Preimplantation genetic testing for mucopolysaccharidosis type II: a case report

Aim: we report of our data of successful preimplantation genetic testing (PGT-M) for mucopolysaccharidosis type II (MPS II, Hunter syndrome). Methods. A couple (32 and 31 years old) with Hunter syndrome affected child asked for PGT-M for MPS II (pathogenic variant c.613delG of the IDS gene). In addition, the woman has an inversion of chromosome 10. A system of targeted preimplantation testing was developed for the family, validated on single lymphocytes and whole genome amplification products.. Nested PCR method and fragmentary analysis were used for molecular genetic studies. Two IVF (in vitro fertilization) programs was carried out. Standard protocols for controlled ovarian hyperstimulation with fertilization by ICSI (intracytoplasmic sperm injection) were used. Embryo biopsy was performed on the 5th day of embryo development (day 6th for one embryo), embryos were vitrified. Transport PGT-M (PGT for monogenic/single gene defects) was carried using system created at pre-examination setup. Prenatal diagnosis was performed using the chorion villus biopsy method; karyotype, IDS gene and fetal sex were analyzed. Results. During setup, 14 STR (short tandem repeat) markers linked to the IDS gene were selected and tested, half of them were informative and acceptable for single cells. Developed for the family the PGT-M MPS II system included analysis of a pathogenic variant of the IDS gene, seven informative STR markers, AMEL and SRY genes. No PGT-A (PGT for aneuploidy) was carried out. In the first IVF program, three embryos were tested and recommended for transfer, but the transfer was postponed at the patient request. In the second IVF program, five embryos were tested, three recommended for transfer. Frozen single embryo transfer of normal male embryo at the second of IVF-PGT-M program was carried out. A singleton pregnancy was achieved. Prenatal diagnosis fully confirmed PGT-M results. A healthy boy was delivered in July 2021. Conclusions. The successful implementation IVF-PGT-M with developed system and good reproductive potential of the couple made it possible to achieve pregnancy and the birth of a healthy child in a family with a high genetic risk for MPS II.

PGT-M, Preimplantation testing for monogenic/single gene defects, Mucopolysaccharidosis type II (MPS II), Hunter syndrome, IDS gene

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