An egg cell in CELL: Single and completely predictable
Peking University, Dec. 20, 2013: A landmark study by Peking University (PKU) scientists reported that a "dream experiment" has been achieved: whole-genome sequencing now can be done on a single egg cell with a high precision. The research team was led by the article's corresponding authors Dr. Jie Qiao from PKU Third Hospital, Drs. Fuchou Tang and Xiaoliang Sunney Xie, who are faculty members of PKU Biodynamic Optical Imaging Center (BIOPIC), while Dr. Xie also being a professor at Harvard University.
Our genetic information is all kept in each cell in DNA, which is a long chain consisting of four types of nucleotides. The combination and sequence of these nucleotides determine genes, the functional units of inheritability. Both in basic research and in clinical work, the determination of the sequences of all genes, collectively called "whole genome" has paramount importance. However, it is extremely difficult to achieve in single cells, due to the fact that each cell has only two copies of each gene. This whole-genome sequencing in a single cell with a high precision was achieved last year by Xie’s lab. Several applications of the technology have been pursued. Among them, in vitro fertilization (IVF) is wherelife begins with single cells. Therefore, single cell sequencing of an egg cell has been the dream experiment for IVF. It is to this line of work, the PKU’s team made a great leap forward.
In the new study published in this issue of CELL, the PKU team put a smart twist and utilized a unique feature in egg cells, the polar body, which is a byproduct of egg division and dispensable without affecting egg cell's normal development. The PKU team invented a method for whole genome sequencing in polar bodies in order to predict what is in each fertilized egg, and select a viable one for transfer.
In addition to the importance in basic research, this work has a great impact in clinical diagnosis and prevention of devastating genetic diseases. This method will allow doctors to detect genetic defects that are inherited from the mother's egg, or from the father's sperms. Dr. Qiao explains, “This year marks the 35th anniversary of in vitro fertilization (IVF) which brought so much happiness to people. Infertility affects married couples by 10-15%, and IVF is one way to treat this common condition. With our technology, we are pursuing a clinical trial to enormously increase the success rate of IVF, especially for older women or women who have had recurrent miscarriages.”
"Since this technology allows us to detect chromosomal abnormalities and DNA sequence variations associated with genetic disorders, we kill two birds with one stone," Dr. Tang further explains, “The potential is to increase the success rate of test tube baby technology from 30% to 60%.”
Currently, the PKU team is relentlessly pursuing in both basic research and clinical trials to materialize the potential of this new method.
BIOPIC of Peking University
BIOPIC of Peking University and Department of Chemistry and Chemical Biology of Harvard University
Third Hospital of Peking University
Source: Biodynamic Optical Imaging Center
Edited by: Zhang Jiang