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After activation in mesoderm and neuroectoderm, expression of the Hoxb-1 gene is progressively restricted to rhombomere (r) 4 in the hindbrain. Analysis of the chick and mouse Hoxb-1 genes identified positive and negative regulatory regions that cooperate to mediate segment-restricted expression during rhombomere formation. An enhancer generates expression(More)
Within the Hoxb homeobox gene complex, Hoxb-1 is the earliest member expressed in the mesoderm and neuroectoderm of primitive streak and presomite embryos, preceding rhombomere-restricted expression in the hindbrain. Ectopic exposure of embryos to retinoic acid alters spatial aspects of Hox gene expression patterns. However, the role of retinoids in(More)
Fushi tarazu (ftz) is one of the Drosophila homeo-box-containing genes required to establish the segmental pattern. Ftz+ transcripts accumulate in cells that form seven equally spaced bands at the blastoderm stage. We have analyzed cis-acting controlling sequences of the ftz gene by germ line transformation. The functional ftz gene includes a transcription(More)
The dorsal thalamus (DT) is a pivotal region in the vertebrate brain that relays inputs from the peripheral sensory organs to higher cognitive centers. It consists of clusters of neurons with relevant functions, called brain nuclei. However, the mechanisms underlying development of the DT, including specification of the neuronal subtypes and morphogenesis(More)
The temporal and spatial regulation of somitogenesis requires a molecular oscillator, the segmentation clock. Through Notch signalling, the oscillation in cells is coordinated and translated into a cyclic wave of expression of hairy-related and other genes. The wave sweeps caudorostrally through the presomitic mesoderm (PSM) and finally arrests at the(More)
A repetitive DNA sequence has been identified in the Drosophila melanogaster genome that appears to be localized specifically within genes of the bithorax and Antennapedia complexes that are required for correct segmental development. Initially identified in cloned copies of the genes Antennapedia, Ultrabithorax and fushi tarazu, the sequence is also(More)
The homeotic genes of the bithorax complex (BX-C) and the Antennapedia complex (ANT-C) of Drosophila appear to specify the developmental fate of segments or parts of segments of the fly. We have previously reported weak DNA sequence homology between 3' portions of the Antennapedia and fushi tarazu genes of the ANT-C and the Ultrabithorax gene of the BX-C.(More)
Segmentation of a vertebrate embryo begins with the subdivision of the paraxial mesoderm into somites through a not-well-understood process. Recent studies provided evidence that the Notch-Delta and the FGFR (fibroblast growth factor receptor) signalling pathways are required for segmentation. In addition, the Mesp family of bHLH transcription factors have(More)
The complex architecture of the limb cartilage pattern probably develops by the sequential segmentation and branching process of precartilaginous cell condensation under the control of positional signalling provided by the zone of polarizing activity (anteroposterior) and the apical ectodermal ridge (proximodistal). This signalling is monitored and(More)
We have investigated by immunocytochemistry the spatial and temporal distribution of cellular retinoic acid-binding protein (CRABP) in the developing nervous system of the chick embryo in order to answer two specific questions: do neural crest cells contain CRABP and where and when do CRABP-positive neuroblasts first arise in the neural tube? With regard to(More)