Preimplantation genetic diagnosis for polycystic kidney disease

A comprehensive PGT-M strategy for ADPKD patients with de novo PKD1 mutations using affected embryo or gametes as proband

Autosomal dominant polycystic kidney disease (ADPKD) is the most common inherited kidney disease characterized by the development of renal cysts and progression to renal failure. Preimplantation genetic testing-monogenic disease (PGT-M) is an alternative option to obtain healthy babies. However, de novo PKD1 mutation of one of the spouses or the absence of a positive family history poses a serious challenge to PGT-M. Here, we described a comprehensive strategy which includes preimplantation genetic testing for aneuploidies (PGT-A) study and monogenic diagnosis study for ADPKD patients bearing de novo mutations. The innovation of our strategy is to use the gamete (polar body or single sperm) as proband for single-nucleotide polymorphism (SNP) linkage analysis to detect an embryo's carrier status. Nine ADPKD couples with either de novo mutation or without a positive family history were recruited and a total of 34 embryos from 13 PGT-M cycles were examined. Within these nine couples, two successfully delivered healthy babies had their genetic status confirmed by amniocentesis. This study provides a creative approach for embryo diagnosis of patients with de novo mutations or patients who lack essential family members for linkage analysis.

Combined Preimplantation Genetic Testing for Autosomal Dominant Polycystic Kidney Disease: Consequences for Embryos Available for Transfer

Autosomal dominant polycystic kidney disease (ADPKD) is the most common hereditary kidney disease and presents with genetic and clinical heterogeneity. ADPKD can also manifest extra-renally, and seminal cysts have been associated with male infertility in some cases. ADPKD-linked male infertility, along with female age, have been proposed as factors that may influence the clinical outcomes of preimplantation genetic testing (PGT) for monogenic disorders (PGT-M). Large PGT for aneuploidy assessment (PGT-A) studies link embryo aneuploidy to increasing female age; other studies suggest that embryo aneuploidy is also linked to severe male-factor infertility. We aimed to assess the number of aneuploid embryos and the number of cycles with transferable embryos in ADPKD patients after combined-PGT. The combined-PGT protocol, involving PGT-M by PCR and PGT-A by next-generation sequencing, was performed in single trophectoderm biopsies from 289 embryos in 83 PGT cycles. Transferable embryos were obtained in 69.9% of cycles. The number of aneuploid embryos and cycles with transferable embryos did not differ when the male or female had the ADPKD mutation. However, a significantly higher proportion of aneuploid embryos was found in the advanced maternal age (AMA) group, but not in the male factor (MF) group, when compared to non-AMA and non-MF groups, respectively. Additionally, no significant differences in the percentage of cycles with transferable embryos were found in any of the groups. Our results indicate that AMA couples among ADPKD patients have an increased risk of aneuploid embryos, but ADPKD-linked male infertility does not promote an increased aneuploidy rate.

Preimplantation genetic diagnosis in assisted reproduction

Despite its novelty, preimplantation genetic diagnosis has become an alternative to traditional prenatal diagnosis, allowing the establishment of only unaffected pregnancies and avoiding the risk of pregnancy termination. In addition, preimplantation genetic diagnosis is presently applied for much wider indications than prenatal diagnosis, including common diseases with genetic predisposition and preimplantation human leukocyte antigen typing, with the purpose of establishing potential donor progeny for stem cell treatment of siblings. Many hundreds of apparently healthy, unaffected children have been born after preimplantation genetic diagnosis, presenting evidence of its accuracy, reliability and safety. Preimplantation genetic diagnosis appears to be of special value for avoiding age-related aneuploidies in patients of advanced reproductive age, improving reproductive outcome, particularly obvious from their reproductive history, and is presently an extremely attractive option for carriers of balanced translocations to have unaffected children of their own.

Place of preimplantation diagnosis in genetic practice

Preimplantation genetic diagnosis (PGD) is currently one of the practical options available for couples at-risk to avoid the birth of children with genetic and chromosomal disorders. Despite its novelty, PGD has already become an alternative to traditional prenatal diagnosis, allowing establishing only unaffected pregnancies avoiding the risk for pregnancy termination. Indications for PGD have currently expanded beyond those practices in prenatal diagnosis, such as late-onset diseases with genetic predisposition, and preimplantation HLA typing with the purpose of establishing potential donor progeny for stem cell treatment of siblings, which makes PGD also an important compliment to prenatal diagnosis. The fact that more than 1,000 apparently healthy unaffected children have been born after PGD suggests its accuracy, reliability, and safety. PGD is presently an excellent option for carriers of balanced translocations, and appears to be of special value for avoiding age-related aneuploidies in patients of advanced reproductive age. The accumulated experience of thousands of PGD cycles for poor prognosis in vitro fertilization (IVF) patients provides strong evidence of the improvement of clinical outcome, particularly obvious from the reproductive history of patients. This makes of practical relevance to inform couples at-risk about availability of PGD option, so they make their own choice in avoiding the birth of affected offspring and having healthy children of their own.

Preimplantation diagnosis: a realistic option for assisted reproduction and genetic practice

PURPOSE OF REVIEW

Preimplantation genetic diagnosis (PGD) allows genetically disadvantaged couples to reproduce, while avoiding the birth of children with targeted genetic disorders. By ensuring unaffected pregnancies, PGD circumvents the possible need and therefore risks of pregnancy termination. This review will describe the current progress of PGD for Mendelian and chromosomal disorders and its impact on reproductive medicine.

RECENT FINDINGS

Indications for PGD have expanded beyond those used in prenatal diagnosis, which has also resulted in improved access to HLA-compatible stem-cell transplantation for siblings through preimplantation HLA typing. More than 1000 apparently healthy, unaffected children have been born after PGD, suggesting its accuracy, reliability and safety. PGD is currently the only hope for carriers of balanced translocations. It also appears to be of special value for avoiding age-related aneuploidies in in-vitro fertilization patients who have a particularly poor prognosis for a successful pregnancy; the accumulated experience of thousands of PGD cycles strongly suggests that PGD can improve clinical outcome for such patients.

SUMMARY

PGD would particularly benefit poor prognosis in-vitro fertilization patients and other at-risk couples by improving reproductive outcomes and avoiding the birth of affected offspring.

Strategies for preimplantation genetic diagnosis of Angelman syndrome caused by mutations in the UBE3A gene

Angelman syndrome (AS) is a neurodevelopmental disorder associated with the loss of maternal gene expression in chromosome region 15q11-q13. AS is caused by a wide variety of genetic mechanisms, including mutations in the UBE3A gene that have been identified in 10-15% of patients; when the mother is heterozygous for the causative mutation, the risk of recurrence in subsequent pregnancies is 50%. The present authors have developed a preimplantation genetic diagnosis (PGD) assay for a family displaying a 10 bp deletion in exon 9 of the UBE3A gene, which was shared by two affected children and their phenotypically normal mother. A duplex polymerase chain reaction protocol was established, allowing the efficient amplification of the mutation together with an informative microsatellite marker (D15S122) located in intron 1 of the UBE3A gene. As most of UBE3A mutations identified so far are unique to one family, the present authors have also developed an indirect single cell protocol based upon the co-amplification of two microsatellite markers located within (D15S122) and close to the UBE3A gene (D15S1506). This strategy may be applied to all informative families requesting PGD for Angelman syndrome associated with mutations in the UBE3A gene.