Biology subjects

Oh, J.-N.

Publications and source records attributed to Oh, J.-N..

3 recordsLinked to original sources

bioRxiv2026

Soluble ZP2 N-terminal fragments activate CatSper-dependent Ca2+ entry and regulate motility and acrosomal exocytosis in mammalian sperm

Sperm motility and function are central to mammalian fertilization and are tightly regulated by intracellular calcium (CaCa2+) signaling. This signaling is primarily orchestrated by the CatSper Ca2+; channel complex located in the flagella of spermatozoa. However, the natural ligands that activate CatSper remain largely unknown in many species, despite the conservation of CatSper in mammals. Here, we present a signaling role for soluble N-terminal ZP2 fragments in regulating CatSper activity and sperm physiology in mice and humans. ZP2 has been implicated in mediating sperm binding and recognition at the oocyte surface interface; however, new evidence is starting to unveil the molecular mechanisms and function of ZP2 during fertilization transition. Here, we show that the during fertilization, cleaved ZP2 N-terminal fragment triggers a rapid and robust increase in intracellular CaCa2+ levels in sperm. This increase depends strictly on CatSper function, as demonstrated through pharmacological analysis and CatSper1 knockout mice. This calcium influx is sufficient to induce acrosomal exocytosis in a subset of human and mouse sperm. AlphaFold-based structural modeling suggests a potentially conserved extracellular interaction site between the soluble N-terminal ZP2 fragments and the CatSper complex. In human sperm, ZP2 treatment significantly modulates motility parameters, including flagellar movement and velocity, while inducing a CatSper-dependent increase in intracellular CaCa2+ similar in magnitude to that evoked by progesterone. Species-matched ZP2 stimulation elicits the stronger calcium response, underscoring evolutionary adaptations in ligand-channel protein pairs. Taken together, our findings reveal a conserved signaling pathway from ZP2 to CatSper that integrates oocyte-derived signals into the regulation of sperm motility and acrosomal exocytosis. This pathway provides new mechanistic insights into fertilization and highlights potential targets.

cell biology↗

bioRxiv2026

CATSPERβ--δ Interaction Governs Hierarchical CatSper Holo-complex Assembly and is Essential for Male Fertility

The sperm-specific CatSper channel is macromolecular Ca2+ channel complex essential for hyperactivated motility and male fertility. The pore-forming channel (CATSPER1-4) associates with a large extracellular domain-containing canopy (CATSPER{beta}-{varepsilon}), a cytosolic Ca{superscript 2} sensing subcomplex (CATSPER{zeta}-EFCAB9-ARMH2), the putative transporter SLCO6C1, and CATSPER{theta}-, arranging into higher-order zigzag rows in the flagellar membrane. However, the molecular mechanism governing holo-complex assembly during spermatogenesis remains largely undefined. Here we demonstrate that the CATSPER{beta}-{delta} interaction represents an essential early step in CatSper biogenesis. CRISPR/Cas9 targeting of Catsperb exon 4 generated a frameshift knockout (Catsperb-/-) and an in-frame deletion mutant (Catsperb{Delta}/{Delta}) that specifically disrupts the {beta}-{delta} interaction interface. Disrupting this interface reduced CATSPER{delta} among canopy subunits, impairing canopy assembly and destabilizing the core pore-forming channel. Consequently, mature spermatozoa completely lacked the entire CatSper complex, phenocopying the knockout. A transgenic line expressing extracellular-domain-truncated CATSPER{delta} lacking the {beta}-binding region likewise phenocopied the Catsperb mutant, confirming the necessity of an intact {beta}-{delta} interface. AlphaFold-Multimer modeling and alanine-substitution mutagenesis identified key hydrogen-bonding residues at this interface that mediate canopy subunit association. Consistent with complex loss, whole-sperm patch-clamp recordings revealed complete absence of CatSper conductance in mutant spermatozoa. Both mutant lines exhibited defective sperm hyperactivation and male infertility despite normal spermatogenesis and baseline motility. Together, these findings establish that canopy formation driven by CATSPER{beta}-{delta} interaction precedes and is required for pore-forming channel assembly, defining a hierarchical assembly pathway for the CatSper holo-complex and highlighting a key structural node for male fertility and contraceptive development.

cell biology↗

bioRxiv2024

Extracellular domains of CATSPERε are essential for CatSper assembly during development and activity modulation in sperm capacitation

The flagellar-specific Ca2+ channel CatSper is a multiprotein complex that is critical for successful fertilization by controlling the sperm Ca2+ signaling in space and time. Large extracellular domains (ECDs) of four single-pass transmembrane subunits, CATSPER{beta}, {gamma}, {delta}, and {varepsilon}, form a unique canopy structure over the pore-forming channel. However, the molecular mechanisms of canopy assembly during development and its physiological function in mature sperm remain unknown. Here, using two genetic mouse models and the biochemical isolation of a bioactive CATSPER{varepsilon} fragment, we report that CATSPER{varepsilon} ECDs are essential for assembling the CatSper canopy, and thus the entire channel complex, and for modulating CatSper function for sperm hyperactivation and fertilization. CATSPER{varepsilon}-deficient males are sterile because their sperm fail to develop hyperactivated motility due to the absence of the entire channel. In transgenic mice overexpressing CATSPER{varepsilon} with truncated ECDs in testicular germ cells, truncated CATSPER{varepsilon} is unable to interact with native CatSper subunits and incorporate into the complex, thus failing to rescue the defective sperm hyperactivation and infertility of Catspere-null males. These findings provide insight into the underlying molecular and developmental mechanisms of CatSper complex assembly and how CatSper channels can be modulated in physiological settings and by therapeutic intervention.

cell biology↗