In vitro calcite crystal morphology is modulated by otoconial proteins otolin-1 and otoconin-90.

Otoconia are formed embryonically and are instrumental in detecting linear acceleration and gravity. Degeneration and fragmentation of otoconia in elderly patients leads to imbalance resulting in higher frequency of falls that are positively correlated with the incidence of bone fractures and death. In this work we investigate the roles otoconial proteins Otolin-1 and Otoconin 90 (OC90) perform in the formation of otoconia. We demonstrate by rotary shadowing and atomic force microscopy (AFM) experiments that Otolin-1 forms homomeric protein complexes and self-assembled networks supporting the hypothesis that Otolin-1 serves as a scaffold protein of otoconia. Our calcium carbonate crystal growth data demonstrate that Otolin-1 and OC90 modulate in vitro calcite crystal morphology but neither protein is sufficient to produce the shape of otoconia. Coadministration of these proteins produces synergistic effects on crystal morphology that contribute to morphology resembling otoconia.

Epithelial expression of the cytosolic retinoid chaperone cellular retinol binding protein II is essential for in vivo imprinting of local gut dendritic cells by lumenal retinoids.

Dendritic cells (DCs) use all-trans retinoic acid (ATRA) to promote characteristic intestinal responses, including Foxp3(+) Treg conversion, lymphocyte gut homing molecule expression, and IgA production. How this ability to generate ATRA is conferred to DCs in vivo remains largely unstudied. Here, we observed that among DCs, retinaldehyde dehydrogenase (ALDH1), which catalyzes the conversion of retinal to ATRA, was preferentially expressed by small intestine CD103(+) lamina propria (LP) DCs. Retinoids induced LP CD103(+) DCs to generate ATRA via ALDH1 activity. Either biliary or dietary retinoids were required to confer ALDH activity to LP DCs in vivo. Cellular retinol-binding protein II (CRBPII), a cytosolic retinoid chaperone that directs enterocyte retinol and retinal metabolism but is redundant to maintain serum retinol, was required to confer ALDH activity to CD103(+) LP DCs. CRBPII expression was restricted to small intestine epithelial cells, and ALDH activity in CRBPII(-/-) DCs was restored by transfer to a wild-type recipient. CD103(+) LP DCs from CRBPII(-/-) mice had a decreased capacity to promote IgA production. Moreover, CD103(+) DCs preferentially associated with the small intestine epithelium and LP CD103(+) DC ALDH activity, and the ability to promote IgA production was reduced in mice with impaired DC-epithelia associations. These findings demonstrate in vivo roles for the expression of epithelial CRBPII and lumenal retinoids to imprint local gut DCs with an intestinal phenotype.

Serum analysis of tryptophan catabolism pathway: correlation with Crohn's disease activity.

BACKGROUND: Indoleamine 2,3 dioxygenase-1 (IDO1) is a tryptophan catabolizing enzyme with immunotolerance-promoting functions. We sought to determine if increased gut expression of IDO1 in Crohn's disease (CD) would result in detectable changes in serum levels of tryptophan and the initial IDO1 pathway catabolite, kynurenine. METHODS: Individuals were prospectively enrolled through the Washington University Digestive Diseases Research Center. The Montreal Classification was used for disease phenotyping. Disease severity was categorized by the Physician's Global Assessment. Serum tryptophan and kynurenine were measured by high-pressure liquid chromatography. IDO1 immunohistochemical staining was performed on formalin-fixed tissue blocks. RESULTS: In all, 25 CD patients and 11 controls were enrolled. Eight CD patients had serum collected at two different timepoints and levels of disease activity compared. Strong IDO1 expression exists in both the lamina propria and epithelium during active CD compared to controls. Suppressed serum tryptophan levels and an elevated kynurenine/tryptophan (K/T) ratio were found in individuals with active CD as compared to those in remission or the control population. K/T ratios correlated positively with disease activity as well as with C-reactive protein and erythrocyte sedimentation rate. In the subgroup of CD patients with two serum measurements, tryptophan levels were elevated while kynurenine levels and the K/T ratio lowered as the disease activity lessened. CONCLUSIONS: IDO1 expression in CD is associated with lower serum tryptophan and an elevated K/T ratio. These levels may serve as a reasonable objective marker of gut mucosal immune activation and as a surrogate for CD activity.

Cooperative interactions among intestinal GATA factors in activating the rat liver fatty acid binding protein gene.

GATA-4, GATA-5, and GATA-6 are endodermal zinc-finger transcription factors that activate numerous enterocytic genes. GATA-4 and GATA-6 but not GATA-5 are present in adult murine small intestinal enterocytes, and we now report the simultaneous presence of all three GATA factors in murine small intestinal enterocytes before weaning age. An immunohistochemical survey detected enterocytic GATA-4 and GATA-6 at birth and 1 wk of age and GATA-5 at 1 wk but not birth. Interactions among GATA factors were explored utilizing a transgene constructed from the proximal promoter of the rat liver fatty acid binding protein gene (Fabp1). GATA-4 and GATA-5 but not GATA-6 activate the Fabp1 transgene through a cognate binding site at -128. A dose-response assay revealed a maximum in transgene activation by both factors, where additional factor did not further increase transgene activity. However, at saturated levels of GATA-4, additional transgene activation was achieved by adding GATA-5 expression construct, and vice versa. Similar cooperativity occurred with GATA-5 and GATA-6. Identical interactions were observed with a target transgene consisting of a single GATA site upstream of a minimal promoter. Furthermore, GATA-4 and GATA-5 or GATA-5 and GATA-6 bound to each other in solution. These results are consistent with tethering of one GATA factor to the Fabp1 promoter through interaction with a second GATA factor to produce increased target gene activation. Cooperative target gene activation was specific to an intestinal cell line and may represent a mechanism by which genes are activated in the small intestinal epithelium during the period before weaning.

Mechanisms of mutual functional interactions between HNF-4alpha and HNF-1alpha revealed by mutations that cause maturity onset diabetes of the young.

Hepatic nuclear factor (HNF)-4alpha and HNF-1alpha are key endodermal transcriptional regulators that physically and functionally interact. HNF-4alpha and HNF-1alpha cooperatively activate genes with binding sites for both factors, whereas suppressive interactions occur at regulatory sequences with a binding site for only one factor. The liver fatty acid binding protein gene (Fabp1) has binding sites for both factors, and chromatin precipitation assays were utilized to demonstrate that HNF-4alpha increased HNF-1alpha Fabp1 promoter occupancy during cooperative transcriptional activation. The HNF4 P2 promoter contains a HNF-1 but not HNF-4 binding site, and HNF-4alpha suppressed HNF-1alpha HNF4 P2 activation and decreased promoter HNF-1alpha occupancy. The apolipoprotein C III (APOC3) promoter contains a HNF-4 but not HNF-1 binding site, and HNF-1alpha suppressed HNF-4alpha APOC3 activation and decreased HNF-4alpha promoter occupancy. Maturity onset diabetes of the young (MODY) as well as defects in hepatic lipid metabolism result from mutations in either HNF-4alpha or HNF-1alpha. We found that MODY missense mutant R127W HNF-4alpha retained wild-type individual Fabp1 activation and bound to HNF-1alpha better than wild-type HNF-4alpha, yet did not cooperate with HNF-1alpha or increase HNF-1alpha Fabp1 promoter occupancy. The R127W mutant was also defective in both suppressing HNF-1alpha activation of HNF4 P2 and decreasing HNF-1alpha promoter occupancy. The HNF-1alpha R131Q MODY mutant also retained wild-type Fabp1 activation and bound to HNF-4alpha as well as the wild type but was defective in both suppressing HNF-4alpha APOC3 activation and decreasing HNF-4alpha promoter occupancy. These results suggest HNF-1alpha-HNF-4alpha functional interactions are accomplished by regulating factor promoter occupancy and that defective factor-factor interactions may contribute to the MODY phenotype.

Differential expression of CYP102 in Bacillus megaterium by 17-beta-estradiol and 4-sec-butylphenol.

Previously we have reported the induction of CYP102 in Bacillus megaterium by 17beta-estradiol (E2) and 4-sec-butylphenol (4-sBP). Electrophoretic mobility shift assay analyses demonstrated that E2 and 4-sBP both cause a dose-dependent disassociation of the Bm3R1 repressor protein from its binding site on the operator sequence of the CYP102 gene. Equimolar combinations of E2 and 4-sBP demonstrated additive induction of CYP102 compared to equivalent samples of E2 and 4-sBP added alone. Two gene constructs were used in this investigation. One construct designated BMC143 contained the entire regulatory region of CYP102. The other gene construct, designated BMA45, had the "Barbie box" sequence deleted. While the induction of CYP102 by 4-sBP was much higher in the BMC 143 construct, E2 induced CYP102 in both constructs to the same extent. This difference in induction of CYP102 by these two inducers indicates that they act at different sites, either on the Bm3R1 repressor protein or on positive regulatory sites, or that they act, in part, through different mechanisms.