Kapasitasyonun Moleküler Temelleri
Erkek ve dişi gametler; yolk kesesi duvarı endoderminden gelişerek, gonad taslaklarına doğru ilerleyen primordial germ hücrelerinden köken alır. Gametler gonadlarda bir dizi mitotik bölünme geçirerek sayılarını artırırlar. Primordial germ hücrelerinden köken alan spermatogonyumlar pubertede spermatogenez ve spermiyogenez sonrasında olgun sperm halini alırlar. Kapasitasyon, olgun spermin dişi genital yollarında metafaz 2'deki oositi dölleme yeteneği kazandığı bütün moleküler ve fizyolojik olayları içeren bir reaksiyondur. Kapasitasyonu başlatan moleküler olaylar arasında sperm membranından kolesterolün ayrılması, artmış membran akışkanlığı, hücre içi iyon konsantrasyonunun modülasyonu, sperm membran hiperpolarizasyonu ve protein tirozin fosforilasyonunda artış sayılabilir. Kapasitasyon sırasında spermatozoonlar oosit etrafındaki korona radiata hücreleri arasına penetrasyon ve zona pellusidaya bağlanma yeteneği kazanır. Bu bağlanma; spermatozoonun akrozomal membranı ile oosit zona pellusidası arasında fenestrasyonların gelişmesiyle gerçekleşen akrozom reaksiyonunu tetikler. Oosit-sperm füzyonundan sonra sperm ve oosit pronukleusları zigotu oluşturmak üzere birleşirler.
Anahtar Kelimeler:
Spermatozoon, Kapasitasyon, Tirozin fosforilasyonu, Akrozom reaksiyonu, Fertilizasyon
Molecular Aspects of Capacitation
Male and female gamets are derived from the primordial germ cells, which migrate from the wall of the yolk sac toward the developing gonads. Following a series of mitotic divisions these cells increase in number at the gonads. The primordial germ cells differentiate into spermatogonia and take the form of mature spermatozoa after spermotogensis and spermotogenesis at puberty. Capacitation is the reaction, which includes all of the molecular and physiological events of mature sperm to gain the ability of fertilizing oocytes at metaphase 2 in the female genital tract. Some molecular events significant in the initiation of capacitation have been identified as cholesterol efflux from the sperm plasma membrane, increased membrane fluidity, modulation of intracellular ion concentration, hyperpolarization of the sperm plasma membrane and increased protein tyrosine phosphorylation. During capacitation, the spermatozoa acquires the ability to penetrate the corona radiata and to bind to the zona pellucida. This binding triggers acrosome reaction which occurs by the development of multiple fenestrations between the outer acrosomal membrane and the plasma membrane of the spermatozoon. After the fusion of oocyte and sperm plasma membranes, sperm and oocyt pronuclei are joined together to compose the zygote.
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- ISSN: 1300-3755
- Yayın Aralığı: Yılda 4 Sayı
- Başlangıç: 1992
- Yayıncı: Çukurova Üniversitesi Tıp Fakültesi