Single-cell expression profiling of bat wing development.

Bats are the only true-flight mammals, with wings formed by elongated digits and wing membranes. Despite the uniqueness, the cellular and molecular aspects of bat wing development remain largely unknown. Here, we use single-cell transcriptomic sequencing to map ~39,000 cells from the limbs of bats (Rhinolophus sinicus) at developmental stages Carnegie stages (CS) 16, 18, and 20. We identify 16 distinct cell populations, including a specific mesenchymal progenitor population (PDGFD+) in bat forelimbs, which may differentiate into the interdigital membrane and promote bone cell proliferation. Developing bat forelimbs exhibit prolonged chondrogenesis and delayed osteogenesis, resulting in more chondrocytes and fewer osteoblasts. The integrative analyses of data from single-cell and bulk RNA sequencing highlight the crucial roles of Notch signaling activation and WNT/β-catenin signaling suppression in bat forelimb development. Our findings provide a comprehensive single-cell atlas of developing bat limbs, offering insights into the mechanisms underlying bat wing development.