Fatty acid binding protein is induced in neurons of the dorsal root ganglia after peripheral nerve injury.

Peripheral nerve trauma induces the expression of genes presumed to be involved in the process of nerve degeneration and repair. In the present study, an in vivo paradigm was employed to identify molecules which may have important roles in these processes. A cDNA library was constructed with RNA extracted from rat dorsal root ganglia (DRG) 3 days after a sciatic nerve crush. After differential hybridization to this library, several cDNAs were identified that encoded mRNAs that were upregulated in the DRG ipsilateral to the crush injury, as opposed to the contralateral or naive DRG. Approximately 0.15% of all the clones screened were found to be induced. This report presents the types of induced sequences identified and characterizes one of them, DA11. The 0.7 kb DA11 full length cDNA clone contains a 405 nucleotide open reading frame that encodes a putative protein of 15.2 kDa (135 amino acid residues) and is a member of the family of fatty acid binding proteins (FABP). The DA11 protein differs by one amino acid residue from the sequence of the C-FAPB protein and by eight residues from the sequence of mal1, proteins found in rat and mouse skin, respectively. Northern and Western blot analyses showed that the DA11 mRNA and protein were induced in the injured DRG. Furthermore, studies using antibodies generated against DA11 found that the DA11-like immunoreactivity was more pronounced in the nuclei of neurons located in the DRG ipsilateral to the sciatic cut than those located in the contralateral DRG. The induction of DA11 mRNA and protein in DRG neurons suggests, for the first time, the involvement of a neuronal FABP in the process of degeneration and repair in the nervous system.

cDNA cloning and tissue distribution of five human EPH-like receptor protein-tyrosine kinases.

We have isolated cDNA clones from a human fetal brain library that encode five members of the EPH sub-family of receptor protein tyrosine kinases (PTKs). Comparison of the DNA sequences of these receptors to the Genbank database reveals that two of our clones correspond to the previously identified HEK and ERK receptors, two are apparently human homologues of the mouse receptors Sek and Bsk and one is novel. With these additions, the number of known human EPH sub-family members is nine and the total in all vertebrate species is 13 making it the largest known sub-family of PTKs. Analysis of the expression pattern of EPH sub-family mRNAs reveals that some are expressed in a wide variety of adult tissues while others are quite restricted. Consistent with the amplification of these sequences from a fetal brain cDNA library, all five members which we have isolated are expressed in the brain. We have named these receptors HEK4, HEK5, HEK7, HEK8 and HEK11, following the nomenclature of Wicks et al. (1992) and the numbering convention set forth by Sajjadi et al. (1991). Analysis of these new EPH sub-family members will increase our understanding of the biology of this receptor family and their isolation will provide reagents for the identification of ligands for this large family of orphan receptors.