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A mex3 homolog is required for differentiation during planarian stem cell lineage development.

Zhu SJ, Hallows SE, Currie KW, Xu C, Pearson BJ - Elife (2015)

Bottom Line: In this study, we used transcriptional profiling of irradiation-sensitive and irradiation-insensitive cell populations and RNA interference (RNAi) functional screening to uncover markers and regulators of postmitotic progeny.We also demonstrated the utility of using mex3-1(RNAi) animals to identify additional progenitor markers.These results identified mex3-1 as a cell fate regulator, broadly required for differentiation, and suggest that mex3-1 helps to mediate the balance between ASC self-renewal and commitment.

View Article: PubMed Central - PubMed

Affiliation: Program in Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, Canada.

ABSTRACT
Neoblasts are adult stem cells (ASCs) in planarians that sustain cell replacement during homeostasis and regeneration of any missing tissue. While numerous studies have examined genes underlying neoblast pluripotency, molecular pathways driving postmitotic fates remain poorly defined. In this study, we used transcriptional profiling of irradiation-sensitive and irradiation-insensitive cell populations and RNA interference (RNAi) functional screening to uncover markers and regulators of postmitotic progeny. We identified 32 new markers distinguishing two main epithelial progenitor populations and a planarian homolog to the MEX3 RNA-binding protein (Smed-mex3-1) as a key regulator of lineage progression. mex3-1 was required for generating differentiated cells of multiple lineages, while restricting the size of the stem cell compartment. We also demonstrated the utility of using mex3-1(RNAi) animals to identify additional progenitor markers. These results identified mex3-1 as a cell fate regulator, broadly required for differentiation, and suggest that mex3-1 helps to mediate the balance between ASC self-renewal and commitment.

No MeSH data available.


Related in: MedlinePlus

Differentiation in p53(RNAi) animals.(A) Stem cell (piwi-1) and epithelial progenitor (prog-1) populations were examined by WISH in RNAi animals. Scale bar, 200 μm. (B) Eye and neural lineage-restricted neoblast progeny were quantified in RNAi animals by FISH (ovo, eye; chat, brain) with PIWI-1 immunolabeling. Arrows indicate example double-positive cells. Scale bars, 50 μm.DOI:http://dx.doi.org/10.7554/eLife.07025.019
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fig6s2: Differentiation in p53(RNAi) animals.(A) Stem cell (piwi-1) and epithelial progenitor (prog-1) populations were examined by WISH in RNAi animals. Scale bar, 200 μm. (B) Eye and neural lineage-restricted neoblast progeny were quantified in RNAi animals by FISH (ovo, eye; chat, brain) with PIWI-1 immunolabeling. Arrows indicate example double-positive cells. Scale bars, 50 μm.DOI:http://dx.doi.org/10.7554/eLife.07025.019

Mentions: We examined whether impaired differentiation toward multiple tissues could be observed in p53(RNAi) animals as well, as p53 knockdown has previously been shown to deplete prog-1+ progeny and increase stem cell proliferation (Pearson and Sánchez Alvarado, 2010). We found that knockdown of p53 did not alter the numbers of PIWI-1+ovo+ eye- or PIWI-1+chat+ brain-specified neoblast progeny (Figure 6—figure supplement 2), demonstrating a broader role for mex3-1 in differentiation. To determine whether mex3-1 knockdown resulted in a global impediment in generating postmitotic cells, we quantified the proportion of piwi-1−PIWI-1+ cells, which are thought to represent immediate stem cell progeny that have permanently exited the cell cycle. We found that mex3-1 RNAi resulted in a significant increase in the number of piwi-1+PIWI-1+ cells and simultaneous decrease in piwi-1−PIWI-1+ cells compared to controls (Figure 6F), supporting a general reduction in the ability of stem cells to progress to a postmitotic state. From these data demonstrating abrogated production of lineage-restricted stem cell progeny, impaired contribution to the turnover of multiple tissue types, and concomitant increases in all known stem cell subclasses, we propose that mex3-1 is a critical regulator for all differentiating progeny, mediating the adoption of a non-stem cell fate.


A mex3 homolog is required for differentiation during planarian stem cell lineage development.

Zhu SJ, Hallows SE, Currie KW, Xu C, Pearson BJ - Elife (2015)

Differentiation in p53(RNAi) animals.(A) Stem cell (piwi-1) and epithelial progenitor (prog-1) populations were examined by WISH in RNAi animals. Scale bar, 200 μm. (B) Eye and neural lineage-restricted neoblast progeny were quantified in RNAi animals by FISH (ovo, eye; chat, brain) with PIWI-1 immunolabeling. Arrows indicate example double-positive cells. Scale bars, 50 μm.DOI:http://dx.doi.org/10.7554/eLife.07025.019
© Copyright Policy
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4507787&req=5

fig6s2: Differentiation in p53(RNAi) animals.(A) Stem cell (piwi-1) and epithelial progenitor (prog-1) populations were examined by WISH in RNAi animals. Scale bar, 200 μm. (B) Eye and neural lineage-restricted neoblast progeny were quantified in RNAi animals by FISH (ovo, eye; chat, brain) with PIWI-1 immunolabeling. Arrows indicate example double-positive cells. Scale bars, 50 μm.DOI:http://dx.doi.org/10.7554/eLife.07025.019
Mentions: We examined whether impaired differentiation toward multiple tissues could be observed in p53(RNAi) animals as well, as p53 knockdown has previously been shown to deplete prog-1+ progeny and increase stem cell proliferation (Pearson and Sánchez Alvarado, 2010). We found that knockdown of p53 did not alter the numbers of PIWI-1+ovo+ eye- or PIWI-1+chat+ brain-specified neoblast progeny (Figure 6—figure supplement 2), demonstrating a broader role for mex3-1 in differentiation. To determine whether mex3-1 knockdown resulted in a global impediment in generating postmitotic cells, we quantified the proportion of piwi-1−PIWI-1+ cells, which are thought to represent immediate stem cell progeny that have permanently exited the cell cycle. We found that mex3-1 RNAi resulted in a significant increase in the number of piwi-1+PIWI-1+ cells and simultaneous decrease in piwi-1−PIWI-1+ cells compared to controls (Figure 6F), supporting a general reduction in the ability of stem cells to progress to a postmitotic state. From these data demonstrating abrogated production of lineage-restricted stem cell progeny, impaired contribution to the turnover of multiple tissue types, and concomitant increases in all known stem cell subclasses, we propose that mex3-1 is a critical regulator for all differentiating progeny, mediating the adoption of a non-stem cell fate.

Bottom Line: In this study, we used transcriptional profiling of irradiation-sensitive and irradiation-insensitive cell populations and RNA interference (RNAi) functional screening to uncover markers and regulators of postmitotic progeny.We also demonstrated the utility of using mex3-1(RNAi) animals to identify additional progenitor markers.These results identified mex3-1 as a cell fate regulator, broadly required for differentiation, and suggest that mex3-1 helps to mediate the balance between ASC self-renewal and commitment.

View Article: PubMed Central - PubMed

Affiliation: Program in Developmental and Stem Cell Biology, The Hospital for Sick Children, Toronto, Canada.

ABSTRACT
Neoblasts are adult stem cells (ASCs) in planarians that sustain cell replacement during homeostasis and regeneration of any missing tissue. While numerous studies have examined genes underlying neoblast pluripotency, molecular pathways driving postmitotic fates remain poorly defined. In this study, we used transcriptional profiling of irradiation-sensitive and irradiation-insensitive cell populations and RNA interference (RNAi) functional screening to uncover markers and regulators of postmitotic progeny. We identified 32 new markers distinguishing two main epithelial progenitor populations and a planarian homolog to the MEX3 RNA-binding protein (Smed-mex3-1) as a key regulator of lineage progression. mex3-1 was required for generating differentiated cells of multiple lineages, while restricting the size of the stem cell compartment. We also demonstrated the utility of using mex3-1(RNAi) animals to identify additional progenitor markers. These results identified mex3-1 as a cell fate regulator, broadly required for differentiation, and suggest that mex3-1 helps to mediate the balance between ASC self-renewal and commitment.

No MeSH data available.


Related in: MedlinePlus