Seminal fluid; the Natural Guard of Seminal DNA

Abstract

The ability of foreign DNA to be introduced into the sperm cells faces many problems. These problems have been emerged from the existence of some inhibitory factors available in the seminal fluid. Add to that, other several factors are involved in this internalization. The purpose of this review is to evaluate the protective or interactive roles of these seminal fluid proteins in the process of foreign DNA internalization into the head of the sperm.

The ability of foreign DNA to be internalized inside sperm cell is become obvious before more than four decades (Brackett et al., 1971). But, the mechanism by which this foreign DNA has the ability to do so is still under debate. However, several papers described certain factors involved in this process. Thus, in order to describe the mechanism of sperm transfection by exogenous DNA, it is necessary to understand the following natural factors that are playing main roles in this scene and they include; inhibitory factor I (IF1), seminal fluid DNase, DNA binding proteins (DBPs), CD4, major histoincompatibility complex class II (MHCII), topoisomerase type II (TOPO II) and reverse transcriptase (RT). They can be further classified into three main groups.

The First group is represented by two factors found in seminal plasma; IF1 and DNase, this group is responsible about inhibiting the internalization process of exogenous DNA.  The fact which refers to the existence of one or more factors in seminal plasma that able to block sperm permeability must be taken into account. This means, extensive washing steps of ejaculate to remove seminal plasma is necessary and should be made before incubating sperm with exogenous DNA. Lauria and Gandolfi reviewed that seminal fluid inhibitors have two ways of inhibition to exogenous DNA, either directly or indirectly (Lauria and Gandolfi, 1993). These seminal plasma inhibitory factors may prevent transfection of intact sperm by foreign DNA (Camaioni et al., 1992).  Gandolfi showed that there is a consensus on the experiments made on seminal fluid of the ejaculated spermatozoa of mammals in the impermeability of sperm cell to the aggression of foreign DNA as long as seminal plasma is not removed (Gandolfi, 2000). Thus, seminal fluid prevents any foreign DNA from binding with its receptor on the sperm cell.