About

Professor Rafael Fissore's research primarily focuses on the mechanisms of calcium signaling and its role in mammalian oocyte activation, fertilization, and early embryonic development. His extensive work investigates intracellular calcium responses in oocytes and eggs across various species including mouse, rabbit, bovine, and porcine models. He has contributed significantly to understanding the patterns and regulation of calcium oscillations triggered by sperm factors and other stimuli during fertilization and parthenogenetic activation. His studies also explore the molecular components involved in calcium release, such as inositol trisphosphate receptors and phospholipase C isoforms, and their modulation during oocyte maturation and activation processes. Additionally, Professor Fissore has examined the biochemical and developmental competence of oocytes, the role of mitogen-activated protein kinase in meiosis resumption, and the effects of postovulatory aging on oocyte activation. His research has implications for reproductive biology, cloning, and assisted reproductive technologies.

Research topics

• Cell biology
• Biology
• Genetics
• Andrology
• Anatomy
• Chemistry
• Medicine
• Biophysics
• Internal medicine

Selected publications

• A domain-swapped CaMKII conformation facilitates linker-mediated allosteric regulation

  Nature Communications · 2025-09-26

  articleOpen access

  Memory formation, fertilization, and cardiac function rely on precise Ca2+ signaling and subsequent Ca2+/calmodulin-dependent protein kinase II (CaMKII) activation. Ca2+ sensitivity of the four CaMKII paralogs in mammals is linked to the length of the variable linker region that undergoes extensive alternative splicing. In this study, we determine that the position of charged residues within the linker modulates the Ca2+/CaM sensitivity. We present an X-ray crystal structure of the full-length CaMKIIδ holoenzyme consisting of domain-swapped dimers within a dodecameric complex, revealing potential contacts for cooperativity and allostery. Based on molecular dynamics (MD) simulations, small-angle X-ray scattering (SAXS) measurements, and live-cell imaging, we propose a model where the domain-swapped conformation positions the charges of the linker region to drive an interaction with the regulatory segment that modulates the degree of autoinhibition. Our findings provide a framework for understanding allosteric regulation of CaMKII by the linker region in Ca2+-sensitive cells. CaMKII is a key enzyme in brain, heart, and egg cells, regulated by calcium signals. Here, authors show that charged residues in the variable linker tune CaMKII activity, a mechanism that may underlie cell type–specific responses.

  PublisherOA PDFDOI

• Editorial: The fertilization success from the Oocyte’s perspective, volume II

  Frontiers in Cell and Developmental Biology · 2025-11-10

  editorialOpen accessSenior author

  A recurrent theme that unites these studies is the intricate dialogue between the oocyte and its environment-a conversation mediated by ions, organelles, hormones, and signaling molecules. Machaty elegantly revisits one of the most emblematic aspects of fertilization: the calcium signal that awakens the quiescent oocyte. His comprehensive analysis of the mechanisms underlying calcium oscillations not only revisits classical paradigms but also integrates emerging data on sperm-derived factors and intracellular pathways that sustain embryo development. By situating these mechanisms within a comparative framework, this work highlights how nature repurposes and adapts molecular strategies to ensure activation across mammalian species. Complementing this molecular perspective, García-Castro et al. examine the phenogenetics of cortical granule dynamics during the zebrafish's oocyte-to-embryo transition. Their study bridges genetic and cell biological approaches to elucidate how maternal factors orchestrate cortical exocytosis, a process that safeguards monospermy while remodeling the egg's surface for the next stage of development. Together, these two contributions underscore that the oocyte is not a passive recipient of fertilizing stimuli, but rather an active participant in its own developmental fate.Chen et al. present a comprehensive review of the influence of dietary and antioxidant supplementation on oocyte quality. Their work synthesizes evidence showing that compounds such as coenzyme Q10, α-ketoglutarate, melatonin, and omega-3 fatty acids modulate mitochondrial metabolism, oxidative stress, and meiotic competence. The review highlights how nutritional and metabolic interventions can shape the oocyte's redox balance and developmental potential, emphasizing the emerging role of diet and systemic physiology as critical contributors to reproductive success. By bridging molecular insights and clinical perspectives, this study opens new avenues for improving oocyte competence through targeted nutritional strategies., with a focus on human blastocyst vitrification. Their updated review confirms vitrification as the current gold standard, offering superior survival and pregnancy outcomes compared to slow-freezing methods. The authors also discuss the potential biological implications of cryoprotectant exposure, osmotic stress, and temperature fluctuations-particularly regarding oxidative and epigenetic stability. By addressing both technical optimization and safety concerns, this review underscores the need for continued refinement of vitrification protocols to safeguard embryo integrity and long-term developmental health.Finally, Zheng et al. provide original evidence that connects hormonal signaling to follicular physiology through the regulation of aquaporin 2 (AQP2). By demonstrating that luteinizing hormone modulates AQP2 expression in human granulosa cells via the ERK1/2 pathway, they reveal a new layer of complexity in the control of follicular fluid formation and follicle growth. This discovery not only advances our understanding of the follicular microenvironment but also identifies potential targets for therapeutic intervention in ovarian dysfunction.Viewed together, these contributions portray the oocyte as a dynamic integrator of signals that extend from the molecular to the systemic level. They remind us that fertilization success depends not solely on the union of gametes but on the precise coordination of events that prepare the egg for that encounter and subsequent development. The studies presented here reflect a field that continues to evolvewhere molecular genetics, physiology, and environmental science converge to explain how life begins and sometimes falters.It becomes evident that the "oocyte's perspective" is not just a metaphor but a necessary shift in focus. By centering on the female gamete, we gain a holistic view of reproduction-one that acknowledges the vulnerability and resilience of the oocyte within its biological and ecological context. The works in this second volume collectively deepen our appreciation of the complexity of fertilization and open new paths for improving fertility preservation, assisted reproduction, and female reproductive health.

  PublisherOA PDFDOI

• The TRPV3 channel is a mediator of zinc influx and homeostasis in murine oocytes

  Proceedings of the National Academy of Sciences · 2025-04-01 · 3 citations

  articleOpen accessSenior authorCorresponding

  Zinc (Zn 2+ ) homeostasis is essential for gametogenesis and reproduction, and its deficiency causes infertility. Oocytes contain higher Zn 2+ levels than somatic cells, and Zn 2+ concentrations in oocytes are far higher than those of other transition metals and increase even more during maturation in preparation for fertilization. Remarkably, it is unknown what transporter(s) or channel(s) mediate Zn 2+ influx in oocytes and whether they are expressed uniformly throughout folliculogenesis. Here, we showed that the functional expression of a member of the t ransient r eceptor p otential family, vanilloid 3, TRPV3, closely follows the dynamics of intracellular Zn 2+ during oocyte maturation, raising the prospect that these events may be functionally linked. Using microfluorometry, we monitored in oocytes of Trpv3 null females the expected rise in Zn 2+ concentrations during maturation. Surprisingly, Zn 2+ levels did not climb, and the overall FluoZin3 signal in Trpv3 null eggs was lower than in control eggs. Electrophysiological recordings showed a large TRPV3 current induced by the agonist 2-APB in WT eggs supplemented with extracellular Zn 2+ that was absent in Trpv3 null eggs; TRPV3 showed a clear preference for Zn 2+ over Ca 2+ . Trpv3 null eggs displayed features associated with Zn 2+ deficient conditions, such as lower IP 3 R1 function, abnormal cortical granule distribution, and disturbed cytoskeletal organization with distinct actin nucleation disorders. Notably, Trpv3 null eggs demonstrated undisturbed Zn 2+ sparks. Our results suggest that TRPV3 is a pivotal member of the Zn 2+ toolkit, mediating Zn 2+ intake during maturation. They also indicate that distinct transporters or channels mediate Zn 2+ influx throughout folliculogenesis.

  PublisherOA PDFDOI

• Zebrafish sperm outsource activation to eggs’ protease-activated receptors

  PLoS Biology · 2025-06-18

  letterOpen access1st authorCorresponding

  The calcium surge that starts embryogenesis varies across species and is elusive in many. A new study in PLOS Biology shows that zebrafish eggs self-activate, initiating a protease-activated receptor calcium wave and uncovering a novel pathway in egg activation.

  PublisherDOI

• The oocyte zinc transporter <i>Slc39a10/Zip10</i> is a regulator of zinc sparks during fertilization in mice

  bioRxiv (Cold Spring Harbor Laboratory) · 2024-09-12

  preprintOpen access

  Abstract In all vertebrates studied to date, a rise(s) in intracellular calcium is indispensable for successful fertilization and further embryonic development. Recent studies demonstrated that zinc is ejected to the extracellular milieu, the ’zinc spark’, and follows the first few calcium rises of fertilization. However, the role of the zinc sparks in fertilization and development, and the supporting influx mechanism(s) are unknown. In this study, we focused on zinc transporters Zip10/Slc39a10 which was expressed in mouse oocytes through follicular development, and investigated the oocyte-specific deficient mice for Zip10 ( Zip10 d/d : Zip10 flox/flox Gdf9 Cre/+ ). Zip10 mRNA or ZIP10 protein was expressed throughout folliculogenesis in the oocyte or plasma membrane, respectively. The number of ovulated oocytes was examined in Zip10 d/d mice, and no change from the number of oocytes was observed. Zip10 d/d oocytes decreased zinc level in the oocytes, but did not affect maturation and metaphase II spindles formation. Fertilization-induced calcium oscillations were present in Zip10 d/d oocytes, but zinc sparks were not observed. Despite other events of egg activation proceeding normally in Zip10 d/d oocytes, embryo development into 4-cells and beyond was compromised. We show here for the first time that the zinc transporter ZIP10 contributes to zinc homeostasis in oocytes and embryos, highlighting the role of labile zinc ions in early development. Submission information The zinc transporter, Slc39a10/Zip10 , is required for the zinc sparks of fertilization in mice.

  PublisherOA PDFDOI

• In memoriam of Shun-ichi Miyazaki 1941–2024

  Cell Calcium · 2024-09-03

  letterSenior author
  PublisherDOI

• Effect of bicarbonate and polyvinyl alcohol on in vitro capacitation and fertilization ability of cryopreserved equine spermatozoa

  Andrology · 2024-05-28 · 5 citations

  article

  BACKGROUND: Factors contributing to the limited success of in vitro fertilization in horses remain to be studied. In this work, we elucidated the effect of different essential capacitation media components, bicarbonate, and bovine serum albumin or polyvinyl-alcohol, and the incubation microenvironment on sperm parameters associated with capacitation, acrosome reaction, and their ability to activate oocytes via heterologous intracytoplasmic spermatozoa injection in equine cryopreserved spermatozoa. METHODS: Frozen-thawed spermatozoa underwent incubation at different time intervals in either Tyrode's albumin lactate pyruvate medium (non-capacitating; NC) or Tyrode's albumin lactate pyruvate supplemented with bicarbonate, bicarbonate and polyvinyl-alcohol, bicarbonate and bovine serum albumin, polyvinyl-alcohol and bovine serum albumin alone. Protein kinase A-phosphorylated substrates and tyrosine phosphorylation levels, sperm motility, and acrosome reaction percentages were evaluated. After determining the best condition media (capacitating; CAP), heterologous intracytoplasmic spermatozoa injection on pig oocytes was performed and the phospholipase C zeta sperm localization pattern was evaluated. RESULTS: Incubation of frozen-thawed equine spermatozoa with bicarbonate and polyvinyl-alcohol in atmospheric air for 45 min induced an increase in protein kinase A-phosphorylated substrates and tyrosine phosphorylation levels compared to NC condition. Sperm incubation in bicarbonate and polyvinyl-alcohol medium showed an increase in total motility and progressive motility with respect to NC (p ≤ 0.05). Interestingly, three parameters associated with sperm hyperactivation were modulated under bicarbonate and polyvinyl-alcohol conditions. The kinematic parameters curvilinear velocity and amplitude of lateral head displacement significantly increased, while straightness significantly diminished (curvilinear velocity: bicarbonate and polyvinyl-alcohol = 120.9 ± 2.9 vs. NC = 76.91 ± 6.9 µm/s) (amplitude of lateral head displacement: bicarbonate and polyvinyl-alcohol = 1.15 ± 0.02 vs. NC = 0.77 ± 0.03 µm) (straightness: bicarbonate and polyvinyl-alcohol = 0.76 ± 0.01 vs. NC = 0.87 ± 0.02) (p ≤ 0.05). Moreover, the spontaneous acrosome reaction significantly increased in spermatozoa incubated in this condition. Finally, bicarbonate and polyvinyl-alcohol medium was established as CAP medium. Although no differences were found in phospholipase C zeta localization pattern in spermatozoa incubated under CAP, equine spermatozoa pre-incubated in CAP condition for 45 min showed higher fertilization rates when injected into matured pig oocytes (NC: 47.6% vs. CAP 76.5%; p ≤ 0.05). CONCLUSION: These findings underscore the importance of bicarbonate and polyvinyl-alcohol in supporting critical events associated with in vitro sperm capacitation in the horse, resulting in higher oocyte activation percentages following heterologous intracytoplasmic spermatozoa injection. This protocol could have an impact on reproductive efficiency in the equine breeding industry.

  PublisherDOI

• Author Response: Zn2+ is essential for Ca2+ oscillations in mouse eggs

  2023-12-15 · 1 citations

  peer-reviewOpen accessSenior author

  Throughout oocyte maturation, there is a simultaneous elevation in the concentrations of Ca2+ and Zn2+, and the fertilization-induced Ca2+ oscillations cease under Zn2+-deficient conditions, implying an interplay between these ions, potentially at the IP3R1 level that harbors a Zn2+-binding domain.

  PublisherDOI

• Editors' Showcase 2022: Insights in Molecular and Cellular Reproduction

  Frontiers research topics · 2023-01-01

  book1st authorCorresponding
  PublisherDOI

• Essential Role of Mg&lt;sup&gt;2 &lt;/sup&gt; for Mouse Preimplantation Embryo Development Revealed by TRPM7 Chanzyme Deficient Gametes

  SSRN Electronic Journal · 2023-01-01

  preprintOpen accessSenior author
  PublisherDOI

Recent grants

• NIH Grant R03HD042498

  NIH · $152k · 2006

• NIH Grant R01HD051872

  NIH · $1.3M · 2014

• Regulation of Ca2+ influx in mouse oocytes and eggs during maturation and fertilization to improve assisted reproductive technologies and modulate fertility

  NIH · $1.5M · 2018–2024

Frequent coauthors

• Manabu Kurokawa

  24 shared

• Jan B. Parys

  KU Leuven

  20 shared

• Sook‐Young Yoon

  18 shared

• Takuya Wakai

  18 shared

• Hoi Chang Lee

  Northwestern University

  15 shared

• Junya Ito

  Azabu University

  13 shared

• Goli Ardestani

  Boston IVF

  13 shared

• Ingrid Carvacho

  Catholic University of the Maule

  13 shared

Awards & honors

• Distinguished Faculty Lecturer 2008
• Chancellor's Medal 2008
• CFNR Outstanding Research Award 2002