Temporary expression of A31 mRNA in nascent dendrites of human fetal brain

A modified differential display method was used to compare patterns of mRNA expression between human fetal and adult brains and we obtained 26 candidates for highly expressed fetal cDNA fragments. A clone, A31, was picked up, which had no significant homology in sequence compared with the DDBJ/EMBL/GenBank databases. A31 mRNA was shown to be expressed only in fetal brain by RT-PCR and Northern blotting. The Northern analysis revealed that the mRNA was about 9kb and highly expressed in middle stage of human brain, and that it was absent in various tissues except brain. Further characterization of this clone was performed by in situ hybridization, which showed that the mRNA was mostly expressed in cell bodies and dendrites of neurons in cortical plates. Our analyses suggest that this mRNA is involved in dendritic development at the middle stage in human fetal brain and that the mRNA is partially transported from cell bodies to dendrites where the protein is synthesized.