To elucidate the involvement of these somatic cells within human spermatogenesis and RA action, a recent study used quantitative polymerase chain reaction (q-PCR) to measure the expression of all RAR and RXR isoforms in healthy human testes compared with testes diagnosed with Sertoli cell-only syndrome (SCOS) and maturational arrest (MA) [36]. Here, RARA is linked to small cell osteogenic sarcoma.