Format

Send to

Choose Destination
Mol Genet Metab. 2013 Aug;109(4):390-6. doi: 10.1016/j.ymgme.2013.05.006. Epub 2013 May 22.

An exon 53 frameshift mutation in CUBN abrogates cubam function and causes Imerslund-Gräsbeck syndrome in dogs.

Author information

1
Laboratory of Comparative Medical Genetics, College of Veterinary Medicine, Michigan State University, East Lansing, MI 48824, USA. fyfe@msu.edu

Abstract

Cobalamin malabsorption accompanied by selective proteinuria is an autosomal recessive disorder known as Imerslund-Gräsbeck syndrome in humans and was previously described in dogs due to amnionless (AMN) mutations. The resultant vitamin B12 deficiency causes dyshematopoiesis, lethargy, failure to thrive, and life-threatening metabolic disruption in the juvenile period. We studied 3 kindreds of border collies with cobalamin malabsorption and mapped the disease locus in affected dogs to a 2.9Mb region of homozygosity on canine chromosome 2. The region included CUBN, the locus encoding cubilin, a peripheral membrane protein that in concert with AMN forms the functional intrinsic factor-cobalamin receptor expressed in ileum and a multi-ligand receptor in renal proximal tubules. Cobalamin malabsorption and proteinuria comprising CUBN ligands were demonstrated by radiolabeled cobalamin uptake studies and SDS-PAGE, respectively. CUBN mRNA and protein expression were reduced ~10 fold and ~20 fold, respectively, in both ileum and kidney of affected dogs. DNA sequencing demonstrated a single base deletion in exon 53 predicting a translational frameshift and early termination codon likely triggering nonsense mediated mRNA decay. The mutant allele segregated with the disease in the border collie kindred. The border collie disorder indicates that a CUBN mutation far C-terminal from the intrinsic factor-cobalamin binding site can abrogate receptor expression and cause Imerslund-Gräsbeck syndrome.

KEYWORDS:

AMN; Amnionless; Animal model; BC; CUB; CUBN; Cubam; Cubilin; GIF; I-GS; Imerslund-Gräsbeck syndrome; Inborn error; MMA; Methylmalonic aciduria; RT; SNP; UCBC; Vitamin B(12); amnionless; an ~110 residue protein domain structure first defined in Complement proteins C1r/C1s, sea Urchin EGF-domain-containing protein (Uegf), Bone morphogenic protein 1 (Bmp1); border collie; cubilin; gastric intrinsic factor; methylmalonic acid; qPCR; quantitative polymerase chain reaction; reverse transcriptase; single nucleotide polymorphism; the functional receptor complex composed of AMN and CUBN subunits; unsaturated cobalamin binding capacity

PMID:
23746554
PMCID:
PMC3729882
DOI:
10.1016/j.ymgme.2013.05.006
[Indexed for MEDLINE]
Free PMC Article

Supplemental Content

Full text links

Icon for Elsevier Science Icon for PubMed Central
Loading ...
Support Center