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Conserved and divergent patterns of expression of DAZL, VASA and OCT4 in the germ cells of the human fetal ovary and testis.

Anderson RA, Fulton N, Cowan G, Coutts S, Saunders PT - BMC Dev. Biol. (2007)

Bottom Line: In the 2nd trimester germ cells can enter meiotic prophase in females whereas in males this does not occur until puberty.In the 1st trimester OCT4 was detected in most germ cells.These data reveal similarities between the expression of key regulatory proteins within germ cells as they mature in male and female fetal human gonads suggesting that in the female these maturational changes are not determined by entry into meiosis.

View Article: PubMed Central - HTML - PubMed

Affiliation: Division of Reproductive and Developmental Sciences, Queen's Medical Research Institute, Edinburgh EH16 4TJ, UK. richard.anderson@ed.ac.uk

ABSTRACT

Background: Germ cells arise from a small group of cells that express markers of pluripotency including OCT4. In humans formation of gonadal compartments (cords in testis, nests in ovary) takes place during the 1st trimester (6-8 weeks gestation). In the 2nd trimester germ cells can enter meiotic prophase in females whereas in males this does not occur until puberty. We have used qRTPCR, Westerns and immunohistochemical profiling to determine which of the germ cell subtypes in the human fetal gonads express OCT4, DAZL and VASA, as these have been shown to play an essential role in germ cell maturation in mice.

Results: OCT4 mRNA and protein were detected in extracts from both 1st and 2nd trimester ovaries and testes. In ovarian extracts a marked increase in expression of VASA and DAZL mRNA and protein occurred in the 2nd trimester. In testicular extracts VASA mRNA and protein were low/undetectable in 1st trimester and increased in the 2nd trimester whereas the total amount of DAZL did not seem to change. During the 1st trimester, germ cells were OCT4 positive but did not express VASA. These results are in contrast to the situation in mice where expression of Vasa is initiated in Oct4 positive primordial germ cells as they enter the gonadal ridge. In the 2nd trimester germ cells with intense cytoplasmic staining for VASA were present in both sexes; these cells were OCT4 negative. DAZL expression overlapped with both OCT4 and VASA and changed from the nuclear to the cytoplasmic compartment as cells became OCT4-negative. In males, OCT4-positive and VASA-positive subpopulations of germ cells coexisted within the same seminiferous cords but in the ovary there was a distinct spatial distribution of cells with OCT4 expressed by smaller, peripherally located, germ cells whereas DAZL and VASA were immunolocalised to larger (more mature) centrally located cells.

Conclusion: OCT4, DAZL and VASA are expressed by human fetal germ cells but their patterns of expression are temporally and spatially distinct. In the 1st trimester OCT4 was detected in most germ cells. In the 2nd trimester the onset of expression of VASA was associated with the formation of oocytes and spermatogonia both of which were OCT-4 negative. Relocation of DAZL from nucleus to cytoplasm paralleled the down regulation of OCT4 and the onset of expression of VASA. These data reveal similarities between the expression of key regulatory proteins within germ cells as they mature in male and female fetal human gonads suggesting that in the female these maturational changes are not determined by entry into meiosis.

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Co-localisation of OCT4 and VASA in 16 week ovary and testes. Panel a, ovary, cells with intense immunopositive staining for OCT4 are found at the periphery of the organ (red nuclei), VASA was detected in the cytoplasm and was most intense in cells located in nests (N) closer to the centre of the ovary. An intermediate population of cells with low intensity nuclear staining for OCT4 and low intensity staining for VASA (arrowheads) was also present. Panel b, testis, OCT4 positive and VASA positive germ cells were found within the same seminiferous cords; germ cells with intense nuclear OCT4 expression (red nuclei) were VASA negative and those with intense cytoplasmic expression of VASA (e.g. arrowed in inset panel b) were OCT 4 negative. Two other populations of male germ cells were identified, a population with low intensity immunoexpression of OCT4 which also had low intensity staining for VASA (arrowheads) and cells with nuclear VASA expression (asterisks) which were typically found in pairs.
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Figure 5: Co-localisation of OCT4 and VASA in 16 week ovary and testes. Panel a, ovary, cells with intense immunopositive staining for OCT4 are found at the periphery of the organ (red nuclei), VASA was detected in the cytoplasm and was most intense in cells located in nests (N) closer to the centre of the ovary. An intermediate population of cells with low intensity nuclear staining for OCT4 and low intensity staining for VASA (arrowheads) was also present. Panel b, testis, OCT4 positive and VASA positive germ cells were found within the same seminiferous cords; germ cells with intense nuclear OCT4 expression (red nuclei) were VASA negative and those with intense cytoplasmic expression of VASA (e.g. arrowed in inset panel b) were OCT 4 negative. Two other populations of male germ cells were identified, a population with low intensity immunoexpression of OCT4 which also had low intensity staining for VASA (arrowheads) and cells with nuclear VASA expression (asterisks) which were typically found in pairs.

Mentions: In 1st trimester ovaries and testes all germ cells contained OCT4 positive nuclei but were immunonegative for VASA (not shown). In the 2nd trimester, OCT4 positive germ cells were located at the periphery of the ovary whereas the most intense immunoexpression of VASA was detected in the cytoplasm of OCT4 negative germ cells (oogonia) located in nests (Figure 5a, labelled N) in the central region. Expression of OCT4 and VASA was almost mutually exclusive although some cells in a transition zone between the peripheral cells that contained intense OCT4 staining and the nests of VASA positive cells (e.g. arrowhead in panel 5a) did appear to have low levels of VASA in their cytoplasm and some nuclear OCT4. In the testes a the majority of germ cells (gonocytes, [8]) containing intense immunoexpression of OCT4 were located in the central portion of the seminiferous cords and these cells were VASA negative (Figure 5b). As in the ovary germ cells that contained intense cytoplasmic staining for VASA were OCT4 negative, these were often found in groups at the periphery of the cords. Nuclear expression of VASA was detected in some germ cells (Figure 5b, asterisks). As in the ovary rare germ cells containing very low levels of cytoplasmic VASA as well as low intensity staining for OCT4 were observed (Figure 5b arrowheads).


Conserved and divergent patterns of expression of DAZL, VASA and OCT4 in the germ cells of the human fetal ovary and testis.

Anderson RA, Fulton N, Cowan G, Coutts S, Saunders PT - BMC Dev. Biol. (2007)

Co-localisation of OCT4 and VASA in 16 week ovary and testes. Panel a, ovary, cells with intense immunopositive staining for OCT4 are found at the periphery of the organ (red nuclei), VASA was detected in the cytoplasm and was most intense in cells located in nests (N) closer to the centre of the ovary. An intermediate population of cells with low intensity nuclear staining for OCT4 and low intensity staining for VASA (arrowheads) was also present. Panel b, testis, OCT4 positive and VASA positive germ cells were found within the same seminiferous cords; germ cells with intense nuclear OCT4 expression (red nuclei) were VASA negative and those with intense cytoplasmic expression of VASA (e.g. arrowed in inset panel b) were OCT 4 negative. Two other populations of male germ cells were identified, a population with low intensity immunoexpression of OCT4 which also had low intensity staining for VASA (arrowheads) and cells with nuclear VASA expression (asterisks) which were typically found in pairs.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC2211489&req=5

Figure 5: Co-localisation of OCT4 and VASA in 16 week ovary and testes. Panel a, ovary, cells with intense immunopositive staining for OCT4 are found at the periphery of the organ (red nuclei), VASA was detected in the cytoplasm and was most intense in cells located in nests (N) closer to the centre of the ovary. An intermediate population of cells with low intensity nuclear staining for OCT4 and low intensity staining for VASA (arrowheads) was also present. Panel b, testis, OCT4 positive and VASA positive germ cells were found within the same seminiferous cords; germ cells with intense nuclear OCT4 expression (red nuclei) were VASA negative and those with intense cytoplasmic expression of VASA (e.g. arrowed in inset panel b) were OCT 4 negative. Two other populations of male germ cells were identified, a population with low intensity immunoexpression of OCT4 which also had low intensity staining for VASA (arrowheads) and cells with nuclear VASA expression (asterisks) which were typically found in pairs.
Mentions: In 1st trimester ovaries and testes all germ cells contained OCT4 positive nuclei but were immunonegative for VASA (not shown). In the 2nd trimester, OCT4 positive germ cells were located at the periphery of the ovary whereas the most intense immunoexpression of VASA was detected in the cytoplasm of OCT4 negative germ cells (oogonia) located in nests (Figure 5a, labelled N) in the central region. Expression of OCT4 and VASA was almost mutually exclusive although some cells in a transition zone between the peripheral cells that contained intense OCT4 staining and the nests of VASA positive cells (e.g. arrowhead in panel 5a) did appear to have low levels of VASA in their cytoplasm and some nuclear OCT4. In the testes a the majority of germ cells (gonocytes, [8]) containing intense immunoexpression of OCT4 were located in the central portion of the seminiferous cords and these cells were VASA negative (Figure 5b). As in the ovary germ cells that contained intense cytoplasmic staining for VASA were OCT4 negative, these were often found in groups at the periphery of the cords. Nuclear expression of VASA was detected in some germ cells (Figure 5b, asterisks). As in the ovary rare germ cells containing very low levels of cytoplasmic VASA as well as low intensity staining for OCT4 were observed (Figure 5b arrowheads).

Bottom Line: In the 2nd trimester germ cells can enter meiotic prophase in females whereas in males this does not occur until puberty.In the 1st trimester OCT4 was detected in most germ cells.These data reveal similarities between the expression of key regulatory proteins within germ cells as they mature in male and female fetal human gonads suggesting that in the female these maturational changes are not determined by entry into meiosis.

View Article: PubMed Central - HTML - PubMed

Affiliation: Division of Reproductive and Developmental Sciences, Queen's Medical Research Institute, Edinburgh EH16 4TJ, UK. richard.anderson@ed.ac.uk

ABSTRACT

Background: Germ cells arise from a small group of cells that express markers of pluripotency including OCT4. In humans formation of gonadal compartments (cords in testis, nests in ovary) takes place during the 1st trimester (6-8 weeks gestation). In the 2nd trimester germ cells can enter meiotic prophase in females whereas in males this does not occur until puberty. We have used qRTPCR, Westerns and immunohistochemical profiling to determine which of the germ cell subtypes in the human fetal gonads express OCT4, DAZL and VASA, as these have been shown to play an essential role in germ cell maturation in mice.

Results: OCT4 mRNA and protein were detected in extracts from both 1st and 2nd trimester ovaries and testes. In ovarian extracts a marked increase in expression of VASA and DAZL mRNA and protein occurred in the 2nd trimester. In testicular extracts VASA mRNA and protein were low/undetectable in 1st trimester and increased in the 2nd trimester whereas the total amount of DAZL did not seem to change. During the 1st trimester, germ cells were OCT4 positive but did not express VASA. These results are in contrast to the situation in mice where expression of Vasa is initiated in Oct4 positive primordial germ cells as they enter the gonadal ridge. In the 2nd trimester germ cells with intense cytoplasmic staining for VASA were present in both sexes; these cells were OCT4 negative. DAZL expression overlapped with both OCT4 and VASA and changed from the nuclear to the cytoplasmic compartment as cells became OCT4-negative. In males, OCT4-positive and VASA-positive subpopulations of germ cells coexisted within the same seminiferous cords but in the ovary there was a distinct spatial distribution of cells with OCT4 expressed by smaller, peripherally located, germ cells whereas DAZL and VASA were immunolocalised to larger (more mature) centrally located cells.

Conclusion: OCT4, DAZL and VASA are expressed by human fetal germ cells but their patterns of expression are temporally and spatially distinct. In the 1st trimester OCT4 was detected in most germ cells. In the 2nd trimester the onset of expression of VASA was associated with the formation of oocytes and spermatogonia both of which were OCT-4 negative. Relocation of DAZL from nucleus to cytoplasm paralleled the down regulation of OCT4 and the onset of expression of VASA. These data reveal similarities between the expression of key regulatory proteins within germ cells as they mature in male and female fetal human gonads suggesting that in the female these maturational changes are not determined by entry into meiosis.

Show MeSH
Related in: MedlinePlus