Cell potency in the context of Unipotency

In biology and genetics, the germline is the population of a multicellular organism's cells that develop into germ cells. In other words, they are the cells that form gametes (eggs and sperm), which can come together to form a zygote. They differentiate in the gonads from primordial germ cells into gametogonia, which develop into gametocytes, which develop into the final gametes. This process is known as gametogenesis.

Germ cells pass on genetic material through the process of sexual reproduction. This includes fertilization, recombination and meiosis. These processes help to increase genetic diversity in offspring.

Embryonic stem cells (ESCs) are pluripotent stem cells derived from the inner cell mass of a blastocyst, an early-stage pre-implantation embryo. Human embryos reach the blastocyst stage 4–5 days post fertilization, at which time they consist of 50–150 cells. Isolating the inner cell mass (embryoblast) using immunosurgery results in destruction of the blastocyst, a process which raises ethical issues, including whether or not embryos at the pre-implantation stage have the same moral considerations as embryos in the post-implantation stage of development.

Researchers focus heavily on the therapeutic potential of embryonic stem cells, with clinical use being the goal for many laboratories. Potential uses include the treatment of diabetes and heart disease. The cells are studied to be used as clinical therapies, models of genetic disorders, and cellular/DNA repair. However, adverse effects in the research and clinical processes such as tumors and unwanted immune responses have also been reported.

The trophoblast (from Greek trephein: to feed; and blastos: germinator) is the outer layer of cells of the blastocyst. Trophoblasts are present four days after fertilization in humans. They provide nutrients to the embryo and develop into a large part of the placenta. They form during the first stage of pregnancy and are the first cells to differentiate from the fertilized egg to become extraembryonic structures that do not directly contribute to the embryo. After blastulation, the trophoblast is contiguous with the ectoderm of the embryo and is referred to as the trophectoderm. After the first differentiation, the cells in the human embryo lose their totipotency because they can no longer form a trophoblast. They become pluripotent stem cells.

Homeobox protein NANOG (hNanog) is a transcriptional factor that helps embryonic stem cells (ESCs) maintain pluripotency by suppressing cell determination factors. hNanog is encoded in humans by the NANOG gene. Several types of cancer are associated with NANOG.

Radial glial cells (RGCs), or radial glial progenitor cells (RGPs), are bipolar-shaped progenitor cells that are responsible for producing all of the neurons in the cerebral cortex. RGPs also produce certain lineages of glia, including astrocytes and oligodendrocytes. Their cell bodies (somata) reside in the embryonic ventricular zone, which lies next to the developing ventricular system.

During development, newborn neurons use radial glia as scaffolds, traveling along the radial glial fibers in order to reach their final destinations. Despite the various possible fates of the radial glial population, it has been demonstrated through clonal analysis that most radial glia have restricted, unipotent or multipotent, fates. Radial glia can be found during the neurogenic phase in all vertebrates (studied to date).

The stem cell controversy concerns the ethics of research involving the development and use of human embryos. Most commonly, this controversy focuses on embryonic stem cells. Not all stem cell research involves human embryos. For example, adult stem cells, amniotic stem cells, and induced pluripotent stem cells do not involve creating, using, or destroying human embryos, and thus are minimally, if at all, controversial. Many less controversial sources of acquiring stem cells include using cells from the umbilical cord, breast milk, and bone marrow, which are not pluripotent.