Mule Regulates the Intestinal Stem Cell Niche via the Wnt Pathway and Targets EphB3 for Proteasomal and Lysosomal Degradation

The E3 ubiquitin ligase Mule is often overexpressed in human colorectal cancers, but its role in gut tumorigenesis is unknown. Here, we show in vivo that Mule controls murine intestinal stem and progenitor cell proliferation by modulating Wnt signaling via c-Myc. Mule also regulates protein levels of the receptor tyrosine kinase EphB3 by targeting it for proteasomal and lysosomal degradation. In the intestine, EphB/ephrinB interactions position cells along the crypt-villus axis and compartmentalize incipient colorectal tumors. Our study thus unveils an important new avenue by which Mule acts as an intestinal tumor suppressor by regulation of the intestinal stem cell niche

Transcription factor Ebf1 regulates differentiation stage-specific signaling, proliferation, and survival of B cells

The transcription factor Ebf1 regulates early B lymphopoiesis by acting in a network with E2A and Pax5. However, the function of Ebf1 at later stages of differentiation in unclear. In this study, Grosschedl and colleagues investigate the role of Ebf1 in B lymphopoiesis by using conditional gene inactivation. The authors show that Ebf1 is required for proliferation and survival of pro-B and mature B cells. In addition, the proliferation defect of Ebf1fl/fl pro-B cells can be overcome by transformation with v-Abl, and the survival defect can be rescued by the expression of the Ebf1 targets c-Myb or Bcl-xL. In mature B cells, Ebf1 deficiency interferes with normal BCR/Akt signaling and the generation of germinal center B cells. Thus, these results delineate novel targets and pathways controlled by Ebf1 at different stages of lymphomagenesis

Pioneering Activity of the C-Terminal Domain of EBF1 Shapes the Chromatin Landscape for B Cell Programming

Lymphopoiesis requires the activation of lineage-specific genes embedded in naive, inaccessible chromatin or in primed, accessible chromatin. The mechanisms responsible for de novo gain of chromatin accessibility, known as "pioneer" function, remain poorly defined. Here, we showed that the EBF1 C-terminal domain (CTD) is required for the regulation of a specific gene set involved in B cell fate decision and differentiation, independently of activation and repression functions. Using genome-wide analysis of DNaseI hypersensitivity and DNA methylation in multipotent Ebf1(-/-) progenitors and derivative EBF1wt- or EBF1ΔC-expressing cells, we found that the CTD promoted chromatin accessibility and DNA demethylation in previously naive chromatin. The CTD allowed EBF1 to bind at inaccessible genomic regions that offer limited co-occupancy by other transcription factors, whereas the CTD was dispensable for EBF1 binding at regions that are occupied by multiple transcription factors. Thus, the CTD enables EBF1 to confer permissive lineage-specific changes in progenitor chromatin landscape

Satb1 and Satb2 regulate embryonic stem cell differentiation and Nanog expression

Satb1 and the closely related Satb2 proteins regulate gene expression and higher-order chromatin structure of multigene clusters in vivo. In examining the role of Satb proteins in murine embryonic stem (ES) cells, we find that Satb1−/− cells display an impaired differentiation potential and augmented expression of the pluripotency determinants Nanog, Klf4, and Tbx3. Metastable states of self-renewal and differentiation competence have been attributed to heterogeneity of ES cells in the expression of Nanog. Satb1−/− cultures have a higher proportion of Nanoghigh cells, and an increased potential to reprogram human B lymphocytes in cell fusion experiments. Moreover, Satb1-deficient ES cells show an increased expression of Satb2, and we find that forced Satb2 expression in wild-type ES cells antagonizes differentiation-associated silencing of Nanog and enhances the induction of NANOG in cell fusions with human B lymphocytes. An antagonistic function of Satb1 and Satb2 is also supported by the almost normal differentiation potential of Satb1−/−Satb2−/− ES cells. Taken together with the finding that both Satb1 and Satb2 bind the Nanog locus in vivo, our data suggest that the balance of Satb1 and Satb2 contributes to the plasticity of Nanog expression and ES cell pluripotency

Technical note: Validation of a semi-automated software tool to determine gait-cycle variables in dairy cows

This paper presents the validation of a software tool called Cow-Gait-Analyzer (University of Bern, Switzerland) to determine gait-cycle variables in lame and non-lame dairy cows using features derived from low-cost, stand-alone 3-dimensional accelerometers (400 Hz). The Cow-Gait-Analyzer automatically extracts the relevant gait events of foot load and toe off, which characterize gait-cycle duration, stance phase, and swing phase during walking. A nonautomatic step is visual inspection of the pedograms. If the software does not automatically choose the right peaks according to pedogram definitions, peaks can be manually chosen. We validated the algorithms by comparing the accelerometer data (pedogram) with the synchronized video data, which we used as a gold standard. We carried out the measurements at the metatarsal level of paired hind limbs during walking. We included 12 non-lame cows and 5 lame cows and expressed overall differences between the Cow-Gait-Analyzer and the gold standard as relative measurement error (RME). We analyzed 34 hind limbs with a mean of 9 gait cycles. The median RME for gait-cycle duration and stance phases were 0 and 1.69%, respectively. The peaks of gait-cycle variables showed RME of 0.67 and 0.24% for foot load and toe off, respectively. The semi-automated Cow-Gait-Analyzer can accurately determine gait-cycle variables in both lame and non-lame cows, and could be used to assess gait patterns in routine clinical and research practice focusing on individual cows