S'pore scientists discover critical protein for embryo survival

SINGAPORE - Singapore scientists have discovered that a protein present in the mother's egg is essential for the survival of a newly formed embryo, and the lack of this protein in some mothers may explain events of multiple miscarriages.

Using genetically identical mice, the researchers led by scientists at A*STAR's Institute of Medical Biology (IMB) discovered that none of the embryos from the fertilisation of eggs lacking the protein TRIM28 survived.

The embryos died at varying stages of development and was observed to have a range of developmental defects.

This allowed the scientists to discover that the timing and amount of this protein made available to the newly formed embryo right after fertilisation greatly impacts the expression of imprinted genes at later developmental stages.

Imprinted genes are genes expressed in a parent-of-origin-specific manner.

While most of the expression of heritable traits from the mother and father is erased from the DNA passed on from the sperm and egg cells, some of these 'epigenetic marks' have to be preserved for the survival of the embryo.

The essential protein thus works to preserve the epigenetic marks of imprinted genes.

Explained through an analogy by Dr Davor Solter of the Wistar Insitute, a pioneer of genomic imprinting, he described a scenario of a teacher writing a long string of formulas on a black board. The protein is then what instructs the 'cleaning lady' on which parts of the formulas she should preserve.

This finding that finally reveals why certain bits of the DNA formula escapes reprogramming is especially important in the field of in vitro fertilisation of eggs for the treatment of infertility.

However, it also sheds a light on the importance of epigenetic mechanisms in development and disease, said Dr Azim Surani of Cambridge University, another pioneer in genomic imprinting.

Dr Barbara Knowles, the senior author of the paper said: "Lack of TRIM28 in their eggs could explain why some women consistently suffer from multiple failed pregnancies where embryos die at different time points, manifesting multiple, different abnormalities."

It is expected that the study will have far-reaching clinical implications for treatments using patient specific cell therapies, thus opening new avenues of formulating medical strategies, said Professor Birgitte Lane, Executive Director of IMB.

yamadak@sph.com.sg