The present invention relates proteins from the group consisting of CNNM1, CNNM2, CNNM 3 and CNNM4, its derivatives or fragments thereof for use as a medicament, for treatment and or diagnostic purposes. The invention further relates to a human genomic DNA, cDNA or mRNA sequence encoding for a functional protein chosen from the group consisting of CNNM1, CNNM2, CNNM3 and CNNM4 and functional derivatives or fragments thereof.