Progressive osseous heteroplasia: a model for the imprinting effects of GNAS inactivating mutations in humans.
BACKGROUND
Heterozygous GNAS inactivating mutations are known to induce pseudohypoparathyroidism type 1a when maternally inherited and pseudopseudohypoparathyroidism when paternally inherited. Progressive osseous heteroplasia (POH) is a rare disease of ectopic bone formation, and studies in different families have shown that POH is also caused by paternally inherited GNAS mutations.


OBJECTIVE
Our purpose was to characterize parental origin of the mutated allele in de novo cases of POH and to draw phenotype/genotype correlations according to maternal or paternal transmission of a same GNAS mutation.


METHODS
We conducted a retrospective study on patients addressed to our referral center for the rare diseases of calcium and phosphorus metabolism.


METHODS
We matched 10 cases of POH with cases of pseudohypoparathyroidism type 1a carrying the same GNAS mutations.


METHODS
The parental origin of the mutated allele was studied using informative intragenic polymorphisms and subcloning of PCR products.


RESULTS
Paternal origin of GNAS mutations was clearly demonstrated in eight POH cases including one patient with mutation in exon 1. Genotype/phenotype analyses suggest that there is no direct correlation between the ossifying process and the position of the inactivating GNAS mutation. It is, however, more severe in patients in whom origin of the mutation is paternal. Severe intrauterine growth retardation was clearly evidenced in paternally inherited mutations.


CONCLUSIONS
Clinical heterogeneity makes genetic counseling a delicate matter, especially in which paternal inheritance is concerned because it can lead to either a mild expression of pseudopseudohypoparathyroidism or a severe expression of POH.
Lebrun
M
M
Department of Genetics and Reproduction, University Hospital-Caen, 14033 Caen, France.
Richard
N
N
Abeguilé
G
G
David
A
A
Coëslier Dieux
A
A
Journel
H
H
Lacombe
D
D
Pinto
G
G
Odent
S
S
Salles
J P
JP
Taieb
A
A
Gandon-Laloum
S
S
Kottler
M L
ML
D001842:Bone and Bones; D002648:Child; D002675:Child, Preschool; D002828:Choristoma / Q000235:genetics* / Q000473:pathology*; D002864:Chromogranins; D019175:DNA Methylation; D030541:Databases, Genetic; D005260:Female; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000235:genetics*; D018392:Genomic Imprinting; D005838:Genotype; D006801:Humans; D007223:Infant; D008297:Male; D009154:Mutation / Q000235:genetics* / Q000502:physiology*; D010281:Parathyroid Hormone / Q000502:physiology; D010375:Pedigree; D020641:Polymorphism, Single Nucleotide; D011547:Pseudohypoparathyroidism / Q000235:genetics; D011556:Pseudopseudohypoparathyroidism / Q000235:genetics; D012313:RNA / Q000235:genetics
D002864:Chromogranins; D010281:Parathyroid Hormone; D012313:RNA; C406732:GNAS protein, human; D019205:GTP-Binding Protein alpha Subunits, Gs