Identification of EpCAM as the gene for congenital tufting enteropathy.
OBJECTIVE
Congenital tufting enteropathy (CTE) is a rare autosomal recessive diarrheal disorder presenting in the neonatal period. CTE is characterized by intestinal epithelial cell dysplasia leading to severe malabsorption and significant morbidity and mortality. The pathogenesis and genetics of this disorder are not well understood. The objective of this study was to identify the gene responsible for CTE.


METHODS
A family with 2 children affected with CTE was identified. The affected children are double second cousins providing significant statistical power for linkage. Using Affymetrix 50K single nucleotide polymorphism (SNP) chips, genotyping was performed on only 2 patients and 1 unaffected sibling. Direct DNA sequencing of candidate genes, reverse-transcription polymerase chain reaction, immunohistochemistry, and Western blotting were performed on specimens from patients and controls.


RESULTS
SNP homozygosity mapping identified a unique 6.5-Mbp haplotype of homozygous SNPs on chromosome 2p21 where approximately 40 genes are located. Direct sequencing of genes in this region revealed homozygous G>A substitution at the donor splice site of exon 4 in epithelial cell adhesion molecule (EpCAM) of affected patients. Reverse-transcription polymerase chain reaction of duodenal tissue demonstrated a novel alternative splice form with deletion of exon 4 in affected patients. Immunohistochemistry and Western blot of patient intestinal tissue revealed decreased expression of EpCAM. Direct sequencing of EpCAM from 2 additional unrelated patients revealed novel mutations in the gene.


CONCLUSIONS
Mutations in the gene for EpCAM are responsible for CTE. This information will be used to gain further insight into the molecular mechanisms of this disease.
Sivagnanam
Mamata
M
Division of Gastroenterology, Hepatology, and Nutrition, Department of Pediatrics, University of California San Diego, La Jolla, California, USA.
Mueller
James L
JL
Lee
Hane
H
Chen
Zugen
Z
Nelson
Stanley F
SF
Turner
Dan
D
Zlotkin
Stanley H
SH
Pencharz
Paul B
PB
Ngan
Bo-Yee
BY
Libiger
Ondrej
O
Schork
Nicholas J
NJ
Lavine
Joel E
JE
Taylor
Sharon
S
Newbury
Robert O
RO
Kolodner
Richard D
RD
Hoffman
Hal M
HM
D017398:Alternative Splicing; D000951:Antigens, Neoplasm / Q000032:analysis / Q000235:genetics*; D015153:Blotting, Western; D016022:Case-Control Studies; D015815:Cell Adhesion Molecules / Q000032:analysis / Q000235:genetics*; D002889:Chromosomes, Human, Pair 2; D004252:DNA Mutational Analysis; D003968:Diarrhea, Infantile / Q000151:congenital / Q000235:genetics* / Q000276:immunology / Q000473:pathology; D004386:Duodenum / Q000276:immunology* / Q000473:pathology; D000071858:Epithelial Cell Adhesion Molecule; D005091:Exons; D020869:Gene Expression Profiling / Q000379:methods; D020022:Genetic Predisposition to Disease; D006239:Haplotypes; D006720:Homozygote; D006801:Humans; D007150:Immunohistochemistry; D007223:Infant; D007231:Infant, Newborn; D007410:Intestinal Diseases / Q000151:congenital / Q000235:genetics* / Q000276:immunology / Q000473:pathology; D007413:Intestinal Mucosa / Q000276:immunology / Q000473:pathology; D020411:Oligonucleotide Array Sequence Analysis; D010375:Pedigree; D020641:Polymorphism, Single Nucleotide; D020133:Reverse Transcriptase Polymerase Chain Reaction
D000951:Antigens, Neoplasm; D015815:Cell Adhesion Molecules; C499379:EPCAM protein, human; D000071858:Epithelial Cell Adhesion Molecule