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Strain-specific polymorphisms in Paneth cell α-defensins of C57BL/6 mice and evidence of vestigial myeloid α-defensin pseudogenes.

ABSTRACT: Paneth cells at the base of small intestinal crypts secrete microbicidal α-defensins, termed cryptdins (Crps) in mice, as mediators of innate immunity. Proteomic studies show that five abundant Paneth cell α-defensins in C57BL/6 mice are strain specific in that they have not been identified in other inbred strains of mice. Two C57BL/6-specific peptides are coded for by the Defcr20 and -21 genes evident in the NIH C57BL/6 genome but absent from the Celera mixed-strain assembly, which excludes C57BL/6 data and differs from the NIH build with respect to the organization of the α-defensin gene locus. Conversely, C57BL/6 mice lack the Crp1, -2, -4, and -6 peptides and their corresponding Defcr1, -2, -4, and -6 genes, which are common to several mouse strains, including those of the Celera assembly. In C57BL/6 mice, α-defensin gene diversification appears to have occurred by tandem duplication of a multigene cassette that was not found in the mixed-strain assembly. Both mouse genome assemblies contain conserved α-defensin pseudogenes that are closely related to functional myeloid α-defensin genes in the rat, suggesting that the neutrophil α-defensin defect in mice resulted from progressive gene loss. Given the role of α-defensins in shaping the composition of the enteric microflora, such polymorphisms may influence outcomes in mouse models of disease or infection.

SUBMITTER: Shanahan MT

PROVIDER: S-EPMC3019906 | biostudies-literature | 2011 Jan

REPOSITORIES: biostudies-literature

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Strain-specific polymorphisms in Paneth cell α-defensins of C57BL/6 mice and evidence of vestigial myeloid α-defensin pseudogenes.

Shanahan Michael T MT Tanabe Hiroki H Ouellette André J AJ

Infection and immunity 20101101 1

Paneth cells at the base of small intestinal crypts secrete microbicidal α-defensins, termed cryptdins (Crps) in mice, as mediators of innate immunity. Proteomic studies show that five abundant Paneth cell α-defensins in C57BL/6 mice are strain specific in that they have not been identified in other inbred strains of mice. Two C57BL/6-specific peptides are coded for by the Defcr20 and -21 genes evident in the NIH C57BL/6 genome but absent from the Celera mixed-strain assembly, which excludes C57 ...[more]

PMID: 21041494

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Project description:AimTo investigate the genetic background of human defensin expression in type 1 and 2 diabetes.MethodsAssociations between DEFA1/DEFA3 gene copy number polymorphism and diabetes as well as between the promoter polymorphisms of DEFB1 and diabetes were studied. The copy number variation of the DEFA1/DEFA3 genes was determined in 257 diabetic patients (117 patients with type 1 and 140 with type 2 diabetes). The control group consisted of 221 age- and gender-matched healthy blood donors. The cumulative copy numbers of the DEFA1/DEFA3 genes were detected by using quantitative PCR analysis. To evaluate the HNP 1-3 (human neutrophil peptide 1-3 or α-defensin) levels in the circulation, plasma HNP 1-3 concentrations were measured by ELISA. The expression of DEFA1/A3 in peripheral leukocytes of the diabetic patients was measured by quantitative RT PCR analysis. Three SNPs of the human DEFB1 (human defensin β-1) gene: DEFB1 G-20A (rs11362), DEFB1 C-44G (rs1800972) and DEFB1 G-52A (rs1799946) were genotyped by Custom TaqMan(®) Real Time PCR assay.ResultsSignificant differences were observed in HNP1-3 levels between the healthy subjects and both groups of diabetic patients. The mean ± SE was 28.78 ± 4.2 ng/mL in type 1 diabetes, and 29.82 ± 5.36 ng/mL in type 2 diabetes, vs 11.94 ± 2.96 ng/mL in controls; P < 0.01 respectively. There was no significant difference between patients with type 1 and type 2 diabetes in the high plasma concentrations of HNP1-3. The highest concentrations of α-defensin were found in diabetic patients with nephropathy (49.4 ± 4.8 ng/mL), neuropathy (38.7 ± 4.8 ng/mL) or cardiovascular complications (45.6 ± 1.45 ng/L). There was no significant difference in the cumulative copy numbers of DEFA1/DEFA3 genes between controls and patients, or between patients with the two types of diabetes. Comparisons of HNP 1-3 plasma level and DEFA1/A3 copy number of the same patient did not reveal significant relationship between defensin-α levels and the gene copy numbers (r (2) = 0.01). Similarly, no positive correlation was observed between the copy numbers and the mRNA expression levels of DEFA1/A3. Regarding the C-44G polymorphism of DEFB1, the GG "protective" genotype was much less frequent (1%-2%) among both groups of patients than among controls (9%).ConclusionElevated HNP1-3 levels in diabetes are independent of DEFA1/DEFA3 copy numbers, but GG genotype of C-44G SNP in DEFB1 gene may result in decreased defensin β-1 production.

Project description:IntroductionThe mechanism underlying radiation-induced gut microbiota dysbiosis is undefined. This study examined the effect of radiation on the intestinal Paneth cell α-defensin expression and its impact on microbiota composition and mucosal tissue injury and evaluated the radio-mitigative effect of human α-defensin 5 (HD5).MethodsAdult mice were subjected to total body irradiation, and Paneth cell α-defensin expression was evaluated by measuring α-defensin mRNA by RT-PCR and α-defensin peptide levels by mass spectrometry. Vascular-to-luminal flux of FITC-inulin was measured to evaluate intestinal mucosal permeability and endotoxemia by measuring plasma lipopolysaccharide. HD5 was administered in a liquid diet 24 hours before or after irradiation. Gut microbiota was analyzed by 16S rRNA sequencing. Intestinal epithelial junctions were analyzed by immunofluorescence confocal microscopy and mucosal inflammatory response by cytokine expression. Systemic inflammation was evaluated by measuring plasma cytokine levels.ResultsIonizing radiation reduced the Paneth cell α-defensin expression and depleted α-defensin peptides in the intestinal lumen. α-Defensin down-regulation was associated with the time-dependent alteration of gut microbiota composition, increased gut permeability, and endotoxemia. Administration of human α-defensin 5 (HD5) in the diet 24 hours before irradiation (prophylactic) significantly blocked radiation-induced gut microbiota dysbiosis, disruption of intestinal epithelial tight junction and adherens junction, mucosal barrier dysfunction, and mucosal inflammatory response. HD5, administered 24 hours after irradiation (treatment), reversed radiation-induced microbiota dysbiosis, tight junction and adherens junction disruption, and barrier dysfunction. Furthermore, HD5 treatment also prevents and reverses radiation-induced endotoxemia and systemic inflammation.ConclusionThese data demonstrate that radiation induces Paneth cell dysfunction in the intestine, and HD5 feeding prevents and mitigates radiation-induced intestinal mucosal injury, endotoxemia, and systemic inflammation.

Dataset Information

Strain-specific polymorphisms in Paneth cell α-defensins of C57BL/6 mice and evidence of vestigial myeloid α-defensin pseudogenes.

Publications

Strain-specific polymorphisms in Paneth cell α-defensins of C57BL/6 mice and evidence of vestigial myeloid α-defensin pseudogenes.

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