Chapter 11 Fertilization in Amphibians: The Cellular and Molecular Events from Sperm Approach to Egg Activation

Iwao, Yasuhiro; Watabe, Mami

doi:10.1007/978-981-15-2290-1_12

Cited by 2 publications

(2 citation statements)

References 164 publications

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“…During amphibian fertilization, a fertilized egg must undergo activation in an appropriate period for the initiation of embryonic development with a diploid configuration. Precocious activation before sperm entry causes parthenogenetic development, while a delay in egg activation results in polyspermy due to the failure to prevent additional sperm entry, termed polyspermy block (Iwao 2000, Iwao & Izaki 2018, Iwao & Watabe 2020, Wozniak & Carlson 2020. The cell cycle of unfertilized amphibian eggs is arrested at meiotic metaphase II.…”

Section: Introductionmentioning

confidence: 99%

“…After egg activation induced by the fertilizing sperm, the eggs resume and complete meiosis to undergo cleavage (mitotic cell division). Polyspermy blocks induced by egg activation are indispensable for ensuring normal development of a diploid genome, and several of these are initiated by egg activation after the entry of the primary sperm (Iwao & Izaki 2018, Iwao & Watabe 2020, Wozniak & Carlson 2020). An increase in intracellular Ca 2+ concentration ([Ca 2+ ] i ) in the egg cytoplasm is the most important signal for egg activation initiation (Iwao 2012, Iwao & Izaki 2018).…”

Section: Introductionmentioning

confidence: 99%

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SPERM FACTORS AND EGG ACTIVATION: Divergent sperm factors for egg activation in amphibian fertilization

Iwao

Ueno

2022

Reproduction

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Mature amphibian eggs arrested at meiotic metaphase II must undergo activation to initiate embryonic development soon after fertilization. Fertilizing sperm provide eggs with a signal that induces egg activation, and an increase in intracellular Ca2+concentration in the egg cytoplasm (a Ca2+ rise) is the most important signal for this initiation. The sperm transmits the signal for the Ca2+ rise, known as the sperm factor, which is divergent between anurans and urodeles. In monospermic anurans, the sperm transmits the signal through a receptor on the egg membrane, causing a single rapid Ca2+ rise. Sperm matrix metalloproteinase-2 is a potential candidate for the receptor-mediated sperm factor in anurans. In physiologically polyspermic urodeles, multiple slower Ca2+ rises are caused by a soluble sperm factor (sperm-specific citrate synthase) which is transferred to the egg cytoplasm after sperm-egg fusion. We discuss the molecular mechanisms of egg activation in amphibian fertilization, focusing on recent progress in characterizing these sperm factors and their divergence during the evolution of tetrapod vertebrates.

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

SPERM FACTORS AND EGG ACTIVATION: Divergent sperm factors for egg activation in amphibian fertilization

Iwao

Ueno

2022

Reproduction

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Sperm MMP‐2 is indispensable for fast electrical block to polyspermy at fertilization in Xenopus tropicalis

Watabe

Hiraiwa

Sakai

et al. 2021

Molecular Reproduction Devel

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Sperm matrix metalloproteinase-2 (MMP-2) is necessary for frog fertilization.Monospermy is ensured by a fast, electrical block to polyspermy mediated by a positive fertilization potential. To determine the role of the MMP-2 hemopexin domain (HPX) in a fast block to polyspermy during fertilization of the frog, Xenopus tropicalis, we prepared mutant frogs deficient in mmp2 gene using the transcription activator-like effector nuclease method. mmp2 ΔHPX (−/−) sperm without MMP-2 protein were able to fertilize wild-type (WT; +/+) eggs. However, polyspermy occurred in some eggs. The mutant sperm generated a normal fertilization potential amounting to 10 mV, and were able to fertilize eggs at 10 mV, at which WT sperm never fertilized. Sensitivity during voltage-dependent fertilization decreased in mutant sperm. This study demonstrates for the first time that the genetic alteration of the MMP-2 molecule in sperm causes polyspermy during fertilization of a monospermic species. Our findings provide reliable evidence that sperm MMP-2 is indispensable for the fast, electrical block to polyspermy during Xenopus fertilization.

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Chapter 11 Fertilization in Amphibians: The Cellular and Molecular Events from Sperm Approach to Egg Activation

Cited by 2 publications

References 164 publications

SPERM FACTORS AND EGG ACTIVATION: Divergent sperm factors for egg activation in amphibian fertilization

SPERM FACTORS AND EGG ACTIVATION: Divergent sperm factors for egg activation in amphibian fertilization

Sperm MMP‐2 is indispensable for fast electrical block to polyspermy at fertilization in Xenopus tropicalis

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