Custom webpart with three column with three editable text

So, you want to have something like default text loaded to the editable region? If yes, then I did this:

Created a custom web part inheriting from CMSAbstractWebPart class.
This is my ascx code (just snippets for inspiration):
<div> <h1 > <cms:CMSEditableRegion ID="TileTitle" runat="server" /> </h1> <p > <cms:CMSEditableRegion ID="TileDesc" runat="server" RegionType="HtmlEditor" /> </p> </div>

Amd in the code behind, you need to use the right event of the control life cycle to call the LoadContent method. I did it in the OnPreRender:

 protected override void OnPreRender(EventArgs e)
    {
        base.OnPreRender(e);
        TileDesc.LoadContent("some content", true);
    }