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Background <p>Despite extensive characterization of sperm structures, certain specialized subcellular structures are still not well understood. Among these, the posterior ring has been recognized for over half a century; yet, its molecular composition and biological role remain unknown. This research aims to define the molecular components and functional roles of the sperm posterior ring.</p> Methods <p>3D-rendered confocal microscopy was used to determine the localization and developmental dynamics of SPEM3 and TEX50 in mature spermatozoa and spermatids at different steps of spermiogenesis. <i>Spem3</i> and <i>Tex50</i> knockout mouse models were generated to explore their physiological functions. Sperm morphology and ultrastructure were investigated through immunofluorescence along with transmission and scanning electron microscopy, whereas sperm motility was evaluated using computer-assisted sperm analysis. Proteomics, coimmunoprecipitation, and immunoblotting were performed to identify SPEM3 and TEX50 as structurally interdependent interacting components of the posterior ring and to elucidate how their loss disrupts sperm architecture and fertility.</p> Results <p>We identified SPEM3 as a core component of the posterior ring located at the sperm head–tail linkage. The posterior ring arises from the marginal ring at the acroplaxome periphery during early spermiogenesis. Loss of <i>Spem3</i> led to severe bending of the head–tail linkage, accompanied by a marked reduction in sperm motility, ultimately leading to male infertility. Furthermore, SPEM3 interacts and colocalizes with TEX50, and deficiency of either protein resulted in similar phenotypes, including disorganization of the posterior ring and postacrosomal region as well as impairment of the sperm connecting piece.</p> Conclusions <p>These findings establish SPEM3 and TEX50 as critical posterior ring components essential for maintaining postacrosomal integrity and anchoring the sperm head to the tail. By resolving the long unknown molecular composition of the posterior ring, this study provides new mechanistic insight into sperm head–tail integrity and the pathogenesis of certain forms of male infertility.</p> Graphical Abstract <p></p>

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The origin and function of the posterior ring in mouse sperm head

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年7月21日

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  • Bingbing Wu,
  • Chenghong Long,
  • Jiayi Liu,
  • Zuobin Zhu,
  • Liling Liu,
  • Qingling Ma,
  • Yan Long,
  • Liying Wang,
  • Huafang Wei,
  • Yanjie Ma,
  • Jingwen Hou,
  • Heying Li,
  • Li Yuan,
  • Wei Li,
  • Chao Liu

摘要

Background

Despite extensive characterization of sperm structures, certain specialized subcellular structures are still not well understood. Among these, the posterior ring has been recognized for over half a century; yet, its molecular composition and biological role remain unknown. This research aims to define the molecular components and functional roles of the sperm posterior ring.

Methods

3D-rendered confocal microscopy was used to determine the localization and developmental dynamics of SPEM3 and TEX50 in mature spermatozoa and spermatids at different steps of spermiogenesis. Spem3 and Tex50 knockout mouse models were generated to explore their physiological functions. Sperm morphology and ultrastructure were investigated through immunofluorescence along with transmission and scanning electron microscopy, whereas sperm motility was evaluated using computer-assisted sperm analysis. Proteomics, coimmunoprecipitation, and immunoblotting were performed to identify SPEM3 and TEX50 as structurally interdependent interacting components of the posterior ring and to elucidate how their loss disrupts sperm architecture and fertility.

Results

We identified SPEM3 as a core component of the posterior ring located at the sperm head–tail linkage. The posterior ring arises from the marginal ring at the acroplaxome periphery during early spermiogenesis. Loss of Spem3 led to severe bending of the head–tail linkage, accompanied by a marked reduction in sperm motility, ultimately leading to male infertility. Furthermore, SPEM3 interacts and colocalizes with TEX50, and deficiency of either protein resulted in similar phenotypes, including disorganization of the posterior ring and postacrosomal region as well as impairment of the sperm connecting piece.

Conclusions

These findings establish SPEM3 and TEX50 as critical posterior ring components essential for maintaining postacrosomal integrity and anchoring the sperm head to the tail. By resolving the long unknown molecular composition of the posterior ring, this study provides new mechanistic insight into sperm head–tail integrity and the pathogenesis of certain forms of male infertility.

Graphical Abstract