The gene encoding DYX1C1 maps in the 15q21 region, which is disrupted by a translocation t(2;15)(q11;q21) and segregates with dyslexia. Two sequence changes in DYX1C1, including one involving the translation initiation sequence and an Elk-1 transcription factor binding site (-3G --> A) and a codon (1249G --> T), introduce a premature stop codon and truncate the protein by 4 amino acids. DYX1C1 encodes a nuclear tetratricopeptide repeat domain protein that is dynamically regulated in brain. In human brain, DYX1C1 protein localizes to a fraction of cortical neurons and white matter glial cells. It is also expressed in lung, kidney and testis.