講演情報
[PE6-2]Application of preimplantation genetic testing in a family segregated with cryptic translocations in cis form with copy number variation
○Lin Chi-Fang1, Ma Gwo-Chin2, Lin Yi-Shing1, Chien Yin-Hsiu3, Chen Ming2 (1.Welgene Biotechnology Company, Taipei, Taiwan, 2.Department of Genomic Medicine, Changhua Christian Hospital, Changhua, Taiwan, 3.Department of Medical Genetics, National Taiwan University Hospital, Taipei, Taiwan)
Cryptic translocation is defined as a chromosome translocation too small to be detected by karyotyping. Here we report a family in which originally only a 15q26.1 microdeletion was discovered by chromosome microarray (CMA). Further genetic analyses revealed a cryptic translocation between 15qter and 18qter. The probands of the family, the father and the son, suffered with developmental delay and hearing impairment. CMA showed that the son inherited a 3.4Mb 11p15.1p14.3 and a 2.9Mb 15q26.1 microdeletion from his father. The 15q26.1 microdeletion overlaps with the region of the chromosome 15q26-qter deletion syndrome (OMIM#612626). Preimplantation genetic testing (PGT) was chosen and three informative STR probes around the 15q26.1 deletion were designed. A twin pregnancy was achieved. However, 15q26.2q26.3 duplication and 18q22.3q23 deletion were detected in the male cotwin by CMA unexpectedly at prenatal diagnosis. The couple decided to perform selective feticide and a term healthy female baby was delivered. The same 15q duplication and 18q deletion was noted again in some embryos of the subsequent PGT cycles, suggesting additional genetic aberration besides 15q26.1 microdeletion was segregating in this family. Fluorescence in situ hybridization (FISH) by using 15qter and 18qter probes demonstrated a cryptic translocation between the father’s 15qter and 18qter, coexisting with the 15q26.1 microdeletion in cis form. A refined PGT covering both genomic aberrations was offered.