他们在徘徊中走出山林

龙龙 龙龙是最后一个在大兴安岭深山密林里撮罗子降生的狩猎部落的小猎民,1988年,他在撮罗子里降生,父母出去打猎的时候,就把他话在树上吊的摇蓝里,稍大一些后,     

Leaving the meristem behind: regulation of KNOX genes

The mechanism by which the plant reserves some cells as pluripotent stem cells while partitioning others into differentiated leaf tissue is fundamental to plant development. New work in Arabidopsis elucidates the genetic circuitry that distinguishes meristem from leaf.     

VEGF shows its attractive side at the midline

Vascular endothelial growth factor (VEGF) family members are best known for their powerful mitotic and angiogenic activities toward endothelial cells. Two independent studies in this issue of Neuron now provide compelling evidence that VEGF-A secreted at the CNS midline functions as an attractant for developing axons of spinal commissural neurons and contralaterally projecting retinal ganglion cells.     

Rhomboid function in the midline of the Drosophila CNS

Rhomboid (Rho), a cell surface, seven-transmembrane domain protein, participates in Spitz-dependent activation of the Drosophila EGF receptor (EGFR). By contrast to transient expression in other embryonic tissues, rho is expressed continuously in the embryonic and larval Midline Glia (MG) lineage and is required upstream of, or in parallel with, S, Spi, and EGFR to establish MG cell number. EGFR signaling is necessary for the expression of rho in the MG and sufficient to stimulate rho expression in additional MG progenitors. rho expression is required continuously from embryonic stage 9-17 to suppress apoptosis in the MG. Although rho misexpression can increase MG number through a non-cell autonomous mechanism, the pattern of normal rho expression suggests that it functions by enhancing autocrine or paracrine signaling among MG cells.