ReactJS Mixin Method Override

How can I create a method on a ReactJS Mixin such that I'm allowed to override it in the Component definition?

HTML

<script src="http://fb.me/JSXTransformer-0.10.0.js"></script>
<script src="http://fb.me/react-with-addons-0.10.0.js"></script>
<script src="http://fb.me/react-js-fiddle-integration.js"></script>

JavaScript 1.7

/** @jsx React.DOM */
 
var Main = React.createClass({
    render: function() {
       var result = this.doRender();
       
       var style = {
         border:'1px solid red'
       };
       
       result.style = style;
       
       return result;
    },
    
    doRender: function() {
        return (
          <div>Test</div>
        );
    }
});

React.renderComponent(<Main/>, document.body);