Guy's Hospital, London

R0075: Improving methods for biopsy and preimplantation diagnosis of inherited genetic disease of human preimplantation embryos

R0133: Correlation of embryo morphology with ability to generate embryonic stem cell lines and subsequent growth differentiative characteristics

Improving methods for biopsy and preimplantation diagnosis of inherited genetic disease of human preimplantation embryos (R0075)

Licence holder: Professor Peter Braude

Lay Summary:

Preimplantation genetic diagnosis (PGD) is an early alternative to prenatal diagnosis (PND) and is suitable for a small group of patients who are at substantial risk of conceiving a pregnancy affected by a known genetic defect. (PGD has been applied in a number of centres around the world for a variety of indications, including the analysis of numerical and structural chromosomal abnormalities, identification of sex for X-linked disease and detection of specific genetic defects in monogenic disorders such as cystic fibrosis.

During PGD, a one or two cell biopsy is removed from an embryo created in vitro and a diagnostic test is carried out on the biopsied cell(s). The genetic status of the embryo is inferred on the basis of the result of the diagnostic test on the biopsy and unaffected or carrier embryos are replaced into the uterus. Therefore, for PGD to be feasible, techniques must be available which allow for the diagnosis of a particular gene defect on just one or two cells.

The thrust of this research project is to move forward existing technology to allow PGD to be applied in new disease areas and to develop new technology to improve the process of biopsy and embryo selection with the ultimate aim of enhancing the clinical success of the treatment.

Embryos which are surplus to treatment and have been donated to research with patients' consent will be used in one of two ways. Embryos will be tested for reliability and accuracy.  For improvements in embryo selection procedures after PGD, embryos will be scored depending on their perceived quality and then subjected to procedures which allow an analysis of either their complete chromosome complement or the location and status of key regulatory molecules which may play in important role in early development. It is hoped that this data will improve methods of selecting embryos with high implantation potential.

Correlation of embryo morphology with ability to generate embryonic stem cell lines and subsequent growth differentiative characteristics (R0133)

Licence holder: Dr Stephen Minger

Lay Summary:

Stem cells are unique cell populations which are able to undergo both self renewal and differentiation. Although stem cells have been found in a wide variety of adult tissues, embryonic stem (ES) cells, which have been isolated from the inner cell mass (ICM) of blastocyst stage embryos, are thought to maintain a higher potential for differentiation into a multiple array of cell types. Mouse ES cells can be expanded indefinitely in culture in an undifferentiated state, whilst retaining the capacity of early embryonic cells to differentiate into derivatives of all three primary germ layers (Robertson, 1987). Extrapolation of these properties to human cells would provide a renewable source of tissue for a range of transplantation therapies (Trounson, 2002). Derivation of mouse ES cells is a relatively straightforward, although specialised, process but so far derivation and long term culture of human ES cells has proved extremely technically demanding. Only nine human ES cell lines are currently available commercially despite over 71 having been derived (Vastag, 2003). The remaining 62 have not been successfully cultured or characterised (Vastag, 2003). Many outstanding issues remain to be resolved regarding ES cell derivation and subsequent usefulness, not least regarding whether the behaviour of the isolated ICM can be used to gain information about the viability and implantation potential of the originating embryo. We propose to isolate ICM from human blastocysts surplus to therapeutic requirements after preimplantation genetic diagnosis and, following careful morphological and cytogenetic analysis of the parent embryo throughout it's development, correlate embryo characteristics with the proliferative, karyoptypic and differentiative behaviour of both the resulting ICM and any ES cell lines derived from them. Should ES lines of suitable morphology be derived as a result of this work, we propose to undertake further studies on the isolation and differentiation of neural and pancreatic islet progenitor cells from human ES cell cultures.

Robertson, E. J. (1987). "Teratocarcinomas and embryonic stem cells." IRL press, Oxford.
Trounson, A. (2002). Human embryonic stem cells: mother of all cell and tissue types. Reprod Biomed Online. 4, 58-63.
Vastag, B. (2003). Medical news & perspectives: effort launched to study stem cell lines, train researchers how to nurture them. JAMA. 289, 1092.