2. Academic Validation
  3. The piRNA-pathway factor FKBP6 is essential for spermatogenesis but dispensable for control of meiotic LINE-1 expression in humans

The piRNA-pathway factor FKBP6 is essential for spermatogenesis but dispensable for control of meiotic LINE-1 expression in humans

  • Am J Hum Genet. 2022 Oct 6;109(10):1850-1866. doi: 10.1016/j.ajhg.2022.09.002.
Margot J Wyrwoll 1,  Channah M Gaasbeek 2,  Ieva Golubickaite 3,  Rytis Stakaitis 4,  Manon S Oud 5,  Liina Nagirnaja 6,  Camille Dion 7,  Emad B Sindi 8,  Harry G Leitch 9,  Channa N Jayasena 8,  Anu Sironen 10,  Ann-Kristin Dicke 1,  Nadja Rotte 1,  Birgit Stallmeyer 1,  Sabine Kliesch 11,  Carlos H P Grangeiro 12,  Thaís F Araujo 13,  Paul Lasko 14,  Genetics of Male Infertility Initiative (GEMINI) consortium,  Kathleen D'Hauwers 15,  Roos M Smits 16,  Liliana Ramos 16,  Miguel J Xavier 17,  Don F Conrad 6,  Kristian Almstrup 18,  Joris A Veltman 17,  Frank Tüttelmann 1,  Godfried W van der Heijden 19
Affiliations

Affiliations

  • 1 Institute of Reproductive Genetics, University of Münster, Münster, Germany.
  • 2 Department of Human Genetics, Radboudumc, Nijmegen, the Netherlands; Donders Institute for Brain, Cognition and Behaviour, Radboudumc, Nijmegen, the Netherlands; Department of Obstetrics and Gynecology, Radboud University Medical Center, Nijmegen, the Netherlands.
  • 3 Division of Genetics, Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, OR, USA; Department of Growth and Reproduction, Copenhagen University Hospital - Rigshospitalet, Copenhagen, Denmark; Department of Genetics and Molecular Medicine, Lithuanian University of Health Sciences, Kaunas, Lithuania.
  • 4 Division of Genetics, Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, OR, USA; Department of Growth and Reproduction, Copenhagen University Hospital - Rigshospitalet, Copenhagen, Denmark; Laboratory of Molecular Neurooncology, Neuroscience Institute, Lithuanian University of Health Sciences, Kaunas, Lithuania.
  • 5 Department of Human Genetics, Radboudumc, Nijmegen, the Netherlands; Donders Institute for Brain, Cognition and Behaviour, Radboudumc, Nijmegen, the Netherlands.
  • 6 Division of Genetics, Oregon National Primate Research Center, Oregon Health and Science University, Beaverton, OR, USA.
  • 7 MRC London Institute of Medical Sciences, London, UK; Institute of Clinical Sciences, Imperial College London, London, UK.
  • 8 Section of Investigative Medicine, Imperial College London, London, UK.
  • 9 MRC London Institute of Medical Sciences, London, UK; Institute of Clinical Sciences, Imperial College London, London, UK; Centre for Paediatrics and Child Health, Faculty of Medicine, Imperial College London, London, UK.
  • 10 Natural Resources Institute Finland, Production Systems, Jokioinen, Finland; Great Ormond Street Institute of Child Health, University College London, London, UK.
  • 11 Centre of Reproductive Medicine and Andrology, Department of Clinical and Surgical Andrology, University Hospital of Münster, Münster, Germany.
  • 12 Complexo Hospitalar of Federal University of Ceará, Fortaleza, Brazil.
  • 13 Department of Genetics, Ribeirão Preto Medical School, University of São Paulo, Ribeirão Preto, Brazil.
  • 14 Department of Human Genetics, Radboudumc, Nijmegen, the Netherlands; Department of Biology, McGill University, Montréal, QC, Canada.
  • 15 Department of Urology, Radboudumc, Nijmegen, the Netherlands.
  • 16 Department of Obstetrics and Gynecology, Radboud University Medical Center, Nijmegen, the Netherlands.
  • 17 Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle Upon Tyne, UK.
  • 18 Department of Growth and Reproduction, Copenhagen University Hospital - Rigshospitalet, Copenhagen, Denmark; Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
  • 19 Department of Obstetrics and Gynecology, Radboud University Medical Center, Nijmegen, the Netherlands. Electronic address: [email protected].
PMID: 36150389 DOI: 10.1016/j.ajhg.2022.09.002
Abstract

Infertility affects around 7% of the male population and can be due to severe spermatogenic failure (SPGF), resulting in no or very few sperm in the ejaculate. We initially identified a homozygous frameshift variant in FKBP6 in a man with extreme oligozoospermia. Subsequently, we screened a total of 2,699 men with SPGF and detected rare bi-allelic loss-of-function variants in FKBP6 in five additional persons. All six individuals had no or extremely few sperm in the ejaculate, which were not suitable for medically assisted reproduction. Evaluation of testicular tissue revealed an arrest at the stage of round spermatids. Lack of FKBP6 expression in the testis was confirmed by RT-qPCR and immunofluorescence staining. In mice, Fkbp6 is essential for spermatogenesis and has been described as being involved in piRNA biogenesis and formation of the synaptonemal complex (SC). We did not detect FKBP6 as part of the SC in normal human spermatocytes, but small RNA sequencing revealed that loss of FKBP6 severely impacted piRNA levels, supporting a role for FKBP6 in piRNA biogenesis in humans. In contrast to findings in piRNA-pathway mouse models, we did not detect an increase in LINE-1 expression in men with pathogenic FKBP6 variants. Based on our findings, FKBP6 reaches a "strong" level of evidence for being associated with male infertility according to the ClinGen criteria, making it directly applicable for clinical diagnostics. This will improve patient care by providing a causal diagnosis and will help to predict chances for successful surgical sperm retrieval.

Keywords

FKBP6; LINE-1; azoospermia; genetics; male infertility; meiosis; oligozoospermia; piRNA-pathway; round spermatid arrest; spermatogenesis.

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