24 exons, exon 24 is non-coding; 34 kb

alternate splicing: 3 different 5 termini; 6.5 kb mRNA; coding sequence: CDS 1 ... 4344

glycoprotein; 12 transmembrane domains, 2 extra cellular loops, intracellular N-term and C-term and sterol-sensing domain (SSD)

widely expressed at low levels; increased levels in cells receiving a hedgehog signal

transmembrane protein, cellular membrane, intracellular vesicles

part of a signalling pathway; opposed by the gene products of hedgehog genes; transmembrane protein; is thought to have a repressive activity on cell proliferation; the recent demonstration of NBCCS syndrome (see below) as a chromosome instability syndrome suggests that this protein has a role in DNA maintenance, repair and/or replication

patched (drosophila segment polarity gene), PTCH2 (human gene with unknown function)

germ-line mutations lead to protein truncation in naevoid basal cell carcinoma syndrome (NBCCS) patients (see below); mutations types are variable : nucleotide substitutions (missense/nonsense), small deletions, or small insertions mainly, leading to protein truncation; these mutations have been observed in most exons; there is, so far, no hot-spot.

mutation and allele loss events in basal cell carcinoma, in NBCCS and in sporadic basal cell carcinoma are, so far, in accordance with the two-hit model for neoplasia, as is found in retinoblastoma; mutation and allele loss have also been found in sporadic primitive neuroectodermal tumours (PNETs), sporadic medulloblastomas and in a few cases of esophageal squamous cell carcinoma and invasive transitional cell carcinoma of the bladder; mutations have also been reported in a low frequency of sporadic trichoepitheliomas and in sporadic odontogenic keratocysts