Limits...
BTG interacts with retinoblastoma to control cell fate in Dictyostelium.

Conte D, MacWilliams HK, Ceccarelli A - PLoS ONE (2010)

Bottom Line: Dictyostelium btg is the only example of non-metazoan member of the BTG family characterized so far, suggesting that a genetic interaction between btg and Rb predated the divergence between dictyostelids and metazoa.While the requirement for retinoblastoma function for BTG antiproliferative activity in metazoans is known, an interaction of these genes in the control of cell fate has not been previously documented.Involvement of a single pathway in the control of mutually exclusive processes may have relevant implication in the evolution of multicellularity.

View Article: PubMed Central - PubMed

Affiliation: Dipartimento Scienze Cliniche e Biologiche Università degli Studi di Torino, Orbassano, Italy.

ABSTRACT

Background: In the genesis of many tissues, a phase of cell proliferation is followed by cell cycle exit and terminal differentiation. The latter two processes overlap: genes involved in the cessation of growth may also be important in triggering differentiation. Though conceptually distinct, they are often causally related and functional interactions between the cell cycle machinery and cell fate control networks are fundamental to coordinate growth and differentiation. A switch from proliferation to differentiation may also be important in the life cycle of single-celled organisms, and genes which arose as regulators of microbial differentiation may be conserved in higher organisms. Studies in microorganisms may thus contribute to understanding the molecular links between cell cycle machinery and the determination of cell fate choice networks.

Methodology/principal findings: Here we show that in the amoebozoan D. discoideum, an ortholog of the metazoan antiproliferative gene btg controls cell fate, and that this function is dependent on the presence of a second tumor suppressor ortholog, the retinoblastoma-like gene product. Specifically, we find that btg-overexpressing cells preferentially adopt a stalk cell (and, more particularly, an Anterior-Like Cell) fate. No btg-dependent preference for ALC fate is observed in cells in which the retinoblastoma-like gene has been genetically inactivated. Dictyostelium btg is the only example of non-metazoan member of the BTG family characterized so far, suggesting that a genetic interaction between btg and Rb predated the divergence between dictyostelids and metazoa.

Conclusions/significance: While the requirement for retinoblastoma function for BTG antiproliferative activity in metazoans is known, an interaction of these genes in the control of cell fate has not been previously documented. Involvement of a single pathway in the control of mutually exclusive processes may have relevant implication in the evolution of multicellularity.

Show MeSH

Related in: MedlinePlus

BTG controls cell fate and is RB-dependent.A–F, Dictyostelium cells constitutively expressing RFP or GFP and overexpressing btg were mixed at a 30∶70 ratio with unlabelled cells of the same strain and allowed to develop. In control experiments the corresponding RFP or GFP strains with no btg overexpression were used. A, RFP-btgOE AX2/AX2; B, RFP-AX2/AX2; C, RFP-btgOE rblA-KO/rblA-KO; D, RFP rblA-KO/rblA-KO; E, GFP btgOE rblA-KO/AX2; F, GFP rblA-KO/AX2; bars represent 20 µm; G, culminants from samples A–F were squashed on a microscope slide and the percentage of RFP- or GFP-positive spores was determinated. Error bars indicate s.e.m.
© Copyright Policy
Related In: Results  -  Collection


getmorefigures.php?uid=PMC2837350&req=5

pone-0009676-g004: BTG controls cell fate and is RB-dependent.A–F, Dictyostelium cells constitutively expressing RFP or GFP and overexpressing btg were mixed at a 30∶70 ratio with unlabelled cells of the same strain and allowed to develop. In control experiments the corresponding RFP or GFP strains with no btg overexpression were used. A, RFP-btgOE AX2/AX2; B, RFP-AX2/AX2; C, RFP-btgOE rblA-KO/rblA-KO; D, RFP rblA-KO/rblA-KO; E, GFP btgOE rblA-KO/AX2; F, GFP rblA-KO/AX2; bars represent 20 µm; G, culminants from samples A–F were squashed on a microscope slide and the percentage of RFP- or GFP-positive spores was determinated. Error bars indicate s.e.m.

Mentions: To study the role of BTG in growth and development of D. discoideum we placed a myc-tagged version of BTG under the strong constitutive actin15 promoter [20]. Cells overexpressing BTG showed little or no increase in doubling time (Fig. S4) indicating the absence of an antiproliferative effect. When the same cells were allowed to develop, morphology as well as developmental timing were overtly normal, but the overexpressors showed preference for the ALC fate. Thus, when we labelled btg overexpressing (btg-OE) AX2 cells (Fig. S4) with a constitutively expressed red fluorescent protein (RFP) [21], and mixed them with an excess of wild type cells, the labelled cells sorted to the upper and lower cups and outer basal disc, the three structures derived from the ALC of the slug (Fig. 4A).


BTG interacts with retinoblastoma to control cell fate in Dictyostelium.

Conte D, MacWilliams HK, Ceccarelli A - PLoS ONE (2010)

BTG controls cell fate and is RB-dependent.A–F, Dictyostelium cells constitutively expressing RFP or GFP and overexpressing btg were mixed at a 30∶70 ratio with unlabelled cells of the same strain and allowed to develop. In control experiments the corresponding RFP or GFP strains with no btg overexpression were used. A, RFP-btgOE AX2/AX2; B, RFP-AX2/AX2; C, RFP-btgOE rblA-KO/rblA-KO; D, RFP rblA-KO/rblA-KO; E, GFP btgOE rblA-KO/AX2; F, GFP rblA-KO/AX2; bars represent 20 µm; G, culminants from samples A–F were squashed on a microscope slide and the percentage of RFP- or GFP-positive spores was determinated. Error bars indicate s.e.m.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2837350&req=5

pone-0009676-g004: BTG controls cell fate and is RB-dependent.A–F, Dictyostelium cells constitutively expressing RFP or GFP and overexpressing btg were mixed at a 30∶70 ratio with unlabelled cells of the same strain and allowed to develop. In control experiments the corresponding RFP or GFP strains with no btg overexpression were used. A, RFP-btgOE AX2/AX2; B, RFP-AX2/AX2; C, RFP-btgOE rblA-KO/rblA-KO; D, RFP rblA-KO/rblA-KO; E, GFP btgOE rblA-KO/AX2; F, GFP rblA-KO/AX2; bars represent 20 µm; G, culminants from samples A–F were squashed on a microscope slide and the percentage of RFP- or GFP-positive spores was determinated. Error bars indicate s.e.m.
Mentions: To study the role of BTG in growth and development of D. discoideum we placed a myc-tagged version of BTG under the strong constitutive actin15 promoter [20]. Cells overexpressing BTG showed little or no increase in doubling time (Fig. S4) indicating the absence of an antiproliferative effect. When the same cells were allowed to develop, morphology as well as developmental timing were overtly normal, but the overexpressors showed preference for the ALC fate. Thus, when we labelled btg overexpressing (btg-OE) AX2 cells (Fig. S4) with a constitutively expressed red fluorescent protein (RFP) [21], and mixed them with an excess of wild type cells, the labelled cells sorted to the upper and lower cups and outer basal disc, the three structures derived from the ALC of the slug (Fig. 4A).

Bottom Line: Dictyostelium btg is the only example of non-metazoan member of the BTG family characterized so far, suggesting that a genetic interaction between btg and Rb predated the divergence between dictyostelids and metazoa.While the requirement for retinoblastoma function for BTG antiproliferative activity in metazoans is known, an interaction of these genes in the control of cell fate has not been previously documented.Involvement of a single pathway in the control of mutually exclusive processes may have relevant implication in the evolution of multicellularity.

View Article: PubMed Central - PubMed

Affiliation: Dipartimento Scienze Cliniche e Biologiche Università degli Studi di Torino, Orbassano, Italy.

ABSTRACT

Background: In the genesis of many tissues, a phase of cell proliferation is followed by cell cycle exit and terminal differentiation. The latter two processes overlap: genes involved in the cessation of growth may also be important in triggering differentiation. Though conceptually distinct, they are often causally related and functional interactions between the cell cycle machinery and cell fate control networks are fundamental to coordinate growth and differentiation. A switch from proliferation to differentiation may also be important in the life cycle of single-celled organisms, and genes which arose as regulators of microbial differentiation may be conserved in higher organisms. Studies in microorganisms may thus contribute to understanding the molecular links between cell cycle machinery and the determination of cell fate choice networks.

Methodology/principal findings: Here we show that in the amoebozoan D. discoideum, an ortholog of the metazoan antiproliferative gene btg controls cell fate, and that this function is dependent on the presence of a second tumor suppressor ortholog, the retinoblastoma-like gene product. Specifically, we find that btg-overexpressing cells preferentially adopt a stalk cell (and, more particularly, an Anterior-Like Cell) fate. No btg-dependent preference for ALC fate is observed in cells in which the retinoblastoma-like gene has been genetically inactivated. Dictyostelium btg is the only example of non-metazoan member of the BTG family characterized so far, suggesting that a genetic interaction between btg and Rb predated the divergence between dictyostelids and metazoa.

Conclusions/significance: While the requirement for retinoblastoma function for BTG antiproliferative activity in metazoans is known, an interaction of these genes in the control of cell fate has not been previously documented. Involvement of a single pathway in the control of mutually exclusive processes may have relevant implication in the evolution of multicellularity.

Show MeSH
Related in: MedlinePlus