In silico and functional evaluation of PTH1R mutations found in patients with primary failure of eruption (PFE).

OBJECTIVES: The genetic basis of PFE (OMIM ID: 125350) was interrogated using molecular functional studies. PFE is a disorder that results in a poor prognosis in the eruption of teeth and by extension, in treatment with a continuous archwire. We tested the hypothesis that PTH1R mutations result in loss of function due to altered protein structure to determine (i) the fate of a functional PTH1R mutation and (ii) the resulting PTH1R protein structure of each functional mutation. METHODS: We used immunofluorescence assay of COS7 cells that were transfected with either the WT or 1092delG PTH1R mutation sequence to compare the fate of the expressed protein. We also performed in silico analysis of the WT PTH1R and four different functional PTH1R mutations RESULTS: Functional studies (IFA) showed a variation in expression between the WT and mutant PTH1R. Further, in silico analysis showed structural differences between WT and mutant PTH1R proteins, particularly in the regions of the 3rd intracellular loop and the 6th transmembrane domain required for efficient PTH1R function. CONCLUSION: PTH1R mutations identified in PFE likely result from diminished function due to truncation of the protein, lack of efficient G-protein interactions and putatively attenuated signal transduction. By identifying the mode of protein dysfunction, scientist-clinicians are better prepared to recognize and thereby develop improved methods of treatment, starting at the molecular level.

Novel mutations in PTH1R associated with primary failure of eruption and osteoarthritis.

Autosomal dominant mutations in PTH1R segregate with primary failure of eruption (PFE), marked by clinical eruption failure of adult teeth without mechanical obstruction. While the diagnosis of PFE conveys a poor dental prognosis, there are no reports of PFE patients who carry PTH1R mutations and exhibit any other skeletal problems. We performed polymerase chain reaction-based mutational analysis of the PTH1R gene to determine the genetic contribution of PTH1R in 10 families with PFE. Sequence analysis of the coding regions and intron-exon boundaries of the PTH1R gene in 10 families (n = 54) and 7 isolated individuals revealed 2 novel autosomal dominant mutations in PTH1R (c.996_997insC and C.572delA) that occur in the coding region and result in a truncated protein. One family showed incomplete penetrance. Of 10 families diagnosed with PFE, 8 did not reveal functional (nonsynonymous) mutations in PTH1R; furthermore, 4 families and 1 sporadic case carried synonymous single-nucleotide polymorphisms. Five PFE patients in 2 families carried PTH1R mutations and presented with osteoarthritis. We propose that the autosomal dominant mutations of PTH1R that cause PFE may also be associated with osteoarthritis; a dose-dependent model may explain isolated PFE and osteoarthritis in the absence of other known symptoms in the skeletal system.