ECRG4 (esophageal cancer-related gene 4 protein), also known as augurin or C2orf40, is a 148 amino acid secreted protein. Belonging to the augurin family, ECRG4 is thought to be a hormone. It has also been suggested that ECRG4 may act as a tumor suppressor. The gene that encodes ECRG4 maps to human chromosome 2, which consists of 237 million bases encoding over 1,400 genes, making up approximately 8% of the human genome. A number of genetic diseases are linked to genes on chromosome 2. Harlequin icthyosis, a rare and morbid skin deformity, is associated with mutations in the ABCA12 gene. The lipid metabolic disorder sitosterolemia is associated with ABCG5 and ABCG8. An extremely rare recessive genetic disorder, Alström syndrome is due to mutations in the ALMS1 gene. Interestingly, chromosome 2 contains what appears to be a vestigial second centromere and vestigial telomeres which gives credence to the hypothesis that human chromosome 2 is the result of an ancient fusion of two ancestral chromosomes.