Jean Yu’s collaboration with Rag & Bone on Friday isn’t her only fashion week debut. On Wednesday, she introduces a new collection, designed with Jack McCollough and Lazaro Hernandez, on the Proenza Schouler runway. Unlike the harness-like underpinnings at Rag & Bone, which featured hardware and backpacklike buckles, this new collection will be in keeping with Yu’s minimal sensibility. In fact, the patterns are lifted straight from her classic triangle bras, simply redone in a variety of colors and materials, some of which are Jean Yu firsts. For example: lace. “I don’t do lace. I find it too decorative and have always avoided it,” said Yu, noting that Proenza Schouler chief executive officer Shirley Cook is a client of hers. “But this was fun to do.” Also in the works for spring: a capsule collection of ready-to-wear basics by the designer, called 180 by Jean Yu.