1p34.1

Various cancers

There are no genetic diseases or tumors where the role of PTCH2 has been clearly demonstrated by the unambiguous detection of PTCH2 mutations that disrupt the protein function.
The various suggestions of a possible role of PTCH2 in tumor development are generally circumstantial and are mostly based on chromosomal deletions that encompass the PTCH2 genomic region. The strongest evidence that PTCH2 hay have a role in tumor development comes from knock-out mouse model systems. Thus while Ptch2(-/-) mice have no obvious phenotype and do not develop tumors, if they are crossed with Ptch1 (+/-) heterozygotes, then the resulting Ptch2(-/-)Ptch1(+/-) mice developed at a higher incidence typical Ptch1(+/-) tumors such as medulloblastomas and rhabdomyosarcomas, suggesting genetic interactions between Ptch2 and Ptch1.
A possible role of PTCH2 in testicular development, acting as a Desert Hedgehog receptor has been suggested.
Overexpression of PTCH2 in basal cell carcinomas cannot compensate for mutated PTCH1 implying distinct roles of the two homologs. This can be rationalized by the very weak capacity of PTCH2 relative to PTCH1 in inhibiting the signaling molecule Smoothened. Additionally, based mostly on chromosomal deletion in the 1p32-34 region where the PTCH2 gene resides, a role in neurofibromas, pituitary tumors, medulloblastomas and meningiomas has been proposed. Also, PTCH2 is implicated in thymus, dental, prostate, ovary, and bone tissue development, as PTCH2 expression has been detected in these tissues.
In a mouse model, deletions of exons 5 to 17 in both Ptch2 alleles did not result in any obvious phenotype. However in the context of Ptch1+/- mice, this deletion of Ptch2 resulted in higher incidence and broader spectrum of tumor formation. In another mouse model of Ptch2, with a targeted insertion in exon 6 that would results in premature termination, the resulting homozygous mice were characterized with alopecia and epidermal hyperplasia.