In humans, CD46 has been detected on the acrosomal membrane in sperm, in contrast to widespread surface expression on somatic cells where it plays a key role in the protection from complement attack. In rodents, CD46 is expressed solely on the acrosomal membrane of mature sperm and their immediate precursors, spermatids. A monoclonal antibody against the short consensus repeat (SCR1) ectodomain of CD46 blocks binding of human sperm to zona-free oocytes in vitro. However, CD46-knockout mice are fertile and have an accelerated spontaneous acrosome reaction. Wild-caught field mice (Apodemus) also exhibit a rapid acrosome reaction and CD46 is not expressed in Apodemus sperm. CD46 may, therefore, play a role in stabilization of the acrosomal membrane. Two other complement regulatory proteins, CD55 and CD59, are localized on the plasma membrane of mammalian sperm. In human sperm, CD55 and CD59 are expressed also on the inner acrosomal membrane. It remains to be clarified what is the role of CD46, CD55 and CD59 during fertilization and what are the advantages of not expressing CD46 in field mice sperm.
Specific transcription factors participate in the decision making process that controls cell fate and differentiation. They function in the environment of chromatin and directly affect its structure and activity. This influence is especially apparent during the development regulation of gametes and in the course of the development of an early embryo. This review focuses on the role that Snf2h (Smarca 5) and Brg1 (Smarca 4), two factors belonging to the SWI/SNF2 family, play in the establishment of chromatin structure in germinal and early embryonic development.
The presence of large amounts of proteins in mammal urine is usually associated with a pathological condition and indicates serious renal lesions. However, there are few species with obligate proteinuria indicating that they must derive some benefit from this condition. Urinary proteins have been most extensively studied in the house mouse and the rat, and findings to date indicate that their function in intraspecific communication is complex and not yet fully understood. Other proteins of the same protein family as MUPs have been also found in urine of some other rodent species, and still less is known about these. In this study we demonstrate the existence of urinary lipocalins in Mastomys coucha for the first time. Our results support the hypothesis that urinary proteins may play an important role in chemical communication, and level of polymorphism of these proteins in different rodents may help us to understand their specific function.