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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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Expression of mRNAs for OCT4, DAZL and VASA in 1st and 2nd trimester ovary and testis. Open columns, 1st trimester, shaded columns 2nd trimester. Concentrations of mRNA are all relative to that of GAPD in the same samples. * P < 0.001 vs 1st trimester. Mean ± sem, n = 5–18 per group.
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Figure 1: Expression of mRNAs for OCT4, DAZL and VASA in 1st and 2nd trimester ovary and testis. Open columns, 1st trimester, shaded columns 2nd trimester. Concentrations of mRNA are all relative to that of GAPD in the same samples. * P < 0.001 vs 1st trimester. Mean ± sem, n = 5–18 per group.

Mentions: In ovaries OCT4 mRNA was detected in both the 1st and 2nd trimester samples with a slight, but non-significant decrease in the older samples (Figure 1A). In contrast the amount of mRNA for DAZL and VASA was very low in 1st trimester ovaries but was markedly increased in the 2nd trimester DAZL 20 fold and VASA 50 fold (both P < 0.001, Figure 1B,C),. Analysis of individual ovarian samples showed a very high correlation between expression of DAZL and VASA mRNAs (Spearman correlation coefficient 0.74, P < 0.0001). In the testis, OCT4 and DAZL mRNAs were detectable in both 1st and 2nd trimester with no significant difference between ages (Figure 1A, B). Expression of VASA mRNA in the testis was low/barely detectable in the 1st trimester and showed a significant increase in the 2nd trimester (p = 0.001) although this was less marked than that seen in ovarian samples (Figure 1C).


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)

Expression of mRNAs for OCT4, DAZL and VASA in 1st and 2nd trimester ovary and testis. Open columns, 1st trimester, shaded columns 2nd trimester. Concentrations of mRNA are all relative to that of GAPD in the same samples. * P < 0.001 vs 1st trimester. Mean ± sem, n = 5–18 per group.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 1: Expression of mRNAs for OCT4, DAZL and VASA in 1st and 2nd trimester ovary and testis. Open columns, 1st trimester, shaded columns 2nd trimester. Concentrations of mRNA are all relative to that of GAPD in the same samples. * P < 0.001 vs 1st trimester. Mean ± sem, n = 5–18 per group.
Mentions: In ovaries OCT4 mRNA was detected in both the 1st and 2nd trimester samples with a slight, but non-significant decrease in the older samples (Figure 1A). In contrast the amount of mRNA for DAZL and VASA was very low in 1st trimester ovaries but was markedly increased in the 2nd trimester DAZL 20 fold and VASA 50 fold (both P < 0.001, Figure 1B,C),. Analysis of individual ovarian samples showed a very high correlation between expression of DAZL and VASA mRNAs (Spearman correlation coefficient 0.74, P < 0.0001). In the testis, OCT4 and DAZL mRNAs were detectable in both 1st and 2nd trimester with no significant difference between ages (Figure 1A, B). Expression of VASA mRNA in the testis was low/barely detectable in the 1st trimester and showed a significant increase in the 2nd trimester (p = 0.001) although this was less marked than that seen in ovarian samples (Figure 1C).

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