RSL1D1, also known as CATX-11, PBK1, L12 or CSIG, is a 490 amino acid nuclear protein that belongs to the ribosomal protein L1P family. Expressed in placenta, RSL1D1 contains many phosphorylated amino acid residues and is encoded by a gene that maps to human chromosome 16p13.13. Chromosome 16 encodes over 900 genes in approximately 90 million base pairs, makes up nearly 3% of human cellular DNA and is associated with a variety of genetic disorders. The GAN gene is located on chromosome 16 and, with mutation, may lead to giant axonal neuropathy, a nervous system disorder characterized by increasing malfunction with growth. The rare disorder Rubinstein-Taybi syndrome is also associated with chromosome 16, though through the CREBBP gene which encodes a critical CREB binding protein. Signs of Rubinstein-Taybi include mental retardation and predisposition to tumor growth and white blood cell neoplasias.