We also provide here, for the first time, an analysis of prelamin A processing in fibroblasts from two unrelated patients with one of the most prevalent laminopathy mutations, LMNA-R644C, which alters an arginine residue near, but not at, the ZMPSTE24 processing site in prelamin A between residues Y646 and L647. This evidence concerns the gene LMNA and laminopathy.