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Somatic and germline expression of piwi during development and regeneration in the marine polychaete annelid Capitella teleta.

Giani VC, Yamaguchi E, Boyle MJ, Seaver EC - Evodevo (2011)

Bottom Line: Ct-piwi1 is expressed in regenerating tissue, and once segments differentiate, it becomes most prominent in the posterior growth zone and immature oocytes in regenerating ovaries of regenerating segments.In C. teleta, piwi genes may have retained an ancestral role as genetic regulators of both somatic and germline stem cells.It is likely that piwi genes, and associated stem cell co-regulators, became restricted to the germline in some taxa during the course of evolution.

View Article: PubMed Central - HTML - PubMed

Affiliation: Kewalo Marine Laboratory, PBRC/University of Hawaii, 41 Ahui St,, Honolulu, HI 96813, USA. seaver@hawaii.edu.

ABSTRACT

Background: Stem cells have a critical role during adult growth and regeneration. Germline stem cells are specialized stem cells that produce gametes during sexual reproduction. Capitella teleta (formerly Capitella sp. I) is a polychaete annelid that reproduces sexually, exhibits adult growth and regeneration, and thus, is a good model to study the relationship between somatic and germline stem cells.

Results: We characterize expression of the two C. teleta orthologs of piwi, genes with roles in germline development in diverse organisms. Ct-piwi1 and Ct-piwi2 are expressed throughout the life cycle in a dynamic pattern that includes both somatic and germline cells, and show nearly identical expression patterns at all stages examined. Both genes are broadly expressed during embryonic and larval development, gradually becoming restricted to putative primordial germ cells (PGCs) and the posterior growth zone. In juveniles, Ct-piwi1 is expressed in the presumptive gonads, and in reproductive adults, it is detected in gonads and the posterior growth zone. In addition, Ct-piwi1 is expressed in a population of putative PGCs that persist in sexually mature adults, likely in a stem cell niche. Ct-piwi1 is expressed in regenerating tissue, and once segments differentiate, it becomes most prominent in the posterior growth zone and immature oocytes in regenerating ovaries of regenerating segments.

Conclusions: In C. teleta, piwi genes may have retained an ancestral role as genetic regulators of both somatic and germline stem cells. It is likely that piwi genes, and associated stem cell co-regulators, became restricted to the germline in some taxa during the course of evolution.

No MeSH data available.


Related in: MedlinePlus

Time course of posterior regeneration in C. teleta from 4 hours to 18 days post-amputation. Adults were amputated at the 12th segment. Panels shown are posterior ends of amputated adults. All animals are oriented in a ventral view with anterior to the left. Black and white dotted lines indicate cut site in all panels. Dark shapes in E, F', I', J and K are within the lumen of the gut. Images F and I are Z-stack projections of confocal micrographs of the posterior end of a regenerate labeled with anti-acyetylated tubulin. Abbreviation: pyg, pygidium. (A) Schematic of an adult worm indicating the cut site at the 12th segment. (B) Adult worm four hours post-amputation. (C) one day post-amputation. (D) three days post-amputation. (E) five days post-amputation. (F) Confocal micrograph of a worm five days post-amputation showing longitudinal axons extending into the regenerating tissue (white arrow). (F') Corresponding DIC image of the same worm shown in F. (G) seven days post-amputation. (H) 10 days post-amputation. (I) Confocal micrograph of a worm 10 days post-amputation showing longitudinal axons (white arrow) and circular nerves (white arrowheads) in the regenerating tissue. (I') Corresponding DIC image of the same adult worm in I; note the lack of external segmentation (black arrow). (J) 14 days post-amputation worm with a distinct pygidium. (K) Adult 18 days post-amputation with numerous differentiated segments in the regenerate. Black arrowheads point to chaetae in two sets of adjacent segments. Scale bar, 50 μm for all panels.
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Figure 2: Time course of posterior regeneration in C. teleta from 4 hours to 18 days post-amputation. Adults were amputated at the 12th segment. Panels shown are posterior ends of amputated adults. All animals are oriented in a ventral view with anterior to the left. Black and white dotted lines indicate cut site in all panels. Dark shapes in E, F', I', J and K are within the lumen of the gut. Images F and I are Z-stack projections of confocal micrographs of the posterior end of a regenerate labeled with anti-acyetylated tubulin. Abbreviation: pyg, pygidium. (A) Schematic of an adult worm indicating the cut site at the 12th segment. (B) Adult worm four hours post-amputation. (C) one day post-amputation. (D) three days post-amputation. (E) five days post-amputation. (F) Confocal micrograph of a worm five days post-amputation showing longitudinal axons extending into the regenerating tissue (white arrow). (F') Corresponding DIC image of the same worm shown in F. (G) seven days post-amputation. (H) 10 days post-amputation. (I) Confocal micrograph of a worm 10 days post-amputation showing longitudinal axons (white arrow) and circular nerves (white arrowheads) in the regenerating tissue. (I') Corresponding DIC image of the same adult worm in I; note the lack of external segmentation (black arrow). (J) 14 days post-amputation worm with a distinct pygidium. (K) Adult 18 days post-amputation with numerous differentiated segments in the regenerate. Black arrowheads point to chaetae in two sets of adjacent segments. Scale bar, 50 μm for all panels.

Mentions: C. teleta has the ability to regenerate lost tissue, and upon amputation will regenerate posterior segments [26]. To aid our interpretations of piwi expression, we characterized posterior regeneration in reproductive adults (eight weeks post-metamorphosis). In C. teleta, there are two distinct body regions: segments 1 to 9 are the thoracic segments, and 40 to 50 abdominal segments are continuously added posteriorly throughout adult development. Transverse amputations were made on adult male and female worms at the segment boundary between the 11th and 12th segment (Figure 2A, dotted line). The rate of regeneration varies among individuals; this variation becomes more pronounced after five days post-amputation, and is likely due to environmental conditions. Within four hours of amputation, wound healing occurs by contraction of the severed edges of the body wall (Figure 2B). The gut is closed off during early stages of regeneration by formation of an intact epithelium covering the wound. At one day post-amputation, the wound has fully healed and a small blastema (mass of undifferentiated cells) is visible (Figure 2C). Between one and three days post-amputation, the blastema grows bigger. In addition, the anus has reopened and the worm can feed and excrete ingested material (Figure 2D). Between three and seven days post-amputation, the blastema continues to grow and elongates, but there are no external signs of segmentation (Figure 2E-G). At five days post-amputation, axons can be observed extending from the severed longitudinal nerves into the blastema, likely invading the regenerating tissue from cell bodies in the pre-existing tissue (Figure 2F). The blastema has a smaller diameter relative to the pre-existing tissue, and a distinct pygidium and posterior growth zone appear between 10 and 14 days post-amputation (Figure 2J). Typically, several small segments also become morphologically apparent between 10 and 14 days post-amputation (Figure 2H-J). Nascent segments are initially visible by the appearance of forming ganglia and circular peripheral nerves extending from the ventral nerve cord (Figure 2I, I', arrow, arrowheads); at this stage there are not yet external signs of segmentation (Figure 2I', arrow). The formation of chaetae and intersegmental furrows of the ectoderm occur a few days later (Figure 2K, arrowheads). When segments form, multiple small segments appear rather than a single segment at a time. As many as 20 segments have regenerated by 18 days post-amputation (Figure 2K).


Somatic and germline expression of piwi during development and regeneration in the marine polychaete annelid Capitella teleta.

Giani VC, Yamaguchi E, Boyle MJ, Seaver EC - Evodevo (2011)

Time course of posterior regeneration in C. teleta from 4 hours to 18 days post-amputation. Adults were amputated at the 12th segment. Panels shown are posterior ends of amputated adults. All animals are oriented in a ventral view with anterior to the left. Black and white dotted lines indicate cut site in all panels. Dark shapes in E, F', I', J and K are within the lumen of the gut. Images F and I are Z-stack projections of confocal micrographs of the posterior end of a regenerate labeled with anti-acyetylated tubulin. Abbreviation: pyg, pygidium. (A) Schematic of an adult worm indicating the cut site at the 12th segment. (B) Adult worm four hours post-amputation. (C) one day post-amputation. (D) three days post-amputation. (E) five days post-amputation. (F) Confocal micrograph of a worm five days post-amputation showing longitudinal axons extending into the regenerating tissue (white arrow). (F') Corresponding DIC image of the same worm shown in F. (G) seven days post-amputation. (H) 10 days post-amputation. (I) Confocal micrograph of a worm 10 days post-amputation showing longitudinal axons (white arrow) and circular nerves (white arrowheads) in the regenerating tissue. (I') Corresponding DIC image of the same adult worm in I; note the lack of external segmentation (black arrow). (J) 14 days post-amputation worm with a distinct pygidium. (K) Adult 18 days post-amputation with numerous differentiated segments in the regenerate. Black arrowheads point to chaetae in two sets of adjacent segments. Scale bar, 50 μm for all panels.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 2: Time course of posterior regeneration in C. teleta from 4 hours to 18 days post-amputation. Adults were amputated at the 12th segment. Panels shown are posterior ends of amputated adults. All animals are oriented in a ventral view with anterior to the left. Black and white dotted lines indicate cut site in all panels. Dark shapes in E, F', I', J and K are within the lumen of the gut. Images F and I are Z-stack projections of confocal micrographs of the posterior end of a regenerate labeled with anti-acyetylated tubulin. Abbreviation: pyg, pygidium. (A) Schematic of an adult worm indicating the cut site at the 12th segment. (B) Adult worm four hours post-amputation. (C) one day post-amputation. (D) three days post-amputation. (E) five days post-amputation. (F) Confocal micrograph of a worm five days post-amputation showing longitudinal axons extending into the regenerating tissue (white arrow). (F') Corresponding DIC image of the same worm shown in F. (G) seven days post-amputation. (H) 10 days post-amputation. (I) Confocal micrograph of a worm 10 days post-amputation showing longitudinal axons (white arrow) and circular nerves (white arrowheads) in the regenerating tissue. (I') Corresponding DIC image of the same adult worm in I; note the lack of external segmentation (black arrow). (J) 14 days post-amputation worm with a distinct pygidium. (K) Adult 18 days post-amputation with numerous differentiated segments in the regenerate. Black arrowheads point to chaetae in two sets of adjacent segments. Scale bar, 50 μm for all panels.
Mentions: C. teleta has the ability to regenerate lost tissue, and upon amputation will regenerate posterior segments [26]. To aid our interpretations of piwi expression, we characterized posterior regeneration in reproductive adults (eight weeks post-metamorphosis). In C. teleta, there are two distinct body regions: segments 1 to 9 are the thoracic segments, and 40 to 50 abdominal segments are continuously added posteriorly throughout adult development. Transverse amputations were made on adult male and female worms at the segment boundary between the 11th and 12th segment (Figure 2A, dotted line). The rate of regeneration varies among individuals; this variation becomes more pronounced after five days post-amputation, and is likely due to environmental conditions. Within four hours of amputation, wound healing occurs by contraction of the severed edges of the body wall (Figure 2B). The gut is closed off during early stages of regeneration by formation of an intact epithelium covering the wound. At one day post-amputation, the wound has fully healed and a small blastema (mass of undifferentiated cells) is visible (Figure 2C). Between one and three days post-amputation, the blastema grows bigger. In addition, the anus has reopened and the worm can feed and excrete ingested material (Figure 2D). Between three and seven days post-amputation, the blastema continues to grow and elongates, but there are no external signs of segmentation (Figure 2E-G). At five days post-amputation, axons can be observed extending from the severed longitudinal nerves into the blastema, likely invading the regenerating tissue from cell bodies in the pre-existing tissue (Figure 2F). The blastema has a smaller diameter relative to the pre-existing tissue, and a distinct pygidium and posterior growth zone appear between 10 and 14 days post-amputation (Figure 2J). Typically, several small segments also become morphologically apparent between 10 and 14 days post-amputation (Figure 2H-J). Nascent segments are initially visible by the appearance of forming ganglia and circular peripheral nerves extending from the ventral nerve cord (Figure 2I, I', arrow, arrowheads); at this stage there are not yet external signs of segmentation (Figure 2I', arrow). The formation of chaetae and intersegmental furrows of the ectoderm occur a few days later (Figure 2K, arrowheads). When segments form, multiple small segments appear rather than a single segment at a time. As many as 20 segments have regenerated by 18 days post-amputation (Figure 2K).

Bottom Line: Ct-piwi1 is expressed in regenerating tissue, and once segments differentiate, it becomes most prominent in the posterior growth zone and immature oocytes in regenerating ovaries of regenerating segments.In C. teleta, piwi genes may have retained an ancestral role as genetic regulators of both somatic and germline stem cells.It is likely that piwi genes, and associated stem cell co-regulators, became restricted to the germline in some taxa during the course of evolution.

View Article: PubMed Central - HTML - PubMed

Affiliation: Kewalo Marine Laboratory, PBRC/University of Hawaii, 41 Ahui St,, Honolulu, HI 96813, USA. seaver@hawaii.edu.

ABSTRACT

Background: Stem cells have a critical role during adult growth and regeneration. Germline stem cells are specialized stem cells that produce gametes during sexual reproduction. Capitella teleta (formerly Capitella sp. I) is a polychaete annelid that reproduces sexually, exhibits adult growth and regeneration, and thus, is a good model to study the relationship between somatic and germline stem cells.

Results: We characterize expression of the two C. teleta orthologs of piwi, genes with roles in germline development in diverse organisms. Ct-piwi1 and Ct-piwi2 are expressed throughout the life cycle in a dynamic pattern that includes both somatic and germline cells, and show nearly identical expression patterns at all stages examined. Both genes are broadly expressed during embryonic and larval development, gradually becoming restricted to putative primordial germ cells (PGCs) and the posterior growth zone. In juveniles, Ct-piwi1 is expressed in the presumptive gonads, and in reproductive adults, it is detected in gonads and the posterior growth zone. In addition, Ct-piwi1 is expressed in a population of putative PGCs that persist in sexually mature adults, likely in a stem cell niche. Ct-piwi1 is expressed in regenerating tissue, and once segments differentiate, it becomes most prominent in the posterior growth zone and immature oocytes in regenerating ovaries of regenerating segments.

Conclusions: In C. teleta, piwi genes may have retained an ancestral role as genetic regulators of both somatic and germline stem cells. It is likely that piwi genes, and associated stem cell co-regulators, became restricted to the germline in some taxa during the course of evolution.

No MeSH data available.


Related in: MedlinePlus