15 exons (with a particularly large 15th exon).

9.0 kb mRNA; 8538 bp open reading frame.

2843 amino acids; 310 kDa.

APC is a classical tumour suppressor protein. The APC gene product indirectly regulates transcription of a number of critical cell proliferation genes, through its interaction with the transcription factor beta catenin. APC binding to beta catenin leads to ubiquitin-mediated beta catenin destruction; loss of APC function increases transcription of beta catenin targets. These targets include cyclin D, C-myc, ephrins and caspases. APC also interacts with numerous actin and microtubule associated proteins. APC itself stabilizes microtubules. Homozygous APC truncation has been shown to affect chromosome attachment in cultured cells. Roles for APC in cell migration have been demonstrated in vitro and in mouse models.

A second family member, APC2, is located on 19p13.3 (see non-annotated genes).

Germline mutations of APC cause a spectrum of diseases under the broad category of familial adenomatous polyposis (FAP).
Mutations typically cluster in or just distal to the armadillo repeat region and truncate the protein near its middle. It is not known which is pathophysiologic - absence of the full-length protein or presence of the truncated version; evidence exists for both. The second hit creates another truncation or gene deletion. There is some evidence that the position of the first hit in the gene determines the pattern of the second hit.
Rare hypomorphic mutations cause attenuated polyposis.

Both copies of the APC gene are mutated in 80% of sporadic colorectal tumours.