Human Pecanex proteins are homologs of the Drosophila Pecanex protein, a maternal-effect neurogenic protein that is involved in normal development of the fly nervous system. Three human Pecanex homologs exist, designated Pecanex, Pecanex 2, also known as PCNXL2 (pecanex-like 2), and Pecanex 3. Pecanex 2 is a 2,137 amino acid multi-pass membrane protein that exists as five alternatively spliced isoforms characterized by high mutational frequencies and biallelic mutations in colorectal tumors, thereby likely functioning as a target gene in these tumors. Pecanex 2 is encoded by a gene that maps to human chromosome 1q42.2, which is linked to an inherited microduplication. This microduplication that includes Pecanex 2 may play a role in autism and mild mental retardation.