Alpha-Defensin DEFA1A3 Gene Copy Number Elevation in Danish Crohn’s Disease Patients
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Background and Purpose of Study
Extensive copy number variation is observed for the DEFA1A3 gene encoding alpha-defensins 1–3. The objective of this study was to determine the involvement of alpha-defensins in colonic tissue from Crohn’s disease (CD) patients and the possible genetic association of DEFA1A3 with CD.
Two-hundred and forty ethnic Danish CD patients were included in the study. Reverse transcriptase PCR assays determined DEFA1A3 expression in colonic tissue from a subset of patients. Immunohistochemical analysis identified alpha-defensin peptides in colonic tissue. Copy number of DEFA1A3 and individual alleles, DEFA1 and DEFA3, were compared with those for controls, by use of combined real-time quantitative PCR and pyrosequencing, and correlated with disease location.
Inflammatory-dependent mRNA expression of DEFA1A3 (P < 0.001), and the presence of alpha-defensin peptides, were observed in colonic tissue samples. Higher DEFA1A3 gene copy number (CD: mean copy number, 7.2 vs. controls 6.7; P < 0.001) and individual DEFA1 alleles (CD mean copy number 5.6 vs. controls 5.1; P < 0.01) were associated with CD, with strong association with colonic location (P < 0.001).
Alpha-defensins are involved in the inflammation of CD, with local mRNA and peptide expression. In combination with the findings that a high DEFA1A3 copy number is significantly linked to CD, these results suggest that a high DEFA1A3 copy number might be important in hindering the normal inflammatory response in CD, particularly colonic CD.
KeywordsCrohn’s disease Colonic tissue Copy number variation Defensin Genetic association Real-time PCR
We thank Britta Hansen and Ida Haugaard Bøtcher for expert technical assistance. We would also like to thank Dr John Armour (University of Nottingham, UK) for kindly providing us with data for DEFA1A3 controls, and Nathaniel and Anne Hong for carefully revising the manuscript. This study was supported by the Danish Colitis and Crohn Association, the Augustinus Foundation, Aase and Ejner Danielsens Foundation, the Lundbeck Foundation, the LEO-Pharma Foundation, The Idella Foundation, and “Fonden til Lægevidenskabens Fremme.”.
Conflict of interest
The study was conducted according to the Declaration of Helsinki and was approved by the Regional Scientific Ethics Committee. All patients included to the study had given their written consent.