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Fetal zones are transient architectonic compartments of the fetal telencephalic wall. While all fetal zones display changing features of cellular composition (e. g., they temporarily contain migratory neurons, growing axons and transient synapses), some contain resident populations of transient fetal cells. The aim of this study is systematic description of these transient cell populations and their compartmental distribution, based on the analysis of extensive and versatile Zagreb Neuroembryological Collection. Our main finding is that besides well-known transient fetal populations of cells (such as Cajal-Retzius cells and subpial granular layer in the marginal zone, or perireticular nucleus in the fetal internal capsule), there are two major populations of transient cells, one residing in the neocortical anlage (subplate cells of the subplate zone), and other residing in the fetal white matter (deep fetal interstitial cells of the intermediate zone). In the adult brain, subplate cells survive as components of cortical layer VI and so-called interstital neurons of the subcortical white matter. On the other hand, deep fetal interstitial cells have no counterpart in the adult brain. In the fetal brain, they reside in major commissural tracts (e. g., corpus callosum, anterior commissure), especially near the midline, and in crossroads of growing axon pathways in the periventricular intermediate zone. Therefore, we suggest that deep fetal interstitial cells are transient cells involved in axon guidance in the fetal brain. Supported by Croatian Ministry of Science, Education & Sport grants No. 108-1081870-1878 (to M. J.) and 108-181870-1876 (to. I. K.). |
