NYU professor and renowned biologist Claude Desplan will be the feature speaker at the seminar. The seminar will be at ECNU, Geo 264 at15:00–16:00 and followed by a reception between 16:00–16:30.
Center for Developmental Genetics, Department of Biology, New York University, New York, USA.
Center for Genomics & Systems Biology, New York University Abu Dhabi, Abu Dhabi, UAE
The Drosophila visual system is composed of the retina and the image processing centers. The retina is composed of two randomly distributed types of unit eyes defined by the expression of Rhodopsins. Stochastic expression of the transcription factor Spineless, which determines the random mosaic pattern, is controlled by a two-step process. First, each allele ofspineless randomly makes an intrinsic, ON/OFF expression decision governed by global activation coupled with stochastic repression. When the expression decisions disagree (one allele ON and one allele OFF), interchromosal communication coordinates expression state between the two alleles. This effect does not depend on chromosomal pairing or endogenousspineless chromosomal position but instead requires specific DNA elements to mediate regulatory interactions. This mechanism coupling stochastic repression with interallelic coordination contrasts starkly with the noisy activation mechanisms seen in bacteria and the mono-allelic, stochastic activation mechanisms observed in the mouse olfactory and human color vision systems.
Patterning of the medulla part of the optic lobes, where motion and color information are processed, is precisely deterministic. The medulla contains 40,000 neurons of more than 70 cell types. These neurons are born from neural stem cells that express five transcription factors in a temporal manner, similar to the sequence of transcription factors observed in embryonic neural stem cells. The neurons emerging from neural stem cells at each stage generally maintain expression of the corresponding gene and become different cell types. We will describe the mechanisms controlling the transition from one neural stem cell stage to the next and how later transcription factors repress the expression of earlier ones.
The medulla neuroepithelium is also highly patterned with each region contributing to generating two types of neurons: ‘Uni-columnar neurons’ that have a 1:1 stoichiometry with the photoreceptors that innervate the medulla and are generated throughout the neuroepithelium. The less numerous ‘non-columnar’ neurons are generated from specific sub-regions of the neuroepithelium and migrate to take on their retinotopic position in the medulla.