The CNNM4 (Cyclin M4) gene encodes metal transporter CNNM4 protein that belongs to the ACDP (ancient conserved domain protein ) family. This family of proteins is characterized by the presence of a highly conserved region found in evolutionarily divergent species from bacteria to mammals. Metal transporter CNNM4 protein is considered to be a metal ion transporter that plays a role in sensory neuron functions due to its interaction with COX11, an intracellular metal ion chaperone. It may also be involved with biomineralization and retinal function. Although the protein shares weak sequence similarity with the cyclin family, it has no cyclin-like function in vivo. Histological studies in mice show the localization of the protein within the retina and in developing teeth, where it is highly expressed.

Mutations in the CNNM4 protein have been implicated in the pathogenesis of Jalili syndrome, a condition characterized by the comorbid occurrence of cone-rod dystrophy and amelogenesis imperfecta. Additionally, CNNM4 gene mutations are also associated with Amaurosis Congenita Cone-Rod Type with Congenital Hypertrichosis.