How are different types of stem cell lines created?
Stem cells in research and medicine
Alternatives to the embryo
Early Development Fertilized egg Totipotent stem cells Totipotent : Can become any cell in body or placenta Fate Decision Pluripotent stem cells Blastocyst Pluripotent : Can become any cell in body Implantation Gastrulation Fate Decision Multipotent stem cells Primary Germ Cells Endoderm (inner) Mesoderm (middle) Ectoderm (outer) Multipotent : Can become any cell within a specific germ layer or cell lineage Embryonic stem cells come from inner cell mass of blastocyst.
Pluripotent — can differentiate into specialized cell types
endoderm mesoderm ectoderm Courtesy of James Thomson, U. Wisconsin-Madison
Is that an Embryonic Stem Cell? Embryonic stem cells injected into a SCID mouse will grow into teratomas, tumors of the germ cell layers. Individual ESCs under the correct conditions will make many different cell types. The true potential of stem cells can only be assessed retrospectively SCID Mouse: Severe Combined ImmunoDeficiency
Stem Cells: From Embryonic to Adult Embryonic stem cells are those removed from the blastocyst before the fate decision from pluripotentiality to multipotentiality. Adult stem cells are those multipotential cells that persist in fully developed tissues. These cells never differentiated into the mature cell types of the tissues in which they reside. http://www.brown.edu/Courses/BI0032
Challenging: In cloned cell lines, about 4% of genes function abnormally, owing to departures from normal activation or expression of certain genes
-Imprinting, methylation state
Limited success: ~25 percent of nuclear transfers led to a blastocyst; 35 percent of blastocysts led to establishment of cell lines Patient-specific embryonic stem cells derived from human SCNT blastocysts. Science 308(5729):1777-1783, 2005. Removing the egg nucleus before transferring a somatic cell nucleus Roslin Institute http://www.roslin.ac.uk/library/