Peanut agglutinin specifically binds to a sperm region between the nucleus and mitochondria in tunicates and sea urchins

Peanut agglutinin (PNA) is an established marker of the mammalian acrosome. However, we observed that PNA specifically binds to a unique intracellular structure alongside the nucleus in ascidian sperm. Here, we characterize the PNA‐binding structure in sperm of marine invertebrates. PNA bound to the...

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Bibliographic Details
Published in:Molecular reproduction and development 2018-06, Vol.85 (6), p.464-477
Main Authors: Nakazawa, Shiori, Shirae‐Kurabayashi, Maki, Sawada, Hitoshi
Format: Article
Language:English
Subjects:
Animals
Calcium
Calcium ionophores
Cell Nucleus - metabolism
Ciona - cytology
Ciona - metabolism
Concanavalin A
Echinoidea
Endoplasmic reticulum
fertilization
Intracellular
intracellular structure
invertebrate
Invertebrates
Ionomycin
Lectins
Male
Mice
Mitochondria
Mitochondria - metabolism
Nuclei
peanut agglutinin
Peanut Agglutinin - chemistry
Polysaccharides
Sea Urchins - cytology
Sea Urchins - metabolism
Sperm
Tunicata
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Summary:Peanut agglutinin (PNA) is an established marker of the mammalian acrosome. However, we observed that PNA specifically binds to a unique intracellular structure alongside the nucleus in ascidian sperm. Here, we characterize the PNA‐binding structure in sperm of marine invertebrates. PNA bound to the region between the mitochondrion and nucleus in spermatozoa of ascidians, sea urchins, and an appendicularian. However, PNA‐binding substances were not exposed by the calcium ionophore ionomycin in three ascidian species, indicating that it is a distinct structure from the acrosome. Instead, the ascidian PNA‐binding region was shed with the mitochondrion from the sperm head via an ionomycin‐induced sperm reaction. The ascidian PNA‐binding substance appeared to be solubilized with SDS, but not Triton X–100, describing its detergent resistance. Lectins, PHA‐L4, SSA, and MAL‐I were detected at an area similar to the PNA‐binding region, suggesting that it contains a variety of glycans. The location and some of the components of the PNA‐binding region were similar to known endoplasmic reticulum (ER)‐derived structures, although the ER marker concanavalin A accumulated at an area adjacent to but not overlapping the PNA‐binding region. Therefore, we conclude that ascidian sperm possess a non‐acrosomal, Triton‐resistant, glycan‐rich intracellular structure that may play a general role in reproduction of tunicates and sea urchins given its presence across a wide taxonomic range.
ISSN:1040-452X
1098-2795
DOI:10.1002/mrd.22982