AG Krivega

Research Group of Gonadal Differentiation and Embryonic Development

Genetic abnormalities have profound consequences for human embryonic development. An abnormal number of chromosomes, known as aneuploidy, is a major cause of spontaneous abortion, while embryos that survive frequently exhibit defects in tissue specification and an increased risk of tumor development. Our research focuses on understanding the molecular mechanisms that preserve genome integrity and regulate cell specification in the context of human reproduction.

The earlier work identified the involvement of signaling pathways, cell cycle regulation, and intercellular communication in cell differentiation during human preimplantation development (Krivega et al., 2014; 2015a; 2015b). More recently, our research has shifted toward understanding the impact of genome quality on cellular fate decisions. We and others have shown that diverse forms of aneuploidy induce shared gene expression changes, activating cellular stress responses and defense mechanisms that interfere with differentiation. These processes are associated with widespread deregulation of signaling networks under genotoxic stress (Krivega et al., 2021; 2022; 2023a). Identifying the molecular origins of these phenotypes is essential for understanding the mechanisms underlying human infertility.

In the clinical setting, we encounter patients with a wide range of infertility phenotypes, many of which lack an identifiable genetic cause and are therefore classified as idiopathic. Particularly severe forms include Differences of Sex Development (DSD), such as Turner syndrome (45,X0) or mosaic variants) and Swyer syndrome (46,XY with female phenotype). These conditions are characterized by gonadal dysgenesis, absence of mature germ cells, and a markedly increased risk of gonadal tumors. Similarly, the genetic etiology of most cases of male idiopathic nonobstructive azoospermia (NOA) remains unknown, posing significant challenges for effective therapeutic intervention.

Our recent studies demonstrate that infertile individuals share common molecular features, including genotoxic stress phenotypes and altered androgen receptor signaling (Krivega et al., 2023b; Zimmer et al., 2024). We aim to further elucidate the signaling cascades that transmit signals from a compromised genome to cellular physiology, leading to pathological outcomes. These pathways contribute to GSPs through dysregulated autophagy and activation of the innate immune response—mechanisms we have directly linked to human infertility.

To address the relevance of genotoxic stress phenotypes in gonadal dysgenesis, tumorigenesis, and infertility, we combine transcriptional profiling, proteomic analyses of primary patient material, and the development of novel in vitro model systems. Through this integrated approach, our research provides new insights into the molecular basis of infertility and aims to identify universal diagnostic markers and therapeutic targets applicable across diverse infertility disorders.

Current Research Projects

Genetic causes of infertility are highly heterogeneous, and many cases remain unexplained despite extensive sequencing efforts. Our research focuses on identifying shared molecular mechanisms underlying pathological infertility phenotypes. Building on our previous findings of common genotoxic stress phenotypes and altered androgen receptor signaling in infertile patients, this project investigates how genomic damage is translated into cellular dysfunction. We focus on the cGAS–STING signaling pathway and its role in dysregulated autophagy, innate immune activation, and telomere maintenance in human gonadal tissue. The aim is to identify molecular pathways with high translational potential for novel diagnostics and targeted therapies in reproductive medicine.

Many infertility cases associated with DSD or NOA share common pathological features despite distinct genetic backgrounds. In this project, we investigate the role of WNT/β-catenin signaling in maintaining genome integrity in human gonadal cells. Our previous work revealed a shared genotoxic stress phenotype, characterized by increased DNA damage, altered autophagy, and elevated innate immune response. We now explore how genotoxic stress affects β-catenin signaling and its interaction partners using functional assays and genome instability analyses. The long-term goal is to identify targets that support germ cell development and improve fertility outcomes.

Retinoic acid (RA) signaling is essential for gonadal development, yet its role in human infertility remains poorly understood. In this project, we investigate how genotoxic stress alters RA signaling in infertile individuals with diagnoses such as NOA and DSD. We observe that genome instability leads to deregulated expression and abnormal nuclear activation of the RA signaling members in Sertoli cells with DNA damage. This altered RA signaling is tightly linked to genotoxic stress phenotypes. Our findings identify RA signaling as a key molecular link between genome instability and infertility, with potential implications for novel diagnostic and therapeutic strategies.

Genome instability in human germ cells is a major contributor to poor gamete quality, abnormal fertilization, impaired embryo development, and reduced live-birth rates. Spermatogonial stem cells and oocytes are particularly vulnerable to defective DNA damage response mechanisms, leading to aneuploidy and activation of genotoxic stress. In this project, we analyze markers of genotoxic stress and innate immune activation in human sperm and oocytes and examine their relationship with reproductive success. We further test approaches to reduce genotoxic stress in germ cells in vitro, aiming to improve assisted reproduction outcomes and advance therapeutic strategies in human infertility.

J. Zimmer, L. Mueller, P. Frank-Herrmann, J. Rehnitz, J.E. Dietrich, M. Bettendorf, T. Strowitzki, M. Krivega. Low androgen signaling rescues genome integrity with innate immune response while reducing fertility in humans. Cell Death & Disease, Nature Publishing Group (2024); https://doi.org/10.1038/s41419-023-06397-5

M. Krivega, J. Zimmer, A. Slezko, P. Frank-Herrmann, J. Rehnitz, M. Hohenfellner, M. Bettendorf, M. Luzarowski, T. Strowitzki. Genomic instability in patients with sex determination defects and germ cell cancer. Cell Death Discovery journal, Nature Publishing Group (2023b); https://doi.org/10.1038/s41420-023-01470-6

M. Krivega, Z. Storchova. Consequencies of trisomy syndromes – 21 and beyond. Trends in Genetics, Cell Press (2023a); https://doi.org/10.1016/j.tig.2022.11.004

M. Krivega, C. Stiefel, Z. Storchova. Consequences of chromosome gain: A new view on trisomy syndromes. American Journal of Human Genetics, Cell Press (2022); https://doi.org/10.1016/j.ajhg.2022.10.014

M. Krivega, C. Stiefel, S. Karbassi, L. Andersen, N. Chunduri, N, Donnelly, A. Pichlmair, Z. Storchova. Genotoxic stress in constitutive trisomies induces autophagy and the innate immune response via the cGAS-STING pathway. Communications Biology, Nature Publishing Group (2021); https://doi.org/10.1038/s42003-021-02278-9

M. Krivega, M. Geens, B. Heindryckx, S. dos Santos Ribeiro, H. Tournaye, H. Van de Velde. Cyclin E1 plays a key role in balancing between totipotency and differentiation in human embryonic cells. Molecular Human Reproduction, Oxford press (2015b); https://doi.org/10.1093/molehr/gav053

M. Krivega, W. Essahib, H. Van de Velde. WNT3 and membrane-associated beta-catenin regulate trophectoderm lineage differentiation in human blastocysts. Molecular Human Reproduction, Oxford press (2015a); https://doi.org/10.1093/molehr/gav036

M. Krivega, M. Geens, H. Van de Velde. CAR expression in human embryos and hESC illustrates its role in pluripotency and tight junctions. Reproduction (2014); doi: 10.1530/REP-14-0253