PGT for translocations: First Pregnancies and live deliveries in India for Robertsonian and Reciprocal translocations and an inversion.

PGT for Robertsonian Translocation:

Preimplantation Genetic Testing (PGT) by fluorescence in situ hybridization (FISH) for a Robertsonian translocation was carried out in a young couple with 2 missed abortions. The wife had a karyotype of 45,XX,rob(13;14)(q10;q10). One normal embryo was obtained in the first cycle and transferred at the blastocyst stage, resulting in a successful pregnancy.

This is the first reported case of PGT for a translocation from India using the FISH technique, resulting in a live delivery. Madon et al., Journal of Prenatal Diagnosis and Therapy, 2010:1(1), 20-22.

PGT for Reciprocal Translocation:

A couple with a history of five early miscarriages due to a balanced reciprocal translocation t(6;19)(p22;q13.4) in the wife, was referred for Preimplantation Genetic Diagnosis (PGD) by fluorescence in situ hybridization (FISH). After oocyte retrieval, nine embryos were obtained. One cell from each embryo was biopsied, fixed and subjected to FISH using centromere and subtelomere probes for chromosomes 6 and 19. Five embryos which had unbalanced translocations, were not transferred. A balanced translocation or absence of translocation was seen in three embryos, which were transferred. One embryo had an anucleate cell and subsequently arrested. A pregnancy was achieved in the first cycle itself and resulted in the birth of a healthy baby.

This is the first baby after PGD for a reciprocal translocation in India. Naik et al., J Fetal Med (2014).

PGT for a Translocation and Inversion:

The technique of pre-implantation genetic diagnosis (PGD) by fluorescence in situ hybridization (FISH) in cases of repeated miscarriages due to parental balanced inversions and translocations is relatively new in India. In a couple with a history of recurrent miscarriages and implantation failures, karyotyping done in three laboratories showed that the husband had an insertion or inversion of chromosome 12. Hence, they were referred to us for PGD. The anomaly turned out to be more complex. A pre-PGD workup using a series of FISH probes on metaphases accompanied by reflex FISH was required to characterize the anomaly. For subsequent PGD, single blastomeres were biopsied from seven embryos obtained by intracytoplasmic sperm injection. FISH analysis had to be carried out using ten probes in four rounds. On pre-PGD workup for inversion 12 by FISH, an additional anomaly of a cryptic translocation between 9qter and 12qter was detected in the husband. His complex karyotype according to the detailed ISCN nomenclature was therefore

46,XY,t(9;12)(9pter→9q34.1:: 12q24.2→12qter),der(12)inv(12)(12pter→2p11.2::12q24.2→12p11.2::9q34.1→9qter).

After PGD, the normal and balanced embryos were transferred, resulting in the birth of healthy twins conceived in the first cycle itself.

This is the first report of PGD by FISH for an inversion coupled with a cryptic translocation from India. Sanap et al., J Fetal Med 2016.

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