Lectin spatial immunolocalization during in vitro capacitation in Tursiops truncatus spermatozoa.

Laura Robles-Gómez,Daniel García-Párraga,Alejandro Romero,María José Gómez-Torres,María Del Carmen Fuentes-Albero,Paula Sáez-Espinosa,Natalia Huerta-Retamal

doi:10.21451/1984-3143-ar2019-0083

Abstract

Spermatozoa interactions with the female reproductive tract and oocyte are regulated by surface molecules such as glycocalyx. The capacitation process comprises molecular and structural modifications which increase zona pellucida binding affinity. Lectins allowed us to describe glycocalyx changes during maturation, capacitation and acrosome reaction. This study had as its aim to identify lectin binding patterns using four lectins with different carbohydrate affinity in bottlenose dolphin (Tursiops truncatus) spermatozoa both before and after in vitro capacitation. Two semen samples from the same dolphin obtained on consecutive days were used, with four different lectin binding patterns becoming visible in both samples before and after capacitation. A highly stained equatorial segment with prolongations at the edges appeared as the most frequent pattern with Wheat germ agglutinin (WGA) in uncapacitated spermatozoa. However, it was homogeneously distributed over the acrosomal region after capacitation. Instead, the use of Peanut agglutinin (PNA) resulted in most spermatozoa showing high labelling in the acrosomal periphery region before capacitation and a homogeneous staining in the acrosomal region within the population of capacitated spermatozoa. Nevertheless, the most representative patterns with Concavalin A (ConA) and Aleuria aurantia agglutinin (AAA) lectins did not change before and after capacitation, labelling the acrosomal region periphery. These findings could contribute to the understanding of the reproductive biology of cetaceans and the improvement of sperm selection techniques.

Highlights

Most of the interactions between the spermatozoon and its environment inevitably have their starting point in an interplay with the sperm glycoprotein and glycolipid covering; the tendency to associate the acquisition of a mature glycocalyx with the achievement of a full sperm fertilizing ability (Schröter et al, 1999)
Lectin binding patterns were named as follows: Pattern 1(P1): highly labelled acrosomal region; Pattern 2 (P2): equatorial segment stained with elevations at the edges; Pattern 3 (P3): highly labelled edges of the acrosomal region, and Pattern 4 (P4): highly stained equatorial segment and weak fluorescence in the acrosomal region
Normal morphology values of 90% have been described in previous studies dedicated to T. truncatus semen (Migliorisi et al, 2011; van der Horst et al, 2018), which suggests that seminal parameters could be better conserved in dolphins

Summary

Introduction

Most of the interactions between the spermatozoon and its environment inevitably have their starting point in an interplay with the sperm glycoprotein and glycolipid covering; the tendency to associate the acquisition of a mature glycocalyx with the achievement of a full sperm fertilizing ability (Schröter et al, 1999). Sperm glycocalyx composition in mammals has already been studied by a variety of authors (Bearer and Friend, 1990; Schröter et al, 1999; Töpfer-Petersen, 1999; Tecle and Gagneux, 2015), most of whom used lectins. These molecules are proteins or glycoproteins of a non-immune nature that bind to specific membrane carbohydrate sequences which could be potentially involved in primary oocyte recognition (Osawa and Tsuji, 1987).

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