A perinuclear theca substructure is formed during epididymal guinea pig sperm maturation and disappears in acrosome reacted cells
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Updated: Oct 18, 2026

Transillumination-Assisted Dissection of Specific Stages of the Mouse Seminiferous Epithelial Cycle for Downstream Immunostaining Analyses
Published on: October 7, 2020
M de Lourdes Juárez-Mosqueda1, A Mújica
1Departamento de Biología Celular, Centro de Investigación y Estudios Avanzados del Instituto Politécnico Nacional, Apdo., México, DF, 07000, México.
Abstract:
The perinuclear theca (PT) is a unique cytoskeletal mammalian sperm structure that surrounds the nucleus. Using negatively stained whole-mount preparations, we detected a PT substructure on the apical region of the postacrosomal theca layer of guinea pig spermatozoa. The PT substructure consists of projections resembling eyelashes, circling the sperm head. The PT substructure was absent in caput but appeared in corpus epidydimal spermatozoa. The same finding was observed in sheep and rabbit spermatozoa. The PT substructure persisted in capacitating spermatozoa, but was absent in acrosome reacted gametes. No labeling of the PT substructure was observed by the immunogold technique using antibodies against calmodulin, spectrin, myosin, and vimentin. A 34-kDa band appeared as a possible PT substructure protein. The PT was positive to the antibodies and the presence of the above-mentioned proteins was confirmed by Western blot. F-actin gold label was observed in mature spermatozoa on the PT substructure base zone. Results using cytochalasin D and phalloidin point to a role of F-actin in the PT substructure formation/disassembly processes. Ca(2+), bicarbonate, and proteases might be involved in the mechanism of the substructure disassembly. Novel PT morphological changes occurring during sperm epidydimal maturation and at acrosome reaction, respectively, are discussed in relation to the PT stability and function.
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