Fe65L2 is a 486 amino acid protein that contains one WW domain and two PID domains. Binding to the intracellular domain of the ∫-Amyloid precursor protein, Fe65L2 is thought to modulate the internalization and, therefore, the accessibility and function of ∫-Amyloid. Via its ability to control the intracellular accumulation of ∫-Amyloid, Fe65L2 is thought to play a role in the pathogenesis of Alzheimer's disease. Fe65L2 exists as four alternatively spliced isoforms designated isoform I, isoform II, isoform III and isoform IV. Fe65L2 interacts with Amyloid-like protein and is encoded by a gene located on human chromosome 5, which contains 181 million base pairs and comprises nearly 6% of the human genome. Deletion of the p arm of chromosome 5 leads to Cri du chat syndrome, while deletion of the q arm or of chromosome 5 altogether is common in therapy-related acute myelogenous leukemias and myelodysplastic syndrome.