The expression of certain proteins involved in BTB formation, including Claudin 11 (134), JAM3, Nectin 2 and certain Cadherins, was the same in the tissue of patients with SCOS or even increased when compared with fertile patients, while GJB2, which codes for Connexin 26, was markedly reduced (130). The gene discussed is CLDN11; the disease is small cell osteogenic sarcoma.