UvA-DARE (Digital Academic Repository) Genome integrity maintenance during spermatogonial development Zheng, Y. Publication date 2018 Document Version Final published version License Other Link to publication Citation for published version (APA): Zheng, Y. (2018). Genome integrity maintenance during spermatogonial development. General rights It is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), other than for strictly personal, individual use, unless the work is under an open content license (like Creative Commons). Disclaimer/Complaints regulations If you believe that digital publication of certain material infringes any of your rights or (privacy) interests, please let the Library know, stating your reasons. In case of a legitimate complaint, the Library will make the material inaccessible and/or remove it from the website. Please Ask the Library: https://uba.uva.nl/en/contact, or a letter to: Library of the University of Amsterdam, Secretariat, Singel 425, 1012 WP Amsterdam, The Netherlands. You will be contacted as soon as possible. UvA-DARE is a service provided by the library of the University of Amsterdam (https://dare.uva.nl) Download date:06 Oct 2021 Genome integrity maintenance during spermatogonial development Yi Zheng Genome integrity maintenance during spermatogonial development PhD Thesis, University of Amsterdam, The Netherlands © Yi Zheng 2018, Amsterdam All rights reserved. No parts of this dissertation may be reproduced, stored in a retrieval system of any nature, or transmitted in any form or by any means without written permission from the author. This thesis describes research performed in the Reproductive Biology Laboratory of the Center for Reproductive Medicine, Academic Medical Center, University of Amsterdam, The Netherlands. ISBN: 978-94-6332-307-9 Cover: SMC5/6 molecule by Dideke Emma Verver Printing: GVO drukkers & vormgevers B.V. Genome integrity maintenance during spermatogonial development ACADEMISCH PROEFSCHRIFT ter verkrijging van de graad van doctor aan de Universiteit van Amsterdam op gezag van de Rector Magnificus prof. dr. ir. K.I.J. Maex ten overstaan van een door het College voor Promoties ingestelde commissie, in het openbaar te verdedigen in de Agnietenkapel op donderdag 15 februari 2018, te 14.00 uur door Yi Zheng geboren te Sichuan, China Promotiecommissie Promotor: Prof. dr. S. Repping AMC-UvA Co-promotor: Dr. G. Hamer AMC-UvA Overige leden: Dr. ir. W.M. Baarends Erasmus Universiteit Rotterdam Prof. dr. N. Zelcer AMC-UvA Prof. dr. C.J.F. van Noorden AMC-UvA Dr. N.A.P. Franken AMC-UvA Prof. dr. D.G. de Rooij Universiteit Utrecht Faculteit der Geneeskunde Table of contents Chapte 1 7 General introduction and outline of the thesis Chapter 2 21 Non-SMC element 2 (NSMCE2) of the SMC5/6 complex helps to resolve topological stress Verver DE#, Zheng Y#, Speijer D, Hoebe R, Dekker HL, Repping S, Stap J, Hamer G #equal contribution International Journal of Molecular Sciences. 2016 Oct 26;17(11). pii: E1782 Chapter 3 49 Trivial role for NSMCE2 during in vitro proliferation and differentiation of male germline stem cells Zheng Y, Jongejan A, Mulder CL, Mastenbroek S, Repping S, Wang Y, Li J, Hamer G Reproduction. 2017 Sep;154(3):81-95 Chapter 4 77 On the increasing sensitivity of differentiating spermatogonia to DNA damage Zheng Y, Jongejan A, Mulder CL, van Daalen SKM, Mastenbroek S, Hwang G, Jordan P, Repping S, Hamer G Submitted Chapter 5 107 Spermatogonial stem cell autotransplantation and germline genomic editing: a future cure for spermatogenic failure and prevention of transmission of genomic diseases Mulder CL#, Zheng Y#, Jan SZ, Struijk RB, Repping S, Hamer G*, van Pelt AM #equal contribution, *corresponding author Human Reproduction Update. 2016 Sep;22(5):561-73 Chapter 6 139 General discussion and implications for future research Chapter 7 155 Summary Samenvatting Acknowledgements 160 PhD portfolio 162 About the author 163 List of publications 164 Chapter 1 General introduction and outline of the thesis 8 Chapter 1 Background Spermatogenic failure An estimated 10-15% of couples suffer from subfertility [1, 2], defined as the inability to conceive after one year of unprotected intercourse [3, 4]. Although the most important factor that affects human fertility is female age, in about half of these couples reduced semen quality is commonly observed [3, 5]. Reduced semen quality can be characterized by low sperm counts (oligozoospermia), low sperm motility (asthenozoospermia), low number of morphologically normal sperm (teratozoospermia) or the most extreme clinical presentation- a complete absence of sperm in the semen (azoospermia) [6]. Azoospermia can be subdivided into obstructive and non-obstructive azoospermia [2]. In the case of obstructive azoospermia, the process of spermatogenesis is most often not affected, but the spermatozoa cannot reach the semen due to a physical obstruction. In the case of non- obstructive azoospermia, the lack of sperm in the semen is caused by severely decreased or absent sperm production in the testis, often referred to as spermatogenic failure. Despite the clinical importance, very little is known about the etiology of spermatogenic failure. There are only a few established causes for spermatogenic failure, including DNA damage caused by chemo- or radiotherapy [7], structural or numerical chromosomal abnormalities [5] and Y- chromosome deletions [8]. Nonetheless, the etiology of spermatogenic failure remains unknown in most cases. It is presumed that genetic mutations lie at the base of many cases of spermatogenic failure [9, 10]. Yet, no direct treatment options for spermatogenic failure are currently available to allow these men to achieve genetic parenthood. The only option to date is the use of testicular sperm extraction (TESE) in combination with intra-cytoplasmic sperm injection (ICSI). The drawback is however that the chance of finding spermatozoa upon TESE in men with non-obstructive azoospermia is roughly 50% and that ICSI implies ovarian hyperstimulation of the unaffected female partner as well as fertilization and culture of the resulting embryos in vitro. If indeed spermatogenic failure is genetic in origin, this would require a precisely patient-specific targeted therapeutic approach, or germline genome modification to restore the genome into its original ‘fertile’ state. This is currently not yet feasible. Spermatogenesis and spermatogonial stem cells (SSCs) Spermatogenesis is an intricate developmental process ultimately leading to the continuous production of spermatozoa. The whole process comprises three consecutive developmental stages: the spermatogonial stage (mitotic proliferation and differentiation), the spermatocyte stage (meiosis) and the spermatid stage (spermiogenesis) [11]. Specifically, General introduction 9 spermatogenesis initiates from type A spermatogonia that undergo multiple mitotic divisions and then differentiate into intermediate and type B spermatogonia. Type B spermatogonia will then divide to form pre-leptotene spermatocytes that replicate their DNA and enter meiosis. The spermatocytes will subsequently undergo two consecutive meiotic divisions (meiosis I and II) to generate round spermatids which then further develop into elongating spermatids and eventually mature sperm. The type A spermatogonia can be divided into undifferentiated and differentiating spermatogonia. The undifferentiated spermatogonia proliferate freely and maintain spermatogonial density in the testis. In contrast, the differentiating spermatogonia are irreversibly committed towards meiosis and their divisions are strictly regulated. An important subset of the undifferentiated spermatogonia are the spermatogonial stem cells (SSCs). These cells can be defined by their ability to generate and maintain donor-derived spermatogenesis when transplanted into infertile recipient testes [12]. To maintain lifelong male fertility, a perfect balance between SSC self-renewal and differentiation is essential. Too much self-renewal may lead to tumor-like germ cell clusters, while excessive differentiation will lead to germ cell depletion [13]. Despite the apparent importance of this balance, knowledge regarding the molecular mechanisms underlying SSC self-renewal and differentiation remains limited [11]. The spermatogonial response to DNA damage DNA damage, for instance caused by irradiation or chemotherapy, often results in germ cell apoptosis. Many cancer patients undergoing chemo- or radiotherapy are therefore confronted with reduced fertility [14-16]. Furthermore, DNA damage in germ cells that is not correctly repaired can lead to genetic mutations or chromosomal aberrations that can be transmitted to the offspring. For this reason it is thought that germ cells hold a unique response to DNA damage. Indeed, they are generally much more prone to undergo apoptosis in response to DNA damage than somatic cells [17, 18]. Even among the different types of spermatogonia differences in radiosensitivity exist. Differentiating spermatogonia are more radiosensitive and inclined to undergo apoptosis in response to irradiation than the undifferentiated spermatogonial population [19]. Even between the undifferentiated spermatogonia differences exist, with the self-renewing SSCs being the most resistant to DNA damage [20-22]. It seems that, while differentiating spermatogonia with DNA damage are readily eliminated, preservation of SSCs, and thus long-term male fertility,