1. Epigenetics: Nuclear transplantation & Reprogramming of the genome

2. Historical perspectives
Big question: ‘nuclear cloning’ is possible?
(genome of differentiated cells is identical to that of undifferentiated cells?)
New concept: ‘Reprogramming’ (somatic to embryonic epigenetic state)
Earlier studies with amphibian (frog eggs)
Later studies with mammals (mouse eggs)

3. Nuclear transfer procedure (frog)

4. Nuclear transfer procedure (mouse)
Earlier attempts: zygotes + nuclei from
cleavage stage donor embryos
Some success in farm animals not in
mouse : lambs
Transition time difference: maternal to
zygotic transcription
‘Dolly’ cloning: mammary gland donor
1st somatic cell nuclear transfer (SCNT)
More than 15 mammalian species cloned

5. Phenotype of cloned animals
More differentiated-stage cells
derive much less success!
Frog nuclear transfers were
successful up to tadpole stage!

6. Phenotype of cloned animals
The majority fails after implantation
G0 or G1 –phase donor cells are more
successful upto blastocyst than S-phase
ES or EC cells.
But more success rates in ES or EC
beyond the blastocyst stage.
Cloned animals (survivors) likely have
some defects that are responsible for
adult-stage health problems.
Large offspring syndrome
(large fraction of placenta-specific genes
are changed in terms of their expression
levels)
Gametogenesis reprogramming is
important for placenta genes

7. Reprogramming of terminally differentiated cells (monoclonal mice)
A little loss of genomic
complement is not a problem
for cloning!

8. Reprogramming of terminally differentiated cells (olfactory neuron)

9. Medical implications of nuclear transplantation
Reproductive cloning vs
Therapeutic cloning

10. Medical implications of nuclear transplantation (demonstration)

11. iPS (Induced Pluripotent Stem) cells
three factors (Oct4, Sox2, Klf4) can transform adult cells into stem cells.
does not require early-stage embryos or cells from patients

12. iPS (Induced Pluripotent Stem) cells