研究開発・学会発表

・Study question:
Are there genetic mutations which may lead to recurrent failures of assisted reproductive technology?

・Summary answer:
In this study, some genes were found to be candidates for causing repeated ART failures.

・What is known already:
Although reproductive aging is one of the greatest hindrances to successful pregnancy, many patients remain infertile, enduring recurrent ART failures, and approximately 20% of infertility is idiopathic. At present, the mutation of 8 genes, PADI6, NLRP2, TLE6, NLRP5, BTG4, KHDC3L, REC114 and OOEP has been reported to cause early embryonic arrest, while the mutation of PATL2 with GV stage arrest; TUBB8 and TRIP13 with failure of polar body extrusion; PANX1 with oocyte death; ZP1, ZP2, ZP3 with empty follicle syndrome; WEE2, TLE6 and CDC20 with fertilization failure have been found.

・Study design, size, duration:
Between January and October 2021, at Hanabusa Women’s Clinic, 25 infertile women, who experienced IVF / ICSI failure more than 5 times, with blastocyst formation rates of less than 10%, were recruited, after informed consent was obtained. 10 staff members of Hanabusa Women’s Clinic who conceived and delivered naturally were compared as normal controls.

・Participants/materials, setting, methods:
Genomic DNA was extracted from whole blood and genomic DNA samples were subjected to whole exome sequencing. High impact variants with allele frequencies of ≦0.20 in the 1000 Genome EAS, which were not found in the control subjects, were selected. Data from the Human Genetic Variation Database (HGVD) was used for the Hardy-Weinberg equation (HWE) to evaluate possible candidates for recurrent ART failures caused by genetic mutations.

・Main results and the role of chance:
High impact homozygous variants were detected in 57 genes among the study subjects of infertile women, but not among the control subjects. Among these 57 genes, significant differences in the allele frequencies between 8.3KJPN and the patients were detected in ADAM33 (p = 0.009), CEP89 (p = 0.012), CRIPAK (p < 0.001), LGALS9B (p < 0.001), PDZRN3 (p = 0.001), RAET1E (p = 0.007), SPATA31A3 (p = 0.045). The HWE of each gene was calculated based on the data from HGVD. Among the 57 genes mentioned above, significantly lower HWE was detected in patients as compared to the HGVD in ADAM33 (p < 0.001), CEP89 (p = 0.033), MICA (p < 0.001), OR2T29 (p = 0.003), OR52J3 (p = 0.0497), RABL2A (p < 0.001), RNF17 (p = 0.0499), SPATA31C1 (p = 0.030), WWTR1 (p < 0.001). Having identified one of the piRNA pathway genes, RNF17, which had significantly reduced HWE, the localization of RNF17 in the primordial follicle was examined. Immunofluorescent staining showed that RNF17 was sporadically localized in the cytoplasm of primordial follicles.

・Limitations, reasons for caution:
The sample size of this study was relatively small, and precise information such as age, gender in the database used in this study did not match that of the study patients, thus, the interpretation of the results is limited and further research is required to confirm our findings.

・Wider implications of the findings:
Among abovementioned genes, one of the piRNA pathway genes, RNF17, and one of the Hippo signal pathway genes, WWER1, were the most likely causes of repeated ART failures. The findings may provide potential diagnostic markers for patients with recurrent ART failures, helping us understand the genetic basis of female infertility.