学院的Nancy是个可爱的小姑娘,是华人第二代。她的研究是有关眼内微循环,正在完成她的博士论文 “Visualising the internal micro-circulation of the ocular lens in rodents”。Nancy给人的印象很阳光,开朗。去年开会时我们的talk在同一session, 并听过她的两次博士项目进展报告。她思路敏捷,语言清晰自信,讲座富有感染力。第二次报告会上她说刚从英联邦运动会归来(大会在印度举办,但击剑分项目在墨尔本)。但我们不知道她,这个小小个的姑娘,竟然获得击剑(fencing)项目的铜牌(团体一员)!
Involvement of MP20 in the formation of macro-molecular diffusion pathway
Cataracts are the leading cause of blindness. In order to understand this disease, we must first understand the underlying physiology of a normal lens.Traditionally, intercellular communication in the avascular lens was thought to be mediated by gap junction (GJ) channels. More recently, an alternative and parallel intercellular communication pathway has been discovered, that develops in the inner-cortex permeable to large macro-molecules and do not normally pass through GJ channels. MP20, a putative lens specific adhesion protein has been implicated in the formation of this macromolecular-diffusion-pathway (MDP), since in MP20 knock-out mice the MDP did not form. In the rat lenses, MP20 has been show to be initially localised in the cytoplasm of differentiating fibre cells, and inserts into the membranes following nuclei degradation, suggesting that MP20 insertion may play a role in the formation of the MDP. In the mouse lens, MP20 insertion into the membrane precedes the loss of nuclei unlike in the rat lens.
To further investigate the relationship between MP20 and MDP formation we have utilised immunocytochemistry and Two-Photon-Excitation-Flash-Photolysis (TPEFP) on half-cut rodent lens loaded with the GJ impermeable caged fluorescein-dextran (MW=10kDa) to correlate MP20 insertion with the formation of the MDP in rodent lens. By exploiting the species specific differences in the differentiation dependent insertion of MP20 detected by immunocytochemistry, and the TPEFP induced transfer of Fluorescein-dextran as a functional indicator of MDP formation, we have shown that formation of the MDP correlates with the insertion of MP20 in both rat and mouse lenses.
In the absence of MP20, caged fluorescein-dextran is restricted within the source cell unable to diffuse to the neighbouring fibre cells indicating the absence of the MDP. This is the first time real-time functional technique has been used to show the importance of MP20 in the formation of MDP.