Single-sperm analysis for recurrence risk assessment of spinal muscular atrophy

Preimplantation genetic testing for embryos predisposed to hereditary cancer: Possibilities and challenges

Preimplantation genetic testing (PGT), which was developed as an alternative to prenatal genetic testing, allows couples to avoid pregnancies with abnormal chromosomes and the subsequent termination of the affected fetus. Originally used for early onset monogenic conditions, PGT is now used to prevent various types of inherited cancer conditions based on the development of PGT technology, assisted reproductive techniques (ARTs), and in vitro fertilization (IVF). This review provides insights into the potential benefits and challenges associated with the application of PGT for hereditary cancer and provides an overview of the existing literature on this test, with a particular focus on the current challenges related to laws, ethics, counseling, and technology. Additionally, this review predicts the future potential applications of this method. Although PGT may be utilized to predict and prevent hereditary cancer, each case should be comprehensively evaluated. The motives of couples must be assessed to prevent the misuse of this technique for eugenic purposes, and non-pathogenic phenotypes must be carefully evaluated. Pathological cases that require this technology should also be carefully considered based on legal and ethical reasoning. PGT may be the preferred treatment for hereditary cancer cases; however, such cases require careful case-by-case evaluations. Therefore, this study concludes that multidisciplinary counseling and support for patients and their families are essential to ensure that PGT is a viable option that meets all legal and ethical concerns.

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

Preimplantation genetic testing for the monogenic disorder (PGT-M) spinal muscular atrophy (SMA) is significantly improved by supplementation of SMN1 deletion detection with marker-based linkage analysis. To expand the availability of informative markers for PGT-M of SMA, we identified novel non-duplicated and highly polymorphic microsatellite markers closely flanking the SMN1 and SMN2 duplicated region. Six of the novel markers within 0.5 Mb of the 1.7 Mb duplicated region containing SMN1 and SMN2 (SMA6863, SMA6873, SMA6877, SMA7093, SMA7115, and SMA7120) and seven established markers (D5S1417, D5S1413, D5S1370, D5S1408, D5S610, D5S1999, and D5S637), all with predicted high heterozygosity values, were selected and optimized in a tridecaplex PCR panel, and their polymorphism indices were determined in two populations. Observed marker heterozygosities in the Chinese and Caucasian populations ranged from 0.54 to 0.86, and 98.4% of genotyped individuals (185 of 188) were heterozygous for ≥2 markers on either side of SMN1. The marker panel was evaluated for disease haplotype phasing using single cells from two parent–child trios after whole-genome amplification, and applied to a clinical IVF (in vitro fertilization) PGT-M cycle in an at-risk couple, in parallel with SMN1 deletion detection. Both direct and indirect test methods determined that none of five tested embryos were at risk for SMA, with haplotype analysis further identifying one embryo as unaffected and four as carriers. Fresh transfer of the unaffected embryo did not lead to implantation, but subsequent frozen-thaw transfer of a carrier embryo produced a pregnancy, with fetal genotype confirmed by amniocentesis, and a live birth at term.

Präimplantationsdiagnostik – methodische Aspekte

Die Präimplantationsdiagnostik erfordert eine enge und vertrauensvolle interdisziplinäre Zusammenarbeit zwischen hoch qualifizierten Fachärzten und Naturwissenschaftlern aus Humangenetik und Reproduktionsmedizin. In einem sehr engen Zeitfenster müssen komplexe Laborabläufe standardisiert und qualitätsgesichert umgesetzt werden. In diesem Beitrag sollen orientierende Empfehlungen zur Umsetzung kurz vorgestellt werden. Zentral haben wir häufigere Problemsituationen thematisiert, welche bereits bei der Indikationsstellung wie auch bei den nachfolgenden Schritten in der genetischen Analyse, Datenauswertung und Befunderstellung mögliche Fehlerquellen darstellen. Ziel unserer verantwortlichen Arbeit an den PID-Zentren sollte eine hohe Geburtenrate bei hoher Diagnosesicherheit mit möglichst wenigen schonenden Behandlungszyklen sein.