Functional differentiation of chick gonads following depletion of primordial germ cells

The endocrine capacity of embryonic chick gonads depleted in germ cells was compared to that of controls to determine whether the somatic elements of germ-cell-depleted gonad$ will undergo normal functional sex differentiation. Primordial germ cells were removed from early embryos, Hamburger and Hamilton stages 7-11, by excision of the anterior germinal crescent. Embryos were sacrificed at 14 days of incubation, and their gonads were analysed for functional differentiation by: (1) electron microscopy to detect ultrastructural cellular morphology characteristic of steroid-secreting cells; (2) growth in cell culture to detect development of characteristic cell morphologies; (3) radioimmunoassay of cell-culture media to detect androgens and oestrogens (androstenedione and oestradiol 17 β) secreted by gonadal cells; and (4) measurement of steroid levels produced by cultures treated with human chorionic gonadotropin (hCG) to detect the ability of gonadal cells to increase steroid production in response to gonadotropin stimulation. As a bioassay of gonadal endocrine activity, a gross morphological analysis was performed on the genital ducts, the development of which is ovary-dependent in females and testis-dependent in males. This study demonstrated that both male and female embryonic gonads exhibit normal functional differentiation following a significant reduction in the number of primordial germ cells. These results confirm and extend our previous finding that morphological differentiation of sterile embryonic gonads is normal (McCarrey & Abbott, 1978). It is concluded frofn the present study that a normal complement of germ cells is not essential to either morphological or functional sex differentiation of the somatic elements of the embryonic ovary or testis, thus arguing against any inductive role for the germ cells in this process.

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Sex differentiation of germ cells in the teleost, Oryzias latipes, during normal embryonic development

Development ◽

10.1242/dev.28.2.385 ◽

1972 ◽

Vol 28 (2) ◽

pp. 385-395

Author(s):

Noriyuki Satoh ◽

Nobuo Egami

Keyword(s):

Germ Cells ◽

Meiotic Prophase ◽

Sex Differentiation ◽

Primordial Germ Cells ◽

Oryzias Latipes ◽

The Other ◽

Histological Structure ◽

The Mean ◽

Further Development ◽

Normal Embryonic Development

Mitotic and meiotic activities of germ cells during early development in the medaka, Oryzias latipes, are dealt with in this report. Primordial germ cells were obviously distinguishable from somatic cells 3 days after fertilization and began to proliferate about 7 days after fertilization. The mean number of primordial germ cells increased during a period of 7–10 days after fertilization, reaching about 90 immediately before hatching. Newly hatched fry could be classified into two types according to the number and the nucleic activity of germ cells in the gonadal rudiment. One type consisted of fry containing about 100 germ cells and no cells in the meiotic prophase. In the other type of fry the number of germ cells increased by mitotic divisions and some of the cells began to enter into the meiotic prophase. During the course of further development the fry of the former type differentiated into males and the latter into females. Therefore it can be concluded that the morphological sex differentiation of germ cells occurs at the time of hatching. However, no sexual differences in the histological structure of somatic elements in the gonad are observable at that time.

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XY oocytes of sex-reversed females with a Sry mutation deviate from the normal developmental process beyond the mitotic stage†

Biology of Reproduction ◽

10.1093/biolre/ioy214 ◽

2018 ◽

Vol 100 (3) ◽

pp. 697-710 ◽

Cited By ~ 1

Author(s):

Akihiko Sakashita ◽

Takuya Wakai ◽

Yukiko Kawabata ◽

Chiaki Nishimura ◽

Yusuke Sotomaru ◽

...

Keyword(s):

Germ Cells ◽

Developmental Process ◽

Sex Differentiation ◽

Primordial Germ Cells ◽

Primordial Follicle ◽

Genetic Ablation ◽

Female Mice ◽

Meiotic Progression ◽

Molecular Etiology ◽

Mitotic Proliferation

Abstract The fertility of sex-reversed XY female mice is severely impaired by a massive loss of oocytes and failure of meiotic progression. This phenomenon remains an outstanding mystery. We sought to determine the molecular etiology of XY oocyte dysfunction by generating sex-reversed females that bear genetic ablation of Sry, a vital sex determination gene, on an inbred C57BL/6 background. These mutant mice, termed XYsry− mutants, showed severe attrition of germ cells during fetal development, resulting in the depletion of ovarian germ cells prior to sexual maturation. Comprehensive transcriptome analyses of primordial germ cells (PGCs) and postnatal oocytes demonstrated that XYsry− females had deviated significantly from normal developmental processes during the stages of mitotic proliferation. The impaired proliferation of XYsry− PGCs was associated with aberrant β-catenin signaling and the excessive expression of transposable elements. Upon entry to the meiotic stage, XYsry− oocytes demonstrated extensive defects, including the impairment of crossover formation, the failure of primordial follicle maintenance, and no capacity for embryo development. Together, these results suggest potential molecular causes for germ cell disruption in sex-reversed female mice, thereby providing insights into disorders of sex differentiation in humans, such as “Swyer syndrome,” in which patients with an XY karyotype present as typical females and are infertile.

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SEX DIFFERENTIATION IN THE PACIFIC SALMON ONCORHYNCHUS KETA (WALBAUM)

Canadian Journal of Zoology ◽

10.1139/z53-007 ◽

1953 ◽

Vol 31 (2) ◽

pp. 73-79 ◽

Cited By ~ 23

Author(s):

J. G. Robertson

Keyword(s):

Germ Cells ◽

Chum Salmon ◽

Pacific Salmon ◽

Sex Differentiation ◽

Primordial Germ Cells ◽

The Other ◽

Oncorhynchus Keta ◽

Progressive Development ◽

The Pacific ◽

Female Phase

The differentiation of the gonad is described in chum salmon embryos and alevins. Contrary to classical findings in teleosts, sex differentiation in the chum salmon proceeds in the male or female direction without an intermediate female phase. From an initially indifferent gonad there is a progressive development of one sex or the other. The organ forms as a fold from the splanchnic mesoderm and, at the time of first appearance, contains primordial germ cells. These enlarge to form the definitive germ cells which, after a series of divisions, form smaller oogonia or spermatogonia. Oogonia are followed by primary and secondary (growing) oocytes, the appearance of which is the criterion of sex distinction. Spermatogonia continue to multiply but do not undergo growth in the alevin. The ovary develops an open endovarial canal and is supported by a prominent mesovarium. The testis remains small and, in the alevin, develops no ducts. It is suspended by a mesorchium.

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Gnrh3 Regulates PGC Proliferation and Sex Differentiation in Developing Zebrafish

Endocrinology ◽

10.1210/endocr/bqz024 ◽

2019 ◽

Vol 161 (1) ◽

Cited By ~ 2

Author(s):

Ke Feng ◽

Xuefan Cui ◽

Yanlong Song ◽

Binbin Tao ◽

Ji Chen ◽

...

Keyword(s):

Germ Cells ◽

Sex Differentiation ◽

Primordial Germ Cells ◽

Mek Inhibitor ◽

Gonadotropin Releasing Hormone ◽

Terminal Deoxynucleotidyl Transferase ◽

Hormone Release ◽

Wild Type ◽

Gnrh Analog ◽

Biased Sex Ratio

Abstract Gonadotropin-releasing hormone (Gnrh) plays important roles in reproduction by stimulating luteinizing hormone release, and subsequently ovulation and sperm release, ultimately controlling reproduction in many species. Here we report on a new role for this decapeptide. Surprisingly, Gnrh3-null zebrafish generated by CRISPR/Cas9 exhibited a male-biased sex ratio. After the dome stage, the number of primordial germ cells (PGCs) in gnrh3-/- fish was lower than that in wild-type, an effect that was partially rescued by gnrh3 overexpression. A terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) analysis revealed no detectable apoptosis of PGCs in gnrh3-/- embryos. Proliferating PGCs could be detected in wild-type embryos, while there was no detectable signal in gnrh3-/- embryos. Compared with wild type, the phosphorylation of AKT was not significantly different in gnrh3-/- embryos, but the phosphorylation of ERK1/2 decreased significantly. Treatment with a Gnrh analog (Alarelin) induced ERK1/2 phosphorylation and increased PGC numbers in both wild-type and gnrh3-/- embryos, and this was blocked by the MEK inhibitor PD0325901. The relative expression of sox9a, amh, and cyp11b were significantly upregulated, while cyp19a1a was significantly downregulated at 18 days post-fertilization in gnrh3-/- zebrafish. Taken together, these results indicate that Gnrh3 plays an important role in early sex differentiation by regulating the proliferation of PGCs through a MAPK-dependent path.

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Response to fibronectin of mouse primordial germ cells before, during and after migration

Development ◽

10.1242/dev.113.4.1365 ◽

1991 ◽

Vol 113 (4) ◽

pp. 1365-1373 ◽

Cited By ~ 6

Author(s):

C. Ffrench-Constant ◽

A. Hollingsworth ◽

J. Heasman ◽

C.C. Wylie

Keyword(s):

Cell Culture ◽

Extracellular Matrix ◽

Germ Cells ◽

Culture System ◽

Primordial Germ Cells ◽

Explant Culture ◽

Double Labelling ◽

Target Tissue ◽

Fibronectin Mrna

The adhesive extracellular matrix glycoprotein fibronectin is thought to play a central role in cell migration during embryogenesis. In order to define this role, we have examined the response to fibronectin in cell culture of mouse primordial germ cells (PGCs) before, during and after their migration from the hindgut into their target tissue, the genital ridges. Using an explant culture system, we show that PGCs will emigrate from tissue fragments containing hindgut, and that fibronectin stimulates this migration. Adhesion assays show that the start of PGC migration is associated with a fall in adhesion to fibronectin. Double-labelling studies using in situ hybridization and histochemistry demonstrate that migrating PGCs do not contain detectable fibronectin mRNA, suggesting that they do not synthesize and secrete the fibronectin within their migratory substratum. Taken together, these findings are consistent with an important role for fibronectin in stimulating PGC migration. In addition, however, they suggest that the interaction between PGCs and fibronectin may be important in timing the start of migration, with the fall in adhesion allowing the PGCs to commence their migration towards the genital ridges.

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Zfx mutation results in small animal size and reduced germ cell number in male and female mice

Development ◽

10.1242/dev.124.11.2275 ◽

1997 ◽

Vol 124 (11) ◽

pp. 2275-2284

Author(s):

S.W. Luoh ◽

P.A. Bain ◽

R.D. Polakiewicz ◽

M.L. Goodheart ◽

H. Gardner ◽

...

Keyword(s):

Turner Syndrome ◽

Germ Cells ◽

Sex Differentiation ◽

Primordial Germ Cells ◽

Small Animal ◽

Cell Number ◽

Targeted Mutagenesis ◽

Mutant Mice ◽

Postnatal Life ◽

Y Chromosomes

The zinc-finger proteins ZFX and ZFY, encoded by genes on the mammalian X and Y chromosomes, have been speculated to function in sex differentiation, spermatogenesis, and Turner syndrome. We derived Zfx mutant mice by targeted mutagenesis. Mutant mice (both males and females) were smaller, less viable, and had fewer germ cells than wild-type mice, features also found in human females with an XO karyotype (Turner syndrome). Mutant XY animals were fully masculinized, with testes and male genitalia, and were fertile, but sperm counts were reduced by one half. Homozygous mutant XX animals were fully feminized, with ovaries and female genitalia, but showed a shortage of oocytes resulting in diminished fertility and shortened reproductive lifespan, as in premature ovarian failure in humans. The number of primordial germ cells was reduced in both XX and XY mutant animals at embryonic day 11.5, prior to gonadal sex differentiation. Zfx mutant animals exhibited a growth deficit evident at embryonic day 12.5, which persisted throughout postnatal life and was not complemented by the Zfy genes. These phenotypes provide the first direct evidence for a role of Zfx in growth and reproductive development.

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EFFECT OF RETINOIC ACID ON SEX DIFFERENTIATION IN XX AND XY PRIMORDIAL GERM CELLS

Biology of Reproduction ◽

10.1093/biolreprod/77.s1.207b ◽

2007 ◽

Vol 77 (Suppl_1) ◽

pp. 207-208

Author(s):

Yukiko Yamazaki ◽

Hirotaka Yoshioka ◽

Eleanor Low ◽

Ryuzo Yanagimachi ◽

Kazuhiro Iwahashi

Keyword(s):

Retinoic Acid ◽

Germ Cells ◽

Sex Differentiation ◽

Primordial Germ Cells

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Differentiation of primordial germ cells in the embryonic development of Thermobia domestica, Pack. (Thysanura): an ultrastructural study

Development ◽

10.1242/dev.38.1.93 ◽

1977 ◽

Vol 38 (1) ◽

pp. 93-114

Author(s):

Jerzy Klag

Keyword(s):

Embryonic Development ◽

Germ Cells ◽

Morphological Changes ◽

Sex Differentiation ◽

Primordial Germ Cells ◽

Postembryonic Development ◽

Thermobia Domestica ◽

Dense Bodies ◽

Accessory Nuclei ◽

High Degree

The primordial germ cells (PGCs) of Thermobia domestica undergo some morphological changes during the embryonic development. Most conspicuous are the changes in the ultrastructure of the nucleus, whose envelope shows a high degree of activity. Two types of vesicles bleb off from the nucleus; the ones with the light interior are called the accessory nuclei, the others, with electron-opaque contents, have been termed the dense bodies. The nucleolus, initially clustered at the nucleus centre, undergoes dispersion and assembles again towards the end of embryonic development. At the same time, the sex differentiation of PGCs takes place. It is preceded by an increase in the activity of Golgi complexes and in the volume of lysosomes and lamellar bodies, the latter giving rise to lipid droplets. At the early stages of postembryonic development, preoogonia and prespermatogonia can readily be distinguished. Preoogonia have a wavy-surfaced nucleus and their cytoplasm contains dense bodies. In prespermatogonia, the nucleus is spherical with smooth envelope and there are no dense bodies in the cytoplasm. Throughout the period studied there occur nucleolus-like bodies and nuage material considered to be the germ-cell determinants in this species.

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A Quantitative Study of Primordial Germ Cells in the Male Rat

Development ◽

10.1242/dev.11.4.715 ◽

1963 ◽

Vol 11 (4) ◽

pp. 715-740

Author(s):

Heather M. Beaumont ◽

Anita M. Mandl

Keyword(s):

Quantitative Study ◽

Germ Cells ◽

Total Population ◽

Developmental Stages ◽

Sex Differentiation ◽

Primordial Germ Cells ◽

Male Rat ◽

Female Rat ◽

Mitotic Proliferation ◽

Prophase Of Meiosis

In mammals, as in other vertebrates, primordial germ cells arise extra-gonadally and migrate to the genital ridges (see Franchi, Mandl & Zuckerman, 1962). In the rat, the gonads undergo sex differentiation on the 14th day of gestation, i.e. some 2 days after the arrival of the primordial germ cells. In the female rat, the number of oögonia increases sharply, due to active mitotic proliferation, between the 14th and 18th day of gestation. Thereafter, the majority of germ cells enter the prophase of meiosis, and thus, by definition, become oöcytes. A large number of oöcytes undergo spontaneous degeneration, with the result that the total population decreases from a peak of about 75,000 (at 18·5 days) to about a third that number 2 days after birth. The decrease in the population is due to three distinct ‘waves’ of degeneration occurring at specific developmental stages (Beaumont & Mandl, 1962).

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