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Btk29A-mediated tyrosine phosphorylation of armadillo/β-catenin promotes ring canal growth in Drosophila oogenesis.

Hamada-Kawaguchi N, Nishida Y, Yamamoto D - PLoS ONE (2015)

Bottom Line: In this study, inactivation of Parcas, a negative regulator of Btk29A, was found to promote Btk29A accumulation on ring canals with a concomitant increase in the ring canal diameter, counteracting the Btk29AficP mutation.This mutation markedly reduced the accumulation of phosphotyrosine on ring canals and in the regions of cell-cell contact, where adhesion-supporting proteins such as DE-cadherin and β-catenin ortholog Armadillo (Arm) are located.We suggest that the dissociation of tyrosine-phosphorylated Arm from DE-cadherin allows dynamic actin to reorganize, leading to ring canal expansion and cell shape changes during the course of oogenesis.

View Article: PubMed Central - PubMed

Affiliation: Department of Developmental Biology and Neurosciences, Tohoku University, Graduate School of Life Sciences, Sendai, Japan.

ABSTRACT
Drosophila Btk29A is the ortholog of mammalian Btk, a Tec family nonreceptor tyrosine kinase whose deficit causes X-linked agammaglobulinemia in humans. The Btk29AficP mutation induces multiple abnormalities in oogenesis, including the growth arrest of ring canals, large intercellular bridges that allow the flow of cytoplasm carrying maternal products essential for embryonic development from the nurse cells to the oocyte during oogenesis. In this study, inactivation of Parcas, a negative regulator of Btk29A, was found to promote Btk29A accumulation on ring canals with a concomitant increase in the ring canal diameter, counteracting the Btk29AficP mutation. This mutation markedly reduced the accumulation of phosphotyrosine on ring canals and in the regions of cell-cell contact, where adhesion-supporting proteins such as DE-cadherin and β-catenin ortholog Armadillo (Arm) are located. Our previous in vitro and in vivo analyses revealed that Btk29A directly phosphorylates Arm, leading to its release from DE-cadherin. In the present experiments, immunohistological analysis revealed that phosphorylation at tyrosine 150 (Y150) and Y667 of Arm was diminished in Btk29AficP mutant ring canals. Overexpression of an Arm mutant with unphosphorylatable Y150 inhibited ring canal growth. Thus Btk29A-induced Y150 phosphorylation is necessary for the normal growth of ring canals. We suggest that the dissociation of tyrosine-phosphorylated Arm from DE-cadherin allows dynamic actin to reorganize, leading to ring canal expansion and cell shape changes during the course of oogenesis.

No MeSH data available.


Related in: MedlinePlus

Ovarian phenotypes of Btk29AficP mutants.(A and B) Germaria and early egg chambers of the wild type (A) and Btk29AficP (B) stained for phalloidin. In the wild type, Region 2b is bordered posteriorly by elongated follicle cells; in Btk29AficP mutants, these cells are interspersed with germ cells having a round appearance, reflecting a wrapping defect. The number of germ cells present in a germarium is variable and the overall shape of the germarium is distorted in Btk29AficP mutants, compared with that of the wild type. At stage 1, a wild-type egg chamber is always oval in shape and invariably contains 16 germ cells. (C and D) Stage 3—stage 8 egg chambers of wild-type (C) and Btk29AficP mutant (D) ovaries. (E and F) Stage 9 mature egg chambers of wild-type (E) and Btk29AficP (F) ovaries. Scale bars: 10 μm for (A-D) and 50 μm for (E and F).
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pone.0121484.g001: Ovarian phenotypes of Btk29AficP mutants.(A and B) Germaria and early egg chambers of the wild type (A) and Btk29AficP (B) stained for phalloidin. In the wild type, Region 2b is bordered posteriorly by elongated follicle cells; in Btk29AficP mutants, these cells are interspersed with germ cells having a round appearance, reflecting a wrapping defect. The number of germ cells present in a germarium is variable and the overall shape of the germarium is distorted in Btk29AficP mutants, compared with that of the wild type. At stage 1, a wild-type egg chamber is always oval in shape and invariably contains 16 germ cells. (C and D) Stage 3—stage 8 egg chambers of wild-type (C) and Btk29AficP mutant (D) ovaries. (E and F) Stage 9 mature egg chambers of wild-type (E) and Btk29AficP (F) ovaries. Scale bars: 10 μm for (A-D) and 50 μm for (E and F).

Mentions: All germ cells are produced by germ stem cells (GSCs) in the germarium, which is subdivided into Regions 1–3 (Region 3 corresponds to the stage 1 egg chamber; see below and Fig. 1A). A GSC divides asymmetrically to generate a GSC and a cystoblast (CB). A CB undergoes 4 rounds of symmetrical divisions, resulting in incomplete cytokinesis and producing a cyst composed of 16 connected cells. 15 cells in the cyst become nurse cells and the remaining posterior cell takes on the oocyte fate. Ring canals are derivatives of the arrested contractile rings resulting from incomplete cytokinesis, in which a contractile ring does not close so that two sib-cells remain connected with a canal. Thus the first ring canal emerges at the first division of the CB in Region 1 of the germarium (Fig. 1A), and two subsequent divisions also take place and produce corresponding ring canals. Other additional ring canals are the products of further incomplete cytokineses which occur in Region 2a and Region 2b (Fig. 1A). In Region 2b, the cyst changes shape and becomes a one cell-thick disc that spans the whole width of the germanium. A cyst in Region 2b continues to develop into a stage 1 egg chamber encapsulated by the follicular layer (Fig. 1A). The egg chamber matures through stages 1–12 (Figs. 1A, 1C and 1E for stages 1–9). Ring canals are therefore composed of molecules constituting contractile rings, the primary component of which is actin.


Btk29A-mediated tyrosine phosphorylation of armadillo/β-catenin promotes ring canal growth in Drosophila oogenesis.

Hamada-Kawaguchi N, Nishida Y, Yamamoto D - PLoS ONE (2015)

Ovarian phenotypes of Btk29AficP mutants.(A and B) Germaria and early egg chambers of the wild type (A) and Btk29AficP (B) stained for phalloidin. In the wild type, Region 2b is bordered posteriorly by elongated follicle cells; in Btk29AficP mutants, these cells are interspersed with germ cells having a round appearance, reflecting a wrapping defect. The number of germ cells present in a germarium is variable and the overall shape of the germarium is distorted in Btk29AficP mutants, compared with that of the wild type. At stage 1, a wild-type egg chamber is always oval in shape and invariably contains 16 germ cells. (C and D) Stage 3—stage 8 egg chambers of wild-type (C) and Btk29AficP mutant (D) ovaries. (E and F) Stage 9 mature egg chambers of wild-type (E) and Btk29AficP (F) ovaries. Scale bars: 10 μm for (A-D) and 50 μm for (E and F).
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Related In: Results  -  Collection

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pone.0121484.g001: Ovarian phenotypes of Btk29AficP mutants.(A and B) Germaria and early egg chambers of the wild type (A) and Btk29AficP (B) stained for phalloidin. In the wild type, Region 2b is bordered posteriorly by elongated follicle cells; in Btk29AficP mutants, these cells are interspersed with germ cells having a round appearance, reflecting a wrapping defect. The number of germ cells present in a germarium is variable and the overall shape of the germarium is distorted in Btk29AficP mutants, compared with that of the wild type. At stage 1, a wild-type egg chamber is always oval in shape and invariably contains 16 germ cells. (C and D) Stage 3—stage 8 egg chambers of wild-type (C) and Btk29AficP mutant (D) ovaries. (E and F) Stage 9 mature egg chambers of wild-type (E) and Btk29AficP (F) ovaries. Scale bars: 10 μm for (A-D) and 50 μm for (E and F).
Mentions: All germ cells are produced by germ stem cells (GSCs) in the germarium, which is subdivided into Regions 1–3 (Region 3 corresponds to the stage 1 egg chamber; see below and Fig. 1A). A GSC divides asymmetrically to generate a GSC and a cystoblast (CB). A CB undergoes 4 rounds of symmetrical divisions, resulting in incomplete cytokinesis and producing a cyst composed of 16 connected cells. 15 cells in the cyst become nurse cells and the remaining posterior cell takes on the oocyte fate. Ring canals are derivatives of the arrested contractile rings resulting from incomplete cytokinesis, in which a contractile ring does not close so that two sib-cells remain connected with a canal. Thus the first ring canal emerges at the first division of the CB in Region 1 of the germarium (Fig. 1A), and two subsequent divisions also take place and produce corresponding ring canals. Other additional ring canals are the products of further incomplete cytokineses which occur in Region 2a and Region 2b (Fig. 1A). In Region 2b, the cyst changes shape and becomes a one cell-thick disc that spans the whole width of the germanium. A cyst in Region 2b continues to develop into a stage 1 egg chamber encapsulated by the follicular layer (Fig. 1A). The egg chamber matures through stages 1–12 (Figs. 1A, 1C and 1E for stages 1–9). Ring canals are therefore composed of molecules constituting contractile rings, the primary component of which is actin.

Bottom Line: In this study, inactivation of Parcas, a negative regulator of Btk29A, was found to promote Btk29A accumulation on ring canals with a concomitant increase in the ring canal diameter, counteracting the Btk29AficP mutation.This mutation markedly reduced the accumulation of phosphotyrosine on ring canals and in the regions of cell-cell contact, where adhesion-supporting proteins such as DE-cadherin and β-catenin ortholog Armadillo (Arm) are located.We suggest that the dissociation of tyrosine-phosphorylated Arm from DE-cadherin allows dynamic actin to reorganize, leading to ring canal expansion and cell shape changes during the course of oogenesis.

View Article: PubMed Central - PubMed

Affiliation: Department of Developmental Biology and Neurosciences, Tohoku University, Graduate School of Life Sciences, Sendai, Japan.

ABSTRACT
Drosophila Btk29A is the ortholog of mammalian Btk, a Tec family nonreceptor tyrosine kinase whose deficit causes X-linked agammaglobulinemia in humans. The Btk29AficP mutation induces multiple abnormalities in oogenesis, including the growth arrest of ring canals, large intercellular bridges that allow the flow of cytoplasm carrying maternal products essential for embryonic development from the nurse cells to the oocyte during oogenesis. In this study, inactivation of Parcas, a negative regulator of Btk29A, was found to promote Btk29A accumulation on ring canals with a concomitant increase in the ring canal diameter, counteracting the Btk29AficP mutation. This mutation markedly reduced the accumulation of phosphotyrosine on ring canals and in the regions of cell-cell contact, where adhesion-supporting proteins such as DE-cadherin and β-catenin ortholog Armadillo (Arm) are located. Our previous in vitro and in vivo analyses revealed that Btk29A directly phosphorylates Arm, leading to its release from DE-cadherin. In the present experiments, immunohistological analysis revealed that phosphorylation at tyrosine 150 (Y150) and Y667 of Arm was diminished in Btk29AficP mutant ring canals. Overexpression of an Arm mutant with unphosphorylatable Y150 inhibited ring canal growth. Thus Btk29A-induced Y150 phosphorylation is necessary for the normal growth of ring canals. We suggest that the dissociation of tyrosine-phosphorylated Arm from DE-cadherin allows dynamic actin to reorganize, leading to ring canal expansion and cell shape changes during the course of oogenesis.

No MeSH data available.


Related in: MedlinePlus