5 2 a Cloning How are mammals cloned

5 -2 a: Cloning • How are mammals cloned? • What is the difference between reproductive cloning and therapeutic cloning?

Hello, Dolly! Dolly and her surrogate mother Roslin Institute Dolly and her lamb, Bonnie Roslin Institute

Mammalian cloning via somatic cell nuclear transfer Anne Mc. Laren, 2001 Nature 414, 129 -131 doi: 10. 1038/35102194

Why has cloning mammals become possible now? • In vitro fertilization technology has come of age. Louise Brown the first “test tube baby” was born in the 1970 s. • Nuclear transfer into human eggs is possible for males with defective sperm. • Embryo transfer is routinely used for reproduction of livestock (cattle)

How easy (efficient) is animal reproductive cloning? Dolly was the only lamb from 277 fused eggs Many animal species have been cloned. Tetra – rhesus monkey Copycat Idaho Gem mule http: //www. businesspundit. com/20 -animals-that-have-been-cloned/

Are cloned animals healthy? Dolly gave birth to a healthy lamb named Bonnie. Dolly suffered prematurely from arthritis and other ailments of old age. Dolly’s telomeres (ends of chromosomes) were shorter than for other sheep of comparable age.

Complications in reproductive cloning • Cloned offspring syndrome – Placental abnormalities – Fetus too large – High rate of spontaneous abortions – Early death • Shorter telomeres? • Genes not imprinted properly – Genes that control placental growth, fetal growth inactivated in maternal chromosomes

Therapeutic cloning produces embryonic stem cells Embryonic stem cell colony

5 -2 b: Stem Cells • What is the difference between embryonic stem cells and adult stem cells? • What legal and ethical issues revolve around cloning and stem cell technologies?

Stem cells: undifferentiated cells that can keep dividing to replenish various differentiated cell populations • • • Totipotent – embryonic stem cells Pluripotent – bone marrow stem cells Oligopotent – hematopoietic stem cells Multipotent – erythropoietic stem cells Unipotent – reticulocytes

Some adult stem cells

mammalan development in vitro from egg to blastocyst http: //yaolab. stanford. edu/research/preimplantation. html

Human development through blastocyst implantation © 2001 Terese Winslow, http: //stemcells. nih. gov/info/scireport/appendix. A. asp

Generating embryonic stem cells for regenerative medicine Klimanskaya I, N Rosenthal, R Lanza 2008, Nature Reviews Drug Discovery 7, 131142 doi: 10. 1038/nrd 2403

Alternatives to embryonic stem cells? • Induced pluripotent stem cells – Aoi et al. 2008, Generation of Pluripotent Stem Cells from Adult Mouse Liver and Stomach Cells, Science 321: 699 -702 – Retroviral vectors used to transduce 4 transcription factors, incl. c-Myc (protooncogene) – ES-like cells in gene expression profile, pluripotency (form tumors containing different cell types, form all 3 major tissue types, germline transmission)