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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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Relationship between CapI-Hox3 and dividing cells in the blastema and PGZ.All panels show posterior ends of juveniles in a ventral view, with anterior to the left. Where appropriate, approximate amputation sites are marked with dotted lines, and all tissue to the right of these lines is newly generated tissue. All panels are confocal images. Images shown in panels A-F were generated from a subset of slices from a z-stack, whereas panels A’-F’ were generated from maximum projections of z-stacks. A DIC image of the CapI-Hox3 expression domain is shown in the first column, EdU-positive cells in the second column, and a DIC/EdU merge shown in the final column. Stages of regeneration are indicated to the left of rows. (A-F) DIC image of CapI-Hox3 expression; (A’-F’) EdU incorporation marking dividing cells; (A”-F”) Merge of DIC and EdU channels. (A-A”) Unamputated juveniles following a one hour EdU pulse; (B-B”) Stage II of regeneration; (C-C”) Stage III; (D-D”) Stage IV; (E-E”) Stage V; (F-F”) Unamputated juveniles following an eight hour EdU pulse. The panels in each row are from a single juvenile. Dark brown shapes within juveniles are deposits within the lumen of the gut. White arrows indicate examples of single EdU-positive cells within the CapI-Hox3 expression domain.
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pone.0149724.g005: Relationship between CapI-Hox3 and dividing cells in the blastema and PGZ.All panels show posterior ends of juveniles in a ventral view, with anterior to the left. Where appropriate, approximate amputation sites are marked with dotted lines, and all tissue to the right of these lines is newly generated tissue. All panels are confocal images. Images shown in panels A-F were generated from a subset of slices from a z-stack, whereas panels A’-F’ were generated from maximum projections of z-stacks. A DIC image of the CapI-Hox3 expression domain is shown in the first column, EdU-positive cells in the second column, and a DIC/EdU merge shown in the final column. Stages of regeneration are indicated to the left of rows. (A-F) DIC image of CapI-Hox3 expression; (A’-F’) EdU incorporation marking dividing cells; (A”-F”) Merge of DIC and EdU channels. (A-A”) Unamputated juveniles following a one hour EdU pulse; (B-B”) Stage II of regeneration; (C-C”) Stage III; (D-D”) Stage IV; (E-E”) Stage V; (F-F”) Unamputated juveniles following an eight hour EdU pulse. The panels in each row are from a single juvenile. Dark brown shapes within juveniles are deposits within the lumen of the gut. White arrows indicate examples of single EdU-positive cells within the CapI-Hox3 expression domain.

Mentions: In uncut 2 week post-metamorphic juveniles, the anterior class Hox genes, CapI-lab and CapI-pb, are expressed in thoracic segments 1–7 and 5–8, respectively, and CapI-Hox3 (paralogy group 3 (PG3)), is expressed exclusively in the PGZ. CapI-lab expression is limited to the ganglia of the VNC, whilst CapI-pb expression is also apparent in the epidermis, in a striped pattern (Fig 4A, 4E and 4I). Although the anterior and posterior boundaries of these genes are invariant, CapI-lab expression is strongest in segments 2 and 3, and weaker in the surrounding segments, while CapI-pb shows strongest expression in segments 6 and 7, with weaker expression in segments 5 and 8. Following amputation, the anterior and posterior boundaries of expression of each gene were unchanged (Fig 4B–4D and Fig 4F–4H). In the case for CapI-Hox3, amputation removes the original expression domain, and CapI-Hox3 expression was not observed in pre-existing segments during any time point examined. CapI-Hox3 expression is initiated in the newly formed tissue at Stages III-V of regeneration (Fig 4J–4L; see also Fig 3G–3J and Fig 5).


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

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

Relationship between CapI-Hox3 and dividing cells in the blastema and PGZ.All panels show posterior ends of juveniles in a ventral view, with anterior to the left. Where appropriate, approximate amputation sites are marked with dotted lines, and all tissue to the right of these lines is newly generated tissue. All panels are confocal images. Images shown in panels A-F were generated from a subset of slices from a z-stack, whereas panels A’-F’ were generated from maximum projections of z-stacks. A DIC image of the CapI-Hox3 expression domain is shown in the first column, EdU-positive cells in the second column, and a DIC/EdU merge shown in the final column. Stages of regeneration are indicated to the left of rows. (A-F) DIC image of CapI-Hox3 expression; (A’-F’) EdU incorporation marking dividing cells; (A”-F”) Merge of DIC and EdU channels. (A-A”) Unamputated juveniles following a one hour EdU pulse; (B-B”) Stage II of regeneration; (C-C”) Stage III; (D-D”) Stage IV; (E-E”) Stage V; (F-F”) Unamputated juveniles following an eight hour EdU pulse. The panels in each row are from a single juvenile. Dark brown shapes within juveniles are deposits within the lumen of the gut. White arrows indicate examples of single EdU-positive cells within the CapI-Hox3 expression domain.
© Copyright Policy
Related In: Results  -  Collection

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

pone.0149724.g005: Relationship between CapI-Hox3 and dividing cells in the blastema and PGZ.All panels show posterior ends of juveniles in a ventral view, with anterior to the left. Where appropriate, approximate amputation sites are marked with dotted lines, and all tissue to the right of these lines is newly generated tissue. All panels are confocal images. Images shown in panels A-F were generated from a subset of slices from a z-stack, whereas panels A’-F’ were generated from maximum projections of z-stacks. A DIC image of the CapI-Hox3 expression domain is shown in the first column, EdU-positive cells in the second column, and a DIC/EdU merge shown in the final column. Stages of regeneration are indicated to the left of rows. (A-F) DIC image of CapI-Hox3 expression; (A’-F’) EdU incorporation marking dividing cells; (A”-F”) Merge of DIC and EdU channels. (A-A”) Unamputated juveniles following a one hour EdU pulse; (B-B”) Stage II of regeneration; (C-C”) Stage III; (D-D”) Stage IV; (E-E”) Stage V; (F-F”) Unamputated juveniles following an eight hour EdU pulse. The panels in each row are from a single juvenile. Dark brown shapes within juveniles are deposits within the lumen of the gut. White arrows indicate examples of single EdU-positive cells within the CapI-Hox3 expression domain.
Mentions: In uncut 2 week post-metamorphic juveniles, the anterior class Hox genes, CapI-lab and CapI-pb, are expressed in thoracic segments 1–7 and 5–8, respectively, and CapI-Hox3 (paralogy group 3 (PG3)), is expressed exclusively in the PGZ. CapI-lab expression is limited to the ganglia of the VNC, whilst CapI-pb expression is also apparent in the epidermis, in a striped pattern (Fig 4A, 4E and 4I). Although the anterior and posterior boundaries of these genes are invariant, CapI-lab expression is strongest in segments 2 and 3, and weaker in the surrounding segments, while CapI-pb shows strongest expression in segments 6 and 7, with weaker expression in segments 5 and 8. Following amputation, the anterior and posterior boundaries of expression of each gene were unchanged (Fig 4B–4D and Fig 4F–4H). In the case for CapI-Hox3, amputation removes the original expression domain, and CapI-Hox3 expression was not observed in pre-existing segments during any time point examined. CapI-Hox3 expression is initiated in the newly formed tissue at Stages III-V of regeneration (Fig 4J–4L; see also Fig 3G–3J and Fig 5).

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