Golgi fragments (green) are found only in the largest dendrite.
Neuronal Golgi is polarized toward and into the longest and most complex dendrites, say April Horton, Michael Ehlers (Duke University, Durham, NC), and colleagues. Thus it may help determine the stereotyped shape of dendritic arbors.The mammalian Golgi is most often seen as a single copy perinuclear organelle, but Golgi “outposts” have been sighted in dendrites before. The Ehlers group found that these outposts were usually only found in the neuron's longest and most complex dendrite and were often positioned at branch points in the dendritic arbor, as if to direct traffic. Additionally, the main Golgi apparatus in the cell body polarized toward what would become the longest dendrite, and there was fourfold greater secretory flux into these favored dendrites. Disruption of Golgi structure left dendritic growth intact, but equalized growth rates between different dendrites.
Dendrites can assert individual identities if their localized ribosomes and mRNAs make soluble proteins. The nonrandom Golgi organization may extend this ability to membrane and secreted proteins.
What controls dendritic Golgi organization is uncertain, but it may well be related to systems that fragment the Golgi during mitosis or reorient it during cell migration.