SPINK2 deficiency causes infertility by inducing sperm defects in heterozygotes and azoospermia in homozygotes

EMBO Mol Med. 2017 Aug;9(8):1132-1149. doi: 10.15252/emmm.201607461.

Zine-Eddine Kherraf ¹, Marie Christou-Kent ¹, Thomas Karaouzene ¹, Amir Amiri-Yekta ¹ ² ³, Guillaume Martinez ¹, Alexandra S Vargas ¹, Emeline Lambert ¹, Christelle Borel ⁴, Béatrice Dorphin ⁵, Isabelle Aknin-Seifer ⁶, Michael J Mitchell ⁷, Catherine Metzler-Guillemain ⁷, Jessica Escoffier ¹, Serge Nef ⁴, Mariane Grepillat ¹, Nicolas Thierry-Mieg ⁸, Véronique Satre ¹ ⁹, Marc Bailly ¹⁰ ¹¹, Florence Boitrelle ¹⁰ ¹¹, Karin Pernet-Gallay ¹², Sylviane Hennebicq ¹ ¹³, Julien Fauré ² ¹², Serge P Bottari ¹ ¹⁴, Charles Coutton ¹ ⁹, Pierre F Ray ¹⁵ ², Christophe Arnoult ¹

Affiliations

1 Genetic Epigenetic and Therapies of Infertility, Institute for Advanced Biosciences, Inserm U1209, CNRS UMR 5309, Université Grenoble Alpes, Grenoble, France.
2 CHU de Grenoble, UF de Biochimie Génétique et Moléculaire, Grenoble, France.
3 Department of Genetics, Reproductive Biomedicine Research Center, Royan Institute for Reproductive Biomedicine, ACECR, Tehran, Iran.
4 Department of Genetic Medicine and Development, University of Geneva Medical School, Geneva 4, Switzerland.
5 Laboratoire d'Aide Médicale à la Procréation, Centre AMP 74, Contamine-sur-Arve, France.
6 Laboratoire de Biologie de la Reproduction, Hôpital Nord, Saint Etienne, France.
7 Aix Marseille Univ INSERM GMGF, Marseille, France.
8 Univ. Grenoble Alpes / CNRS, TIMC-IMAG, Grenoble, France.
9 CHU de Grenoble, UF de Génétique Chromosomique, Grenoble, France.
10 Department of Reproductive Biology and Gynaecology, Poissy General Hospital, Poissy, France.
11 EA 7404 GIG, Université de Versailles Saint Quentin Montigny le Bretonneux, France.
12 Grenoble Neuroscience Institute, INSERM 1216, Grenoble, France.
13 CHU de Grenoble, UF de Biologie de la procréation, Grenoble, France.
14 CHU de Grenoble, UF de Radioanalyses, Grenoble, France.
15 Genetic Epigenetic and Therapies of Infertility, Institute for Advanced Biosciences, Inserm U1209, CNRS UMR 5309, Université Grenoble Alpes, Grenoble, France [email protected].

PMID: 28554943 DOI: 10.15252/emmm.201607461

Abstract

Azoospermia, characterized by the absence of spermatozoa in the ejaculate, is a common cause of male infertility with a poorly characterized etiology. Exome sequencing analysis of two azoospermic brothers allowed the identification of a homozygous splice mutation in SPINK2, encoding a serine protease inhibitor believed to target acrosin, the main sperm acrosomal protease. In accord with these findings, we observed that homozygous Spink2 KO male mice had azoospermia. Moreover, despite normal fertility, heterozygous male mice had a high rate of morphologically abnormal spermatozoa and a reduced sperm motility. Further analysis demonstrated that in the absence of Spink2, protease-induced stress initiates Golgi fragmentation and prevents acrosome biogenesis leading to spermatid differentiation arrest. We also observed a deleterious effect of acrosin overexpression in HEK cells, effect that was alleviated by SPINK2 coexpression confirming its role as acrosin inhibitor. These results demonstrate that SPINK2 is necessary to neutralize proteases during their cellular transit toward the acrosome and that its deficiency induces a pathological continuum ranging from oligoasthenoteratozoospermia in heterozygotes to azoospermia in homozygotes.

Keywords

azoospermia; exome sequencing; genetics; infertility; spermatogenesis.

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