LMBR1 is a 490 amino acid multi-pass membrane protein that is widely expressed with strongest expression in heart and pancreas. Belonging to the LIMR family, LMBR1 shares 95% sequence identity with the mouse protein and may play crucial role in the evolution of limb and skeletal system. LMBR1 is critical for expression of sonic hedgehog (Shh) in the developing posterior limb bud mesenchyme. Mutations in the gene encoding LMBR1 is the cause of several rare conditions such as acheiropody (ACHP) and syndactyly type 4 (SDYT4). ACHP is an autosomal recessive inherited disorder characterized by bilateral congenital amputations of the hands and feet. LMBR1L (limb region 1 protein homolog-like), also known as LIMR (Lipocalin-1-interacting membrane receptor), is a 489 amino acid multi-pass membrane protein that is thought to act as a receptor for Lipocalin-1 and may also assist in its endocytosis.