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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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Immunoexpression of OCT4, DAZL and VASA. OCT4 positive germ cell nuclei were detectable in both the 1st and 2nd trimester ovaries (a, 62 d; b, 16 wk) and testes (c, 64 d; d, 16 wk). DAZL positive germ cells were rare in the 1st trimester (e, ovary 61 d; g, testis 64 d) but groups of cells ('nests', labelled N) with cytoplasmic staining were present in the 2nd trimester ovaries (f, 20 wk). During the 2nd trimester VASA protein was detected in the cytoplasm of female germ cells (i, 14 wk; j, 18 wk) throughout the ovary with the exception of the sub-epithelial layer. In the testes (k, 15 wk; l, 16 wk) VASA-positive germ cells were found in all cords.
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Figure 3: Immunoexpression of OCT4, DAZL and VASA. OCT4 positive germ cell nuclei were detectable in both the 1st and 2nd trimester ovaries (a, 62 d; b, 16 wk) and testes (c, 64 d; d, 16 wk). DAZL positive germ cells were rare in the 1st trimester (e, ovary 61 d; g, testis 64 d) but groups of cells ('nests', labelled N) with cytoplasmic staining were present in the 2nd trimester ovaries (f, 20 wk). During the 2nd trimester VASA protein was detected in the cytoplasm of female germ cells (i, 14 wk; j, 18 wk) throughout the ovary with the exception of the sub-epithelial layer. In the testes (k, 15 wk; l, 16 wk) VASA-positive germ cells were found in all cords.

Mentions: Immunoexpression of OCT4, DAZL and VASA was germ cell specific in all samples. OCT4 positive germ nuclei were detected in both 1st and 2nd trimester ovaries (Figure 3a, b) and testes (Figure 3c, d). In both sexes immunopositive cells were distributed throughout the organ during the 1st trimester. In 2nd trimester testes OCT4 positive germ cells were detected in all seminiferous cords whereas in the ovary expression of OCT4 positive nuclei was largely confined to the peripheral cortex (Figure 3b). DAZL was immunolocalised to the nuclei of germ cells in 1st trimester gonads in both sexes. In 2nd trimester ovaries DAZL immunostaining was largely cytoplasmic and appeared to be most prominent in groups of cells (N in Figure 3f), whereas in the testes germ cells with nuclear or cytoplasmic staining were detected throughout the organ (Figure 3h). No VASA immunopositive cells were detected in 1st trimester gonads from either sex (not shown). In the 2nd trimester ovaries VASA staining was cytoplasmic and more intense in germ cells less peripherally located than those expressing OCT4 (Figure 3i, j); in testes VASA positive cells were distributed throughout the organ.


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)

Immunoexpression of OCT4, DAZL and VASA. OCT4 positive germ cell nuclei were detectable in both the 1st and 2nd trimester ovaries (a, 62 d; b, 16 wk) and testes (c, 64 d; d, 16 wk). DAZL positive germ cells were rare in the 1st trimester (e, ovary 61 d; g, testis 64 d) but groups of cells ('nests', labelled N) with cytoplasmic staining were present in the 2nd trimester ovaries (f, 20 wk). During the 2nd trimester VASA protein was detected in the cytoplasm of female germ cells (i, 14 wk; j, 18 wk) throughout the ovary with the exception of the sub-epithelial layer. In the testes (k, 15 wk; l, 16 wk) VASA-positive germ cells were found in all cords.
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 3: Immunoexpression of OCT4, DAZL and VASA. OCT4 positive germ cell nuclei were detectable in both the 1st and 2nd trimester ovaries (a, 62 d; b, 16 wk) and testes (c, 64 d; d, 16 wk). DAZL positive germ cells were rare in the 1st trimester (e, ovary 61 d; g, testis 64 d) but groups of cells ('nests', labelled N) with cytoplasmic staining were present in the 2nd trimester ovaries (f, 20 wk). During the 2nd trimester VASA protein was detected in the cytoplasm of female germ cells (i, 14 wk; j, 18 wk) throughout the ovary with the exception of the sub-epithelial layer. In the testes (k, 15 wk; l, 16 wk) VASA-positive germ cells were found in all cords.
Mentions: Immunoexpression of OCT4, DAZL and VASA was germ cell specific in all samples. OCT4 positive germ nuclei were detected in both 1st and 2nd trimester ovaries (Figure 3a, b) and testes (Figure 3c, d). In both sexes immunopositive cells were distributed throughout the organ during the 1st trimester. In 2nd trimester testes OCT4 positive germ cells were detected in all seminiferous cords whereas in the ovary expression of OCT4 positive nuclei was largely confined to the peripheral cortex (Figure 3b). DAZL was immunolocalised to the nuclei of germ cells in 1st trimester gonads in both sexes. In 2nd trimester ovaries DAZL immunostaining was largely cytoplasmic and appeared to be most prominent in groups of cells (N in Figure 3f), whereas in the testes germ cells with nuclear or cytoplasmic staining were detected throughout the organ (Figure 3h). No VASA immunopositive cells were detected in 1st trimester gonads from either sex (not shown). In the 2nd trimester ovaries VASA staining was cytoplasmic and more intense in germ cells less peripherally located than those expressing OCT4 (Figure 3i, j); in testes VASA positive cells were distributed throughout the organ.

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