Combine ricotta cheese, egg, spinach, salt, pepper and nutmeg in medium bowl; set aside. Spread 1/4 cup Sauce in 13 x 9-inch baking dish. Arrange 4 lasagna noodles, then top with 1/2 of the ricotta mixture, 1/4 cup sauce and 1/3 of the mozzarella cheese; repeat layers, ending with noodles. Top with remaining 1/4 cup Sauce.
Cover with aluminum foil and bake 40 minutes. Remove foil, then top with remaining mozzarella cheese. Bake an additional 10 minutes or until cheese is melted and lasagna is lightly browned. Let stand 10 minutes before serving.