Sunday, October 09, 2011

NEW AVENUES TO OBTAIN THE FIRST HUMAN CLONE



Figure taken from Nature




Somatic cell nuclear transfer into oocytes without fertilization and non nuclear removal (modification of somatic cell nuclear transfer: SCNT, which allows to create a clone of the sheep Dolly), has allowed scientists from the New York Stem Cell Foundation Laboratory (Dieter Egli Scott Noggle et al), reprogram transferred somatic cells to a pluripotent stage, creating blastocysts containing 100 stem cells, that generate 3 germ cell layers opening the possibility to generate replacement cells to treat type I diabetes, Parkinson's or Alzheimer's. Also demonstrating that removal of the oocyte genome (standard cloning technique) is unsuccessful because developments failures after exchanging genomes (detained late division stages associated with transcriptional abnormalities of the blastocyst generated).

While the procedure can be customized the specific cell implantation will not cause immune rejection, keeping pluripotency, opening the possibility of creating human clones from blastocysts obtained, which now face technical difficulties: they would be not true clones because the DNA from the resulting stem cells, is not exactly equal to the donated somatic cells. And while in 2006 were created induced pluripotent adult stem cells (iPS) to develop embryos reprogrammed by the addition of a few genetic factors (instead of using full oocytes), in recent years has been discovered that iPS cells differ from natural embryonic stem cells that lead to the formation of a human being. It is now known that the DNA of the oocyte is able to direct proper embryonic development and of preimplantation embryo in parthenogenetic development. Oocyte also contains transcriptional factors of early embryonic development (Oct4), which help to reprogram the somatic cell nucleus.


CAMINO A LA OBTENCIÓN DEL PRIMER CLON HUMANO

La trasferencia nuclear de células somaticas a oocitos sin fertilizar y sin remoción nuclear (modificacion de trasferencia nuclear de células somaticas :SCNT, que posibilito crear un clon de la oveja Dolly), ha permitido a científicos del New York Stem Cell Foundation Laboratory (Dieter Egli, Scott Noggle et al), reprogramar células somaticas transferidas a un estadio pluripotencial, creando blastocistos de 100 celulas madre, que desarrollan 3 capas germinativas celulares embrionarias, abriendo la posibilidad de generar celulas finales de reemplazo para tratar Diabetes tipo I, Parkinson o Alzheimer, demostrando de paso que la remocion del genoma del oocito (técnica standard de clonación), es causa de fallidos desarrollos tras intercambiar genomas (detenidos en estadios de división tardia asociados a anomalías transcripcionales del blastocisto generado).
En tanto el procedimiento puede ser personalizado la implantación de células especificas finales no ocasionaria rechazo inmune, manteniendose la pluripotencia, quedando abierta la posibilidad de crear clones humanos a partir de los blastocistos obtenidos, que por ahora afrontan dificultades técnicas : no serian verdaderos clones porque el DNA de las celulas madres resultantes, no es exactamente igual al de las células somaticas donadas. Y, aunque en el 2006 se crearon células madre adultas pluripotentes inducidas (iPS), reprogramadas para desarrollar embriones mediante adicion de pocos factores geneticos (en lugar de emplear oocitos), en los ultimos años se ha descubierto que esyas células difieren de las celulas madres embrionarias que conducen a la formación de un ser humano. Se sabe ahora que el DNA del oocito es capaz de dirigir un desarrollo embrionario apropiado y la preimplantacion en desarrollos partenogeneticos embrionarios. El oocito además contiene factores maternos de transcripccion del desarrollo embrionario temprano (Oct4), que ayudan a reprogramar al nucleo de celulas somaticas. Principio del formulario

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