Absence of spermatozoal CD46 protein expression and associated rapid acrosome reaction rate in striped field mice (Apodemus agrarius)

Abstract

Background: In rodents, the cell surface complement regulatory protein CD46 is expressed solely on the spermatozoal acrosome membrane. Ablation of the CD46 gene is associated with a faster acrosome reaction. Sperm from Apodemus flavicollis (yellow-necked field mice), A. microps (pygmy field mice) and A. sylvaticus (European wood mice) fail to express CD46 protein and exhibit a more rapid acrosome reaction rate than Mus (house mice) or BALB/c mice. A. agrarius (striped field mice) belong to a different Apodemus subgenus and have pronounced promiscuity and large relative testis size. The aim of this study was to determine whether A. agrarius sperm fail to express CD46 protein and, if so, whether A. agrarius have a faster acrosome reaction than Mus.

Progress of sperm IZUMO1 relocation during spontaneous acrosome reaction

“…Recently, it has been shown (Inoue et al 2011a) that mouse acrosome-reacted sperm pass through ZP and fertilise. In close correlation, it was then suggested that AR is triggered by cumulus oophorus cells (Clift et al 2009). However, again what happens with the amount of mouse sperm undergoing spontaneous AR remains unclear.…”

“…It is general knowledge that induced AR would never happen without capacitation and it is related to the molecular changes and dynamic movements of the actin cytoskeleton (Breitbart et al 2005, Dvorakova et al 2005, which is also responsible for IZUMO1 relocation ). Spontaneous AR is a well-documented phenomenon in the field IZUMO1 relocation during acrosome reaction mouse (Apodemus) species (Moore et al 2002, Johnson et al 2007, Clift et al 2009) and so far it is not understood whether these sperm are capable of fertilisation. Moreover, it is not clear whether sperm that undergo the spontaneous AR previously underwent capacitation.…”

“…The presented results imply that the actual IZUMO1 relocation may not be fully related to the acrosome stability. The sperm of wild Apodemus species do not translate the CD46 protein (Johnson et al 2007, Clift et al 2009 and have the same phenotype as CD46 knockout mice, displaying acrosome instability but with a higher fertility rate (Inoue et al 2003). In Apodemus sperm compared with BALB/c, the initial relocation of IZUMO1 takes place 20-30 min earlier, which is significant in terms of the timing of fertilisation.…”

“…In highly promiscuous field mice (Apodemus) with documented multiple paternities (Bryja & Stopka 2005, Bryja et al 2008, Johnson et al 2007, where up to 60% of their sperm undergo synchronised spontaneous AR (Moore et al 2002, Johnson et al 2007, Clift et al 2009), every minute may count in the sperm race to fertilise the egg. Several molecular mechanisms may be involved in speeding up the fertilising process.…”

Paternal Lymphocyte Alloimmunization in the Treatment of Infertility: A New Look at an Old Problem

“…В последнем случае антитела против от-цовских лимфоцитов получили название СКЛ-блокирующих факторов (БФ) [26]. Выработка аллореактивных антител у нерожавших женщин может индуцироваться экспрессируемыми на сперматозоидах TLX (трофобласт-лимфоцит-кроссреагирующими) антигенами, имеющими перекрестные детерминанты с НLA-молекулами II класса и эпитопами антигенов трофобласта [10], а при беременности индуцироваться анти-генными детерминантами клеток трофобласта и плода [35].…”