What is Somatic cell nuclear transfer(SCNT)

Somatic cell nuclear transfer (SCNT) is a laboratory technique for creating an ovum with a donor nucleus . It can be used in embryonic stem cell research, or in regenerative medicine where it is sometimes referred to as "therapeutic cloning." It can also be used as the first step in the process of reproductive cloning.

In SCNT the nucleus, which contains the organism's DNA, of a somatic cell (a body cell other than a sperm or egg cell) is removed and the rest of the cell discarded. At the same time, the nucleus of an egg cell is removed. The nucleus of the somatic cell is then inserted into the enucleated egg cell. After being inserted into the egg, the somatic cell nucleus is reprogrammed by the host cell. The egg, now containing the nucleus of a somatic cell, is stimulated with a shock and will begin to divide. After many mitotic divisions in culture, this single cell forms a blastocyst (an early stage embryo with about 100 cells) with almost identical DNA to the original organism.

Stem Cells & Cloning Lecture

About Speaker
Robert A. Weinberg '64, PhD '69
Founding Member, MIT Center for Cancer Research

Member, Whitehead Institute Daniel K. Ludwig and American Cancer Society Professor for Cancer Research Department of Biology

Robert A. Weinberg has earned some of the top honors in his field. Most recently, he won the 2006 Landon-AACR Prize for Basic and Translational Cancer Research. He is also a 1997 National Medal of Science awardee.

Weinberg's laboratory discovered the first human oncogene and the first tumor suppressor gene. Today, much of his research focuses on new models of breast cancer development including the stages of tumor invasiveness and metastasis.

Part 2

He earned his Ph.D. in biology from MIT in 1969, and was one of the Founding Members of the MIT Center for Cancer Research in 1973. He was appointed a professor at MIT in 1982, the same year he joined the Whitehead Institute. Weinberg was named American Cancer Society Research Professor in 1985 and received the Daniel K. Ludwig Professorship for Cancer Research in 1997. He is a member of the National Academy of Sciences and the Institute of Medicine.

Nuclear Cloning and Cell Therapy: Fact and Fiction

Cloning can instantly spark passionate debate: Will it enable us to resurrect beloved family members, or create Frankensteins? Rudolf Jaenisch wants to remove “hot air” from the discussion. His talk provides a clear picture of what is and is not scientifically feasible. Animal cloning, first pioneered in Dolly the sheep, used non-reproductive cells to create a carbon copy of the donor animal. This technique, tested many times, fails frequently and yields severe abnormalities. Consequently, Jaenisch believes the cloning of humans will never prove practical. But another variety of cloning generates far fewer genetic glitches and holds immense medical promise. The earliest cells of embryos can be manipulated to develop into neurons, or blood, or muscle, making them very useful tools in therapy for diseases like diabetes, Parkinson’s or leukemia. Jaenisch says these embryonic stem (ES) cells could be “an inexhaustible source of any tissue type and tailored to the needs of the patient.” But in spite of the potential rewards of this work, federal agencies and many others oppose it because so far the only source of ES cells has been human embryos. Jaenisch seeks a middle ground: scientists may not attempt cloning a human being, but may harvest and grow ES cells for therapeutic purposes from a human embryo.

About the Speaker

Rudolf Jaenisch

Professor of Biology, MIT Founding Member, Whitehead Institute for Biomedical Research

Jaenisch is one of the founders of transgenic science (gene transfer to create mouse models of human disease). His lab has produced mouse models leading to new understanding of cancers and various neurological diseases.

He received his doctorate in medicine from the University of Munich in 1967. He came to the Whitehead from the University of Hamburg in Germany, where he was head of the Department of Tumor Virology at the Heinrich Pette Institute.

Jaenisch received the 2002 Robert Koch Prize for Excellence in Scientific Achievement. In 2003, he was awarded the Charles Rodolphe Brupbacher Prize for basic research in oncology and was elected a member of the National Academy of Sciences.

Jaenisch is a fellow of the American Academy of Arts and Sciences and the American Academy of Microbiology, and a member of the American Association for the Advancement of Science

Mammalian Cloning and Stem Cell Therapy: Problems and Promise

In this talk, leading genetist Rudolf Jaenisch delivers a clear overview of the challenges facing the cloning, dispelling many of the misconceptions about cloning that are pervasive in popular media.

Professor of Biology, MIT Founding Member, Whitehead Institute for Biomedical Research

Jaenisch is one of the founders of transgenic science (gene transfer to create mouse models of human disease). His lab has produced mouse models leading to new understanding of cancers and various neurological diseases.

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He received his doctorate in medicine from the University of Munich in 1967. He came to the Whitehead from the University of Hamburg in Germany, where he was head of the Department of Tumor Virology at the Heinrich Pette Institute.

Jaenisch received the 2002 Robert Koch Prize for Excellence in Scientific Achievement. In 2003, he was awarded the Charles Rodolphe Brupbacher Prize for basic research in oncology and was elected a member of the National Academy of Sciences.

Jaenisch is a fellow of the American Academy of Arts and Sciences and the American Academy of Microbiology, and a member of the American Association for the Advancement of Science.

From Egg to Adult and back Again: Cloning ,stem cells,and cell Replacement

Lecture is presented by Sir John Bertrand Gurdon ,In 1962, Gurdon, then at Oxford University, announced that he had used the nucleus of fully differentiated adult intestinal cells to clone South African clawed frogs (Xenopus laevis).This was the first demonstration in animals that the nucleus of a differentiated somatic cell retains the potential to develop into all cell types (ie, is totipotent) and paved the way for future somatic cell nuclear transfer experiments, including the 1996 cloning of the sheep, Dolly.

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Gurdon began cloning experiments using nonembryonic cells—specifically, cells from the intestinal lining of tadpoles. Gurdon believed that the tadpoles were old enough so that cells taken from them would be differentiated. Gurdon exposed a frog egg to ultraviolet light, which destroyed its nucleus. He then removed the nucleus from the tadpole intestinal cell and implanted it in the enucleated egg. The egg grew into a tadpole that was genetically identical to the DNA-donating tadpole. But the tadpoles cloned in Gurdon’s early experiments never survived to adulthood and scientists now believe that many of the cells used in these experiments may not have been differentiated cells after all. In later work, however, Gurdon successfully produced sexually mature adult frogs from eggs into which genetically marked nuclei had been transplanted from differentiated tadpole cells.

Gurdon’s experiments captured the attention of the scientific community and the tools and techniques he developed for nuclear transfer are still used today. The term clone (from the Greek word klōn, meaning “twig”) had already been in use since the beginning of the 20th century in reference to plants. In 1963 the British biologist J. B. S. Haldane, in describing Gurdon’s results, became one of the first to use the word clone in reference to animals.

Recent research

Gurdon's recent research has focused on analyzing inter cellular signal ling factors involved in cell differentiation, and on elucidating the mechanisms involved in reprogramming the nucleus in transplantation experiments, including demethylation of the transplanted DNA.

Honours and awards

Gurdon was made a Fellow of the Royal Society in 1971, and was knighted in 1995. In 2004, Wellcome/CR UK Institute for Cell Biology and Cancer was renamed the Gurdon Institute in his honour. He has also received numerous awards(Wolf Prize in Medicine (1989), medals and honorary degrees.

Cloning

Clones are organisms that have identical genetic material. In other words, the sequence of bases n their DNA is exactly same. Long before the birth of Dolly the sheep, clones had bee observed in both nature and in the laboratory.When a couple has an identical twin or identical triplets, the children are clones of one another.A plant cutting can also be used to generate a clone.

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Prior to 199, it was thought that cloning an entire animal could only be done with embryonic cells-cells present in the early stages of an organism’s development. In the 1950's, scientists generated entire frogs from embryonic frog cells.

After a small number of cell divisions, embryonic cells start to change into the different types of cells that form muscle, blood, liver, etc. This process is called differntiation. Although each of these cells has the same genetic material, each cell can only access the genes needed for its particular function.

Before the experiment at the roslin institute, it was thought that once cells differentiated, they could not be used to generate an entire organism, for instance, in sheep udder cells could generate other udder cells, but not an entire sheep.

The scientist of roslin institute solved this problem by growing sheep udder cells under starvation conditions, this put the cells in a state similar to embryonic cells. This is called the G0 state.

An egg cell was taken from another sheep. The nucleus (which contains the genetic material) was removed from the egg cell using fine needle. They then used electric shock to fuse one starved udder cell with one nucleus free egg cell. They made 277 of these fused cells.

Although the egg cell came from a black-faced sheep, notice that the nucleus with the genetic material came from the white-faced sheep.

The fused egg cell was then inserted into several different sheep. These surrogate mothers also black-faced.

Of the 277 fused cells, only one progressed to form a developed lamb. Dolly was born on July 5, 1996.Scientist found that dolly had same DNA as the udder cells she came from. She is a clone of these udder cells.Dolly has given birth to a lamb named Bonnie, produced the natural way.Other lambs have been born at the roslin institute through their cloning process, some carry genes that will produce usable human drugs.

A laboratory in Hawaii run by Dr.Ryuzo Yanagimachi was the second group to successfully clone an animal from an adult cell. They cloned mice using cumulus cells, a cell type found in the ovaries.

The cloning method used by the lab in Hawaii was different in two ways from the method used to clone Dolly. First, the cells used to clone the mice were not grown in culture, but instead were used immediately.

Second the nucleus was removed from the cumulus cell and then directly injected into the egg cell. This egg cell's nucleus had already been removed.

The yabagimachi lab used coat color to track genetic heritage. The cumulus cell comes from an agouti (brown) mouse, and the cell comes from a black mouse.

The egg cell now had the same genetic information as the nucleus donor mouse. The egg cell was then activated and implanted into a white host mother. On October 3, 1997 the host mouse gave birth to cumulina, named after the cumulus cells she was cloned from.

Cumulina is the same color as the mouse that donated the nucleus. The DNA fingerprinting confirmed that cumulina had the same DNA as the nucleus donor.

The scientist has taken cells from cumulina to make more clones. They have successfully made several generations of clones and all mice seem normal.Dolly the sheep died at the age of 6. Since the world said hello to Dolly, Several other animals have also been cloned.

Both Dolly and cumulina were cloned from cells in the female reproductive system; cows have also been cloned using ovary and cumulus cells with the same method that was used to clone Dolly.Pigs have been added to the cloned animal menagerie. Scientist hopes to use cloned pigs to grow organs that can be transplanted into humans.