Reproductive Research

(Professor Wong Peng Cheang, Dr Huang Zhongwei)

Preimplantation Genetic Diagnostic

Preimplantation Genetic Testing

For couples at risk of transmitting an inherited or other genetic disorder to their offspring, preimplantation genetic testing offers the promise of embarking on a clinically unaffected pregnancy through the uterine transfer of only genetically unaffected embryos. Advances in single cell genomic methodologies have also facilitated comprehensive chromosome screening to identify only euploid preimplantation embryos for uterine transfer to reduce time to pregnancy and to improve healthy live-birth success.

Current research is heavily focused on the development of innovative solutions to simplify preimplantation genetic testing of common and rare monogenic disorders (PGT-M), including the alpha- and beta-thalassemias, spinal muscular atrophy, haemophilia A, and repeat expansion disorders such as fragile X syndrome, myotonic dystrophy, Huntington disease and the spinocerebellar ataxias. More recently, attention has turned to developing novel strategies for preimplantation genetic testing for aneuploidy (PGT-A) and also unbalanced structural rearrangements (PGT-SR) using second and third generation sequencing platforms. Aside from the development and provision of preimplantation genetic testing services to all IVF centres in Singapore, we are embarking on new research to better understand the relationship between aneuploidy and implantation failure, through correlation between cell-specific aneuploidies and their transcriptome signatures.

Publications

Chen M, Chan JK, Nadarajah S, Tan AS, Chan ML, Mathew J, Saw EE, Lim C, Wong W, Cheah FS, Law HY, Wong PC, Chong SS. Single-tube nonaplex microsatellite PCR panel for preimplantation genetic diagnosis of Hemoglobin Bart’s hydrops fetalis syndrome. Prenatal Diagnosis 35:534-43 (2015).
Chen M, Loh SF Yu SL, Nair S, Tan HH, Nadarajah S, Wong PC, Ng SC, Prasath EB, Tan AS, Cheah FS, Saw EE, Chong SS. Rapid and reliable preimplantation genetic diagnosis of common Hb Bart’s hydrops fetalis syndrome and Hb H disease determinants using an enhanced single-tube decaplex PCR assay. American Journal of Hematology 90(9):E194-6 (2015).
Chen M, Tan AS, Cheah FS, Saw EE, Chong SS. Identification of novel microsatellite markers <1 Mb from the HBB gene and development of a single-tube pentadecaplex PCR panel of highly polymorphic markers for preimplantation genetic diagnosis of beta-thalassemia. Electrophoresis 36:2914-24 (2015).
Zhao M, Chen M, Lee CG, Chong SS. Identification of novel microsatellite markers <1 Mb from the HTT CAG repeat and development of a single-tube tridecaplex PCR panel of highly polymorphic markers for preimplantation genetic diagnosis of Huntington disease. Clinical Chemistry 62(8):1096-105 (2016).
Chen M, Zhao M, Lee CG, Chong SS. Identification of microsatellite markers <1 Mb from the FMR1 CGG repeat and development of a single-tube tetradecaplex PCR panel of highly polymorphic markers for preimplantation genetic diagnosis of fragile X syndrome. Genetics in Medicine 18(9):869-75 (2016).
Lian M, Zhao M, Lee CG, Chong SS. Single-tube dodecaplex PCR panel of polymorphic microsatellite markers closely linked to the DMPK CTG repeat for preimplantation genetic diagnosis of myotonic dystrophy type 1. Clinical Chemistry 63(6):1127-40 (2017)
Zhao M, Chen M, Tan AS, Cheah FS, Mathew J, Wong PC, Chong SS. Single-tube tetradecaplex panel of highly polymorphic microsatellite markers <1 Mb from F8 for simplified preimplantation genetic diagnosis of haemophilia A. Journal of Thrombosis and Haemostasis 15:1473-83 (2017)
Rajan-Babu IS, Lian M, Cheah FS, Chen M, Tan AS, Prasath EB, Loh SF, Chong SS. FMR1 CGG repeat expansion mutation detection and linked haplotype analysis for reliable and accurate preimplantation genetic diagnosis of fragile X syndrome. Expert Reviews in Molecular Medicine 19:e10 (2017)
Lian M, Lee CG, Chong SS. Robust preimplantation genetic testing strategy for myotonic dystrophy type 1 by bidirectional triplet-primed PCR combined with multi-microsatellite haplotyping following whole genome amplification. Frontiers in Genetics 2019 Jun 26;10:589. https://doi.org/10.3389/fgene.2019.00589.
Zhao M, Lian M, Cheah FSH, Tan AS, Agarwal A, Chong SS. Identification of novel microsatellite markers flanking the SMN1 and SMN2 duplicated region and inclusion into a single-tube tridecaplex panel for haplotype-based preimplantation genetic testing of spinal muscular atrophy. Frontiers in Genetics 2019 Nov 6; 10.1105. https://doi.org/10.3389/fgene.2019.01105.
Zhao M, Cheah FS, Tan AS, Lian M, Phang GP, Agarwal A, Chong SS. Improved preimplantation genetic testing of Huntington disease by triplet-primed PCR detection of the HTT CAG repeat expansion and simultaneous multi-microsatellite haplotype phasing following whole genome amplification. Scientific Reports 2019 Nov 11;9:16481. https://doi.org/10.1038/s41598-019-52769-3.

Reproductive Ageing, Longevity and Fertility

Reproductive Ageing and Longevity Studies

As an understudied area, it is imperative that work at our department led by Zhongwei to push the boundaries of this field in order to change the narrative of inevitability that a woman will lose her reproductive potential and health as she ages because her ovaries age before any other body systems. We will tackle this essential problem in a three-prong approach:

Population health studies – As part of N.1 Institute of Health, Institute of Digital Medicine (WisDM) and the GUSTO team, we will use existing longitudinal health population data on local women to study demographical and clinical factors that determine reproductive health and longevity. We are also examining the ovarian reserve as determined by Anti-Mullerian hormone levels of IVF-naïve Asian women seeking fertility help to assess ethnic and race-specific differences in ovarian reserve. This industry-supported collaborative effort aims to understand the implications of ovarian reserve on Asian women reproductive longevity.
Basic ovarian biology and translational studies – We are using various murine models with collaborators from NUS Centre of Healthy Longevity and Department of Physiology to determine if reproductive ageing can be delayed via manipulating the ageing pathways involving the upstream and downstream targets of AMPK and mTORC1 by applying various longevity agents and assessing reproductive outcomes.
Clinical studies – Advanced maternal age has dire consequences on reproductive outcomes; we are assessing relaxin and other circulating factors in older women who are undergoing fertility treatment and pregnant women who are diagnosed with hypertensive disorders during pregnancy with the aim of targeting relaxin-like family peptide receptor 1 and other receptors as potential treatment for implantation and pregnancy induced hypertensive disorders

Fertility studies

Fertility research is pertinent to unravel novel solutions and improve the management of couples with fertility problems. We engage in the following translational studies in close collaboration within the Clinic of Human Reproduction, NUH, and our collaborators:

Male factor fertility studies – Collaborating with the Singapore Institute of Clinical Sciences, we are studying the effects of paternal smoking on the small non-coding RNA of the sperm and deciphering the potential mechanisms of inter-generational inheritance. We are also embarking to examine the factors leading to reproductive outcomes in couples who underwent intrauterine insemination at our centre.
Implantation and Embryological studies – As a woman ages, the quality of her oocytes gets poorer due to the higher risks of meiotic division related-aneuploidy. We endeavour to study at the individual cell level in human aneuploid blastocysts donated for research on how this phenomenon arise and propose novel solutions to avert this biological phenomenon that will lead to poor implantation outcomes and hence reduce reproductive success.