A hyaluronidase activity of the sperm plasma membrane protein PH-20 enables sperm to penetrate the cumulus cell layer surrounding the egg.
A typical mammalian egg is surrounded by an outer layer of about 3,000 cumulus cells embedded in an extracellular matrix rich in hyaluronic acid. A current, widely proposed model is that the fertilizing sperm, while it is acrosome intact, passes through the cumulus cell layer and binds to the egg zona pellucida. This current model lacks a well-supported explanation for how sperm penetrate the cumulus layer. We report that the sperm protein PH-20 has a hyaluronidase activity and is present on the plasma membrane of mouse and human sperm. Brief treatment with purified, recombinant PH-20 can release all the cumulus cells surrounding mouse eggs. Acrosome intact mouse sperm incubated with anti-PH-20 antibodies can not pass through the cumulus layer and thus can not reach the zona pellucida. These results, indicating that PH-20 enables acrosome intact sperm to penetrate the cumulus barrier, reveal a mechanism for cumulus penetration, and thus provide the missing element in the current model.
Lin
Y
Y
Department of Physiology, University of Connecticut Health Center, Farmington 06030.
Mahan
K
K
Lathrop
W F
WF
Myles
D G
DG
Primakoff
P
P
D000818:Animals; D001483:Base Sequence; D015815:Cell Adhesion Molecules / Q000378:metabolism*; D002462:Cell Membrane / Q000201:enzymology*; D017931:DNA Primers / Q000737:chemistry; D005260:Female; D006801:Humans; D006821:Hyaluronoglucosaminidase / Q000378:metabolism*; D008253:Macaca mulatta; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D013084:Sperm-Ovum Interactions; D013094:Spermatozoa / Q000201:enzymology*; D010738:Type C Phospholipases / Q000378:metabolism
D015815:Cell Adhesion Molecules; D017931:DNA Primers; D010738:Type C Phospholipases; D006821:Hyaluronoglucosaminidase; C066852:hyaluronidase PH-20