A mouse with an N-Ethyl-N-nitrosourea (ENU) Induced Trp589Arg Galnt3 mutation represents a model for hyperphosphataemic familial tumoural calcinosis.
Mutations of UDP-N-acetyl-alpha-D-galactosamine polypeptide N-acetyl galactosaminyl transferase 3 (GALNT3) result in familial tumoural calcinosis (FTC) and the hyperostosis-hyperphosphataemia syndrome (HHS), which are autosomal recessive disorders characterised by soft-tissue calcification and hyperphosphataemia. To facilitate in vivo studies of these heritable disorders of phosphate homeostasis, we embarked on establishing a mouse model by assessing progeny of mice treated with the chemical mutagen N-ethyl-N-nitrosourea (ENU), and identified a mutant mouse, TCAL, with autosomal recessive inheritance of ectopic calcification, which involved multiple tissues, and hyperphosphataemia; the phenotype was designated TCAL and the locus, Tcal. TCAL males were infertile with loss of Sertoli cells and spermatozoa, and increased testicular apoptosis. Genetic mapping localized Tcal to chromosome 2 (62.64-71.11 Mb) which contained the Galnt3. DNA sequence analysis identified a Galnt3 missense mutation (Trp589Arg) in TCAL mice. Transient transfection of wild-type and mutant Galnt3-enhanced green fluorescent protein (EGFP) constructs in COS-7 cells revealed endoplasmic reticulum retention of the Trp589Arg mutant and Western blot analysis of kidney homogenates demonstrated defective glycosylation of Galnt3 in Tcal/Tcal mice. Tcal/Tcal mice had normal plasma calcium and parathyroid hormone concentrations; decreased alkaline phosphatase activity and intact Fgf23 concentrations; and elevation of circulating 1,25-dihydroxyvitamin D. Quantitative reverse transcriptase-PCR (qRT-PCR) revealed that Tcal/Tcal mice had increased expression of Galnt3 and Fgf23 in bone, but that renal expression of Klotho, 25-hydroxyvitamin D-1α-hydroxylase (Cyp27b1), and the sodium-phosphate co-transporters type-IIa and -IIc was similar to that in wild-type mice. Thus, TCAL mice have the phenotypic features of FTC and HHS, and provide a model for these disorders of phosphate metabolism.
Academic Endocrine Unit, Nuffield Department of Clinical Medicine, University of Oxford, Oxford Centre for Diabetes, Endocrinology and Metabolism, Churchill Hospital, Oxford, United Kingdom.
Christopher T
CT
Esapa
Rosie A
RA
Head
Jeshmi
J
Jeyabalan
Holly
H
Evans
Tertius A
TA
Hough
Michael T
MT
Cheeseman
Eugene G
EG
McNally
Andrew J
AJ
Carr
Gethin P
GP
Thomas
Matthew A
MA
Brown
Peter I
PI
Croucher
Steve D M
SD
Brown
Roger D
RD
Cox
Rajesh V
RV
Thakker
D000818:Animals; D017209:Apoptosis / Q000235:genetics; D015153:Blotting, Western; D001842:Bone and Bones / Q000378:metabolism; D019556:COS Cells; D002114:Calcinosis / Q000235:genetics* / Q000473:pathology*; D002522:Chlorocebus aethiops; D004195:Disease Models, Animal; D005038:Ethylnitrosourea / Q000633:toxicity; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors / Q000378:metabolism; D005808:Genes, Recessive / Q000235:genetics; D049452:Green Fluorescent Proteins / Q000235:genetics / Q000378:metabolism; D006958:Hyperostosis, Cortical, Congenital / Q000235:genetics* / Q000473:pathology*; D054559:Hyperphosphatemia / Q000235:genetics* / Q000473:pathology*; D008297:Male; D051379:Mice; D020125:Mutation, Missense / Q000187:drug effects / Q000235:genetics*; D017350:N-Acetylgalactosaminyltransferases / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012708:Sertoli Cells / Q000473:pathology; D013094:Spermatozoa / Q000473:pathology; D013737:Testis / Q000166:cytology; D000097763:Polypeptide N-acetylgalactosaminyltransferase
D005038:Ethylnitrosourea; D000089703:Fibroblast Growth Factor-23; D005346:Fibroblast Growth Factors; D049452:Green Fluorescent Proteins; D017350:N-Acetylgalactosaminyltransferases; D000097763:Polypeptide N-acetylgalactosaminyltransferase; C000717428:Fgf23 protein, mouse; C485184:enhanced green fluorescent protein