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Drosophila myoblast city encodes a conserved protein that is essential for myoblast fusion, dorsal closure, and cytoskeletal organization.

Erickson MR, Galletta BJ, Abmayr SM - J. Cell Biol. (1997)

Bottom Line: It is also expressed in the pole cells and in ectodermally derived tissues, including the epidermis.Consistent with this latter expression, mbc mutant embryos exhibit defects in dorsal closure and cytoskeletal organization in the migrating epidermis.Both the mesodermal and ectodermal defects are reminiscent of those induced by altered forms of Drac1 and suggest that mbc may function in the same pathway.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biology and Center for Gene Regulation, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.

ABSTRACT
The Drosophila myoblast city (mbc) locus was previously identified on the basis of a defect in myoblast fusion (Rushton et al., 1995. Development [Camb.]. 121:1979-1988). We describe herein the isolation and characterization of the mbc gene. The mbc transcript and its encoded protein are expressed in a broad range of tissues, including somatic myoblasts, cardial cells, and visceral mesoderm. It is also expressed in the pole cells and in ectodermally derived tissues, including the epidermis. Consistent with this latter expression, mbc mutant embryos exhibit defects in dorsal closure and cytoskeletal organization in the migrating epidermis. Both the mesodermal and ectodermal defects are reminiscent of those induced by altered forms of Drac1 and suggest that mbc may function in the same pathway. MBC bears striking homology to human DOCK180, which interacts with the SH2-SH3 adapter protein Crk and may play a role in signal transduction from focal adhesions. Taken together, these results suggest the possibility that MBC is an intermediate in a signal transduction pathway from the rho/rac family of GTPases to events in the cytoskeleton and that this pathway may be used during myoblast fusion and dorsal closure.

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Spatial expression pattern of mbc mRNA in wild-type embryos. In all panels, anterior is to the left. In A, D, E, F, and G, dorsal  is at the top. (A) Lateral view, early stage 4, before cellularization. (B) Dorsal view, stage 5. (C) Ventral view, stage 6; the invaginating  ventral furrow is evident. (D) Lateral view, stage 9. (E) Lateral view of the ectoderm, late stage 12; arrows highlight ectodermal stripes.  (F) Lateral view focusing on the mesoderm and endoderm of the same embryo as in E. (G) Lateral view, stage 14; focusing on mesodermal cells. (H) Dorsal view, stage 14; arrowheads indicate the visceral musculature. (I) Dorsal view; stage 16; expression is evident in the  cardial and pericardial cells of the dorsal vessel.
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Figure 4: Spatial expression pattern of mbc mRNA in wild-type embryos. In all panels, anterior is to the left. In A, D, E, F, and G, dorsal is at the top. (A) Lateral view, early stage 4, before cellularization. (B) Dorsal view, stage 5. (C) Ventral view, stage 6; the invaginating ventral furrow is evident. (D) Lateral view, stage 9. (E) Lateral view of the ectoderm, late stage 12; arrows highlight ectodermal stripes. (F) Lateral view focusing on the mesoderm and endoderm of the same embryo as in E. (G) Lateral view, stage 14; focusing on mesodermal cells. (H) Dorsal view, stage 14; arrowheads indicate the visceral musculature. (I) Dorsal view; stage 16; expression is evident in the cardial and pericardial cells of the dorsal vessel.

Mentions: The earliest expression of the mbc transcript is in the pole cells (Fig. 4 A). It is later found in lateral portions of the embryo during cellularization (Fig. 4 B) but is not evident at the termini. Surprisingly, the ventral furrow, which will invaginate during gastrulation to form the mesoderm, shows no expression at this time (Fig. 4 C). At germband elongation, expression is still quite strong in the ectoderm (Fig. 4 D). By late stage 12, the mRNA appears to be decreasing in the ectoderm, leaving a pattern of stripes (Fig. 4 E, arrows). mbc is expressed in both the mesoderm and endoderm during stage 12 (Fig. 4 F). Expression decreases in both the epidermal layer and the somatic mesoderm during stage 14 (Fig. 4 G) but remains strong in the visceral musculature (Fig. 4 H, arrowheads). Examination of a stage 16 embryo revealed mRNA in both the cardial and pericardial cells of the dorsal vessel (Fig. 4 I). Of note, the mbc transcript is not observed in mature muscle fibers.


Drosophila myoblast city encodes a conserved protein that is essential for myoblast fusion, dorsal closure, and cytoskeletal organization.

Erickson MR, Galletta BJ, Abmayr SM - J. Cell Biol. (1997)

Spatial expression pattern of mbc mRNA in wild-type embryos. In all panels, anterior is to the left. In A, D, E, F, and G, dorsal  is at the top. (A) Lateral view, early stage 4, before cellularization. (B) Dorsal view, stage 5. (C) Ventral view, stage 6; the invaginating  ventral furrow is evident. (D) Lateral view, stage 9. (E) Lateral view of the ectoderm, late stage 12; arrows highlight ectodermal stripes.  (F) Lateral view focusing on the mesoderm and endoderm of the same embryo as in E. (G) Lateral view, stage 14; focusing on mesodermal cells. (H) Dorsal view, stage 14; arrowheads indicate the visceral musculature. (I) Dorsal view; stage 16; expression is evident in the  cardial and pericardial cells of the dorsal vessel.
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Related In: Results  -  Collection

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Figure 4: Spatial expression pattern of mbc mRNA in wild-type embryos. In all panels, anterior is to the left. In A, D, E, F, and G, dorsal is at the top. (A) Lateral view, early stage 4, before cellularization. (B) Dorsal view, stage 5. (C) Ventral view, stage 6; the invaginating ventral furrow is evident. (D) Lateral view, stage 9. (E) Lateral view of the ectoderm, late stage 12; arrows highlight ectodermal stripes. (F) Lateral view focusing on the mesoderm and endoderm of the same embryo as in E. (G) Lateral view, stage 14; focusing on mesodermal cells. (H) Dorsal view, stage 14; arrowheads indicate the visceral musculature. (I) Dorsal view; stage 16; expression is evident in the cardial and pericardial cells of the dorsal vessel.
Mentions: The earliest expression of the mbc transcript is in the pole cells (Fig. 4 A). It is later found in lateral portions of the embryo during cellularization (Fig. 4 B) but is not evident at the termini. Surprisingly, the ventral furrow, which will invaginate during gastrulation to form the mesoderm, shows no expression at this time (Fig. 4 C). At germband elongation, expression is still quite strong in the ectoderm (Fig. 4 D). By late stage 12, the mRNA appears to be decreasing in the ectoderm, leaving a pattern of stripes (Fig. 4 E, arrows). mbc is expressed in both the mesoderm and endoderm during stage 12 (Fig. 4 F). Expression decreases in both the epidermal layer and the somatic mesoderm during stage 14 (Fig. 4 G) but remains strong in the visceral musculature (Fig. 4 H, arrowheads). Examination of a stage 16 embryo revealed mRNA in both the cardial and pericardial cells of the dorsal vessel (Fig. 4 I). Of note, the mbc transcript is not observed in mature muscle fibers.

Bottom Line: It is also expressed in the pole cells and in ectodermally derived tissues, including the epidermis.Consistent with this latter expression, mbc mutant embryos exhibit defects in dorsal closure and cytoskeletal organization in the migrating epidermis.Both the mesodermal and ectodermal defects are reminiscent of those induced by altered forms of Drac1 and suggest that mbc may function in the same pathway.

View Article: PubMed Central - PubMed

Affiliation: Department of Biochemistry and Molecular Biology and Center for Gene Regulation, The Pennsylvania State University, University Park, Pennsylvania 16802, USA.

ABSTRACT
The Drosophila myoblast city (mbc) locus was previously identified on the basis of a defect in myoblast fusion (Rushton et al., 1995. Development [Camb.]. 121:1979-1988). We describe herein the isolation and characterization of the mbc gene. The mbc transcript and its encoded protein are expressed in a broad range of tissues, including somatic myoblasts, cardial cells, and visceral mesoderm. It is also expressed in the pole cells and in ectodermally derived tissues, including the epidermis. Consistent with this latter expression, mbc mutant embryos exhibit defects in dorsal closure and cytoskeletal organization in the migrating epidermis. Both the mesodermal and ectodermal defects are reminiscent of those induced by altered forms of Drac1 and suggest that mbc may function in the same pathway. MBC bears striking homology to human DOCK180, which interacts with the SH2-SH3 adapter protein Crk and may play a role in signal transduction from focal adhesions. Taken together, these results suggest the possibility that MBC is an intermediate in a signal transduction pathway from the rho/rac family of GTPases to events in the cytoskeleton and that this pathway may be used during myoblast fusion and dorsal closure.

Show MeSH
Related in: MedlinePlus