The growth of world population in general and Indonesia in particular continues to increase from year to year. The impact of this population increase is a decrease in people’s quality of life. To control population growth, it is necessary to increase the role of family planning through the use of contraception.
Until now, contraceptive methods are dominated by women and there is a lack of innovation to increase the role of men. The development of non-hormonal male contraceptives by targeting proteins or genes involved in the spenna maturation process in the epididymis is very promising for controlling male fertility. One candidate epididymis gene that can be used as a contraceptive is D4b20. The study results show that Defb20 has characteristics of an epididymal protein which plays a role in the sperm maturation process, such as being specifically expressed in the epididymis during puberty, regulated by androgens and is a secretory protein. This indicates a specific function of Defh20 in the epididymis, but data from previous studies have not yet confirmed the gene’s function in sperm maturation. The research was carried out by Luluk Yunaini (FKUI Biomedical Science Doctoral Program student and teaching staff at the FKUI Medical Biology Department) under the guidance of a team of promoters headed by Dwi Ari Pujianto Ph.D. carried out functional analysis of Dejb20 using in silico and in vitro study approaches. The in silico approach is by carrying out bioinformatic predictions of the interaction of Defb20 with other proteins, while the in vitro approach is carried out by suppressing Dejb20 gene expression using the Defb20 siRNA transfection method in mouse epididymis culture cells. Suppression of defb20 gene expression aims to stop the formation of DEFB20 protein, resulting in a decrease in Defb20 protein levels in mouse epididymal head culture cells.
The results of research using an in silico study approach illustrate the interaction between the Detb20 protein and the CatSper protein, which is an ion channel protein. The mouse defb20 protein can interact with both the mouse CatSper protein and the human CatSper protein. These results predict that Defb20 plays a role in spenna maturation through calcium signaling processes. Detb20 is thought to block the ion transfer region in the CatSper protein, thereby preventing premature capacitation and/or spontaneous acrosome reactions so that sperm can fuse with the egg cell optimally.
Human sperm cells co-cultured with mouse epididymal head epithelial cells transfected with Defb20 siRNA showed an increase in total calcium levels followed by a significant decrease in motility. In addition, there was a trend of decreasing tyrosine phosphorylation, increasing acrosome reaction and Caspase-3 activity. These results indicate that the absence of Defb20 protein can induce sperm cell death.
The results of this study provide a good understanding of the interactions of DEFB20 with other proteins and their implications for sperm function. Apart from that, this information opens up insight into the potential of DEFB20 as an important protein for overcoming fertility problems related to spenna cell motility and capacitation. On the other hand, inhibiting the Detb20 protein has the potential to be developed as a non-hormonal male contraceptive.
Dr. Luluk Yunaini, S.Sc., M.Biomed obtained a Doctorate degree with the title of Summa Cum Laude with a perfect GPA of 4.00. Apart from that, Dr. Luluk is the first graduate of the research class (degree by research) in the Biomedical Sciences Doctoral Program – Faculty of Medicine, University of Indonesia.