In somatic cells, imprinted genes are expressed monoallelically according to parent-of-origin. In contrast, in 11.5 days post-coitum primordial germ cells (PGCs), and later stage germ cells, these same genes are expressed biallelically, suggesting that imprints inherited from the gametes are largely erased by this stage. To determine when in germ cell development this biallelic expression pheno...

The germ line is unique in that highly specialised cells must be formed while retaining genomic totipotency. In mice, germ cells are derived from the pluripotent epiblast cells under the influence of inductive signals. This specification event involves reactivation or maintenance of core regulators of pluripotency, activation of germ line specific genetic programs, silencing of somatic cell pro...

Many metazoans start germ cell development during embryogenesis, while some metazoans possessing pluripotent stem cells undergo postembryonic germ cell development. The latter reproduce asexually but develop germ cells from pluripotent stem cells or dormant primordial germ cells when they reproduce sexually. Sexual induction of the planarian Dugesia ryukyuensis is an important model for postemb...

Stem cells have capacity to differentiate into a variety of cell types. The inner cell mass of epiblast and primordial germ cells (PGCs) are pluripotent in nature. Nanog3 has been identified as a pluripotent transcription factor belongs to homeobox family of protein required for the survival of primordial germ cell differentiation. Spermatogenesis is associated with highly specialized kind of g...

In animals, primordial germ cells (PGCs) give rise to the germ lines, the cell lineages that produce sperm and eggs. PGCs form in embryogenesis, typically by one of two modes: a likely ancestral mode wherein germ cells are induced during embryogenesis by cell-cell signaling (induction) or a derived mechanism whereby germ cells are specified by using germ plasm-that is, maternally specified germ...

Suggestive evidence for the extragonadal origin of germ cells in birds was first presented by Swift (1914), who described primordial germ cells in the chick embryo at as early a stage as the primitive streak. According to Swift, primordial germ cells are originally located extra-embryonically in the anterior part of the blastoderm and occupy a crescent-shaped region ('germinal crescent') on the...

Ultraviolet light (u.v.) irradiation of the vegetal hemisphere of Xenopus laevis eggs resulted in the elimination of primordial germ cells in tadpoles. Quantitative studies were performed on this phenomenon. The stage sensitivity to u.v. inactivation of germ cell formation was obtained for the early developmental stages ranging from immediately after fertilization to small-cell blastula. It was...

background: over recent decades a possible decrease in sperm quality and an increase in the incidence of testicular cancer have been reported in many populations. some recent findings, as cohort studies, showed an increased risk of testicular cancer in men with abnormal semen analysis. case: a 30 years old man referred to our clinic with chief compliant of infertility for 3 years. spermogram re...

Epigenetic processes affect three stages of germline development, namely (1) specification and formation of primordial germ cells and their germline derivatives through lineage-specific epigenetic modifications, in the same manner as other embryonic lineages are formed, (2) a largely genome-wide erasure and re-establishment of germline-specific epigenetic modifications that only occurs in the e...

Primordial germ cells (PGCs) give rise to the germ line in animals. PGCs are specified during embryogenesis either by an ancestral mechanism of cell-cell signalling (induction) or by a derived mechanism of maternally provided germ plasm (preformation). Recently, a hypothesis was set forth purporting that germ plasm liberates selective constraint and accelerates an organism's protein sequence ev...