QUICK SEARCH:   [advanced] Author: Keyword(s):
Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents

First published online March 1, 2004
doi: 10.1242/10.1242/dev.01003

This Article Summary Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Email this article to a friend Related articles in Development Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Narbonne, K. Articles by Busson, D. Search for Related Content PubMed PubMed Citation Articles by Narbonne, K. Articles by Busson, D. Social Bookmarking                         What's this?

polyhomeotic is required for somatic cell proliferation and differentiation during ovarian follicle formation in Drosophila

Karine Narbonne, Florence Besse, Jeanine Brissard-Zahraoui, Anne-Marie Pret^* and Denise Busson^*,

Institut Jacques Monod, (UMR 7592 - CNRS/Université Pierre et Marie Curie/Université Denis Diderot), Laboratoire de Génétique du Développement et Evolution, 2 place Jussieu, 75251 Paris Cedex 05, France

View larger version (30K): [in a new window]   Fig. 1. The Drosophila germarium. Schematic drawing of the Drosophila germarium, modified from Zhang and Kalderon (Zhang and Kalderon, 2001). Germarial regions 1, 2a, 2b and 3 are indicated above the drawing. At the most anterior part of the germarium, overlying somatic cells (terminal filament and cap cells) create a niche to maintain the germline stem cells. Anterior region 1 contains two to three germline stem cells (GSCs); GSC division is asymmetric and generates both a daughter stem cell and a differentiated daughter cell called a cystoblast. Each cystoblast undergoes four rounds of mitosis with incomplete cytokinesis to produce a syncytium of 16 cystocytes, the germline cyst. One of these 16 cells becomes the oocyte, while the remaining 15 cells develop as nurse cells. The population of germline cysts during these stages is surrounded by somatic inner sheath cells. In region 2a/2b, approximately two somatic stem cells (SSCs), represented in green, give rise to a population of undifferentiated cells, the prefollicular cells, in blue, which migrate to envelop each germline cyst individually. These cells diverge soon after to give rise to: two pairs of polar cells, in pink, which mark the anterior and posterior poles of the follicle; interfollicular stalk cells, in purple, which are responsible for follicle budding from the germarium; and epithelial follicular cells, in yellow, which form a polarized epithelium around each follicle.

View larger version (55K): [in a new window]   Fig. 2. Overexpression of ph leads to defects in follicle formation. All ovarioles are oriented with the anterior towards the top left corner. (A,B,C) DAPI staining of 4061/+ (A) and 4061/+; da-Gal4/+ (B,C) ovarioles. (B) Compound follicle with a `curved' aspect to the follicular epithelium (arrow). (C) The first cysts in the germarium are contained within a single epithelium, without follicle individualization (arrowhead); arrow points to apposed follicles. (D) Representation of P{y+}UAS and PlacW insertions at the ph locus in the P[4061] and phlac lines, respectively. The P{y+}UAS is inserted 99 pb upstream of the ATG, in the sense orientation, whereas the PlacW is inserted in the first intron. (E-H) Control (F) and mosaic ovarioles (E,G,H) in which ph overexpressing cellular clones are detected by the expression of a GFP reporter construct (E',G',H'-H'''). Ovarioles are stained with DAPI (E,F,G,H), anti-Orb antibodies (E'') and anti-Fas III antibodies (F',G'',H'-H'''). Compound follicle (E), with a `curved' epithelium, results from encapsulation of two oocytes as visualized by Orb staining (E'', arrowheads). (G-G''') Abnormal accumulation of germline cysts in an entirely clonal germarium (compare G'' and F'); prefollicular cells that overexpressed ph began to migrate over germline cysts (G'', asterisks) but failed to completely individualize them. (H) Compound follicle with two germline cysts encapsulated together; this follicle contains four groups of polar cells (arrowheads, H'-H''': three different focal planes of the same follicle).

View larger version (80K): [in a new window]   Fig. 3. polyhomeotic is required specifically within somatic cells to control somatic cell differentiation. (A-F) ph0 mosaic follicles stained with DAPI (A,C,E, gray; D, blue), Propidium Iodide (B,F, red), anti-ß-Gal (A',C', green), anti-Orb (A'', red), anti-Hts (B', white; C'', red), anti-Eya (D,D',E'', red), or anti-Fas III (F', insert and F'', white) antibodies. Mutant clones for ph0 are detected by the absence of anti-ß-Gal antibody staining (A',C', white tracing) or by the absence of GFP fluorescence (B,D',E',F', green). (A-A'') Mosaic compound follicle (A), bearing a small ph0 mutant somatic cell clone (A') and exhibiting three oocytes (A''). (B,B') ph0 prefollicular cells (asterisks in insets), in contrast to wild-type cells (B', arrow), are found at the periphery and do not extend thin processes over germline cysts. (C-C'') Abnormal mosaic ph0 and ph+ interfollicular stalk. Hts accumulates at the membrane of interfollicular stalk cells (C''). (D-D') In a late stage follicle, a clone of ph0 cells exhibiting five polar cells (D,D', marked by the absence of anti-Eya staining). (E-E'') ph0 cells (E') expulsed from the follicular epithelium (E, bracket) express the Eya protein (E''). Arrowheads in E'' point to pairs of polar cells at each follicle extremity that do not express Eya. (F-F'') ph0 follicular clones (F', insert) upregulate Fas III compared with adjacent ph+ follicular cells (F''), but nonetheless express lower levels of Fas III compared with polar cells (F'', arrowhead). ph0 clones are delimited by a dotted line in A' and C'.

View larger version (68K): [in a new window]   Fig. 5. polyhomeotic function is required for interfollicular stalk and polar cell differentiation. (A-C) Nuclear DAPI staining reveals the presence of long stalks in phlac mutant ovarioles (B,C, compare to wild-type, A). (A) In wild-type interfollicular stalk cells, -Spectrin (-Spe) is strongly expressed (A', inset), whereas Fas III (FIII) is almost absent (A'', inset). (B,C) In phlac ovarioles, long interfollicular stalks fail to differentiate correctly as interfollicular stalk cells express both -Spe (B', inset) and Fas III (C', inset). (D,E) phlac follicles with fewer (D) or more (E) than 16 germline cells, containing one pair of polar cells at each pole, as revealed after staining with anti-Fas III antibody (D',E'). (F,F') DAPI staining (F) and anti-ß-Gal antibody staining (F') of a compound stage 4 follicle in a phlac/phlac;A101/+ ovary. (G) Percentage of phlac/+; A101/+ (blue) and phlac/phlac; A101/+ (pink) stage 2 to 6 egg chambers containing 0-5 and more polar cells (n34 for phlac/+; A101/+ and n56 for phlac/phlac; A101/+for each stage). These data concern anterior polar cells.

View larger version (80K): [in a new window]   Fig. 4. phlac mutant germaria exhibit abnormal encapsulation by prefollicular cells and abnormal budding of germline cysts. (A-G) DAPI staining (A-G,E'',F'') and anti-Fas III staining (D',E',E'',F',F'',G') of phlac mutant ovarioles. (A,B) arrows point to compound follicles, with the same degree (A), or different degree (B) of polyploidy of the nurse cells. (C) phlac follicle with fewer than 16 nurse cells (one nurse cell, arrow). No complementary chamber could be found, probably due to nurse cell degeneration (empty arrowhead points to pycnotic nucleus). (D-G) In phlac germaria, cysts are haphazardly distributed (D', arrowheads), and prefollicular cells fail to migrate, remaining at the periphery (D',G', asterisks). Encapsulation defects include splitting of germline cysts (E',E'', arrowhead and empty arrowhead point to follicles with fewer than 15 nurse cells, having the same degree of polyploidy as the last egg chamber in germarial region 3) or to several cysts encapsulated together (F',F''; arrows point to an absence of prefollicular cell migration between adjacent germline cysts, whereas arrowheads point to an invagination of prefollicular cells). (G) In strongly affected ovarioles, prefollicular cells completely failed to migrate (G', asterisks), leading to the inclusion of several germline cysts in the same follicle. Arrowhead points to a `highly multicystic' follicle.

View larger version (90K): [in a new window]   Fig. 6. Mutations in the Sce1 gene lead to ovarian defects. (A-E) Sce1 mosaic follicles stained with DAPI (A,B), anti-Fas III (A'',B',C,C',E,E'), or anti--Spectrin (D,D') antibodies. Mutant clones for Sce1 are detected by the absence of GFP (A',B',C,D,E, green). (A-A'') Compound follicle (A, arrows point to oocyte nuclei) bearing several Sce1 clones marked by the absence of GFP staining (A') and exhibiting two pairs of polar cells at the anterior and posterior poles (A''). (B-) Mosaic Sce1/Sce+ germarium. Sce1 mutant prefollicular cells do not migrate correctly arround germline cysts (B', bracket). Arrowhead points to an abnormal interfollicular stalk with Sce1 cells on another focal plane. (C,D) Interfollicular stalks are very long and all cells express Fas III (C,C') as well as -Spectrin (D,D') at high levels compared with adjacent follicle cells. Empty arrowhead (C) points to one Sce1 cell (four other Sce1 cells are present in this stalk). (E-E') Mosaic Sce1/Sce+ follicle. Sce1 follicular cells strongly express Fas III protein compared with adjacent Sce+ cells.

CiteULike

Complore

Connotea

Del.icio.us

Digg

Reddit

Technorati

Twitter