Making Germ Cells from Human Embryonic Stem Cells - Male Germline Stem Cells Developmental and Regenerative Potential - page 76

Fig. 3.7 Several methods used to obtain mature germ cells from ES cells. ( a ) This diagram shows
the differentiation of mouse ES cells that contain the ∆PE-Oct4-eGFP germ cell reporter and
subsequent isolation of Oct4-GFP+ cells from embryoid bodies by FACS analysis. Oct4-GFP+
cells are then mixed with wild-type fetal mouse ovary tissue, transplanted into the kidney capsule
of live mice, and then the re-aggregated tissue is examined at various time-points for GFP-
expressing oocytes. ( b ) This illustration shows the differentiation of human ES cells containing
the VASA-GFP reporter, subsequent isolation of GFP+ germ cells from differentiating embryoid
bodies or adherent cultures, and culturing of germ cells in conditions that promote the formation
of normal mature gametes (images provided by A.M. Schuh-Huerta, S.M. Schuh-Huerta, and
C. Nicholas)
formation of a haploid genome, have not been completed to assess germ cell quality,
fidelity, and functionality. The need for more stringent assessments and criteria is
highlighted by the fact that only one group to date has successfully used ESC-
derived gametes for in vitro fertilization to generate viable offspring (Nayernia et al.
2006 ). In fact, although this is a remarkable accomplishment, these ES cell-derived
offspring had growth defects (were either smaller or larger than controls), shorter life
spans, abnormal methylation patterns resulting from disturbed male germline-
specific methylation imprints, and phenotypic abnormalities. These observations
highlight the need for improved methods, analysis, and screening of germ cells
derived in culture.