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 .
Mutations in protocadherin genes and their expression may play a role in schizophrenia  and Usher Syndrome.
Notes and References
- Sano K, Tanihara H, Heimark RL, et al. Protocadherins: a large family of cadherin-related molecules in central nervous system. Embo J.. 12. 6. 2249–56. 1993. June. 8508762. 413453.
- Unterseher F, Hefele JA, Giehl K, De Robertis EM, Wedlich D, Schambony A. Paraxial protocadherin coordinates cell polarity during convergent extension via Rho A and JNK. Embo J.. 23. 16. 3259–69. 2004. August. 15297873. 514506. 10.1038/sj.emboj.7600332.
- Kalmady SV, Venkatasubramanian G. Evidence for positive selection on Protocadherin Y gene in Homo sapiens: Implications for schizophrenia. Schizophr. Res.. 2008. October. 18938061. 10.1016/j.schres.2008.09.015.
- Alagramam KN, Yuan H, Kuehn MH, et al. Mutations in the novel protocadherin PCDH15 cause Usher syndrome type 1F. Hum. Mol. Genet.. 10. 16. 1709–18. 2001. August. 11487575. 10.1093/hmg/10.16.1709.