Transcript Cell potential and cloning

Cell potential, animal cloning
Can any cell develop into a complete organism?
How do you clone a sheep?
Regenerating plants from a single cell
Testing the developmental potential of nuclei from
differentiated cells
(or suck out meiotic spindle with pipette)
Does tadpole
develop?
(Needle prick can activate some eggs)
Fig. 2. (A) In Amphibia, nuclear transfer success declines rapidly as cells differentiate
Gurdon, J. B. and Byrne, J. A. (2003) Proc. Natl. Acad. Sci. USA 100, 8048-8052
Copyright ©2003 by the National Academy of Sciences
Success of nuclear transplant experiments
Donor nucleus
Stages reached
Zygote
blastula, tadpole, adult
Blastula
blastula, tadpole, adult
Tadpole intestine
blastula, tadpole, adult
Cultured skin cell
(differentiated)
blastula
Cleavage divisions in the frog Xenopus
animal
vegetal
Blastula
Why do frogs from nuclear transplant experiments often
arrest at the blastula stage?
The mid-blastula transition
(after about 12 rounds of cleavage)
• Growth phases added to Cell Cycle
• Embryo starts transcribing its own RNA
Could some genes be missing from differentiated cells?
Donor nucleus
Stages reached
Zygote
blastula, tadpole, adult
Blastula
blastula, tadpole, adult
Tadpole intestine
blastula, tadpole, adult
Cultured skin cell
blastula
Blastula from above
blastula, tadpole
(see handout)
Conclusions of nuclear transplantation experiments in
amphibians:
Nuclei of differentiated cells have the potential to program
development of many or all cells. (Therefore, the nuclei
must contain all the necessary genes.)
Their capacity to direct development is restricted as they
differentiate.
The ooctye cytoplasm can reprogram differentiated nuclei
to allow them to direct complete development.
07_37_Protein.produc.jpg
Nuclear effect –
ability of genes to
be expressed
Cytoplasm effects –
signals to nucleus
(transcription factors,
signaling pathways)
Genes need to be accessible to be expressed
08_14_chromatin.struc.jpg
Histone modification state may limit gene expression potential
05_30_histone tails.jpg
DNA methylation state may limit gene expression potential
Cloning frogs from a single nuclear donor
Cloning mammals from adult cells
08_02_genetic.instruction.part2
(also activates egg)
(from Nature 405: 800-802)
(from Nature 405: 800-802)
NY Times, June 3, 2006
Clones' Debut Is a Test of Genetics, and Bettors' Wits
By BILL FINLEY
Anyone trying to select a winner at the mule races this weekend in Winnemucca, Nev.,
will no doubt have a hard time choosing between Idaho Gem and Idaho Star. They may
have different names, but they are not necessarily different mules.
Idaho Gem and Idaho Star are clones. They are two of three mules who were born in
2003 as the result of a cloning project at the University of Idaho and Utah State
University. Leased from the University of Idaho for racing by Don Jacklin, an Idaho
businessman, Gem and Star will make their first career starts today in separate 350-yard
elimination races. The top eight finishers, based on time, will meet in tomorrow's final.
There is parimutuel wagering on the races.
Jacklin is confident the two mules will make the final, which could be part mule race,
part science experiment. Who is faster, Idaho Gem or Idaho Star, or will they cross the
finish line in unison?
"Genetically, they should have equal ability," Jacklin said. "But you have to factor in the
environmental effects. They can make a big difference."
Jacklin counts his identical twin among the reasons that he is interested in the genetic
sciences. He put up $400,000 to help create the clones.
Dr. Gordon L. Woods, one of the veterinary scientists involved in the project, mated the
parents of a champion mule named Taz and took cells from the resulting fetus. The cells
were implanted in surrogates. Mules are a cross between female horses and male
donkeys and are typically sterile.