SCLT1 (sodium channel and clathrin linker 1), also known as CAP1A or hCAP-1A, is a 688 amino acid cytoplasmic protein that acts as a linker between the voltage-gated sodium channel, Na+ CP type X? and clathrin. SCLT1 is abundantly expressed in DRG (dorsal root ganglia) neurons and colocalizes with Na+ CP type X? SCLT1 regulates Na+ CP type X?channel activity by promoting channel internalization. SCLT1 exists as four alternatively spliced isoforms and is encoded by a gene located on human chromosome 4, which encodes nearly 6% of the human genome and has the largest gene deserts (regions of the genome with no protein encoding genes) of all human chromosomes. Defects in some of the genes located on chromosome 4 are associated with Huntington's disease, Ellis-van Creveld syndrome, methylmalonic acidemia and polycystic kidney disease.