New variants in the Enpp1 and Ptpn6 genes cause low BMD, crystal-related arthropathy, and vascular calcification.
A large genome-wide, recessive, N-ethyl-N-nitrosourea (ENU)-induced mutagenesis screen was performed on a mixed C57BL/6J and C3H.SW-H2/SnJ mouse background to identify genes regulating bone mass. Approximately 6500 male and female G(3) hybrid mice were phenotyped at 8 and 10 wk of age by DXA analysis for evidence of changes in unadjusted or body weight-adjusted BMD or BMC. Phenodeviant lines were identified based on statistical criteria that included a false discovery rate (FDR) <20% and Z-score >2.8. Genome-wide mapping scans were initiated on 22 lines, with evidence of high or low BMD or BMC that deviated by approximately -30% to +50% from the means. Several lines were discontinued as showing lack of heritability, but two heritable lines were identified with narrow chromosomal regions that allowed sequencing of potential mutant candidate genes. Novel mutations were identified in the Enpp1 (C397S) gene on chromosome 10 (line 4482) and the Ptpn6 (I482F) gene on chromosome 6 (line 4489) that were both associated with low bone mass. In addition, the phenotype of the Enpp1 mice showed a striking joint disease and calcification of blood vessels including the aorta, myocardium, and renal arteries and capillaries. These results support a role for the Enpp1 gene in the pathogenesis associated with mineralization of articular cartilage and vascular calcification. This work confirms the utility of the chemical mutagenesis approach for identification of potential disease genes and confirms the role of Enpp1 and Ptpn6 in regulating mineralization and skeletal bone mass.
Babij
Philip
P
Department of Metabolic Disorders, Amgen, Thousand Oaks, California 91320, USA. pbabij@amgen.com
Roudier
Martine
M
Graves
Tom
T
Han
Chun-Ya E
CY
Chhoa
Mark
M
Li
Chi-Ming
CM
Juan
Todd
T
Morony
Sean
S
Grisanti
Mario
M
Li
Xiaodong
X
Yu
Longchuan
L
Dwyer
Denise
D
Lloyd
David J
DJ
Bass
Michael B
MB
Richards
William G
WG
Ebeling
Christine
C
Amato
Julie
J
Carlson
George
G
D015502:Absorptiometry, Photon; D000818:Animals; D001483:Base Sequence; D015519:Bone Density / Q000235:genetics*; D002114:Calcinosis / Q000235:genetics*; D002874:Chromosome Mapping; D017931:DNA Primers; D005038:Ethylnitrosourea / Q000633:toxicity; D005260:Female; D007592:Joint Diseases / Q000235:genetics*; D008297:Male; D051379:Mice; D008809:Mice, Inbred C3H; D008810:Mice, Inbred C57BL; D016296:Mutagenesis; D009153:Mutagens / Q000633:toxicity; D010727:Phosphoric Diester Hydrolases / Q000235:genetics*; D016133:Polymerase Chain Reaction; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6 / Q000235:genetics*; D011755:Pyrophosphatases / Q000235:genetics*; D014652:Vascular Diseases / Q000235:genetics*
D017931:DNA Primers; D009153:Mutagens; D053824:Protein Tyrosine Phosphatase, Non-Receptor Type 6; C509248:Ptpn6 protein, mouse; D010727:Phosphoric Diester Hydrolases; C065962:ectonucleotide pyrophosphatase phosphodiesterase 1; D011755:Pyrophosphatases; D005038:Ethylnitrosourea