A homozygous NOBOX truncating variant causes defective transcriptional activation and leads to primary ovarian insufficiency.
Does a novel homozygous NOBOX truncating variant, identified in whole exome sequencing (WES) of patients with primary ovarian insufficiency (POI), cause defective transcriptional activation of multiple oocyte-related genes?



A novel homozygous truncating mutation of NOBOX was confirmed to exhibit a loss-of-function effect using well-defined molecular and functional analyses.



Several NOBOX mutations have been reported to be associated with POI but all of them are heterozygous mutations.



This is a cross sectional study in 96 patients diagnosed with POI and 211 women not diagnosed with POI in China.



Blood samples collected from the participants were subjected to whole exome sequencing. Full-length transcript of NOBOX was cloned directly from human fetal ovary (FO). Functional analysis was performed for a NOBOX sequence variant associated with POI.



One novel homozygous truncating variant, chr7:144098161delC, in the NOBOX gene was found in a POI patient. The truncating variant showed a severe defect in transcriptional activation of GDF9 a well-known target NOBOX. Furthermore, using real-time quantitative PCR analysis, we found many oocyte-related genes were expressed at lower level in truncating variant cells than in control cells. In addition, we found that the truncated NOBOX lost its ability to induce the G2/M arrest.Notably, our results confirmed that the 1725 bp NOBOX transcript is expressed in human FO and is the only functional isoform in transcriptional activation assays.



Although the in vitro assays demonstrated the loss-of-function effect of truncating mutation on NOBOX transcriptional activation, further studies are needed to validate its long-term effects on folliculogenesis and POI.



This is the first homozygous mutation of NOBOX associated with POI showing a loss-of-function effect using well-defined molecular and functional analyses. These results will aid both researchers and clinicians in understanding the molecular pathology of NOBOX and POI to develop diagnostic assays or therapeutic approaches.



Research funding is provided by the Ministry of Science and Technology of China [2012CB944704; 2012CB966702], the National Natural Science Foundation of China [Grant number: 31171429] and Beijing Advanced Innovation Center for Structural Biology. The authors declare no conflict of interest.
School of Life Sciences, Tsinghua University, Haidian District, Beijing 100084, China.|Department of Basic Medical Sciences, School of Medicine, Center for Stem Cell Biology and Regenerative Medicine, Tsinghua University, Haidian District, Beijing 100084, China.
Lin
L
Li
Center for Genetics, National Research Institute for Family Planning, 12, Dahuisi Road, Haidian, Beijing 100081, China.|Graduate School of Peking Union Medical College, Dongdan three 9, Dongcheng, Beijing 100730, China.
Binbin
B
Wang
Center for Genetics, National Research Institute for Family Planning, 12, Dahuisi Road, Haidian, Beijing 100081, China.|Graduate School of Peking Union Medical College, Dongdan three 9, Dongcheng, Beijing 100730, China.
Wei
W
Zhang
Department of Obstetrics and Gynecology, Reproductive Medicine Center, The First Affiliated Hospital of Anhui Medical University, Meishan Road, Shushan, Hefei 230022, China.
Beili
B
Chen
Center for Genetics, National Research Institute for Family Planning, 12, Dahuisi Road, Haidian, Beijing 100081, China.
Minna
M
Luo
Department of Medical Genetics and Developmental Biology, School of Basic Medical Sciences, Capital Medical University, No. 10 Xitoutiao, Youanmenwai, Fengtai, Beijing 100069, China.
Jing
J
Wang
Center for Genetics, National Research Institute for Family Planning, 12, Dahuisi Road, Haidian, Beijing 100081, China.
Xi
X
Wang
Department of Obstetrics and Gynecology, Reproductive Medicine Center, The First Affiliated Hospital of Anhui Medical University, Meishan Road, Shushan, Hefei 230022, China caoyunxia_profr@126.com kkee@mail.tsinghua.edu.cn.|Institute of Reproductive Genetics, Anhui Medical University, Meishan Road, Shushan, Hefei 230032, China.|Anhui Provincial Engineering Technology Research Center for Biopreservation and Artificial Organs, Meishan Road, Shushan, Hefei 230027, China.
Yunxia
Y
Cao
Department of Basic Medical Sciences, School of Medicine, Center for Stem Cell Biology and Regenerative Medicine, Tsinghua University, Haidian District, Beijing 100084, China caoyunxia_profr@126.com kkee@mail.tsinghua.edu.cn.
Kehkooi
K
Kee
D000328:Adult; D002681:China; D003430:Cross-Sectional Studies; D005260:Female; D005640:Follicle Stimulating Hormone / Q000097:blood; D056726:Genetic Association Studies; D018398:Homeodomain Proteins / Q000235:genetics*; D006801:Humans; D009154:Mutation; D016649:Primary Ovarian Insufficiency / Q000097:blood / Q000235:genetics*; D014157:Transcription Factors / Q000235:genetics*; D015533:Transcriptional Activation / Q000235:genetics*; D055815:Young Adult
D018398:Homeodomain Proteins; C506600:NOBOX protein, human; D014157:Transcription Factors; D005640:Follicle Stimulating Hormone
G2/M arrest; GDF9; NOBOX; homozygous truncating variant; primary ovarian insufficiency