A New ENU-Induced Mutant Mouse with Defective Spermatogenesis Caused by a Nonsense Mutation of the Syntaxin 2/Epimorphin (Stx2/Epim) Gene

Abstract

Abstract.Repro34 is an N-ethyl-N-nitrosourea (ENU)-induced mutation in mice showing male-specific infertility caused by defective spermatogenesis. In the present study, we investigated pathogenesis and molecular lesions in relation to spermatogenesis in the repro34/repro34 homozygous mouse. Histological examination of the testis showed that the seminiferous epithelium of the repro34/repro34 mouse contained spermatogonia and spermatocytes but no round and elongating spermatids. Instead of these haploid cells, multinucleated giant cells occupied the niche of the seminiferous tubules. Immunohistochemical staining for Hsc70t, an elongating spermatid specific protein, confirmed the absence of elongating spermatids. Furthermore, RT-PCR showed that there were significantly reduced expressions of the marker genes specifically expressed in the spermatid and that there was no difference in the expressions of the spermatocyte specific marker genes. These findings indicated interruption of the spermatogenesis during transition from the spermatocyte to spermatid in the repro34/repro34 mouse. The repro34 locus has been mapped on a 7.0-Mb region of mouse chromosome 5 containing the Syntaxin 2/Epimorphin (Stx2/Epim) gene, and targeted disruption of this gene has been reported to cause defective spermatogenesis. We therefore sequenced the entire coding region of the Stx2/Epim gene and found a nucleotide substitution that results in a nonsense mutation of this gene. The expression pattern of the Stx2/Epim gene during the first wave of spermatogenesis, increased expression at later stages of spermatogenesis, was in agreement with the affected phase of spermatogenesis in the adult repro34/repro34 testis. We therefore concluded that the male infertility of the repro34/repro34 mouse is caused by the interruption of spermatogenesis during transition from the spermatocyte to spermatid and that the nonsense mutation of the Stx2/Epim gene is responsible for the interruption of spermatogenesis. Key words: ENU mutagenesis, Infertility, Mouse, Mutation, Spermatogenesis, Syntaxin 2/Epimorphin (Stx2/Epim) gene (J. Reprod. Dev. 54: [122][123][124][125][126][127][128] 2008) ammalian spermatogenesis is one of the most dynamic proc e s s e s o f c e l l p r o l i f e r a t i o n , d i f f e r e n t i a t i o n a n d morphogenesis and involves numerous cellular and molecular steps. In order to understand the mechanisms underlying mammal i a n s p e r m a t o g e n e s i s , a n i m a l m o d e l s w i t h d e f e c t i v e spermatogenesis are essential tools to identify the signaling pathways and molecules involved in regulation of spermatogenesis [1,2]. So far, a large number of infertile genetic animal models have been established by spontaneous mutations and gene targeting technologies [2]. These animal models have contributed to understanding of the mechanisms involved in mammalian spermatogenesis [1][2][3][4][5][6]. They are also valuable for better understanding of the pathogenesis of human male infertility, which is mostly caused by defe...

ELOVL2 controls the level of n-6 28:5 and 30:5 fatty acids in testis, a prerequisite for male fertility and sperm maturation in mice

“…The histological phenotype of the Elovl2 Ϫ / Ϫ mice testis resembles in part the morphology seen in two mouse strains with disruption of the epimorphin gene, a member of the SNARE family, which plays an essential role in membrane fusion at the terminal step of cytokinesis and vesicle fusion during exocytosis (20)(21)(22). As in the case of Elovl2 ablation, those germ cells failed to complete the meiotic division to generate haploid cells, thereby resulting in the formation of multinucleated cells in the lumens of the seminiferous tubules.…”

Leydig Cell Hyperplasia in an ENU-induced Mutant Mouse with Germ Cell Depletion

“…Although a significant portion of male infertilities is believed to be caused by autosomal recessive mutations [1], the genetic factors that underlay most nonsyndromic male infertilities have not yet been identified, with a few exceptions [2,3]. Mutant mice established by gene targeting technology, chemical mutagenesis and spontaneous mutations [4][5][6][7], showing various features of infertility are expected to be useful animal models for investigating the pathogenesis and genetic factors of human infertilities. However, only a limited number of mouse models for Sertoli cell-only syndrome or germ cell depletion have been reported [8][9][10][11].…”

Characterization and Linkage Mapping of an ENU-Induced Mutant Mouse with Defective Spermatogenesis

“…It is to be noted that these mutants with arrest of spermatogenesis show distinctive phenotypes. For example, repro34 mice show interruption of spermatogenesis during transition from the spermatocyte to spermatid [1], while repro7 show arrest of spermatogenesis at the mid-pachytene stage, and repro46 at the late pachytene stage. Currently we have not yet identified the precise pathogenesis of the repro23 mouse, but the repro23/repro23 mouse shows apparently unique features.…”

“…Although a significant portion of male infertilities is believed to be caused by autosomal recessive mutations [18], apart from a few exceptions, the genetic factors that underlie most nonsyndromic male infertilities have not yet been identified [6,21,25]. Mutant mice established by gene targeting technology, chemical mutagenesis and spontaneous mutations [1,5,[14][15][16]19], showing various features of infertility are expected to be useful animal models for investigating the pathogenesis and genetic factors of human infertilities [4].…”

“…In the Reproductive Genomics Program, more than 30 mutants with reproductive abnormalities, including male and female infertility, have so far been established by phenotypic screening of EnU-mutagenized mice [1,14,16]. repro23 is one of these ENU-induced mutations and it shows male-specific infertility caused by defective spermatogenesis.…”