Preheat oven to 400 degrees. Lightly coat muffin tins with cooking spray, or use liners. In a large bowl, stir together the all purpose flour, rye flour, oat bran, cornmeal, sugar, baking powder, and salt until well combined. Make a well in the center of the flour mixture. In a small bowl, stir together the milk, oil, and egg, then pour the mixture into the well of the dry ingredients. Stir until just combined. Spoon the batter into the muffin cups filling them 2/3 full. Bake for 20 minutes, or until a toothpick inserted in the center comes out clean. Let the muffins cool in the pan for 5 minutes, then turn them out onto a wire rack to finish cooling.