Bindin is essential for fertilization in the sea urchin

Abstract

Species-specific sperm−egg interactions are essential for sexual reproduction. Broadcast spawning of marine organisms is under particularly stringent conditions, since eggs released into the water column can be exposed to multiple different sperm. Bindin isolated from the sperm acrosome results in insoluble particles that cause homospecific eggs to aggregate, whereas no aggregation occurs with heterospecific eggs. Therefore, Bindin is concluded to play a critical role in fertilization, yet its function has never been tested. Here we report that Cas9-mediated inactivation of the bindin gene in a sea urchin results in perfectly normal-looking embryos, larvae, adults, and gametes in both males and females. What differed between the genotypes was that the bindin−/− sperm never fertilized an egg, functionally validating Bindin as an essential gamete interaction protein at the level of sperm–egg cell surface binding.

The Structure and Function of Gut Microbiomes of Two Species of Sea Urchins, Mesocentrotus nudus and Strongylocentrotus intermedius, in Japan

“…Sea urchin has been used for over a hundred years as a model organism in developmental biology research (Wilson, 1895). Knowledge of sea urchins in the field of biology has expanded to include (1) the effects of toxic substances on their immune system, reproduction, and development (Nobre et al, 2015;Brown et al, 2020;Pikula et al, 2020;Rendell-Bhatti et al, 2021), (2) the gene expression involved in sea urchin fertilization and development stages (Li et al, 2020;Wessel et al, 2021;Cui et al, 2022), (3) the nervous system (Wood et al, 2018;Martín-Durán and Hejnol, 2021;Formery et al, 2021), and (4) sea urchin genomes (Sodergren et al, 2006;Kudtarkar and Cameron, 2017;Kinjo et al, 2018;Warner et al, 2021). Sea urchins have also been studied in various aspects related to the impact of current changing environments, such as ocean acidification and global warming to their development and growth (Dworjanyn and Byrne, 2018;García et al, 2018;Zhao et al, 2018;Houlihan et al, 2020).…”

Recurrent Co-Option and Recombination of Cytokine and Three Finger Proteins in Multiple Reproductive Tissues Throughout Salamander Evolution

“…Gametic fusion is an essential biological process for the reproduction of most animal species, yet despite more than a century of research, it largely remains a molecular enigma as to how these highly specialized cells mechanistically accomplish this feat with species-specificity. The earliest studies of fertilization were in external fertilizing marine invertebrates where large numbers of gametes could be easily isolated for biochemical fractionation, and research continues for classic models such as sea urchins and abalone where the molecular interactions of sperm and egg proteins are best characterized ( Wilburn et al, 2019 ; Wessel et al, 2021 ). Advances in gene editing technologies have elevated genetic knockouts as one of the primary tools to identify gamete recognition proteins, especially in mammals, but high rates of gene duplication and functional redundancy in gametic proteins can confound such studies ( Baba et al, 1994 ; Isotani et al, 2017 ; Hirose et al, 2020 ).…”

Cell–Cell Mating Interactions: Overview and Potential of Single-Cell Force Spectroscopy

“…Unidentified sperm lectins initially bind species-specific sulfated glycans in the egg jelly coat, and then trigger the acrosome reaction [17][18][19]. Bindin is an acrosomal protein of sperm that can agglutinate conspecific eggs, but not heterospecific eggs [20]. Bindin-deleted sperm are infertile.…”