Protocadherins were discovered by Shintaro Suzuki's group, when they used PCR to find new members of the cadherin family. The PCR fragments that corresponded to Protocadherins were found in vertebrate and invertebrate species. This prevalence in a wide range of species suggested that the fragments were part of an ancient cadherin and were thus termed "Protocadherins" as the "first cadherins".
It turns out that protocadherins are the largest subfamily of cadherins present in mammals  as differentiators of specific cells. Their function has also been linked to homophilic adhesion, and the protocadherins have been identified as mediators of this adhesion. However, further evidence suggests that protocadherins can also act as signaling or receptor molecules.
- Sano K, Tanihara H, Heimark RL, et al. (June 1993). "Protocadherins: a large family of cadherin-related molecules in central nervous system". EMBO J. 12 (6): 2249–56. PMC 413453. PMID 8508762.
- Hulpiau, P.; van Roy, F. (2009). "Molecular evolution of the cadherin superfamily". Int J Biochem Cell Biol. 41 (2): 349–69. doi:10.1016/j.biocel.2008.09.027. PMID 18848899
- Unterseher F, Hefele JA, Giehl K, De Robertis EM, Wedlich D, Schambony A (August 2004). "Paraxial protocadherin coordinates cell polarity during convergent extension via Rho A and JNK". EMBO J. 23 (16): 3259–69. doi:10.1038/sj.emboj.7600332. PMC 514506. PMID 15297873.
- Kalmady SV, Venkatasubramanian G (October 2008). "Evidence for positive selection on Protocadherin Y gene in Homo sapiens: Implications for schizophrenia". Schizophr. Res. 108 (1–3): 299–300. doi:10.1016/j.schres.2008.09.015. PMID 18938061.
- Alagramam KN, Yuan H, Kuehn MH, et al. (August 2001). "Mutations in the novel protocadherin PCDH15 cause Usher syndrome type 1F". Hum. Mol. Genet. 10 (16): 1709–18. doi:10.1093/hmg/10.16.1709. PMID 11487575.[dead link]
- Koppelman GH, Meyers DA, et al. (November 2009). "Identification of PCDH1 as a Novel Susceptibility Gene for Bronchial Hyperresponsiveness". Respir. Crit. Care Med. 180 (10): 929–935. doi:10.1164/rccm.200810-1621OC. PMC 2778155. PMID 19729670.