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We studied the expression of mouse HES-6, a new member of the Hairy/Enhancer of split family of basic helix-loop-helix transcription factors. HES-6 is expressed in all neurogenic placodes and their derivatives and in the brain, where it is patterned along both the anteroposterior and dorsoventral axes. HES-6 is also expressed in the trunk, in the dorsal(More)
How complex networks of activators and repressors lead to exquisitely specific cell-type determination during development is poorly understood. In the Drosophila eye, expression patterns of Rhodopsins define at least eight functionally distinct though related subtypes of photoreceptors. Here, we describe a role for the transcription factor gene defective(More)
Segmentation, or metamerism, consists of the subdivision of the body into discrete units that subsequently acquire regional specializations. In vertebrates, the most obvious manifestation of this phenomenon is seen during the formation of the mesodermal somites and their derivatives. This review surveys three different models for how somites form, and how(More)
The Drosophila eye is a mosaic that results from the stochastic distribution of two ommatidial subtypes. Pale and yellow ommatidia can be distinguished by the expression of distinct rhodopsins and other pigments in their inner photoreceptors (R7 and R8), which are implicated in color vision. The pale subtype contains ultraviolet (UV)-absorbing Rh3 in R7 and(More)
In visual and olfactory sensory systems with high discriminatory power, each sensory neuron typically expresses one, or very few, sensory receptor genes, excluding all others. Recent studies have provided insights into the mechanisms that generate and maintain sensory receptor expression patterns. Here, we review how this is achieved in the fly retina and(More)
The compound eye of Drosophila melanogaster consists of about 750 ommatidia (unit eyes). Each ommatidium is composed of about 20 cells, including lens-secreting cone cells, pigment cells, a bristle cell and eight photoreceptors (PRs) R1-R8. The PRs have specialized microvillar structures, the rhabdomeres, which contain light-sensitive pigments, the(More)
Sensory systems with high discriminatory power use neurons that express only one of several alternative sensory receptor proteins. This exclusive receptor gene expression restricts the sensitivity spectrum of neurons and is coordinated with the choice of their synaptic targets. However, little is known about how it is maintained throughout the life of a(More)
head-tail axis and developmental time was put forward by Pieter Nieuwkoop in 1952 and is now widely known as the " activation-transformation " model (reviewed in Stern, 2001). Nieuwkoop proposed that the earliest cells of the nervous system to be induced (" activated ") have an anterior (cranial) character, and that later signals " transform " (or(More)
We describe a novel chick WD-protein, cSWiP-1, expressed in somitic mesoderm and developing limb buds as well as in other embryonic structures where Hedgehog signalling has been shown to play a role. Using embryonic manipulations we show that in somites cSWiP-1 expression integrates two signals originating from structures adjacent to the segmental mesoderm:(More)
Sensory systems generally contain a number of neuronal subtypes that express distinct sensory receptor proteins. This diversity is generated through deterministic and stochastic cell fate choices, while maintaining the subtype often requires a distinct mechanism. In a study published in the February 1, 2009, issue of Genes & Development, Lesch and(More)
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