Advances in preimplantation genetic diagnosis/screening

Advances in Genetic Diagnosis of Kallmann Syndrome and Genetic Interruption

Kallmann syndrome (KS) is a rare hereditary disease with high phenotypic and genetic heterogeneity. Congenital hypogonadotropic hypogonadism and hyposmia/anosmia are the two major characterized phenotypes of KS. Besides, mirror movements, dental agenesis, digital bone abnormalities, unilateral renal agenesis, midline facial defects, hearing loss, and eye movement abnormalities can also be observed in KS patients. Because of the phenotypic heterogeneity, genetic diagnosis become increasingly valuable to distinguish KS from other disorders including normosmic congenital hypogonadotropic hypogonadism, constitutional delay of growth and puberty, CHARGE syndrome, and functional hypogonadotropic hypogonadism. Application of next-generation sequencing has promoted the discovery of novel pathogenic genes in KS pedigrees. Prenatal diagnosis is an effective method in clinical settings to decrease birth defects and block transmission of genetic disorders. However, pregnant women may suffer from physical and psychological distress when fetuses are diagnosed with congenital defects. Preimplantation genetic testing (PGT) is a prospective approach during the in vitro fertilization process that helps to interrupt transmission of hereditary diseases to offspring at an early stage. Thus, genetic testing and counseling are recommended to KS patients with family histories, prenatal diagnosis and PGT are considered to be useful options.

Management of a multiple endocrine neoplasia type 1 during pregnancy: a case with primary hypertension

Multiple endocrine neoplasia type 1 (MEN 1) is a rare hereditary disease which transmitted as autosomal dominant disorder with high penetrance. MEN1 includes vary combinations of more than 20 endocrine and non-endocrine tumors. Clinically, MEN1 is characterized by tumor or hyperplasia in two or more endocrine tissues (parathyroid, pituitary, pancreas, adrenal glands). Since it is a rare condition, there are no guidelines with respect to the follow-up of pregnant women with MEN 1, here we the first Asian case of a 32-year-old primigravida with a confirmed diagnosis of MEN1 and primary hypertension prior to conception, cesarean section was performed at 34⁺²weeks for severe preeclampsia and potential risks, both the patient and fetus recovered well.

Affected-embryo-based SNP haplotyping with NGS for the preimplantation genetic testing of Marfan syndrome

Marfan syndrome (MFS), an autosomal dominant heritable disease of the connective tissue, is characterized by broad clinical manifestations in the musculoskeletal, cardiovascular, pulmonary, and ocular systems. In this study, a male patient with MFS caused by a heterozygous mutation NM_000138.5(FBN1):c.6037 + 2 T > C in the fibrillin 1 gene (FBN1) underwent preimplantation genetic testing (PGT) by using affected-embryo-based single nucleotide polymorphism (SNP) haplotyping. Multiple displacement amplification was used for whole genome amplification of biopsied trophectoderm cells after controlled ovarian stimulation. Sanger sequencing and next-generation sequencing (NGS) were used to detect the state of FBN1 mutation. A total of 14 blastocysts formed after intracytoplasmic sperm injection were biopsied. After NGS, 60 informative polymorphic SNP markers located upstream and downstream of the FBN1 gene and its pathogenic mutation site were linked to individual alleles. Sanger sequencing further confirmed that 8 blastocysts carried the mutation NM_000138.5(FBN1):c.6037 + 2 T > C, while 6 did not. Four of the non-carriers were euploid verified by copy number variation results. A female infant without MFS was born at 37 weeks gestation after a subsequent frozen embryo transfer. In conclusion, the successful case indicates that SNP haplotyping using sibling embryos as a reference is applicable to PGT in monogenetic diseases.Abbreviations MFS: Marfan syndrome; PGT: preimplantation genetic testing; FBN1: fibrillin 1 gene; NGS: next-generation sequencing; SNP: single nucleotide polymorphism.

The Clinical Effectiveness of Preimplantation Genetic Diagnosis for Chromosomal Translocation Carriers: A Meta-analysis

Published data on the relationship between pregnancy outcomes of preimplantation genetic diagnosis (PGD) in translocation carriers have implicated inconclusive results. To identify potentially eligible reports, an electronic search was conducted in several databases, including PubMed, Scopus, Web of Knowledge, and Cochrane. Pooled odd ratios (ORs) and 95% confidence intervals (Cis) were estimated based on a random-effect model to evaluate the strength of association between PGD and successful pregnancy outcome in translocation carriers. A total of six cohort studies were included in the current study. The meta-analysis of these studies revealed that the PGD method was associated with an increased successful pregnancy outcome of translocation carriers (OR = 8.58; 95%CI: 1.40–52.76). In subgroup analysis, there was no significant association according to the chromosomal translocation carrier origin and the type of translocated chromosomes, as well as country. In developed countries, the pregnancy outcome of PGD was significantly improved in translocation carriers (OR = 21.79; 95%CI: 1.93–245.52). The current meta-analysis demonstrated that the PGD method is associated with successful pregnancy outcome in both types of reciprocal and Robertsonian translocation carriers, especially in developed countries.

Preimplantation genetic diagnosis for a patient with multiple endocrine neoplasia type 1: case report

Preimplantation genetic diagnosis was carried out for embryonic analysis in a patient with multiple endocrine neoplasia type 1 (MEN1). This is a rare autosomal-dominant cancer syndrome and the patients with MEN1 are characterized by the occurrence of tumors in multiple endocrine tissues, associated with germline and somatic inactivating mutations in the MEN1 gene. This case report documents a successful preimplantation genetic diagnosis (PGD) involving a couple at-risk for MEN1 syndrome, with a birth of a healthy infant. The couple underwent a cycle of controlled ovarian stimulation and intracytoplasmic sperm injection (ICSI). Embryos were biopsied at the blastocyst stage and cryopreserved; we used PCR-based DNA analysis for PGD testing. Only one of the five embryos analyzed for MEN1 syndrome was unaffected. This embryo was thawed and transferred following endometrial preparation. After positive βHCG test; clinical pregnancy was confirmed by ultrasound, and a healthy infant was born. PGD for single gene disorders has been an emerging therapeutic tool for couples who are at risk of passing a genetic disease on to their offspring.

Genetic and epigenetic risks of assisted reproduction

Assisted reproductive technology (ART) is used primarily for infertility treatments to achieve pregnancy and involves procedures such as in vitro fertilization (IVF), intracytoplasmic sperm injection (ICSI), and cryopreservation. Moreover, preimplantation genetic diagnosis (PGD) of ART is used in couples for genetic reasons. In ART treatments, gametes and zygotes are exposed to a series of non-physiological processes and culture media. Although the majority of children born with this treatment are healthy, some concerns remain regarding the safety of this technology. Animal studies and follow-up studies of ART-borne children suggested that ART was associated with an increased incidence of genetic, physical, or developmental abnormalities, although there are also observations that contradict these findings. As IVF, ICSI, frozen-thawed embryo transfer, and PGD manipulate gametes and embryo at a time that is important for reprogramming, they may affect epigenetic stability, leading to gamete/embryo origins of adult diseases. In fact, ART offspring have been reported to have an increased risk of gamete/embryo origins of adult diseases, such as early-onset diabetes, cardiovascular disease, and so on. In this review, we will discuss evidence related to genetic, especially epigenetic, risks of assisted reproduction.

Reproductive outcome following pre-implantation genetic diagnosis (PGD) in the UK

In 2013, the National Health Service Commissioning board centralized the funding in England for up to three cycles of pre-implantation genetic diagnosis (PGD) for couples who have, or are carriers of, a specific genetic disorder. This study presents the historical data of PGD cycles and their clinical outcomes in UK as extrapolated from the national data registry. Retrospective analysis of outcome of cycles undergoing pre-implantation genetic diagnosis in the UK over the past 20 years was performed from the Human Fertilisation and Embryology Authority database (n = 2974). Binary logistic regression was used to determine trends over time and adjusted for maternal age. Briefly, the number of PGD cycles has risen 127-fold from 1991 to 2012 with 3.6-fold increase (360% rise) from 2004 to 2012. A total of one in four embryos following pre-implantation genetic diagnosis did not reach embryo transfer and 92% of these were due to a failure to survive. The live birth rate has risen over 20 years and there has been a steady decline in reported incidence of congenital abnormalities (p < 0.07). PGD has thus emerged as a safe and effective alternative to prenatal diagnosis but with ever evolving technological advances, a robust system of data collection that incorporates techniques used and reporting of mutation-specific clinical outcomes is suggested.

Molecular analysis of DNA in blastocoele fluid using next-generation sequencing

BACKGROUND

Preimplantation genetic testing (PGT) requires an invasive biopsy to obtain embryonic material for genetic analysis. The availability of a less invasive procedure would increase the overall efficacy of PGT. The aim of the study was to explore the potential of blastocoele fluid (BF) as an alternative source of embryonic DNA for PGT.

METHODS

Collection of BF was performed by aspiration with a fine needle prior to vitrification. BF DNA was subjected to whole-genome amplification (WGA) and analyzed by high-resolution next-generation sequencing (NGS).

RESULTS

A high-quality WGA product was obtained from 8 of 11 (72.7 %) samples. Comparison of matching BF and blastomere samples showed that the genomic representation of sequencing reads was consistently similar with respect to density and regional coverage across the 24 chromosomes. A genome-wide survey of the sample sequencing data also indicated that BF was highly representative of known single gene sequences, and this observation was validated by PCR analyses of ten randomly selected genes, with an overall efficiency of 84 %.

CONCLUSION

This study provides further evidence that BF is a promising alternative source of DNA for PGT.

Live births after simultaneous avoidance of monogenic diseases and chromosome abnormality by next-generation sequencing with linkage analyses

In vitro fertilization (IVF), preimplantation genetic diagnosis (PGD), and preimplantation genetic screening (PGS) help patients to select embryos free of monogenic diseases and aneuploidy (chromosome abnormality). Next-generation sequencing (NGS) methods, while experiencing a rapid cost reduction, have improved the precision of PGD/PGS. However, the precision of PGD has been limited by the false-positive and false-negative single-nucleotide variations (SNVs), which are not acceptable in IVF and can be circumvented by linkage analyses, such as short tandem repeats or karyomapping. It is noteworthy that existing methods of detecting SNV/copy number variation (CNV) and linkage analysis often require separate procedures for the same embryo. Here we report an NGS-based PGD/PGS procedure that can simultaneously detect a single-gene disorder and aneuploidy and is capable of linkage analysis in a cost-effective way. This method, called "mutated allele revealed by sequencing with aneuploidy and linkage analyses" (MARSALA), involves multiple annealing and looping-based amplification cycles (MALBAC) for single-cell whole-genome amplification. Aneuploidy is determined by CNVs, whereas SNVs associated with the monogenic diseases are detected by PCR amplification of the MALBAC product. The false-positive and -negative SNVs are avoided by an NGS-based linkage analysis. Two healthy babies, free of the monogenic diseases of their parents, were born after such embryo selection. The monogenic diseases originated from a single base mutation on the autosome and the X-chromosome of the disease-carrying father and mother, respectively.

Digital Microfluidics for Manipulation and Analysis of a Single Cell

The basic structural and functional unit of a living organism is a single cell. To understand the variability and to improve the biomedical requirement of a single cell, its analysis has become a key technique in biological and biomedical research. With a physical boundary of microchannels and microstructures, single cells are efficiently captured and analyzed, whereas electric forces sort and position single cells. Various microfluidic techniques have been exploited to manipulate single cells through hydrodynamic and electric forces. Digital microfluidics (DMF), the manipulation of individual droplets holding minute reagents and cells of interest by electric forces, has received more attention recently. Because of ease of fabrication, compactness and prospective automation, DMF has become a powerful approach for biological application. We review recent developments of various microfluidic chips for analysis of a single cell and for efficient genetic screening. In addition, perspectives to develop analysis of single cells based on DMF and emerging functionality with high throughput are discussed.