- Oligophrenin 1 (OPHN1)
- Opticin (OPTC)
- Osteosarcoma Amplified 9 (OS9)
- Oxysterol Binding Protein (OSBP)
- Osteoclast Associated Receptor (OSCAR)
- Osteopetrosis Associated Transmembrane Protein 1 (OSTM1)
- Organic Solute Transporter Beta (OSTb)
- Otoferlin (OTOF)
- Otoraplin (OTOR)
- Oviductal Glycoprotein 1 (OVGP1)
- Optic Atrophy 3 (OPA3)
- Optineurin (OPTN)
- Oxoguanine Glycosylase 1 (OGG1)
- Oxytocin Receptor (OXTR)
- Tumor Protein p73 (TP73)
