spacer gif spacer gif spacer gif spacer gif spacer gif
QUICK SEARCH:   [advanced]


spacer gif
     Home     Help     Feedback     Subscriptions     Archive     Search     Table of Contents    

doi: 10.1242/10.1242/dev.00484

This Article
Right arrow Summary Freely available
Right arrow Full Text
Right arrow Full Text (PDF)
Right arrow Alert me when this article is cited
Right arrow Alert me if a correction is posted
Services
Right arrow Email this article to a friend
Right arrow Related articles in Development
Right arrow Similar articles in this journal
Right arrow Similar articles in PubMed
Right arrow Alert me to new issues of the journal
Right arrow Download to citation manager
Right arrow reprints & permissions
Citing Articles
Right arrow Citing Articles via HighWire
Right arrow Citing Articles via Google Scholar
Google Scholar
Right arrow Articles by Han, Z.
Right arrow Articles by Bodmer, R.
Right arrow Search for Related Content
PubMed
Right arrow PubMed Citation
Right arrow Articles by Han, Z.
Right arrow Articles by Bodmer, R.
Social Bookmarking
Add to CiteULike   Add to Complore   Add to Connotea   Add to Del.icio.us   Add to Digg   Add to Reddit   Add to Technorati   Add to Twitter  
What's this?

Myogenic cells fates are antagonized by Notch only in asymmetric lineages of the Drosophila heart, with or without cell division

Zhe Han* and Rolf Bodmer{dagger}

Department of Molecular, Cellular and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
* Present address: Department of Molecular Biology, UT Southwestern Medical Center, 6000 Harry Hines Boulevard, NA8.510, Dallas, TX 75390-9148, USA



View larger version (80K):

[in a new window]
  		Fig. 1. Progenitors of the mesodermal Eve lineage adopt a muscle cell fate when their asymmetric divisions are blocked. (A-D) Antibody staining of Eve (red) and Mef2 (green) in stage 13 embryos. Five hemisegments of segment A2-A7 are shown in each panel. (A) Six Mef2-expressing myocardial cells, two EPCs, and one DA1 muscle are present in each hemisegment in wild-type stage 13 embryos. (B) In CycA mutants, the number of Mef2 myocardial cells is reduced to four per hemisegment; no EPCs are specified, but the DA1 muscles are present. (C) In Rca1 mutants, four myocardial cells are present in each hemisegment; most EPCs are absent. (D) Pan-mesodermal expression of dap reduces the number of myocardial cells to four and the EPCs to one per hemisegment. The DA1 muscles are present. (E) In the mesodermal Eve lineage model of Park et al. (Park et al., 1998Go), two progenitors are formed per hemisegment, each giving rise to an EPC and a muscle founder. (F) In the model of Carmena et al. (Carmena et al., 1998Go), two progenitors are also formed in each hemisegment, but one (P2) gives rise to both EPCs and one muscle founder, whereas the other (P15) generates only the DA1 founder. This EPC progenitor is a daughter cell of an asymmetric cell division that also generates the DO2 muscle founder.

 


View larger version (48K):

[in a new window]
  		Fig. 9. Model of cardiac lineages, the effect of cell cycle arrest and the function of Numb-Notch in determining cardiac cell fates. (A) The Drosophila heart is from T3-A8 segments. Black lines indicate lineage relationships based on this study, Ward and Skeath (Ward and Skeath, 2000Go), and Alvarez et al. (Alvarez et al., 2003). (B) The effects of cell cycle arrest, numb mutants and double mutants of numb and CycA. (C) Block of cell divisions in A2-A7 abdominal segments are as indicated. Asymmetric segregation of Numb into one daughter cell, or blocking precursor division, promotes myocardial cell fate by inhibition of Notch signaling. By contrast, activation of Notch signaling or the absence of Numb causes the daughter cell, or undivided precursor, to adopt a non-myogenic pericardial cell fate. SMC, Svp myocardial cell; TMC, Tinman myocardial cell; SOPC, Svp-Odd pericardial cell; EPC Eve pericardial cell; TMLC, Tinman-Lbe myocardial cell; LPC, Lbe pericardial cell; OPC, Odd pericardial cell; DA1, dorsal acute muscle; DO2, dorsal oblique muscle 2; DA1sib; SSP, Svp-positive super progenitor; TSP, Tin-positive super progenitor. FEPC, FDO2, FDA1 and FDA1sib are founders of EPCs, DO2, DA1 and DA1sib, respectively. P2 and P15 are progenitors of the above founder cells.

 


View larger version (110K):

[in a new window]
  		Fig. 2. Progenitors of the Svp lineage adopt a myocardial cell fate when their asymmetric divisions are blocked. (A-D) Antibody staining of Tinman (red) and Eve (green), (E,F) Odd (red) and Eve (green), (G) Lbe (red) and Eve (green), and (H) Lbe (red) and ß-Gal (green). Five stage 13 A2-A7 hemisegments are shown in each panel. (A) In wild-type embryos, four out of six myocardial cells are labeled with Tinman. (B) In CycA mutants, the number of Tinman myocardial cells is reduced to two per hemisegment; no EPCs, only DA1 muscles, are specified. (C) In Rca1 mutants, two Tinman myocardial cells are present per hemisegment; EPCs are usually absent but sometimes appear as a single cell. (D) Mesodermal overexpression of dap: two Tinman myocardial cells, one EPC and normal DA1 muscles forms in each hemisegment. (E) In wild type, four pericardial cells express odd (OPC) in each hemisegment. (F) In CycA mutants, the number of Odd pericardial cells is reduced to one per hemisegment. (G) In wild type, two lbe-expressing myocardial cells (TLMC) and two lbe-expressing pericardial cells (LPC) are present in each hemisegment. (H) In CycA mutants, only one TLMC and one LPC are present in each hemisegment. emeA-lacZ shows two Eve lineage derived muscle founders form in each hemisegment (see also Fig. 6C).

 


View larger version (92K):

[in a new window]
  		Fig. 3. Segmental differences of the Drosophila cardiac lineages. Stage 15 embryos stained for (A,B) Mef2 (green) and Eve (red), (C,D) Tinman (red) and Eve (green), or Tinman only (E,F). (A) In the wild-type embryos, six myocardial cells and two EPCs are present in each hemisegment from T3 to A7. (B) Overexpression of dap in the mesoderm reduces the myocardial cells from six to four per hemisegment in A2-A7 segments, and in T3-A1 to about three. (C) In wild-type segments A2-A7, four out of six myocardial cells express tinman in each hemisegment; in segment A8, two out of four express tinman; however, in segments T3-A1, all six myocardial cells express tinman. (D) Overexpression of dap in the mesoderm reduces the tinman-expressing myocardial cells in A2-A7 from four to two, in A8 from two to one, and in T3-A1 from six to about three (see insert). (E,F) In CycA or Rca1 mutants, tinman-expressing myocardial cells are reduced from four to two in hemisegments A2-A7, from two to one in A8. However, there is no change in hemisegments T3-A1 in that all six myocardial cells express tinman. Note that the change in myocardial cell number in A2-7 affects heart tube assembly in the posterior abdominal segments, but not in T3-A1 (F).

 


View larger version (119K):

[in a new window]
  		Fig. 4. Cardiac cell types in CycA-;CycB-double mutants and in stg mutants. (A-F,I-J) A2-A7 hemisegments of stage 13 embryos are labeled for (A,B,I) Mef2 (green) and Eve (red), (C,D,J) Tinman (red) and Eve (green), or (E,F) Lbe (red) alone. (G,H) Stage 15 embryos labeled for Tinman (red). (A,B) In CycA;CycB double mutants, two instead of six myocardial cells are present in each hemisegment, DA1 muscles but no EPCs are formed. (C,D) Double labeling for Tinman and Eve shows that only one of the two myocardial cells per hemisegment in the CycA;CycB double mutant expresses tinman (D). (E,F) Lbe staining shows that the single tinman-expressing myocardial cells in each hemisegment are not Lbe positive. (G,H) About three tinman-expressing myocardial cells remain in each T3-A1 hemisegment in the mutant (H), but only one in A2-A7. Note that some hemisegments show one TMC cell and one tinman-expressing pericardial cell. (I,J) In stg- mutants, the overall mesodermal segmentation is significantly affected, in addition to the arrest at cell cycle 14. The Mef2-, tinman- and eve-expressing cells are reduced dramatically. However, the cells that maintain eve expression often appear in pairs and co-express Mef2, but not tinman, indicating that they acquire a myogenic cell fate.

 


View larger version (126K):

[in a new window]
  		Fig. 5. The Notch pathway functions through activation of Su(H) to specify a pericardial cell fate in asymmetric lineages. A2-A7 hemisegments of stage 13 embryos were labeled with (A-D) Mef2 (green) and Eve (red), or (E-H) Eve only. (A,B) In numb mutants, the number of myocardial cells per hemisegment is reduced from six to four; the number of EPC is increased from two to an average of 3.6 per hemisegment; DA1 muscles are not formed. (C) Overexpression of numb in the mesodermal eve lineage (eme>numb) abolishes the formation of all EPCs and sometimes more than one DA1 muscle per hemisegments seems to be generated. (D) Overexpression of the eme>N(icd) either generate three or four EPCs per hemisegment, or abolish eve expression altogether. No DA1 muscle founders are formed, as judged by the absence of Eve and Mef2 double labeling. (E) Overexpression of eme-Su(H) does not seem to alter eve expression. (F) By contrast, eme>Su(H)vp16 exhibits a similar phenotype as eme-N(icd), in that no eve-expressing cells or only EPCs form in most segments. Occasionally, four EPCs as well as one forming DA1 muscle are observed, suggesting that these two cell types are specified independently (see text). (G) Overexpression of numb together with the N(icd) [eme>N(icd)+numb] in the mesodermal Eve lineage generates an intermediate phenotype. (H) By contrast, overexpression of numb together with Su(H)vp16 [eme>Su(H)vp16+numb] generates a phenotype that is indistinguishable from overexpression of Su(H)vp16 alone [eme>Su(H)vp16].

 


View larger version (41K):

[in a new window]
  		Fig. 6. emeA-lacZ marks the mesodermal Eve lineage. (A-F) Double labeling for Eve (green) and ß-Gal (marking emeA-lacZ expression in red) of two hemisegments in stage 13 embryos. (A) In wild type, emeA-lacZ labels the two EPCs, as well as both the DA1 and DO2 muscle founders. (B) In embryos with ectopic dap in the mesoderm, the number of EPCs is reduced to one per hemisegment, but the DA1 and DO2 founders are unaffected. (C) In CycA mutants, no EPCs are specified but both muscle founder cells are unaffected. (D) In numb mutants, the number of EPCs is increased from 2 to average 3.6 per hemisegment with loss of both muscle founders. (E) eme-specific overexpression of numb causes a twofold increase in the number of DA1 and DO2 founders concomitantly with a loss of EPCs. (F) eme-specific overexpression of N(icd), as in numb mutants, causes a loss of the eve muscle founder and a doubling of EPCs.

 


View larger version (113K):

[in a new window]
  		Fig. 7. Progenitors of asymmetric Eve lineage adopt a pericardial EPC cell fate in numb,CycA double mutants. (A-F) A2-A7 hemisegments of stage 13 embryos labeled for Mef2 (green) and Eve (red). (A-C) In CycA mutants, no EPCs only DA1 muscles, whereas in numb mutants, up to four EPCs but no DA1 muscles are present in each hemisegment. Both CycA and numb single mutants show four instead of six myocardial cells per hemisegment. (D) Double mutants of numb and CycA show two myocardial cells and a EPC in each hemisegment. (E) Embryos overexpressing N(icd) with heat shock promoter (see Park et al., 1998Go) exhibit twice the normal number of EPCs as do numb mutants. (F) Overexpression of N(icd) in CycA mutant embryos, as in numb,CycA double mutants, also produces one EPC and two myocardial cells per hemisegment.

 


View larger version (119K):

[in a new window]
  		Fig. 8. Progenitors of the Svp lineage adopt a pericardial cell fate in numb,CycA double mutants. A2-A7 hemisegments of stage 13 embryos labeled for (A-D,G,H) Tinman (red) and Eve (green), or (E-F) Odd (red) and Eve (green). (A-D) Although both numb and CycA mutants exhibit four myocardial cells per hemisegment, only two express tinman (TMC) in CycA mutants (B) (asterisks indicate position of SMC), but in numb mutants (C) all four express tinman (no SMC form). In numb,CycA double mutants (D), two myocardial cells are formed, both expressing tinman; thus, no SMCs form. (E) The number of odd-expressing pericardial cells (OPC) is increased from four (Fig. 2E) to six in numb mutants. (F) In CycA mutants, only one OPC is formed (Fig. 2F), in CycA;numb double mutants, three OPCs are usually observed. (G) Overexpression of N(icd) not only increases the number of EPCs, but also reduces the number of the myocardial cells from six (Fig. 7E) to four, all of which exhibit TMC characteristics. (H) Overexpression of N(icd) in CycA mutants generates one EPC and the two myocardial cells (seen in Fig. 7F), both of which express tinman (TMC).

 

Add to CiteULike CiteULike   Add to Complore Complore   Add to Connotea Connotea   Add to Del.icio.us Del.icio.us   Add to Digg Digg   Add to Reddit Reddit   Add to Technorati Technorati   Add to Twitter Twitter    What's this?



© The Company of Biologists Ltd 2003