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Selfish spermatogonial selection: evidence from an immunohistochemical screen in testes of elderly men.

Lim J, Maher GJ, Turner GD, Dudka-Ruszkowska W, Taylor S, Rajpert-De Meyts E, Goriely A, Wilkie AO - PLoS ONE (2012)

Bottom Line: The dominant congenital disorders Apert syndrome, achondroplasia and multiple endocrine neoplasia-caused by specific missense mutations in the FGFR2, FGFR3 and RET proteins respectively-represent classical examples of paternal age-effect mutation, a class that arises at particularly high frequencies in the sperm of older men.We found numerous small (less than 200 cells) cellular aggregations with distinct immunohistochemical characteristics, localised to a portion of the seminiferous tubule, which are of uncertain significance.However more infrequently we identified additional regions where entire seminiferous tubules had a circumferentially altered immunohistochemical appearance that extended through multiple serial sections that were physically contiguous (up to 1 mm in length), and exhibited enhanced staining for antibodies both to FGFR3 and a marker of downstream signal activation, pAKT.

View Article: PubMed Central - PubMed

Affiliation: Clinical Genetics Group, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom.

ABSTRACT
The dominant congenital disorders Apert syndrome, achondroplasia and multiple endocrine neoplasia-caused by specific missense mutations in the FGFR2, FGFR3 and RET proteins respectively-represent classical examples of paternal age-effect mutation, a class that arises at particularly high frequencies in the sperm of older men. Previous analyses of DNA from randomly selected cadaveric testes showed that the levels of the corresponding FGFR2, FGFR3 and RET mutations exhibit very uneven spatial distributions, with localised hotspots surrounded by large mutation-negative areas. These studies imply that normal testes are mosaic for clusters of mutant cells: these clusters are predicted to have altered growth and signalling properties leading to their clonal expansion (selfish spermatogonial selection), but DNA extraction eliminates the possibility to study such processes at a tissue level. Using a panel of antibodies optimised for the detection of spermatocytic seminoma, a rare tumour of spermatogonial origin, we demonstrate that putative clonal events are frequent within normal testes of elderly men (mean age: 73.3 yrs) and can be classed into two broad categories. We found numerous small (less than 200 cells) cellular aggregations with distinct immunohistochemical characteristics, localised to a portion of the seminiferous tubule, which are of uncertain significance. However more infrequently we identified additional regions where entire seminiferous tubules had a circumferentially altered immunohistochemical appearance that extended through multiple serial sections that were physically contiguous (up to 1 mm in length), and exhibited enhanced staining for antibodies both to FGFR3 and a marker of downstream signal activation, pAKT. These findings support the concept that populations of spermatogonia in individual seminiferous tubules in the testes of older men are clonal mosaics with regard to their signalling properties and activation, thus fulfilling one of the specific predictions of selfish spermatogonial selection.

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Structure and organisation of the human testis and seminiferous tubules.A. Macroscopic appearance. The testis is divided into compartments (lobules) separated by connective tissue. There are an estimated 250 lobules per testis, which vary in size; for clarity only 7 lobules are illustrated here. B. (i) Diagrammatic representation of the highly convoluted organisation of 3 seminiferous tubules (blue, black, grey) within a lobule. (ii) A magnified cross section through the lobule in i reveals how the tubules would appear in thin microscopic sections. Dashed lines (above section) and solid lines (below section) join the contiguous tubules. C. Cross section through an individual seminiferous tubule. Spermatogonia, located at the basal lamina of the seminiferous tubules, comprise a heterogeneous population of diploid germ cells. These can be classified according to their morphologies and correspond to three main maturation stages: Adark spermatogonia, which are considered to represent the reserve stem cell population; highly proliferating Apale spermatogonia; and more mature B spermatogonia that give rise to primary spermatocytes. Primary spermatocytes undergo meiosis to form secondary spermatocytes that differentiate to form spermatids, which when fully formed are released into the central lumen as spermatozoa that progress to the rete testis. Spermatogenesis is supported by the presence of the somatic Sertoli cells. The vascular and connective tissue network lie external to the wall of the seminiferous tubule.
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pone-0042382-g001: Structure and organisation of the human testis and seminiferous tubules.A. Macroscopic appearance. The testis is divided into compartments (lobules) separated by connective tissue. There are an estimated 250 lobules per testis, which vary in size; for clarity only 7 lobules are illustrated here. B. (i) Diagrammatic representation of the highly convoluted organisation of 3 seminiferous tubules (blue, black, grey) within a lobule. (ii) A magnified cross section through the lobule in i reveals how the tubules would appear in thin microscopic sections. Dashed lines (above section) and solid lines (below section) join the contiguous tubules. C. Cross section through an individual seminiferous tubule. Spermatogonia, located at the basal lamina of the seminiferous tubules, comprise a heterogeneous population of diploid germ cells. These can be classified according to their morphologies and correspond to three main maturation stages: Adark spermatogonia, which are considered to represent the reserve stem cell population; highly proliferating Apale spermatogonia; and more mature B spermatogonia that give rise to primary spermatocytes. Primary spermatocytes undergo meiosis to form secondary spermatocytes that differentiate to form spermatids, which when fully formed are released into the central lumen as spermatozoa that progress to the rete testis. Spermatogenesis is supported by the presence of the somatic Sertoli cells. The vascular and connective tissue network lie external to the wall of the seminiferous tubule.

Mentions: In approaching the challenge of how to visualise putative clones within the whole testis, it is important to appreciate the structural organisation of the seminiferous epithelium, which is organised into highly convoluted tubules (Figure 1A). Each testis comprises an average of 500 seminiferous tubules that are ∼70–80 cm in length and ∼120–300 µm in diameter [25]. All tubules start and end at the rete testis, where the sperm are collected, and are organised into tightly packed testicular lobules comprising a small number (1–4) of tubules bound together by connective tissue and surrounded by interstitial cells and vascular structures. As a consequence, cross-sections through testicular tissue show several distinct sections of the length of the same tubule (Figure 1B). At higher magnification, tubular cross-sections reveal the architecture of the seminiferous epithelium (Figure 1C), in which spermatogenesis occurs in a highly regulated manner [26], [27]. Spermatogonia, the proliferating diploid germline stem cells, form a single layer on the basal lamina of the tubule; differentiation proceeds in an organised centripetal sequence from type A and B spermatogonia, to spermatocytes, which undergo two meiotic divisions to form haploid spermatids that, after maturation, are released into the lumen of the tubule (Figure 1C).


Selfish spermatogonial selection: evidence from an immunohistochemical screen in testes of elderly men.

Lim J, Maher GJ, Turner GD, Dudka-Ruszkowska W, Taylor S, Rajpert-De Meyts E, Goriely A, Wilkie AO - PLoS ONE (2012)

Structure and organisation of the human testis and seminiferous tubules.A. Macroscopic appearance. The testis is divided into compartments (lobules) separated by connective tissue. There are an estimated 250 lobules per testis, which vary in size; for clarity only 7 lobules are illustrated here. B. (i) Diagrammatic representation of the highly convoluted organisation of 3 seminiferous tubules (blue, black, grey) within a lobule. (ii) A magnified cross section through the lobule in i reveals how the tubules would appear in thin microscopic sections. Dashed lines (above section) and solid lines (below section) join the contiguous tubules. C. Cross section through an individual seminiferous tubule. Spermatogonia, located at the basal lamina of the seminiferous tubules, comprise a heterogeneous population of diploid germ cells. These can be classified according to their morphologies and correspond to three main maturation stages: Adark spermatogonia, which are considered to represent the reserve stem cell population; highly proliferating Apale spermatogonia; and more mature B spermatogonia that give rise to primary spermatocytes. Primary spermatocytes undergo meiosis to form secondary spermatocytes that differentiate to form spermatids, which when fully formed are released into the central lumen as spermatozoa that progress to the rete testis. Spermatogenesis is supported by the presence of the somatic Sertoli cells. The vascular and connective tissue network lie external to the wall of the seminiferous tubule.
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC3412839&req=5

pone-0042382-g001: Structure and organisation of the human testis and seminiferous tubules.A. Macroscopic appearance. The testis is divided into compartments (lobules) separated by connective tissue. There are an estimated 250 lobules per testis, which vary in size; for clarity only 7 lobules are illustrated here. B. (i) Diagrammatic representation of the highly convoluted organisation of 3 seminiferous tubules (blue, black, grey) within a lobule. (ii) A magnified cross section through the lobule in i reveals how the tubules would appear in thin microscopic sections. Dashed lines (above section) and solid lines (below section) join the contiguous tubules. C. Cross section through an individual seminiferous tubule. Spermatogonia, located at the basal lamina of the seminiferous tubules, comprise a heterogeneous population of diploid germ cells. These can be classified according to their morphologies and correspond to three main maturation stages: Adark spermatogonia, which are considered to represent the reserve stem cell population; highly proliferating Apale spermatogonia; and more mature B spermatogonia that give rise to primary spermatocytes. Primary spermatocytes undergo meiosis to form secondary spermatocytes that differentiate to form spermatids, which when fully formed are released into the central lumen as spermatozoa that progress to the rete testis. Spermatogenesis is supported by the presence of the somatic Sertoli cells. The vascular and connective tissue network lie external to the wall of the seminiferous tubule.
Mentions: In approaching the challenge of how to visualise putative clones within the whole testis, it is important to appreciate the structural organisation of the seminiferous epithelium, which is organised into highly convoluted tubules (Figure 1A). Each testis comprises an average of 500 seminiferous tubules that are ∼70–80 cm in length and ∼120–300 µm in diameter [25]. All tubules start and end at the rete testis, where the sperm are collected, and are organised into tightly packed testicular lobules comprising a small number (1–4) of tubules bound together by connective tissue and surrounded by interstitial cells and vascular structures. As a consequence, cross-sections through testicular tissue show several distinct sections of the length of the same tubule (Figure 1B). At higher magnification, tubular cross-sections reveal the architecture of the seminiferous epithelium (Figure 1C), in which spermatogenesis occurs in a highly regulated manner [26], [27]. Spermatogonia, the proliferating diploid germline stem cells, form a single layer on the basal lamina of the tubule; differentiation proceeds in an organised centripetal sequence from type A and B spermatogonia, to spermatocytes, which undergo two meiotic divisions to form haploid spermatids that, after maturation, are released into the lumen of the tubule (Figure 1C).

Bottom Line: The dominant congenital disorders Apert syndrome, achondroplasia and multiple endocrine neoplasia-caused by specific missense mutations in the FGFR2, FGFR3 and RET proteins respectively-represent classical examples of paternal age-effect mutation, a class that arises at particularly high frequencies in the sperm of older men.We found numerous small (less than 200 cells) cellular aggregations with distinct immunohistochemical characteristics, localised to a portion of the seminiferous tubule, which are of uncertain significance.However more infrequently we identified additional regions where entire seminiferous tubules had a circumferentially altered immunohistochemical appearance that extended through multiple serial sections that were physically contiguous (up to 1 mm in length), and exhibited enhanced staining for antibodies both to FGFR3 and a marker of downstream signal activation, pAKT.

View Article: PubMed Central - PubMed

Affiliation: Clinical Genetics Group, Weatherall Institute of Molecular Medicine, University of Oxford, Oxford, United Kingdom.

ABSTRACT
The dominant congenital disorders Apert syndrome, achondroplasia and multiple endocrine neoplasia-caused by specific missense mutations in the FGFR2, FGFR3 and RET proteins respectively-represent classical examples of paternal age-effect mutation, a class that arises at particularly high frequencies in the sperm of older men. Previous analyses of DNA from randomly selected cadaveric testes showed that the levels of the corresponding FGFR2, FGFR3 and RET mutations exhibit very uneven spatial distributions, with localised hotspots surrounded by large mutation-negative areas. These studies imply that normal testes are mosaic for clusters of mutant cells: these clusters are predicted to have altered growth and signalling properties leading to their clonal expansion (selfish spermatogonial selection), but DNA extraction eliminates the possibility to study such processes at a tissue level. Using a panel of antibodies optimised for the detection of spermatocytic seminoma, a rare tumour of spermatogonial origin, we demonstrate that putative clonal events are frequent within normal testes of elderly men (mean age: 73.3 yrs) and can be classed into two broad categories. We found numerous small (less than 200 cells) cellular aggregations with distinct immunohistochemical characteristics, localised to a portion of the seminiferous tubule, which are of uncertain significance. However more infrequently we identified additional regions where entire seminiferous tubules had a circumferentially altered immunohistochemical appearance that extended through multiple serial sections that were physically contiguous (up to 1 mm in length), and exhibited enhanced staining for antibodies both to FGFR3 and a marker of downstream signal activation, pAKT. These findings support the concept that populations of spermatogonia in individual seminiferous tubules in the testes of older men are clonal mosaics with regard to their signalling properties and activation, thus fulfilling one of the specific predictions of selfish spermatogonial selection.

Show MeSH
Related in: MedlinePlus