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

(Needle prick can activate some eggs)

(or suck out meiotic spindle with pipette)

Does tadpole develop?

Copyright ©2003 by the National Academy of Sciences

Gurdon, J. B. and Byrne, J. A. (2003) Proc. Natl. Acad. Sci. USA 100, 8048-8052

Fig. 2. (A) In Amphibia, nuclear transfer success declines rapidly as cells differentiate

Copyright ©2003 by the National Academy of Sciences

Gurdon, J. B. and Byrne, J. A. (2003) Proc. Natl. Acad. Sci. USA 100, 8048-8052

Fig. 2. (A) In Amphibia, nuclear transfer success declines rapidly as cells differentiate

Donor nucleus Stages reached

Zygote blastula, tadpole, adult

Blastula blastula, tadpole, adult

Tadpole intestine blastula, tadpole, adult

Cultured skin cell blastula(differentiated)

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 blastula

Blastula from above blastula, tadpole

Could some genes be missing from differentiated skin cells?

Serial nuclear transfer improves the efficiency of cloning

Conclusions of nuclear transplantation experiments in amphibians:

1) Nuclei of differentiated cells have the potential to program development of many or all cells. (Therefore, the nuclei must contain all the necessary genes.)

Conclusions of nuclear transplantation experiments in amphibians:

1) Nuclei of differentiated cells have the potential to program development of many or all cells. (Therefore, the nuclei must contain all the necessary genes.)

2) The capacity of nuclei to direct development is restricted as they differentiate.

3) The ooctye cytoplasm can reprogram differentiated nuclei to allow them to direct complete development.

07_37_Protein.produc.jpgNuclear effect – ability of genes to be expressed

Cytoplasm effects – signals to nucleus (transcription factors, signaling pathways)

08_14_chromatin.struc.jpgGenes need to be accessible to be expressed

05_30_histone tails.jpgHistone modification state may limit gene expression potential

DNA methylation state may limit gene expression potential

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

Cloning frogs from a single nuclear donor

08_02_genetic.instruction.part2Cloning mammals from adult cells

(also activates egg)

(from Nature 405: 800-802)

(from Nature 405: 800-802)

NY Times, June 3, 2006Clones' 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.

Would it be ethical to clone humans? If so, for what purpose?