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dvdy21422-DVDY21422FigureS1.tif1785K Suppl. Fig. 1.Prox1 protein expression is down-regulated in the motoneuron domain co-incident with the appearance of Isl1/2+ motoneurons. Immunofluorescent double-labelling for Prox1 (green) and Isl1/2 (red) between stages 15–19 at the onset of neurogenesis in the thoracic region of the chick spinal cord. Initially, Prox1 expression is seen in ventral territories where motoneurons will be generated, but is gradually down-regulated here as Isl1-1/2 expression in post-mitotic motoneurons is initiated. At stages 15–17, a few cells co-expressing Prox1 and Isl-1/2 can be seen. By stage 19, Prox1 is no longer detected in the motoneuron domain, and very few if any cells co-express these proteins.
dvdy21422-DVDY21422FigureS2.tif2396K Suppl. Fig. 2.Mis-expression of Prox1 in post-mitotic neurons does not impede their differentiation.A,B:Electroporation of GFP under the control of the β-tubulin regulatory elements (REF) results in expression that is largely restricted to post-mitotic neurons (marked by co-expression of NeuN and β-tubulin proteins) in the lateral MZ.C,D:Co-expression of a full-length Prox1 cDNA in progenitors using the pCIG vector with a reporter construct expressinglacZunder the control of the β-tubulin enhancer results in up-regulation oflacZexpression in Prox-transfected progenitors. In contrast, transfection of neurogenic factors such as Mash1 induceslacZexpression only in MZ cells.E–J:Transfection of a full-length Prox1 cDNA under the control of the β-tubulin regulatory elements restricts ectopic expression to lateral MZ cells. The expression of proteins expressed in post-mitotic neurons in the MZ is not altered in any of these experiments.

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