P-element-induced wimpy testis (PIWI)-interacting RNAs (piRNAs) are short (21 to 35 nucleotides in length) and noncoding and are found almost exclusively in germ cells, where they regulate aberrant expression of transposable elements and postmeiotic gene expression. Critical to the processing of piRNAs is the protein poly(A)-specific RNase-like domain containing 1 (PNLDC1), which trims their 3' ends and, when disrupted in mice, causes azoospermia and male infertility.
We performed exome sequencing on DNA samples from 924 men who had received a diagnosis of nonobstructive azoospermia. Testicular-biopsy samples were analyzed by means of histologic and immunohistochemical tests, in situ hybridization, reverse-transcriptase-quantitative-polymerase-chain-reaction assay, and small-RNA sequencing.
Four unrelated men of Middle Eastern descent who had nonobstructive azoospermia were found to carry mutations in PNLDC1: the first patient had a biallelic stop-gain mutation, p.R452Ter (rs200629089; minor allele frequency, 0.00004); the second, a novel biallelic missense variant, p.P84S; the third, two compound heterozygous mutations consisting of p.M259T (rs141903829; minor allele frequency, 0.0007) and p.L35PfsTer3 (rs754159168; minor allele frequency, 0.00004); and the fourth, a novel biallelic canonical splice acceptor site variant, c.607-2A→T. Testicular histologic findings consistently showed error-prone meiosis and spermatogenic arrest with round spermatids of type Sa as the most advanced population of germ cells. Gene and protein expression of PNLDC1, as well as the piRNA-processing proteins PIWIL1, PIWIL4, MYBL1, and TDRKH, were greatly diminished in cells of the testes. Furthermore, the length distribution of piRNAs and the number of pachytene piRNAs was significantly altered in men carrying PNLDC1 mutations.
Our results suggest a direct mechanistic effect of faulty piRNA processing on meiosis and spermatogenesis in men, ultimately leading to male infertility. (Funded by Innovation Fund Denmark and others.).
The New England journal of medicine. 2021 Aug 04 [Epub ahead of print]
Liina Nagirnaja, Nina Mørup, John E Nielsen, Rytis Stakaitis, Ieva Golubickaite, Manon S Oud, Sofia B Winge, Filipa Carvalho, Kenneth I Aston, Francesca Khani, Godfried W van der Heijden, C Joana Marques, Niels E Skakkebaek, Ewa Rajpert-De Meyts, Peter N Schlegel, Niels Jørgensen, Joris A Veltman, Alexandra M Lopes, Donald F Conrad, Kristian Almstrup
From the Division of Genetics, Oregon National Primate Research Center, Oregon Health and Science University, Beaverton (L.N., D.F.C.); the Center for Embryonic Cell and Gene Therapy, Oregon Health and Science University, Portland (D.F.C.); the Department of Growth and Reproduction (N.M., J.E.N., R.S., I.G., S.B.W., N.E.S., E.R.-D.M., N.J., K.A.) and the International Center for Research and Research Training in Endocrine Disruption of Male Reproduction and Child Health (N.M., J.E.N., R.S., I.G., S.B.W., N.E.S., E.R.-D.M., N.J., K.A.), Rigshospitalet, and the Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences (K.A.), University of Copenhagen, Copenhagen; the Laboratory of Molecular Neurooncology, Neuroscience Institute (R.S.), and the Institute of Biology Systems and Genetic Research (I.G.), Lithuanian University of Health Sciences, Kaunas, Lithuania; the Department of Human Genetics, Donders Institute for Brain, Cognition, and Behavior (M.S.O., G.W.H.), and the Department of Obstetrics and Gynecology (G.W.H.), Radboud University Medical Center, Nijmegen, the Netherlands; Serviço de Genética, Departamento de Patologia, Faculdade de Medicina da Universidade do Porto (F.C., C.J.M.), Instituto de Investigação e Inovação em Saúde, Universidade do Porto (F.C., C.J.M., A.M.L.), and the Institute of Molecular Pathology and Immunology of the University of Porto (A.M.L.) - all in Porto, Portugal; the Andrology and In Vitro Fertilization Laboratory, Department of Surgery (Urology), University of Utah School of Medicine, Salt Lake City (K.I.A.); the Departments of Pathology and Laboratory Medicine (F.K.) and Urology (P.N.S.), Weill Cornell Medicine, New York; and the Biosciences Institute, Faculty of Medical Sciences, Newcastle University, Newcastle upon Tyne, United Kingdom (J.A.V.).