GMNN and Merkel cell skin cancer: As depicted in Figure 2, the initial stages of MCC differentiation involve protein interactions, including GEMININ (encoded by GMNN), GEMC1 (Geminin coiled-coil-domain-containing protein 1, encoded by GMNC), MCIDAS, E2F transcription factor (E2F4/5), and DEUP1 [11,12,13].