staining (Forbes et al., 1996b). Hub cells at third instar — enhancer trap(Forbes et al., 1996b). 
    TF, Cap, IS cells, by enhancer trap(Forbes et al., 1996b).  
   Ptc Somatic and germ line cells throughout the ovary, by Ab staining(Forbes et al., 1996a). Cyst cells — ptcGAL4 (Schulz et al.,2002). 
Pum, Nos (transcriptional repression) GSC maintenance Not described Pum High levels in GSCs, lower in cystoblasts, by Ab staining(Forbes and Lehmann, 1998). Not described 
 Cyst differentiation  Nos GSCs and their immediate daughters. Very high in a fraction of 16-cell cysts,by Ab staining (Gilboa and Lehmann,2004; Wang and Lin,2004). Not described 
Zpg (gap junction communication) GSC differentiation and survival GSC differentiation and survival Zpg Germ line cells from PGCs to late egg chambers, by Ab staining(Gilboa et al., 2003; Tazuke et al., 2002). Germ line cells from PGCs to spermatocytes, by Ab staining(Tazuke et al., 2002). 
Bam (novel) Cystoblast differentiation Cyst development (limiting mitosis/promoting meiosis) or gonialblast differentiation BamC Cystoblast and dividing cysts, by Ab staining(McKearin and Ohlstein, 1995). Dividing cysts, by Ab staining and promoter construct(Brawley and Matunis, 2004; Gonczy et al., 1997; Kawase et al., 2004; Shivdasani and Ingham, 2003). 
 Cyst division  BamF GSCs to dividing cysts, by Ab staining(McKearin and Ohlstein, 1995). Not described 
EGF signaling pathway FC differentiation, axis determination, BC migration Differentiation of SSCs or their daughters EGFR Somatic cells from region 2b of the germarium onward, by Ab staining(Sapir et al., 1998). Cyst cells, inferred genetically by requirement for germ line cyst differentiation (Kiger et al.,2000). 
   raf Follicle cells, inferred genetically by requirement for follicle cell differentiation (Brand and Perrimon,1994). Cyst cells, inferred genetically by requirement for germ line cyst differentiation (Tran et al.,2000). 
   Activated MAPK IS cells, by Ab staining (Schulz et al.,2002). Hub cells, cyst cells, GSCs, spermatocytes, by Ab staining(Kiger et al., 2000; Schulz et al., 2002). 
Stet Early germ cell differentiation Early germ cell differentiation stet Required genetically in early germ cells(Schulz et al., 2002). Required genetically in early germ cells(Schulz et al., 2002). 
    Germ cells in region 2B and 3 of germarium, by ISH(Schulz et al., 2002).  
Notch signaling pathway FC differentiation Not described N Germ line region 1 of the germarium, low levels, by Ab staining(Xu et al., 1992). GSCs, gonialblasts, spermatogonia, by Ab staining(Kiger et al., 2000). 
    Somatic cells region 2 of the germarium onward, by Ab staining(Xu et al., 1992).  
En (transcription factor) Not described Not described En TF, Cap cells, by Ab staining (Forbes et al., 1996a). Not described 
Wg (cell-cell signaling) SSC maintenance Not described wg Cap cells, by enhancer trap (Forbes et al., 1996a). Cyst cells, by enhancer trap (Schulz et al., 2002). 
Arm, E-cadherin (cell adhesion, cell-cell signaling) GSC attachment to niche cells GSC attachment to niche cells Arm High levels between GSCs and cap cells, by Ab staining(Song et al., 2002). Hub cells, GSCs, by Ab staining (Yamashita et al., 2003). 
   E-cadherin High levels between GSCs and cap cells, by Ab staining(Song et al., 2002). High levels between GSCs and hub cells, by Ab staining(Yamashita et al., 2003). 
Function*
Expression
PathwayFemalesMalesGene/proteinFemalesMales
TGF-β signaling pathway GSC maintenance and rate of division Cyst development (limiting mitosis/promoting meiosis) or gonialblast differentiation dpp/gbb dpp- Cap, IS cells, by ISH (Xie and Spradling, 2000). Not detected by enhancer trap(Forbes et al., 1996a). gbb- IS or early follicle cells or both, by RT-PCR(Song et al., 2004). dpp- Not detected by enhancer trap(Matunis et al., 1997). No ISH data. gbb-SSCs, by ISH(Shivdasani and Ingham, 2003). Hub cells and SSCs/somatic cyst cells, by RT-PCR(Kawase et al., 2004). 
 Possible later role in cyst development Possible role in GSC survival/maintenance tkv, med, mad, pnt GSCs, inferred by genetic requirement for maintenance(Xie and Spradling, 1998). GSCs, inferred by genetic requirement for maintenance(Kawase et al., 2004). 
   Phosphorylated Mad Strong expression in GSCs. Weaker in dividing cysts, by Ab staining(Gilboa et al., 2003; Kai and Spradling, 2003). GSCs, by Ab staining (Kawase et al.,2004). 
   pnt. shn GSCs, inferred by genetic requirement for maintenance(Xie and Spradling, 1998; Xie and Spradling, 2000). Cyst cells, inferred by genetic requirement for germ line cyst differentiation(Matunis et al., 1997). 
JAK/STAT signaling pathway FC differentiation, BC migration GSC, and possibly SSC maintenance upd Polar cells, possibly cap cells, by ISH(Silver and Montell, 2001). Hub cells, by ISH (Kiger et al.,2001; Tulina and Matunis,2001). 
 Possible minor or indirect role in GSC maintenance  stat92E Cap cells, by ISH (Silver and Montell,2001). GSCs, inferred by genetic requirement for maintenance(Kiger et al., 2001; Tulina and Matunis, 2001). 
Piwi GSC maintenance, rate of division GSC maintenance piwi TF, by ISH (Cox et al., 1998). Early germ cells, at anterior tip, by ISH(Schulz et al., 2002). 
(PPD family protein)   Piwi TF, Cap, IS, GSCs, dividing cysts, by Ab staining of a tagged piwitransgene (Cox et al., 2000).  
Yb (novel) GSC maintenance, cyst differentiation, follicle cell patterning Males fertile Yb TF, by ISH (King and Lin,1999). Expressed in males, by western blot (King and Lin, 1999). 
Hh signaling pathway Major function — SSC maintenance No function in GSC maintenance Hh TF, Cap cells, by Ab staining (Forbes et al., 1996b). Hub cells at third instar — enhancer trap(Forbes et al., 1996b). 
    TF, Cap, IS cells, by enhancer trap(Forbes et al., 1996b).  
   Ptc Somatic and germ line cells throughout the ovary, by Ab staining(Forbes et al., 1996a). Cyst cells — ptcGAL4 (Schulz et al.,2002). 
Pum, Nos (transcriptional repression) GSC maintenance Not described Pum High levels in GSCs, lower in cystoblasts, by Ab staining(Forbes and Lehmann, 1998). Not described 
 Cyst differentiation  Nos GSCs and their immediate daughters. Very high in a fraction of 16-cell cysts,by Ab staining (Gilboa and Lehmann,2004; Wang and Lin,2004). Not described 
Zpg (gap junction communication) GSC differentiation and survival GSC differentiation and survival Zpg Germ line cells from PGCs to late egg chambers, by Ab staining(Gilboa et al., 2003; Tazuke et al., 2002). Germ line cells from PGCs to spermatocytes, by Ab staining(Tazuke et al., 2002). 
Bam (novel) Cystoblast differentiation Cyst development (limiting mitosis/promoting meiosis) or gonialblast differentiation BamC Cystoblast and dividing cysts, by Ab staining(McKearin and Ohlstein, 1995). Dividing cysts, by Ab staining and promoter construct(Brawley and Matunis, 2004; Gonczy et al., 1997; Kawase et al., 2004; Shivdasani and Ingham, 2003). 
 Cyst division  BamF GSCs to dividing cysts, by Ab staining(McKearin and Ohlstein, 1995). Not described 
EGF signaling pathway FC differentiation, axis determination, BC migration Differentiation of SSCs or their daughters EGFR Somatic cells from region 2b of the germarium onward, by Ab staining(Sapir et al., 1998). Cyst cells, inferred genetically by requirement for germ line cyst differentiation (Kiger et al.,2000). 
   raf Follicle cells, inferred genetically by requirement for follicle cell differentiation (Brand and Perrimon,1994). Cyst cells, inferred genetically by requirement for germ line cyst differentiation (Tran et al.,2000). 
   Activated MAPK IS cells, by Ab staining (Schulz et al.,2002). Hub cells, cyst cells, GSCs, spermatocytes, by Ab staining(Kiger et al., 2000; Schulz et al., 2002). 
Stet Early germ cell differentiation Early germ cell differentiation stet Required genetically in early germ cells(Schulz et al., 2002). Required genetically in early germ cells(Schulz et al., 2002). 
    Germ cells in region 2B and 3 of germarium, by ISH(Schulz et al., 2002).  
Notch signaling pathway FC differentiation Not described N Germ line region 1 of the germarium, low levels, by Ab staining(Xu et al., 1992). GSCs, gonialblasts, spermatogonia, by Ab staining(Kiger et al., 2000). 
    Somatic cells region 2 of the germarium onward, by Ab staining(Xu et al., 1992).  
En (transcription factor) Not described Not described En TF, Cap cells, by Ab staining (Forbes et al., 1996a). Not described 
Wg (cell-cell signaling) SSC maintenance Not described wg Cap cells, by enhancer trap (Forbes et al., 1996a). Cyst cells, by enhancer trap (Schulz et al., 2002). 
Arm, E-cadherin (cell adhesion, cell-cell signaling) GSC attachment to niche cells GSC attachment to niche cells Arm High levels between GSCs and cap cells, by Ab staining(Song et al., 2002). Hub cells, GSCs, by Ab staining (Yamashita et al., 2003). 
   E-cadherin High levels between GSCs and cap cells, by Ab staining(Song et al., 2002). High levels between GSCs and hub cells, by Ab staining(Yamashita et al., 2003). 

Abbreviations: Ab, antibody; BamC, cytoplasmic Bam; BamF, fusomal Bam; BC,border cells; FC, follicle cells; GSC, germ line stem cell; IS, inner sheath cell; ISH, in-situ hybridization; PGC, primordial germ cell; SSC, somatic stem cell; TF, terminal filament.

*

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