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A Stable Thoracic Hox Code and Epimorphosis Characterize Posterior Regeneration in Capitella teleta.

de Jong DM, Seaver EC - PLoS ONE (2016)

Bottom Line: In situ hybridization shows that seven of the ten Hox genes examined are expressed in the blastema, suggesting roles in patterning the newly forming tissue, although neither spatial nor temporal co-linearity was detected.However, the three Hox genes, CapI-lox4, CapI-lox2 and CapI-Post2, each shift its anterior expression boundary by one segment, and each shift includes a subset of cells in the ganglia.In C. teleta, thoracic segments exhibit stable positional identity with limited morphallaxis, in contrast with the extensive body remodeling that occurs during regeneration of some other annelids, planarians and acoel flatworms.

View Article: PubMed Central - PubMed

Affiliation: Whitney Laboratory for Marine Bioscience, University of Florida, St. Augustine, Florida, United States of America.

ABSTRACT
Regeneration, the ability to replace lost tissues and body parts following traumatic injury, occurs widely throughout the animal tree of life. Regeneration occurs either by remodeling of pre-existing tissues, through addition of new cells by cell division, or a combination of both. We describe a staging system for posterior regeneration in the annelid, Capitella teleta, and use the C. teleta Hox gene code as markers of regional identity for regenerating tissue along the anterior-posterior axis. Following amputation of different posterior regions of the animal, a blastema forms and by two days, proliferating cells are detected by EdU incorporation, demonstrating that epimorphosis occurs during posterior regeneration of C. teleta. Neurites rapidly extend into the blastema, and gradually become organized into discrete nerves before new ganglia appear approximately seven days after amputation. In situ hybridization shows that seven of the ten Hox genes examined are expressed in the blastema, suggesting roles in patterning the newly forming tissue, although neither spatial nor temporal co-linearity was detected. We hypothesized that following amputation, Hox gene expression in pre-existing segments would be re-organized to scale, and the remaining fragment would express the complete suite of Hox genes. Surprisingly, most Hox genes display stable expression patterns in the ganglia of pre-existing tissue following amputation at multiple axial positions, indicating general stability of segmental identity. However, the three Hox genes, CapI-lox4, CapI-lox2 and CapI-Post2, each shift its anterior expression boundary by one segment, and each shift includes a subset of cells in the ganglia. This expression shift depends upon the axial position of the amputation. In C. teleta, thoracic segments exhibit stable positional identity with limited morphallaxis, in contrast with the extensive body remodeling that occurs during regeneration of some other annelids, planarians and acoel flatworms.

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Blastema formation, cell division patterns and nerve cord dynamics during posterior regeneration of C. teleta.All panels show posterior ends of amputated juveniles in ventral view, with anterior to the left. Amputations were conducted at the boundary of segment 10 and 11. White dotted lines indicate approximate position of amputation, and all tissue to the right of dotted lines is regenerated tissue. The panels in each row are from a single individual. The regenerative process is described as progressing through different stages (left of rows), and specific stain, chemical or antibody is indicated at the top of columns. (A-G) Hoechst 33342 staining showing nuclei; (A’-G’) EdU incorporation marking dividing cells; (A”-G”) anti-acetylated α-tubulin labeling neurites. Scale bars in A”-G” are 50 μm. White circle in A”, F” and G” shows cilia of the hindgut. White arrowheads show mature ganglia in A, A”, B, B”, G and G”. Open arrowheads show peripheral nerves in A” and G”. White arrows in A”, F” and G” mark the Y-shaped neurites which extend into the pygidium. Blue arrows in E” mark nerve tracts. Blue arrows in F” mark medial axons that branch from the ventral nerve cord and red arrows mark axons that branch from lateral nerves. White arrows in E’ indicate bilateral clusters of EdU-positive cells. Chaetae are autofluorescent and are visible in A’, B’, C’ and D’.
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pone.0149724.g002: Blastema formation, cell division patterns and nerve cord dynamics during posterior regeneration of C. teleta.All panels show posterior ends of amputated juveniles in ventral view, with anterior to the left. Amputations were conducted at the boundary of segment 10 and 11. White dotted lines indicate approximate position of amputation, and all tissue to the right of dotted lines is regenerated tissue. The panels in each row are from a single individual. The regenerative process is described as progressing through different stages (left of rows), and specific stain, chemical or antibody is indicated at the top of columns. (A-G) Hoechst 33342 staining showing nuclei; (A’-G’) EdU incorporation marking dividing cells; (A”-G”) anti-acetylated α-tubulin labeling neurites. Scale bars in A”-G” are 50 μm. White circle in A”, F” and G” shows cilia of the hindgut. White arrowheads show mature ganglia in A, A”, B, B”, G and G”. Open arrowheads show peripheral nerves in A” and G”. White arrows in A”, F” and G” mark the Y-shaped neurites which extend into the pygidium. Blue arrows in E” mark nerve tracts. Blue arrows in F” mark medial axons that branch from the ventral nerve cord and red arrows mark axons that branch from lateral nerves. White arrows in E’ indicate bilateral clusters of EdU-positive cells. Chaetae are autofluorescent and are visible in A’, B’, C’ and D’.

Mentions: The posterior end of unamputated juveniles contains mature abdominal segments (aqua bar in Fig 2A–2A”), a subterminal posterior growth zone (PGZ; green bar in Fig 2A–2A”), and a terminal pygidium (white bar in Fig 2A–2A”). The ventral nerve cord of each mature abdominal segment contains a ganglion (Fig 2A and 2A”, white arrowhead marks one in each panel), with three peripheral nerves extending laterally (Fig 2A”, open arrowheads showing three peripheral nerves). In uncut juveniles, we define the PGZ as the area anterior to the pygidium, but posterior to the posterior-most segment containing a well-defined ganglion. Segments immediately anterior to the PGZ tend to be smaller than segments further anterior, consistent with them undergoing significant growth after segment boundaries initially form. In the posterior end of the animal, the lumen of the hindgut contains cilia that can be visualized by anti-acetylated α-tubulin (Fig 2A”, white circle; S2A Fig). The pygidium of C. teleta is simple in morphology and lacks terminal projections such as anal cirri. Neurites extend from the posterior-most ganglion in a posterior direction into the pygidium. The lateral-most of these have a Y-shaped pattern as they extend through the PGZ, and innervate the pygidium with a diagonal orientation with respect to the anterior-posterior axis of the body (Fig 2A”, white arrows).


A Stable Thoracic Hox Code and Epimorphosis Characterize Posterior Regeneration in Capitella teleta.

de Jong DM, Seaver EC - PLoS ONE (2016)

Blastema formation, cell division patterns and nerve cord dynamics during posterior regeneration of C. teleta.All panels show posterior ends of amputated juveniles in ventral view, with anterior to the left. Amputations were conducted at the boundary of segment 10 and 11. White dotted lines indicate approximate position of amputation, and all tissue to the right of dotted lines is regenerated tissue. The panels in each row are from a single individual. The regenerative process is described as progressing through different stages (left of rows), and specific stain, chemical or antibody is indicated at the top of columns. (A-G) Hoechst 33342 staining showing nuclei; (A’-G’) EdU incorporation marking dividing cells; (A”-G”) anti-acetylated α-tubulin labeling neurites. Scale bars in A”-G” are 50 μm. White circle in A”, F” and G” shows cilia of the hindgut. White arrowheads show mature ganglia in A, A”, B, B”, G and G”. Open arrowheads show peripheral nerves in A” and G”. White arrows in A”, F” and G” mark the Y-shaped neurites which extend into the pygidium. Blue arrows in E” mark nerve tracts. Blue arrows in F” mark medial axons that branch from the ventral nerve cord and red arrows mark axons that branch from lateral nerves. White arrows in E’ indicate bilateral clusters of EdU-positive cells. Chaetae are autofluorescent and are visible in A’, B’, C’ and D’.
© Copyright Policy
Related In: Results  -  Collection

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Show All Figures
getmorefigures.php?uid=PMC4764619&req=5

pone.0149724.g002: Blastema formation, cell division patterns and nerve cord dynamics during posterior regeneration of C. teleta.All panels show posterior ends of amputated juveniles in ventral view, with anterior to the left. Amputations were conducted at the boundary of segment 10 and 11. White dotted lines indicate approximate position of amputation, and all tissue to the right of dotted lines is regenerated tissue. The panels in each row are from a single individual. The regenerative process is described as progressing through different stages (left of rows), and specific stain, chemical or antibody is indicated at the top of columns. (A-G) Hoechst 33342 staining showing nuclei; (A’-G’) EdU incorporation marking dividing cells; (A”-G”) anti-acetylated α-tubulin labeling neurites. Scale bars in A”-G” are 50 μm. White circle in A”, F” and G” shows cilia of the hindgut. White arrowheads show mature ganglia in A, A”, B, B”, G and G”. Open arrowheads show peripheral nerves in A” and G”. White arrows in A”, F” and G” mark the Y-shaped neurites which extend into the pygidium. Blue arrows in E” mark nerve tracts. Blue arrows in F” mark medial axons that branch from the ventral nerve cord and red arrows mark axons that branch from lateral nerves. White arrows in E’ indicate bilateral clusters of EdU-positive cells. Chaetae are autofluorescent and are visible in A’, B’, C’ and D’.
Mentions: The posterior end of unamputated juveniles contains mature abdominal segments (aqua bar in Fig 2A–2A”), a subterminal posterior growth zone (PGZ; green bar in Fig 2A–2A”), and a terminal pygidium (white bar in Fig 2A–2A”). The ventral nerve cord of each mature abdominal segment contains a ganglion (Fig 2A and 2A”, white arrowhead marks one in each panel), with three peripheral nerves extending laterally (Fig 2A”, open arrowheads showing three peripheral nerves). In uncut juveniles, we define the PGZ as the area anterior to the pygidium, but posterior to the posterior-most segment containing a well-defined ganglion. Segments immediately anterior to the PGZ tend to be smaller than segments further anterior, consistent with them undergoing significant growth after segment boundaries initially form. In the posterior end of the animal, the lumen of the hindgut contains cilia that can be visualized by anti-acetylated α-tubulin (Fig 2A”, white circle; S2A Fig). The pygidium of C. teleta is simple in morphology and lacks terminal projections such as anal cirri. Neurites extend from the posterior-most ganglion in a posterior direction into the pygidium. The lateral-most of these have a Y-shaped pattern as they extend through the PGZ, and innervate the pygidium with a diagonal orientation with respect to the anterior-posterior axis of the body (Fig 2A”, white arrows).

Bottom Line: In situ hybridization shows that seven of the ten Hox genes examined are expressed in the blastema, suggesting roles in patterning the newly forming tissue, although neither spatial nor temporal co-linearity was detected.However, the three Hox genes, CapI-lox4, CapI-lox2 and CapI-Post2, each shift its anterior expression boundary by one segment, and each shift includes a subset of cells in the ganglia.In C. teleta, thoracic segments exhibit stable positional identity with limited morphallaxis, in contrast with the extensive body remodeling that occurs during regeneration of some other annelids, planarians and acoel flatworms.

View Article: PubMed Central - PubMed

Affiliation: Whitney Laboratory for Marine Bioscience, University of Florida, St. Augustine, Florida, United States of America.

ABSTRACT
Regeneration, the ability to replace lost tissues and body parts following traumatic injury, occurs widely throughout the animal tree of life. Regeneration occurs either by remodeling of pre-existing tissues, through addition of new cells by cell division, or a combination of both. We describe a staging system for posterior regeneration in the annelid, Capitella teleta, and use the C. teleta Hox gene code as markers of regional identity for regenerating tissue along the anterior-posterior axis. Following amputation of different posterior regions of the animal, a blastema forms and by two days, proliferating cells are detected by EdU incorporation, demonstrating that epimorphosis occurs during posterior regeneration of C. teleta. Neurites rapidly extend into the blastema, and gradually become organized into discrete nerves before new ganglia appear approximately seven days after amputation. In situ hybridization shows that seven of the ten Hox genes examined are expressed in the blastema, suggesting roles in patterning the newly forming tissue, although neither spatial nor temporal co-linearity was detected. We hypothesized that following amputation, Hox gene expression in pre-existing segments would be re-organized to scale, and the remaining fragment would express the complete suite of Hox genes. Surprisingly, most Hox genes display stable expression patterns in the ganglia of pre-existing tissue following amputation at multiple axial positions, indicating general stability of segmental identity. However, the three Hox genes, CapI-lox4, CapI-lox2 and CapI-Post2, each shift its anterior expression boundary by one segment, and each shift includes a subset of cells in the ganglia. This expression shift depends upon the axial position of the amputation. In C. teleta, thoracic segments exhibit stable positional identity with limited morphallaxis, in contrast with the extensive body remodeling that occurs during regeneration of some other annelids, planarians and acoel flatworms.

Show MeSH
Related in: MedlinePlus