Peking University, Sep.24, 2014: On September 19, 2014, the first in vitro fertilization (IVF) baby with preimplantation genomic screening based on MALBC was born in the Peking University Third Hospital, Beijing, China. MALBAC is a newly developed whole genome amplification method, allowing for the precise selection of embryos in the IVF process when combined with next generation sequencing. This event brings the good news to patients with monogenic diseases around the world that they can now expect their off springs free from their disorders.
In this case, the husband suffers from Hereditary Multiple Exostoses, an autosomal dominant hereditary disorder, which is characterized by multiple bony spurs or lumps on the bones at an early age. There is a frame-shift point mutation at the EXT2 gene of this patient, which has a 50% chance of transmitting this disorder to his children. To avoid this risk, a normal embryo free from the husband’s disease allele was selected by Dr. Jie Qiao’s group at Peking University Third Hospital using the MALBAC technique that was developed by Sunney Xie’s lab.
Total 18 embryos at blastocyst stage were obtained from the couple during IVF cycle, and a few cells were biopsied from each of the day 5 or day 6 embryo. Genomic DNAs of the obtained cells were amplified evenly and accurately with the MALBAC method for the whole genome sequencing analyses. Combined with the targeted PCR and next generation sequencing techniques, all the numerical and structural chromosome abnormalities and the mutated allele of the genetic disease were accurately detected with low depth sequencing data (0.1X).
The team identified three embryos with neither the inherited mutated allele nor chromosome copy number abnormalities from these 18 embryos, and finally chose one healthy embryo to transfer back to the wife. The embryo implanted successfully, grew normally, and later the amniotic fluid cells from the baby were isolated and analyzed as free of aneuploidy and mutated allele. Now the baby was born successfully, with 4.03 kg of weight and 53 cm of length. Umbilical cord blood genome detection confirmed the baby is free of the mutated allele.
Monogenic diseases are the diseases caused by one or one pair of mutated alleles, showing Mendelian inheritance patterns. Monogenic diseases have distinct inheritance patterns including autosomal dominant, recessive and X-linked inheritance. There are about 7,000 known monogenic diseases, and the mutated genes of about 4,000 monogenic diseases are already known by now. Although the morbidity for single monogenic disease is low, the population morbidity is high due to the fact that there are many different types of monogenic diseases. Most monogenic diseases show phenotypes early in infants and children, less than 10% monogenic diseases do after adolescence, and only about 1% show phenotypes after menopause. Most monogenic diseases can cause death, disability or congenital malformation, and only a few can be treated effectively with some medical treatment. Monogenic diseases seriously affect the health of human beings and bring heavy economic and mental burdens to the society and families.
Pre-implantation genetic diagnosis (PGD) is a technique that helps selecting normal embryos to transfer into uterine using IVF. It is an early prenatal diagnosis technology to obtain a healthy offspring by avoiding the genetic diseases.
Currently, the widely used PGD technologies are fluorescence in situ hybridization (FISH), polymerase chain reaction (PCR), and comparative genomic hybridization (Array-CGH) and single-nucleotide polymorphism (SNP-array). So far, these techniques have been used to either detect specific point mutations (by PCR) or chromosome abnormality, which is caused by chromosome segregation errors, particularly for advanced age women. However, it has been highly desirable, but has not yet been reported to simultaneously detect monogenic point mutations and chromosome abnormalities. MALBAC allows for simultaneous circumvention of point mutations and chromosome abnormalities with high accuracy. Furthermore, the procedure developed by the team has used low depth sequencing, allowing low cost and fast PGD.
MALBAC, a powerful single cell whole genome amplification method, which was first developed and reported by Sunney Xie’s lab in 2012, is the key technique in this project. Since MALBAC use linear instead of exponential amplification, it is much more accurate and uniform than the traditional DOP-PCR and MDA methods. So MALBAC can be used to analyze the genomes of rare and limited materials. At the end of 2013, Sunney Xie’s lab cooperated with Jie Qiao’s team and Fuchou Tang’s lab and demonstrated the proof of principle of using MALBAC for PGD in IVF, which was published in Cell.
The project is done with the support from the Ministry of Science and Technology, Beijing Municipal Science and Technology Commission, the National Natural Science Foundation of China, and 985 project of Peking University. The project is accomplished under the cooperation of the three partners: Jie Qiao’ team in Peking University Third Hospital, Sunney Xie’s lab and Fuchou Tang’s lab in Biological dynamic Optical Imaging Center (BIOPIC) of Peking University.
Source: Peking University Third Hospital