The perforatorium and postacrosomal sheath of rat spermatozoa share common developmental origins and protein constituents†

Abstract

The perinuclear theca (PT) is a cytosolic protein capsule that surrounds the nucleus of eutherian spermatozoa. Compositionally, it is divided into two regions: the subacrosomal layer (SAL) and the postacrosomal sheath (PAS). In falciform spermatozoa, a third region of the PT emerges that extends beyond the nuclear apex called the perforatorium. The formation of the SAL and PAS differs, with the former assembling early in spermiogenesis concomitant with acrosome formation, and the latter dependent on manchette descent during spermatid elongation. The perforatorium also forms during the elongation phase of spermiogenesis, suggesting that like the PAS, its assembly is facilitated by the manchette. The temporal similarity in biogenesis between the PAS and perforatorium led us to compare their molecular composition using cell fractionation and immunodetection techniques. Although the perforatorium is predominantly composed of its endemic protein FABP9/PERF15, immunolocalization indicates that it also shares proteins with the PAS. These include WBP2NL/PAWP, WBP2, GSTO2, and core histones, which have been implicated in early fertilization and zygotic events. The compositional homogeny between the PAS and perforatorium supports our observation that their development is linked. Immunocytochemistry indicates that both PAS and perforatorial biogenesis depend on the transport and deposition of cytosolic proteins by the microtubular manchette. Proteins translocated from the manchette pass ventrally along the spermatid head into the apical perforatorial space prior to PAS deposition in the wake of manchette descent. Our findings demonstrate that the perforatorium and PAS share a mechanism of developmental assembly and thereby contain common proteins that facilitate fertilization.

Differential Expression of Kisspeptin System and Kisspeptin Receptor Trafficking during Spermatozoa Transit in the Epididymis

“…In the hook shaped spermatozoa, the perinuclear theca comprises the subacrosomal layer, the post acrosomal sheet, and also the perforatorium, the curve pointed region particularly enlarged in falciform rat spermatozoa that encircles and extends beyond the nuclear apex. Its biogenesis involves the transport and deposition of proteins that, during the spermiogenesis, move ventrally from the microtubular manchette to reach the apical region of spermatid head [ 48 ]. In this respect, the intracellular trafficking of Kiss1R during sperm maturation recapitulates the trafficking occurring during sperm elongation.…”

Core Histones Are Constituents of the Perinuclear Theca of Murid Spermatozoa: An Assessment of Their Synthesis and Assembly during Spermiogenesis and Function after Gametic Fusion

“…As was found in bull spermatozoa, these non-nuclear histones assemble as part of the postacrosomal sheath (PAS) of the perinuclear theca (PT) in murids but additionally assemble as constituents of the perforatorium (PERF). As recently investigated, the perforatorium is an apical extension of the PT, found in falciform spermatozoa of murids, which shares developmental and compositional similarities with the PAS [ 15 ]. It should be emphasized that the histones assembled in the perinuclear theca make up the majority of the histone content in both the murid and bovine sperm heads to the extent that after high-salt extraction of the PT histones, little to no antigenic traces of histones can be found in the extracted sperm heads, even though their nuclei remain intact; therefore, investigators exploring solely nuclear histones in spermatozoa should take precaution to extract the PT histones, either with an ionic detergent or high salt buffer, from the sperm head before attempting compositional analysis and histone immunolabeling studies of the sperm nucleus.…”

“…Labels: HCS, displaced head cap segment: VS, ventral spur. Adapted from Protopapas et al [ 15 ], Oko and Maravei [ 16 ], and Lalli and Clermont [ 17 ].…”

“…Based on compositional and functional considerations, the PT can be divided into two compartments: the subacrosomal layer (SAL), which houses proteins involved in the assembly and attachment of the acrosome to the spermatid nucleus during spermiogenesis [ 1 , 2 , 3 , 4 , 5 , 6 ], and the post-acrosomal sheath (PAS), which houses proteins implicated in oocyte activation and zygote development during and after fertilization [ 1 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 ]. In murids, the PT has an additional third compartment termed the perforatorium [ 15 ] ( Figure 1 ). The perforatorium is a hook-shaped extension of the PT unique to falciform spermatozoa that encircles and extends beyond the apical nucleus.…”

“…The perforatorium is a hook-shaped extension of the PT unique to falciform spermatozoa that encircles and extends beyond the apical nucleus. It is compositionally distinct from the SAL but has developmental, compositional, and functional similarities with the PAS [ 15 ].…”