Fig. 8. Schematic model for the proposed role of TNFIP6 in the stabilization of the cumulus extracellular matrix. For simplicity, only two hyaluronan chains are shown, but the proposed interactions can crosslink many of these chains creating a very stable hyaluronan meshwork. Asterisks indicate covalent interactions (ester bonds) between the heavy chains (HCs) and hyaluronan. All other protein-hyaluronan interactions are non-covalent. The presence of HC(1 or 2)-TNFIP6 complexes in the cumulus matrix was demonstrated in our previous study (Mukhopadhyay et al., 2001). Note that the exact structure of the HC-TNFIP6 has not yet been elucidated, therefore two hypothetical complex structures are shown. `?' indicates that no HC3-TNFIP6 complex has been detected yet. CS, chondroitin sulfate.