Timothy Mohun

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Xenopus cerberus (Xcer) is a cytokine expressed in anterior mesendoderm overlapping and surrounding Spemann's gastrula organiser. When misexpressed in blastomeres, Xcer can induce ectopic heads with well-defined brain, cement gland, olfactory placodes, cyclopic eye, and occasionally liver and heart. We report here the identification of mCer-1, a murine gene(More)
Bone morphogenetic protein-4 (BMP-4) is thought to play an important role in early Xenopus development by acting as a "ventralizing factor' and as an epidermal determinant: local inhibition of BMP-4 function in whole embryos causes the formation of an additional dorsal axis, and inhibition of BMP-4 function in isolated ectodermal cells causes the formation(More)
We describe a technique suitable for routine three-dimensional (3-D) analysis of mouse embryos that is based on episcopic fluorescence images captured during serial sectioning of wax-embedded specimens. We have used this procedure to describe the cardiac phenotype and associated blood vessels of trisomic 16 (Ts16) and Cited2-null mutant mice, as well as the(More)
We have examined the role of two RSRF/MEF2 proteins in the onset of skeletal and cardiac muscle differentiation in early Xenopus embryos. In normal development, zygotic expression of SL1 (MEF2D) precedes that of SL2 (MEF2A) by several hours, but neither gene is expressed prior to the accumulation of MyoD and Myf5 transcripts in the somitic mesoderm. Ectopic(More)
We have isolated two members of the RSRF protein family, SL-1 and SL-2, in Xenopus laevis. Both proteins contain SRF-type DNA binding domains and are related to the human protein, RSRFC4. SL-1 constitutes a novel member of the RSRF family whilst SL-2 is similar to human RSRFC4 throughout its length. SL-1 protein recognizes the consensus DNA sequence(More)
The presomitic mesoderm of vertebrates undergoes a process of segmentation in which cell-cell interactions mediated by the Notch family of receptors and their associated ligands are involved. The vertebrate homologues of Drosophila &Dgr ; are expressed in a dynamic, segmental pattern within the presomitic mesoderm, and alterations in the function of these(More)
The developing mouse limb is widely used as a model system for studying tissue patterning. Despite this, few references are available that can be used for the correct identification of developing limb structures, such as muscles and tendons. Existing textual references consist of two-dimensional (2D) illustrations of the adult rat or mouse limb that can be(More)
Proper functioning of the musculoskeletal system requires the precise integration of bones, muscles, and tendons. Complex morphogenetic events ensure that these elements are linked together in the appropriate three-dimensional configuration. It has been difficult, however, to tease apart the mechanisms that regulate tissue morphogenesis. We find that(More)
Establishment of the left-right axis is a fundamental process of vertebrate embryogenesis. Failure to develop left-right asymmetry leads to incorrect positioning and morphogenesis of numerous internal organs, and is proposed to underlie the etiology of several common cardiac malformations. The transcriptional modulator Cited2 is essential for embryonic(More)
Muscle actin genes are the earliest yet described to show cell type-specific activation in amphibian embryos. Gene-specific probes show that alpha-skeletal and alpha-cardiac actin genes start to be transcribed simultaneously at the end of gastrulation, but only in those regions of the mesoderm that subsequently form embryonic muscle. Their expression(More)