PTCH1 isoform 1b is the major transcript in the development of basal cell nevus syndrome

Mutations of PTCH1 gene in two pedigrees with bifid rib-basal cell nevus-jaw cyst syndrome

Two male patients with bifid rib-basal cell nevus-jaw cyst syndrome (BCNS) were admitted to Department of Stomatology, the First Affiliated Hospital of Bengbu Medical College due to radiological findings of multiple low density shadows in the jaw. Clinical and imaging findings showed thoracic malformation, calcification of the tentorium cerebellum and falx cerebrum as well as widening of the orbital distance. Whole exon high-throughput sequencing was performed in two patients and their family members. The heterozygous mutations of c.C2541C>A(p.Y847X) and c.C1501C>T(p.Q501X) in PTCH1 gene were detected in both patients. Diagnosis of BCNS was confirmed. The heterozygous mutations of PTCH1 gene locus were also found in the mothers of the two probands. Proband 1 showed clinical manifestations of low intelligence, and heterozygous mutations of c.C2141T(p.P714L) and c.G3343A(p.V1115I) were detected in FANCD2 gene. Proband 2 had normal intelligence and no FANCD2 mutation. The fenestration decompression and curettage of jaw cyst were performed in both patients. Regular follow-up showed good bone growth at the original lesion, and no recurrence has been observed so far.

Genetic control of tumor development in malformation syndromes

One of the questions that arises frequently when caring for an individual with a malformation syndrome, is whether some form of tumor surveillance is indicated. In some syndromes there is a highly variable increased risk to develop tumors, while in others this is not the case. The risks can be hard to predict and difficult to explain to affected individuals and their families, and often also to caregivers. The queries arise especially if syndrome causing mutations are also known to occur in tumors. It needs insight in the mechanisms to understand and explain differences of tumor occurrence, and to offer optimal care to individuals with syndromes. Here we provide a short overview of the major mechanisms of the control for tumor occurrences in malformation syndromes.

A novel splicing mutation of PTCH1 in a Chinese family with nevoid basal cell carcinoma syndrome

Nevoid basal cell carcinoma syndrome (NBCCS) is a rare autosomal dominant disease characterized by the development of multiple jaw keratocysts and basal cell carcinomas (BCC) and accompanied by diverse phenotypes. The establishment of diagnosis lies on the identification of a heterozygous germline pathogenic variant in the patched homolog 1 gene (PTCH1). PTCH1 has alternative splicing and selective initial coding exon, leading to three types of encoding proteins (PTCHL, PTCHM and PTCHS). The expression of each protein in NBCCS remains ambiguous, especially the importance of the first two exons in translation. Here, we report a Chinese NBCCS family of a novel PTCH1 heterozygous mutation (IVS 2, c.394+1G>T, g.10652G>T) identified by genomic sequencing and reverse-transcription-PCR as aberrant splicing. To the best of our knowledge, this is the first report of NBCCS with a splicing site mutation in intron 2 resulting in exon 2 skipping. Our finding suggests that exon 2 plays an important role in the development of NBCCS and further speculates that the role of longer isoforms PTCHL and PTCHM is crucial in NBCCS, while that of short isoform PTCHS might be dispensable.