Deciphering a transcriptional regulatory code: modeling short-range repression in the Drosophila embryo

A well-defined set of transcriptional regulatory modules was created and analyzed in the Drosophila embryo.Fractional occupancy-based models were developed to explain the interaction of short range transcriptional repressors with endogenous activators by using quantitative data from these modules.Our fractional occupancy-based modeling uncovered specific quantitative features of short-range repressors; a complex nonlinear quenching relationship, similar quenching efficiencies for different activators, and modest levels of cooperativityThe extension of the study to endogenous enhancers highlighted several features of enhancer architecture design in Drosophila embryos

Interaction between IRF6 and TGFA Genes Contribute to the Risk of Nonsyndromic Cleft Lip/Palate

Previous evidence from tooth agenesis studies suggested IRF6 and TGFA interact. Since tooth agenesis is commonly found in individuals with cleft lip/palate (CL/P), we used four large cohorts to evaluate if IRF6 and TGFA interaction contributes to CL/P. Markers within and flanking IRF6 and TGFA genes were tested using Taqman or SYBR green chemistries for case-control analyses in 1,000 Brazilian individuals. We looked for evidence of gene-gene interaction between IRF6 and TGFA by testing if markers associated with CL/P were overtransmitted together in the case-control Brazilian dataset and in the additional family datasets. Genotypes for an additional 142 case-parent trios from South America drawn from the Latin American Collaborative Study of Congenital Malformations (ECLAMC), 154 cases from Latvia, and 8,717 individuals from several cohorts were available for replication of tests for interaction. Tgfa and Irf6 expression at critical stages during palatogenesis was analyzed in wild type and Irf6 knockout mice. Markers in and near IRF6 and TGFA were associated with CL/P in the Brazilian cohort (p<10-6). IRF6 was also associated with cleft palate (CP) with impaction of permanent teeth (p<10-6). Statistical evidence of interaction between IRF6 and TGFA was found in all data sets (p = 0.013 for Brazilians; p = 0.046 for ECLAMC; p = 10-6 for Latvians, and p = 0.003 for the 8,717 individuals). Tgfa was not expressed in the palatal tissues of Irf6 knockout mice. IRF6 and TGFA contribute to subsets of CL/P with specific dental anomalies. Moreover, this potential IRF6-TGFA interaction may account for as much as 1% to 10% of CL/P cases. The Irf6-knockout model further supports the evidence of IRF6-TGFA interaction found in humans. © 2012 Letra et al

Alveolar socket healing in 5-lipoxygenase knockout aged female mice treated or not with high dose of zoledronic acid

This study investigated the role 5-lypoxigenase (5-LO) on alveolar socket healing in aged female mice treated with zoledronic acid (ZL). Forty 129/Sv female mice (64-68 weeks old), 20 wild type (WT) and 20 5-LO knockout (5LOKO) were equally distributed according to ZL treatment: WT Control, WT ZL, 5LOKO Control, and 5LOKO ZL. ZL groups were treated with an intraperitoneal injection of 250 µg/Kg of ZL, while controls were treated with saline. Treatments were administered once a week, starting four weeks before surgery for tooth extraction and until 7 and 21 days post-surgery. Mice were euthanized for a comprehensive microscopic analysis (microCT, histomorphometry and immunohistochemistry). WT ZL mice presented intense inflammatory infiltrate (7 days), delayed bone formation (21 days), reduced collagenous matrix quality, and a deficiency in Runx-2 + , TRAP + , and macrophages as compared to controls. 5LOKO ZL animals presented decreased number of Runx-2 + cells in comparison to 5LOKO Control at 7 days, but no major changes in bone healing as compared to WT or 5LOKO mice at 21 days. The knockout of 5LO favored intramembranous bone healing in aged female mice, with a direct impact on inflammatory response and bone metabolism on the development of ONJ-like lesions

Temperature Changes during Implant Osteotomy Preparations in Human Cadaver Tibiae Comparing MIS&reg; Straight Drills with Densah&reg; Burs

(1) Background: Several studies showed a sustained temperature of 47 &deg;C or 50 &deg;C for one minute resulted in vascular stasis and bone resorption with only limited bone regrowth over a 3&ndash;4-week healing period. The purpose of the present study was to evaluate the temperature changes (&Delta;&Tau;) that occur during the preparation of dental implant osteotomies using MIS&reg; straight drills versus Densah&reg; burs in a clockwise (cutting) drilling protocol. (2) Methods: Two hundred forty (240) osteotomies of two different systems&rsquo; drills were prepared at 6 mm depth at 800, 1000, and 1200 revolutions per minute (RPM), in fresh, unembalmed tibiae, obtained by a female cadaver. &Delta;&Tau; was calculated by subtracting the baseline temperature on the tibial surface, from the maximum temperature-inside the osteotomy (&Delta;T = Tmax &minus; Tbase). The variables were evaluated both for their individual and for their synergistic effect on &Delta;&Tau; with the use of one-, two-, three- and four-way interactions; (3) Results: An independent and a three-way interaction (drill design, drill width, and RPM) was found in all three RPM for the Densah&reg; burs and at 1000 RPM for the MIS&reg; straight drills. As Densah&reg; burs diameter increased, &Delta;&Tau; decreased. The aforementioned pattern was seen only at 1000 RPM for the MIS&reg; straight drills. The usage of drills 20 times more than the implant manufacturers&rsquo; recommendation did not significantly affect the &Delta;&Tau;. A stereoscopic examination of the specimens confirmed the findings. (4) Conclusions: The independent and synergistic effect of drills&rsquo; diameter, design and RPM had a significant effect on &Delta;&Tau; in human tibiae, which never exceeded the critical threshold of 47 &deg;C

A cleft lip and palate gene, Irf6

Background: Interferon Regulatory Factor 6 (IRF6) plays a critical role in embryonic tissue development including differentiation of epithelial cells. Besides orofacial clefting due to haploinsufficiency of IRF6, recent human genetic studies indicated that mutations in IRF6 are linked to small mandible and digit abnormalities. The function of IRF6 has been well studied in oral epithelium, however its role in craniofacial skeletal formation remains unknown. In this study, we investigated the role of Irf6 in craniofacial bone development using comparative analyses between wild-type and Irf6-null littermate mice Results: Immunostaining revealed the expression of IRF6 in hypertrophic chondrocytes, osteocytes and bone matrix of craniofacial tissues. Histological analysis of Irf6-null mice showed a remarkable reduction in the number of lacunae, embedded osteocytes in matrices and a reduction in mineralization during bone formation. These abnormalities may explain the decreased craniofacial bone density detected by micro-CT, loss of incisors and mandibular bone abnormality of Irf6-null mice. To validate the autonomous role of IRF6 in bone, extracted primary osteoblasts from calvarial bone of WT and Irf6-null pups showed no effect on osteoblastic viability and proliferation. However, a reduction in mineralization was detected in Irf6-null cells. Conclusions: Altogether, these findings suggest an autonomous role of Irf6 in regulating bone differentiation and mineralization