Developmental pattern of expression of the alpha chemokine stromal cell-derived factor 1 in the rat central nervous system

Stromal cell-derived factor 1 (SDF-1) is an alpha-chemokine that stimulates migration of haematopoietic progenitor cells and development of the immune system. SDF-1 is also abundantly and selectively expressed in the developi ng and mature CNS, as we show here. At embryonic day 15, SDF-1 transcripts were detected in the germinal periventricular zone and in the deep layer of the forming cerebral cortex. At birth, granule cells in the cerebellum and glial cells of the olfactory bulb outer layer showed an SDF-1 in situ hybr idization signal that decreased progressively within the next 2 weeks. In o ther regions such as cortex, thalamus and hippocampus, SDF-1 transcripts de tected at birth progressively increased in abundance during the postnatal p eriod. SDF-1 protein was identified by immunoblot and/or immunocytochemistr y in most brain regions where these transcripts were detected. SDF-1 was se lectively localized in some thalamic nuclei and neurons of the fifth cortic al layer as well as in pontine and brainstem nuclei which relay the nocicep tive response. The presence of SDF-1 transcripts in cerebellar granule cell s was correlated with their migration from the external to the inner granul ar layers with disappearance of the signal when migration was completed. In contrast, SDF1 mRNA signal increased during formation of the hippocampal d entate gyrus and stayed high in this region throughout life. The selective and regulated expression of SDF-1 in these regions suggests a role in precu rsor migration, neurogenesis and, possibly, synaptogenesis. Thus this alpha chemokine may be as essential to nervous system function as it is to the i mmune system.