DOC PREVIEW
UCSD BGGN 231 - The Drosophila Ovarian and Testis Stem Cell Niches

This preview shows page 1-2-3 out of 10 pages.

Save
View full document
View full document
Premium Document
Do you want full access? Go Premium and unlock all 10 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 10 pages.
Access to all documents
Download any document
Ad free experience
View full document
Premium Document
Do you want full access? Go Premium and unlock all 10 pages.
Access to all documents
Download any document
Ad free experience
Premium Document
Do you want full access? Go Premium and unlock all 10 pages.
Access to all documents
Download any document
Ad free experience

Unformatted text preview:

The Drosophila Ovarian and Testis Stem Cell Niches: Similar Somatic Stem Cells and SignalsIntroductionResultsIGS Cells Resemble Testis Cyst CellsIGS Cells Cycle and Move PosteriorlyCycling IGS Cells Do Not Exit Region 2bDividing IGS Cells Are Not Derived from SSCsDividing IGS Cells Are Maintained by Stem Cells Located near the Cap CellsEscort Stem Cells Are Morphologically Distinctive and Resemble Testis Cyst Progenitor CellsESCs Are Not Affected by Disrupting Early Germ Cell DevelopmentThe Ovarian Niche Requires JAK/STAT SignalingAnterior Germarium Structure Depends on JAK/STAT SignalingStat92E Is Required in the Escort Cell LineageDiscussionThe Female GSC Niche Contains a Second Type of Stem CellEscort Cells Resemble Testis Somatic Cyst CellsEscort Cells Require JAK/STAT Signals to Maintain the Structure and Function of the Anterior GermariumMale and Female GSC Niches Are More Similar Than Previously RecognizedGermline Sex Determination and Sexually Dimorphic Gonad DevelopmentExperimental ProceduresDrosophila Strains and CultureGeneration and Analysis of IGS Cell ClonesImmunostaining and Fluorescence MicroscopyElectron MicroscopyApopTag StainingSupplemental DataAcknowledgmentsReferencesDevelopmental Cell, Vol. 9, 501–510, October, 2005, Copyright ©2005 by Elsevier Inc. DOI 10.1016/j.devcel.2005.08.012The Drosophila Ovarian and Testis Stem Cell Niches:Similar Somatic Stem Cells and SignalsEva Decotto and Allan C. Spradling1,*Howard Hughes Medical Institute ResearchLaboratoriesDepartment of EmbryologyCarnegie Institution of Washington3520 San Martin DriveBaltimore, Maryland 21218SummaryThe stem cell niches at the apex of Drosophila ovariesand testes have been viewed as distinct in two majorrespects. While both contain germline stem cells, thetestis niche also contains “cyst progenitor” stem cells,which divide to produce somatic cells that encase de-veloping germ cells. Moreover, while both niches uti-lize BMP signaling, the testis niche requires a keyJAK/STAT signal. We now show, by lineage marking,that the ovarian niche also contains a second type ofstem cell. These “escort stem cells” morphologicallyresemble testis cyst progenitor cells and their daugh-ters encase developing cysts before undergoing apo-ptosis at the time of follicle formation. In addition, weshow that JAK/STAT signaling also plays a criticalrole in ovarian niche function, and acts within escortcells. These observations reveal striking similaritiesin the stem cell niches of male and female gonads,and suggest that they are largely governed by com-mon mechanisms.IntroductionStem cells are controlled within local tissue microenvi-ronments known as niches that are generated bynearby stromal cells (reviewed in Ohlstein et al., 2004;Yamashita et al., 2005). One of the best-characterizedniches supports germline stem cells (GSCs) within theDrosophila ovary (Xie and Spradling, 2000; see Figure1A). A GSC niche is located at the tip of each ovariolewithin the germarium, a generative region that is di-vided into regions: 1, 2a, 2b, and 3 (Figure 1A). Theniche itself contains five to seven nondividing somaticcap cells that anchor two or three GSCs via adherensjunctions (Song et al., 2002) and stimulate reception ofan essential BMP signal (Xie and Spradling, 1998). Fol-lowing each GSC division, the posterior daughter cellleaves the niche, differentiates into a “cystoblast,” un-dergoes four synchronous, incomplete divisions toform a 16-cell germline cyst (de Cuevas and Spradling,1998), and steadily moves in a posterior directionthrough the germarium. The niche signal directly regu-lates stem cell fate by repressing transcription of thecystoblast determinant gene bag-of-marbles (bam)intheir proximal, but not their distal, daughters (Chen and*Correspondence: [email protected] address: http://ww w.hhmi.org/r e se ar c h/ investigators/spradl ing .htmlMcKearin, 2003a, 2003b; Kai and Spradling, 2003; Songet al., 2004). Less is known about the anatomy and reg-ulation of a second niche that controls the somaticstem cells (SSCs) located midway along the germariumnear the start of region 2b. SSCs divide in response tosomatic Hedgehog signals to produce follicle cells thatencapsulate passing cysts (Margolis and Spradling,1995; Forbes et al., 1996; Zhang and Kalderon, 2000).Inner germarium sheath (IGS) cells, which line thesurface of regions 1 and 2a (Figure 1A), support germcell differentiation and somatic cell production. Thin cy-toplasmic processes from IGS cells envelop cys-toblasts and cysts for several days prior to follicle for-mation (Mahowald and Strassheim, 1970; King, 1970;Mahowald and Kambysellis, 1980). In addition, IGScells located halfway down the germarium anchorSSCs via adherens junctions and are postulated to playa critical role in defining the SSC niche (Song and Xie,2002). Both anterior IGS cells and those near the SSCshave been reported to be differentiated and immobilebut capable of maintaining parity with cyst number byundergoing sporadic division or death (King, 1970; Mar-golis and Spradling, 1995; Xie and Spradling, 2000).Following GSC loss, IGS cells gradually disappear byapoptosis as preexisting cysts leave the anterior germ-arium and acquire follicle cells (Xie and Spradling, 2000;Kai and Spradling, 2003). This destroys the SSC niches,but the released SSCs can often associate with capcells in the vacated GSC niche and continue to divide(Kai and Spradling, 2003).The stem cell niche located at the apical tip of theDrosophila testis shows both similarities and differ-ences to this model of the ovarian niche (compare Fig-ures 1A and 1B; reviewed by Lin, 2002; Gilboa and Leh-mann, 2004). As in the ovary, critical signals are sent bya small cluster of somatic cells, the hub, that directlycontact GSCs, but not their gonialblast (cystoblast)daughters. In both males and females, newly formedcysts can revert to the stem cell state under certaincircumstances (Kai and Spradling, 2004; Brawley andMatunis, 2004). However, testis GSCs require JAK/STATsignals from the hub (Tulina and Matunis, 2001; Kigeret al., 2001), while this signaling pathway in the ovaryhas been reported to act later, during follicle formation(Ghiglione et al., 2002; Baksa et al., 2002; McGregor etal., 2002). Recently, BMP signals that repress bam havealso been shown to contribute to testis stem cell main-tenance, but do not control cyst initiation (Shivdasaniand Ingham, 2003; Kawase et al., 2004; Schulz et al.,2004). A further


View Full Document
Download The Drosophila Ovarian and Testis Stem Cell Niches
Our administrator received your request to download this document. We will send you the file to your email shortly.
Loading Unlocking...
Login

Join to view The Drosophila Ovarian and Testis Stem Cell Niches and access 3M+ class-specific study document.

or
We will never post anything without your permission.
Don't have an account?
Sign Up

Join to view The Drosophila Ovarian and Testis Stem Cell Niches 2 2 and access 3M+ class-specific study document.

or

By creating an account you agree to our Privacy Policy and Terms Of Use

Already a member?