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A mouse with an N-Ethyl-N-Nitrosourea (ENU) induced Trp589Arg Galnt3 mutation represents a model for hyperphosphataemic familial tumoural calcinosis

Abstract

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-1alpha-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. PLoS One. 2012;7(8):e43205. Epub 2012 Aug 13.

Type Journal
ISBN 1932-6203 (Electronic) 1932-6203 (Linking)
Authors Esapa, C. T.; Head, R. A.; Jeyabalan, J.; Evans, H.; Hough, T. A.; Cheeseman, M. T.; McNally, E. G.; Carr, A. J.; Thomas, G. P.; Brown, M. A.; Croucher, P. I.; Brown, S. D.; Cox, R. D.; Thakker, R. V.;
Garvan Authors Prof Peter Croucher
Publisher Name PLoS ONE
Published Date 2012-01-01 00:00:00
Published Volume 7
Published Issue 8
Published Pages e43205
URL http://www.ncbi.nlm.nih.gov/pubmed/22912827
Status Published In-print
OpenAccess Link https://publications.gimr.garvan.org.au/download.php?11467_11931/12 Esapa PlosOne_.pdf