Embryonic Stem Cells and Induced Pluripotent Stem Cells
The inner cell mass is the source of the embryo proper as well as of embryonic stem cells.
Cultured embryonic stem cells (ES cells) are pluripotent, capable of giving rise to all differentiated cell types of the organism with the exception of extraembryonic tissues. They are useful in the production of genetically altered mice and offer the potential for therapeutic uses.
The pluripotency of ES cells is controlled by multiple factors, including the state of DNA methylation, chromatin regulators, certain micro-
Animal cloning establishes that cell differentiation can be reversed.
Induced pluripotent stem (iPS) cells can be formed from somatic cells by expression of combinations of key transcription factors, including KLF4, Sox2, Oct4, and Myc.
As exemplified by ALS, differentiated cells produced in culture from human iPS cells can be used to understand the underlying cause of a disease as well as to screen drugs that could be used to treat the disease.
β islet cells produced in culture from human iPS cells secrete insulin normally in response to an elevation of glucose in the media and reverse the high glucose levels in diabetic mice.