Dr. W.M. (Willy) Baarends

Willy Baarends is associate professor (IUS promovendi) at the Department of Developmental Biology. She received her PhD from Erasmus University Rotterdam in 1995 where she cloned and characterized the anti-mullerian hormone type II receptor. This sparked her interest in gonadal differentiation and germ cell development. Much of her research in the past decades has focused on meiosis, studying how DNA double-strand break repair is adapted in meiosis to facilitate homology recognition in mouse and human meiocytes. She uses mouse models of infertility, and state of the art microscopic analyses.

Currently, her lab is developing an in vitro differentiation protocols starting from mouse ES cells and human iPSC cells to obtain embryonic gonadal cells of either sex, that should be able to act as a niche and support differentiation of primordial germ cell-like cells.  The results contribute to basic mechanistic understanding of fundamental processes in sexual reproduction applicable to fields of sex differences in development, infertility, assisted reproduction and early embryogenesis.

1. Lakshmipathi M, Dartée N, Puchkina A, Vaz Santos M, de Bruin IJ, Hamer G, van Pelt AMM, Chuva de Sousa Lopes SM, Mulder CL, Baarends WM. Hum Reprod Update. 2025 Nov 1;31(6):559-587. doi: 10.1093/humupd/dmaf012.
2. Koornneef L, Slotman JA, Sleddens-Linkels E, van Cappellen WA, Barchi M, Tóth A, Gribnau J, Houtsmuller AB, Baarends WM (2022). Multi-color dSTORM microscopy in Hormad1-/- spermatocytes reveals alterations in meiotic recombination intermediates and synaptonemal complex structure. PLoS Genet. 18(7):e1010046.
3. Ghouil R, Miron S, Koornneef L, Veerman J, Paul MW, Le Du MH, Sleddens-Linkels E, van Rossum-Fikkert SE, van Loon Y, Felipe-Medina N, Pendas AM, Maas A, Essers J, Legrand P, Baarends WM, Kanaar R, Zinn-Justin S, Zelensky AN (2021) BRCA2 binding through a cryptic repeated motif to HSF2BP oligomers does not impact meiotic recombination. Nature Commun 12(1): 4605
4. Krausz, C, Riera-Escamilla, A, Moreno-Mendoza, D, Holleman, K, Cioppi, C, Algaba, F, Pybus, M, Friedrich, C, Wyrwoll, MJ, Casamonti, E, Pietroforte, S, Nagirnaja, L, Lopes, AM, Kliesch, S, Pilatz, A, Carrell, DT, Conrad, DF, Ars, E, Ruiz-Castañé, E, Aston, KI, Baarends, WM^*, Tüttelmann F^* (*shared last authors) 2020 Genetic dissection of spermatogenic arrest through exome analysis: clinical implications for the management of azoospermic men, Genet Med, Dec;22(12):1956-1966
5. Slotman, JA, Paul, MW, Carofiglio, F, Vergroesen, T, Koornneef, L, van Cappellen, WA, Houtsmuller, AB, and Baarends, WM (2020) Super-resolution imaging of RAD51 and DMC1 in DNA repair foci reveals dynamic distribution patterns in meiotic prophase, PloS Genet, 16(6)e1008595
6. Enguita-Marruedo, A, Sleddens-Linkels, E, Ooms ^,M, de Geus, V, Wilke, M, Blom, E, Dohle, GR, Looijenga, LHJ, van Cappellen, W, Baart, EB, and Baarends, WM. (2019) Meiotic arrest occurs most frequently at metaphase and is often incomplete in azoospermic men, Fertility and Sterility, Dec;112(6):1059-1070.e3
7. Enguita-Marruedo, A, Van Cappellen, WA, Hoogerbrugge, JW, Carofiglio, F, Wassenaar, E, Slotman, JA, Houtsmuller, A, and Baarends, WM (2018) Live cell analyses of synaptonemal complex dynamics and chromosome movements in cultured mouse testis tubules and embryonic ovaries. Chromosoma 2018 Sep;127(3):341-359. doi: 10.1007/s00412-018-0668-7. 
8. Carofiglio, F., Sleddens-Linkels, E., Wassenaar, E., Inagaki, A., van Cappellen, W. A., Grootegoed, J. A., Toth, A. and Baarends, WM (2018). Repair of exogenous DNA double-strand breaks promotes chromosome synapsis in SPO11-mutant mouse meiocytes, and is altered in the absence of HORMAD1. DNA Repair (Amst) 63, 25-38.
9. Mulugeta E, Wassenaar E, Sleddens-Linkels E, van IWF, Heard E, Grootegoed, JA, Just, W, Gribnau, J, and Baarends WM. (2016) Genomes of Ellobius species provide insight into the evolutionary dynamics of mammalian sex chromosomes. Genome Res 26: 1202-1210.
10. van de Werken C, van der Heijden GW, Eleveld C, Teeuwssen M, Albert M, Baarends WM, Laven JS, Peters AH, Baart EB (2014) Paternal heterochromatin formation in human embryos is H3K9/HP1 directed and primed by sperm-derived histone modifications. Nat Commun 5: 5868.