CHD7 in oocytes is essential for female fertility.

Original Article Page 1 of 12 CHD7 in oocytes is essential for female fertility Jie Cheng1,2#, Qian Dong3,4#, Yujia Lu5, Liya Shi6, Guangxin Yao1,2, Chaojun Wang1,2, Cheng Zhou7, Zhaoming Zhou7, Zhuxi Huang5, Ziang Han5, Ming Zhu5, Weijun Feng5 1 Center for Reproductive Medicine, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China; 2Shanghai Key Laboratory for Assisted Reproduction and Reproductive Genetics, Shanghai, China; 3Department of Obstetrics and Gynecology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China; 4Shanghai Key Laboratory of Gynecologic Oncology, Renji Hospital, School of Medicine, Shanghai Jiao Tong University, Shanghai, China; 5Institute of Pediatrics, Children’s Hospital of Fudan University, Shanghai Key Laboratory of Medical Epigenetics, International Co-Laboratory of Medical Epigenetics and Metabolism, Ministry of Science and Technology, Institutes of Biomedical Sciences, Fudan University, Shanghai, China; 6Department of Reproductive Medicine Center, Shanghai East Hospital, Tongji University School of Medicine, Shanghai, China; 7Department of Radiation Oncology, Nanfang Hospital, Southern Medical University, Guangzhou, China Contributions: (I) Conception and design: J Cheng, Q Dong, W Feng; (II) Administrative support: G Yao, C Wang, W Feng; (III) Provision of study materials: L Shi, Z Huang, Z Han, M Zhu; (IV) Collection and assembly of data: J Cheng, Q Dong, Y Lu; (V) Data analysis and interpretation: J Cheng, Q Dong, C Zhou, Z Zhou; (VI) Manuscript writing: All authors; (VII) Final approval of manuscript: All authors. # These authors contributed equally to this work. Correspondence to: Dr. Weijun Feng. Institute of Pediatrics, Children’s Hospital of Fudan University, Shanghai Key Laboratory of Medical Epigenetics, International Co-Laboratory of Medical Epigenetics and Metabolism, Ministry of Science and Technology, Institutes of Biomedical Sciences, Fudan University, No. 399, Wanyuan Road, Minhang District, Shanghai 201102, China. Email: . Background: Chromodomain helicase DNA-binding protein 7 (CHD7), which is associated with CHARGE (Coloboma, Heart defect, Atresia choanae, Restricted growth, Genital hypoplasia and Ear abnormality) syndrome is an important regulator in many vital developmental processes. However, its role during oocyte development remains unknown. Methods: We screened the Gene Expression Omnibus (GEO) database for expression levels of CHD7 during folliculogenesis. We generated a conditional knockout (cKO) mouse strain with oocyte-specific deletion of CHD7 (Gdf9-Cre:Chd7f/f) using the Cre-loxP approach. Evaluation of follicle numbers and reproductive ability was then conducted. In addition, granulosa cell (GC) apoptosis was assessed by terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay and cleaved caspase-3, using immunohistochemistry (IHC) and immunofluorescence (IF). GC proliferation was measured by Ki67 staining as evaluated by IHC. Results: In our study, we demonstrated that CHD7 has high expression throughout all developmental stages of the oocyte. We found that deletion of Chd7 in oocytes can cause infertility or sub-fertility in female mice and is associated with decreased follicle numbers at all stages. In addition, we found that GC apoptosis was significantly higher in cKO mice. Conclusions: To our knowledge, our study has been the first to show that CHD7 plays a specific role during oogenesis. Our findings provide new insights into CHD7-related infertility. Keywords: Chromodomain helicase DNA-binding protein 7 (CHD7); folliculogenesis; oocyte; fertility; reproduction Submitted Jan 14, 2022. Accepted for publication Mar 01, 2022. doi: 10.21037/atm-22-609 View this article at: https://dx.doi.org/10.21037/atm-22-609 © Annals of Translational Medicine. All rights reserved. Ann Transl Med 2022;10(5):260 | https://dx.doi.org/10.21037/atm-22-609 Page 2 of 12 Introduction The chromodomain helicase DNA-binding protein 7 (CHD7) is an adenosine triphosphate (ATP)-dependent chromatin remodeler that plays pivotal functions during various developmental processes. ATP-dependent chromatin remodeling complexes consist of 4 subfamilies: the switching/sucrose nonfermenting (SWI-SNF) family, the imitation switch (ISWI) family, the CHD family, and the inositol-requiring 80 (INO80) family (1). These chromatin remodeling complexes share a similar ATPasecontaining domain which can use ATP hydrolysis to alter histone-DNA contacts, exerting critical roles in normal development and cancer (2). Previous studies have revealed that chromatin remodeling regulated by CHD7 is involved in key developmental processes at the transcriptional level, including neural crest cell formation, neuronal differentiation, great vessel, and cardiovascular development (3-6). CHD7 can regulate the transcription initiation and elongation at the enhancer and promoter region of the gene. For example, CHD7 can regulate neural differentiation in brain development by its transcriptional regulation in progenitor cells (7). Even heterozygous mutations of CHD7 can cause a severe congenital disease known as CHARGE (Coloboma, Heart defect, Atresia choanae, Restricted growth, Genital hypoplasia and Ear abnormality) syndrome, with pathogenic mutations at the rate of approximately 60% to 70%. CHARGE syndrome is a rare disorder characterized by a specific pattern of defects, including ocular coloboma, heart malformations, atresia of the nasal choanae, growth retardation, genital hypoplasia, and ear abnormalities (8). Although CHD7-related CHARGE syndrome manifests in genital abnormalities, including cryptorchidism, micropenis, and abnormal morphology of female internal genitalia, its physiological roles in the female reproductive system remain less understood (9,10). Many researchers attribute these symptoms to a deficiency of gonadotropin-releasing hormone (GnRH)-induced gonadotropin secretion, which is caused by decreased GnRH neurons in the hypothalamus and decreased GnRH receptors in the pituitary gland (11). In patients with congenital hypogonadotropic hypogonadism (CHH), the percentage of CHD7 variants has been reported to be approximately 6–16% (12,13). CHH is also characterized by a deficiency in GnRH-induced gonadotropin secretions (14). These gonadotropin deficiencies can result in delayed puberty and agenesis of the uterus and ovaries (15). However, the clinical and molecular genetic features of © Annals of Translational Medicine. All rights reserved. Cheng et al. CHD7 in oocytes is essential for female fertility patients with CHD7 allelic variants remain unclear. Firstly, not all patients with CHD7 alterations and CHH symptoms respond well to cyclical gonadotropin therapy (16). In addition, patients with CHH have an almost 10% spontaneous recovery of their hypothalamic-pituitarygonadal (HPG) axis function in later adulthood (17,18). So far, no recovery of the HPG ax (...truncated)