The clinical application of single-sperm-based single-nucleotide polymorphism haplotyping for PGT of patients with genetic diseases.

Research Question: Is there a simple and effective method for male patients with genetic disorders in families with no identified haplotype and with Robertsonian translocations to avoid the transfer of embryos carrying translocated chromosomes?

Design: Single spermatozoa were separated to identify by next-generation sequencing (NGS) those that were genetically abnormal, to establish a sperm-based single-nucleotide polymorphism (SNP) haplotype. Blastocysts that developed to day 5 or 6 were then biopsied for whole genome amplification and screening for chromosomal aneuploidy. Normal embryos were selected by comparison with a single-sperm-based SNP haplotype and were transferred. The results were verified by second trimester amniocentesis.

Results: Two blastocysts obtained from patients with neurofibroma type 1 (NF1) were found to be normal after NGS according to single-sperm-based SNP haplotype analysis (13 SNP sites). Three and one blastocysts, respectively, were obtained from the patients with Robertsonian translocation. Blastocysts B9 and B7 were found to be normal after NGS according to the single-sperm-based SNP haplotype analysis (12 and 13 SNP sites selected on chromosomes 14 and 22 for the first patient; 12 and 9 SNP sites selected on chromosomes 13 and 14 for the second patient). Successful pregnancies after blastocyst transfer occurred in all three patients. The identification of embryos was verified by mid-trimester amniocentesis. All three patient couples successfully delivered healthy babies.

Conclusion: This study preliminarily summarized the process of single-sperm-based SNP haplotyping, which could be applied as preimplantation genetic testing for male patients without identified disease-causing haplotypes and with Robertsonian translocations.