Preheat oven to 375 degrees F. Lightly coat twelve 2 1/2-inch muffin cups with cooking spray; set aside. In a medium bowl stir together wheat bran, flour, cornmeal, baking soda, baking powder, and salt. Make a well in the center of flour mixture; set aside.
In a small bowl combine egg, buttermilk, 3 tablespoons syrup, and oil. Add egg mixture all at once to flour mixture. Stir just until moistened (batter should be slightly lumpy). Spoon batter into the prepared muffin cups, filling each about one-third full. Bake about 10 minutes or until a wooden toothpick inserted in the centers comes out clean. Cool in muffin cups on a wire rack for 10 minutes. Remove from muffin cups. Cut each muffin in half horizontally.
Meanwhile, in a medium bowl combine sausage and mustard. Shape mixture into twelve 2 1/2-inch-diameter patties. Coat a medium nonstick skillet with cooking spray; heat skillet over medium-high heat. Add patties; cook about 6 minutes or until brown, turning once.
To serve, place bottoms of muffins on a serving platter. Top with half of the apple slices, the sausage patties, the remaining apple slices, and 2 tablespoons syrup. Replace tops of muffins. If desired, secure with wooden skewers.