Figure 22–47 Use of iPS cells for drug discovery and for analysis and treatment of genetic disease. the left side of the diagram shows how differentiated cells that are generated from ipS cells derived from a patient with a genetic disease can be used for analysis of the disease mechanism and for discovery of therapeutic drugs. the right side of the diagram shows how the genetic defect might be repaired in the ipS cells, which could then be induced to differentiate in an appropriate way and grafted back into the patient without danger of immune rejection. (based on d.a. Robinton and G.Q. daley, Nature 481:295–305, 2012).
In the adult mammalian body, the various types of stem cells are highly specialized, each giving rise to a limited range of differentiated cell types. Cells become restricted size? how do the cells in each tissue to specific pathways of differentiation during embryonic development. One way know when to terminate their growth to force a return to a pluripotent or totipotent state is by nuclear transplantation: and division, so as to limit the size of the nucleus of a differentiated cell can be injected into an enucleated oocyte, whose an organ or tissue appropriately?
cytoplasm reprograms the genome back to an approximation of an early embryonic state. This allows production of an entire new individual. The reversion of the • what is the fundamental molecular genome to this state involves radical, genome-wide changes in chromatin structure difference that distinguishes a stem and DNA methylation. cell?
Remarkably, cells taken from the inner cell mass of an early mammalian embryo • how is the correct balance between can be propagated in culture indefinitely in a pluripotent state. When transplanted stem cells, progenitor cells, and back into a host early embryo, these embryonic stem (ES) cells can contribute cells to any tissue, including the germ line. ES cells have been invaluable for genetic engi tissue or organ?
neering in mice. Cells with similar properties, called induced pluripotent stem cells (iPS cells), can be generated from adult differentiated cells such as fibroblasts by • what role does chromatin structure forced expression of a cocktail of key transcription regulators. A similar method play in cell memory and in cell reprogramming?
can be used to reprogram adult cells directly from one specialized state to another. In principle, iPS cells generated from cells biopsied from an adult human patient • how are molecules inherited could be used for tissue repair in that same individual, avoiding the problem of asymmetrically during cell division?
immune rejection. More immediately, they provide a source of specialized cells that can be used to analyze in vitro the effects of mutations affecting human cells and for • how do germ cells avoid aging? screening for drugs for treatment of genetic diseases.
Which statements are true? explain why or why not.
22–1 In the small intestine, stem cells in the crypts divide asymmetrically to maintain the population of cells that make up the villi; after each division, one daughter remains a stem cell and the other begins to divide rapidly to produce differentiated progeny.
22–2 Stem cells, being stem cells, are by definition the same in all tissues.
22–3 Every tissue that can be renewed is renewed from a tissue-specific population of stem cells.
22–4 Disturbance of the balance in the activities of osteoblasts and osteoclasts in favor of osteoclasts can give rise to the condition known as osteoporosis, the brittle-bone syndrome of the elderly.
Discuss the following problems.