The colonial ascidian Botryllus schlosseri continuously regenerates entire bodies in an asexual budding process. The germ line of the newly developing bodies is derived from migrating germ cell precursors, but the signals governing this homing process are unknown. Here we show that germ cell precursors can be prospectively isolated based on expression of aldehyde dehydrogenase and integrin alph...

An important mechanism for the specification and development of the animal germ line is the localization of specific molecules to the germ plasm. Restriction of these molecules to the germ line is considered to be critical for proper development of the germ line as well as the soma. Cytoplasmic localization alone, however, may not be sufficient to achieve germ line-specific expression. While ze...

Germ-line specification is essential for sexual reproduction. In the ovules of most flowering plants, only a single hypodermal cell enlarges and differentiates into a megaspore mother cell (MMC), the founder cell of the female germ-line lineage. The molecular mechanisms restricting MMC specification to a single cell remain elusive. We show that the Arabidopsis transcription factor WRKY28 is exc...

The origin of premeiotic ribosomal DNA (rDNA) amplification in germ-line cells of Xenopus laevis has been examined using in situ RNA-DNA hybridization on cytological preparations, tritiated thymidine autoradiography, and isopycnic density gradient centrifugation. Primordial germ cells (PGC), from the time they first become localized in the genital ridge at day no. 4 of development, until approx...

Germ line p53 mutations represent a genetic predisposition for cancer development. At the present time, their detection requires extensive work and their functional significance must be documented. Therefore, we have designed a simple biological assay which detects functionally significant germ line p53 mutations. This assay is based on the cloning of the patient's p53 complementary DNA into a ...

The ability to identify stem cells and trace their descendants in vivo has yielded insights into how self-renewal, proliferation, and differentiation are regulated in adult stem cell lineages. Analysis of male germ-line stem cells in Drosophila has revealed the importance of local signals from the microenvironment, the stem cell niche, in controlling stem cell behavior. Germ-line stem cells phy...

We report a generally applicable strategy for transferring zygotic lethal mutations through the zebrafish germ line. By using a morpholino oligonucleotide that blocks primordial germ cell (PGC) development, we generate embryos devoid of endogenous PGCs to serve as hosts for the transplantation of germ cells derived from homozygous mutant donors. Successful transfers are identified by the locali...

The germ-cell lineage in mammals is believed to separate from somatic lineages around the time of gastrulation. We present data showing that germline cells can originate from a human hepatic cell line (HL7702) in vitro. In specific culture conditions, the HL7702 cells gave rise to a subpopulation of morphologically distinct cells, some of which expressed germline-specific markers, consistent wi...

In most organisms, primordial germ cells are set aside from the cells of the body early in development. To form an embryonic gonad, germ cells often have to migrate along complex routes through and along diverse tissues until they reach the somatic part of the gonad. Recent advances have been made in the genetic analysis of these early stages of germ line development. Here we review findings fr...

Throughout spermatogenesis multiplication, maturation and differentiation of germ cells results in the formation of the male gamete. The understanding of spermatogenesis needs detailed informations about the organization of the germinal epithelium, the structure and function of different types of germ cells, endocrine and paracrine cells and mechanisms, intratesticular and extratesticular regul...