How to extract a subgraph from a dot file

Question

I have a dot file generated by a software called egypt. The dot file contains many nodes and edges. If I use this dot file to draw a picture, it is very hard see the picture clearly as there are too many nodes. And what I need is only a subgraph starting from a node, and I don't need the whole picture.

Is there any way to draw a subgraph from a specified node (such as start_node) using this dot file?