Preimplantation genetic testing (PGT) has evolved into a well-established alternative to invasive prenatal diagnosis, even though genetic testing of single or few cells is quite challenging. PGT-M is in theory available for any monogenic disorder for which the disease-causing locus has been unequivocally identified. In practice, the list of indications for which PGT is allowed may vary substantially from country to country, depending on PGT regulation. Technically, the switch from multiplex PCR to robust generic workflows with whole genome amplification followed by SNP array or NGS represents a major improvement of the last decade: the waiting time for the couples has been substantially reduced since the customized preclinical workup can be omitted and the workload for the laboratories has decreased. Another evolution is that the generic methods now allow for concurrent analysis of PGT-M and PGT-A. As innovative algorithms are being developed and the cost of sequencing continues to decline, the field of PGT moves forward to a sequencing-based, all-in-one solution for PGT-M, PGT-SR, and PGT-A. This will generate a vast amount of complex genetic data entailing new challenges for genetic counseling. In this review, we summarize the state-of-the-art for PGT-M and reflect on its future.
Ten microsatellite DNA loci were surveyed to investigate the effects of heavy metal pollution on the genetic diversity and population genetic structure of seven wood mouse (Apodemus sylvaticus) populations along a heavy metal pollution gradient away from a nonferrous smelter in the south of Antwerp (Flanders, Belgium). Analysis of soil heavy metal concentrations showed that soil Ag, As, Cd, Cu, and Pb decreased with increasing distance from the smelter. Genetic analyses revealed high levels of genetic variation in all populations, but populations from the most polluted sites in the gradient did not differ from those of less-polluted sites in terms of mean observed and expected heterozygosity level and mean allelic richness. No correlation was found between measures of genetic diversity and the degree of heavy metal pollution. However, an analysis of molecular variance and a neighbor-joining tree suggested a contamination-related pattern of genetic structuring between the most polluted and less polluted sites. Pairwise F(ST) values indicated that populations were significantly genetically differentiated, and assignment tests and direct estimates of recent migration rates suggested restricted gene flow among populations. Additionally, genetic differentiation increased significantly with geographical distance, which is consistent with an isolation-by-distance model. We conclude that, at least for our microsatellite DNA markers, genetic diversity in the studied wood mouse populations is not affected greatly by the heavy metal pollution.
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