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Immunohistochemical Profiling of Germ Cells: DISCUSSION(9)

DISCUSSION(9)

In summary, gonocytes are a population of single, round cells characterized as OCT4pos/C-KITpos/MAGE-A4neg. Intermediate cells usually occur in pairs and are characterized as C-KITneg/MAGE-A4neg/OCT4low/neg. Both these cell populations are PCNA-positive and, therefore, would be grouped together as M prospermatogonia according to the criteria outlined by Wartenberg. A third population of “prespermatogonia” usually occurs as groups of cells at the periphery of the cords and is characterized as OCT4neg/ C-KITneg/MAGE-A4pos; these cells are PCNA-negative and, in gross appearance, appear similar to the cells classified as T1 spermatogonia by Wartenberg.

Immunohistochemical Profiling of Germ Cells: DISCUSSION(8)

In our studies on the fetal testes, we have never found a germ cell that coexpressed C-KIT and MAGE-A4, and our preliminary observations (unpublished) suggest that although C-KITpos and MAGE-A4pos CIS cells can be detected, the two proteins are not coexpressed in the same cell. One interpretation of these findings is that cells with a CIS phenotype can develop not only from gonocytes but also from the OCT4neg/C-KITneg/ MAGE-A4pos population (prespermatogonia). Alternatively, it is possible that some CIS cells undergo partial differentiation that is characterized by loss of expression of OCT4 and onset of expression of MAGE-A4.

Immunohistochemical Profiling of Germ Cells: DISCUSSION(7)

DISCUSSION(7)

A comparison between the patterns of protein expression seen in the germ cell subpopulations identified in the current study and the patterns of protein expression reported for CIS cells appears to provide further data relevant to determining the cells that contribute to the CIS population. In a series of studies, CIS cells have been shown to be immunopositive for CHK2, DAZL, PLAP, C-KIT, and VASA. A recent study also demonstrated that CIS cells im-munopositive for C-KIT also express OCT4. The authors suggested that the expression of OCT4 in the CIS population is consistent with the maintenance of pluripotent potential in this cell type. buy cheap allegra

Immunohistochemical Profiling of Germ Cells: DISCUSSION(6)

Wartenberg classified the fetal germ cell population into M prosper-matogonia (proliferating), T1 spermatogonia (nonproliferating), and T2 prospermatogonia (those T spermatogonia that had resumed mitotic activity). In follow-up studies, we have been examining the mitotic activity of human fetal germ cells using antibodies specific to proliferating cell nuclear antigen (PCNA) and phosphorylated histone H3. These studies have revealed that the MAGE-A4-pos-itive cell population (prespermatogonia) did not express PCNA, although staining was readily detectable in the nuclei of somatic cells and in the other germ cells. Canadian Levtra

Immunohistochemical Profiling of Germ Cells: DISCUSSION(5)

DISCUSSION(5)

In mice, expression of Oct4 in germ cells has been studied using a transgene in which expression of green fluorescent protein was driven by an 18-kilobase fragment encompassing the Oct-4 gene. In the fetal testes, OCT4-posi-tive germ cells were mitotically active and expressed C-KIT at Embryonic Day 11.5. By Embryonic Day 16.5, mitotic activity had ceased, and C-KIT expression was down-regulated. On the day of birth, all the OCT4-positive germ cells were C-KIT-negative. These results suggest that in contrast to those obtained during the present study, in mice, expression of C-KIT is not correlated with expression of OCT4.

Immunohistochemical Profiling of Germ Cells: DISCUSSION(4)

In the present study, consistent with these observations, we noted that germ cells with distinctive morphologies (small, round, and single vs. larger, peripheral groups) were present in second-trimester samples. OCT4 (POU5F1 ), a transcription factor that is expressed in pluripotent embryonic stem cells, was immunolocalized to the nuclei of most germ cells in first-trimester testes, consistent with reports that pluripotent embryonic germ (EG) cell lines can be derived by culturing PGCs. Notably, we found that expression of OCT4 persisted in a subpopulation of germ cells during the second trimester and that these cells also expressed C-KIT on their surface.

Immunohistochemical Profiling of Germ Cells: DISCUSSION(3)

DISCUSSION(3)

The patterns of expression of C-KIT and PCTAIRE-1 were similar, with a reduction in the proportion of positive germ cells in 17- to 19-wk samples compared to less mature samples. Mice that lack a functional C-KIT receptor contain less germ cells because of reduced survival of migratory PGCs; it is assumed that expression of C-KIT is also essential for PGC migration in humans, which would be consistent with detection of the protein on the surface of the OCT4-positive germ cells. Studies in rats have demonstrated that the kit ligand is a prosurvival factor for germ cells, and expression of C-KIT by human fetal germ cells may contribute to their survival.

Immunohistochemical Profiling of Germ Cells: DISCUSSION(2)

Results from studies in rodent are in broad agreement with those in humans and indicate that functional maturation of Leydig cells occurs after formation of MIS-positive seminiferous cords and that AR immunoexpression is not detectable in the nuclei of Sertoli cells or Leydig cells during fetal life.

Immunolocalization of proteins expressed in the germ cell population revealed that although germ cells in the first trimester appeared to represent a largely homogeneous population, in the second trimester a number of distinct subpopulations were present. canadian neighbor pharmacy

Immunohistochemical Profiling of Germ Cells: DISCUSSION(1)

DISCUSSION(1)

In the present study, functional Sertoli cells were identified by immunostaining for MIS. In samples dated as 4964 days of gestation, the degree to which the MIS-positive cells were organized into ‘‘cords’’ varied considerably between samples. In all cases, the cords were not as distinct as those seen in the tissue obtained during the second trimester This is consistent with previously published studies, which reported the production of functional MIS in testes obtained at 7-8 wk of gestation. Our findings also agree with reports that cord formation takes place gradually over the period of 6-8 wk of gestation.

Immunohistochemical Profiling of Germ Cells: RESULTS(4)http://health-and-you-life.com/immunohistochemical-profiling-of-germ-cells-9.html

Cells in population 3 were larger than those in the other two populations. Because of the presence of more cytoplasm, their nuclei did not contain such a prominent nucleolus as populations 1 or 2, and these cells were typically found in groups at the periphery of the cord (labeled 3 in Fig. 3). Population 3 was particularly noticeable in sections taken from testes at 18 and 19 wk of gestation.

Identification of Germ Cell Subpopulations by Immunohistochemical Profiling

OCT 4. OCT4 was immunolocalized to the nuclei of the majority of germ cells in the testes from the first trimester (Fig. 4, a and b). In testes from the second trimester (Fig. 4, c and d), OCT4 immunopositive staining was restricted to a subset of germ cell nuclei that, based on their morphological appearance, were identified as belonging to those of population 1.

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