By ChIP, we also found that H3K4me2 was present at DXZ1 alpha satellite DNA, at or below the level found on the INCB28060 c-Met inhibitor control genes in the two hybrids we analyzed. These results argue that Cenp-A chromatin in mouse cells may be organized differently than in humans and insects and that when present in hybrid cell lines, human centromere organization reflects that of the mouse host centromere. Optical mapping of different human chromosomes retained in somatic cell hybrids using chromatin fibers might provide further insights into long-range organization of euchromatic and heterochromatic modifications within human centromeres. Other than mazEF and relBE, most other E. coli TA systems have been discovered only recently. Each of them inhibits translation; however, the various toxins differ in their primary targets and modes of action. chpBIK is partially homologous to mazEF. Like MazF, the toxin ChpK is also an endoribonuclease that cleaves mRNAs in a ribosome-independent manner. Given that no previous studies have documented PAD expression in the mammary gland nor have previous reports demonstrated that PAD-mediated citrullination occurs in mammary tissue, we believe that this study provides significant new insight into PAD biology. For example, our finding that PADmediated citrullination in mammary tissue appears to be restricted to epithelial cells during a distinct stage of the estrous cycle and limited to a small subset of targets suggests that PAD activity is likely facilitating a specific event during diestrus. Further, the observation that histone citrullination correlates with PAD2 expression in mammary epithelium at diestrus and that a fraction of PAD2 is nuclear in these cells, raises the possibility that PAD2 may play a role regulating gene activity in the mammary epithelium. The model predicts covariation among morphological variables, such as tooth size, intercusp distances, and cusp size. The model hinges on the molecular signaling activity of enamel knots, transient structures composed of nonproliferating epithelium that direct the folding of the dental epithelium at the future sites of cusp tips. In addition to promoting epithelial and mesenchymal growth, enamel knots also produce inhibitors which prevent the formation of new enamel knots within a zone surrounding them. As the distance from a preexisting enamel knot increases, the likelihood of escaping the inhibition field surrounding that enamel knot increases, which may result in the formation of a new enamel knot, and thus a new cusp. All else being equal, a larger tooth bud or a tooth with smaller distances between the earlier forming enamel knots may be more likely to allow late-forming enamel knots to initiate around the periphery of a tooth crown. The model is applicable to all vertebrate teeth and has been used successfully to predict patterns of cusp expression in other mammalian species.