The RAIG family member, GPRC5D, is associated with hard-keratinized structures.

@article{Inoue2004TheRF,
  title={The RAIG family member, GPRC5D, is associated with hard-keratinized structures.},
  author={Shinichi Inoue and Tadahiro Nambu and Toshiyasu Shimomura},
  journal={The Journal of investigative dermatology},
  year={2004},
  volume={122 3},
  pages={565-73}
}
Retinoic acid-inducible gene-1 was originally identified as an orphan G-protein coupled receptor induced by retinoic acid. Three highly homologous oGPCR (GPRC5B, GPRC5C, and GPRC5D) have since been classified into the RAIG1 family. We describe here, the unique tissue distribution of GPRC5D and its mechanism of expression. Hybridization in situ has shown that GPRC5D is expressed in differentiating cells that produce hard keratin, including cortical cells of the hair shaft, the keratogenous zone… CONTINUE READING