how we learned to roll uphill

Chapter 2 How We Learned to Roll Uphill 

Remove the nucleus manually from an egg, inject in a nucleus form an adult cell(without damaging anything), then keep culturing the cells really really carefully until they can be implanted into the uterus of another female. → this is incredibly intensive and painstaking work and er can only do it one cell at a time.  

Treat Sample of cells scraped form the skin  in the laboratory, adding specific genes, or proteins, or chemicals. → this treatment would change the way the nuclei of these cells behaved. Instead of acting like the nucleus of a skin cell, they would act the same way as nuclei form newly fertilized eggs.  

Stem cell → metaphorically near the top of Waddingtons’s epigenetic landscape. → what we need are cells that have the potential to turn into lots of other cell types.  

Cardiomyocytes are referred to as terminally differentiated. → unlike bone marrow or liver, the heart doesn’t have an accessible reservoir of less specialized cells(cardiac stem cells) that could turn into new cardiomyocytes. → can not make new cardiac muscle cell. → brain cells are lost Alzheimer’s disease. Cartilage producing cells disappear during osteoarthritis.  

Toad and Dolly have taught us that the cytoplasm of the egg is absolutely key. Something or some things, in that egg cytoplasm actively reprogrammed the adult nucleus that the experimenter injected into it. → nobody really understood how the cytoplasm of eggs could convert adult nuclei into ones like zygotes.  

Zygote → blastocyst (trophectoderm + inner cell mass(ICM) → ICM can be grown in the lab in culture dishes. → ES cell(embryonic stem cell) they are not totipotent because they can’t make placenta → pluripotent  

There are genes that keep the ES cells in a pluripotent state. → scientist identified a whole slew of gens that were important for keeping the cells pluripotent.  

24 genes were titally important in ES cells.  Called pluripotency genes. → yamanaka found 4 genes(Oct4, Sox2, Klf4, c-MYc ) make fibroblast to induced pluripotent stem cells →iPS cells. 

Follow the money  

Type I diabetes   1 million dollar X 1 million patients   → us spend over a billion dollars every four years.  

RBS no nucleus→ need in battlefield and traffic accident. → well established method for taking immature blood stem cell and growing them under specific stimuli so that they will differentiate to form red blood cells.   

When egg and sperm fuse, the reprogramming process efficient and is all over within 36 hours. → reprogrammed iPS cells  took weeks.  → this is epigenetics → differentiated cells are epigenetically modified in specific ways, at a molecular level. This why skin fibroblasts will normally always remain as skin fibroblasts and not turn into cardiomyocytes, for example. When differentiated cells are reprogrammed to become pluripotent cells – whether by somatic cell nuclear transfer or by the use of the four Yamanaka factors.- the differentiation -specific epigenetic signature must be removed so that the nucleus becomes more like that of a newly fertilized zygote.  

The cytoplasm of an egg is incredibly efficient at reversing the epigenetic memory on our genes, acting as a giant molecular eraser.