We have used the nervous system of the medicinal leech as a preparation to study the molecular basis of neural repair. The leech central nervous system, unlike mammalian CNS, can regenerate to restore function, and contains identified nerve cells of known function and connectivity. We have constructed subtractive cDNA probes from whole and regenerating ganglia of the ventral nerve cord and have used these to screen a serotonergic Retzius neuron library. This identifies genes that are regulated as a result of axotomy, and are expressed by the Retzius cell. This approach identifies many genes, both novel and known. Many of the known genes identified have homologues in vertebrates, including man. For example, genes encoding thioredoxin (TRX), Rough Endoplasmic Reticulum Protein 1 (RER-1) and ATP synthase are upregulated at 24 h postinjury in leech nerve cord. To investigate the functional role of regulated genes in neuron regrowth we are using microinjection of antisense oligonucleotides in combination with horseradish peroxidase to knock down expression of a chosen gene and to assess regeneration in single neurons in 3-D ganglion culture. As an example of this approach we describe experiments to microinject antisense oligonucleotide to a leech isoform of the structural protein, Protein 4.1. Our approach thus identifies genes regulated at different times after injury that may underpin the intrinsic ability of leech neurons to survive damage, to initiate regrowth programs and to remake functional connections. It enables us to determine the time course of gene expression in the regenerating nerve cord, and to study the effects of gene knockdown in identified neurons regenerating in defined conditions in culture.

ABSTRACT. Fur color is an important, genetically determined characteristic of domestic rabbits, and rabbit furs are of great economic value. To investigate the molecular genetics associated with fur color determination in domestic rabbits, we used Solexa-sequencing technology to probe gene expression in dorsal skin tissues sampled from full-sibling Rex rabbits of different colors. The number of expressed genes in each sample was approximately 14,700. Among the top 30 genes and transcription factors with the highest reads per kilobase per million values, the elongation factor-alpha 1 gene was highly expressed in all samples, as were genes of the ribosomal protein and keratin gene families. Compared with the chinchilla (C) Rex rabbit control sample, the numbers of genes in the black (B) and white (W) rabbit samples were 1809 and 460, respectively, and the number of common differentially expressed genes was 257. Clustering analysis of these 257 genes revealed that 32 were up-regulated in sample B and down- regulated in sample W. Of these 32 genes, we identified some that are related to fur formation, including Tyrosinase-related protein 1 (TYRP1) and Tyrosinase (TYR), as well as genes with unknown functions. Quantitative real-time polymerase chain reaction was used to verify the expression patterns of those genes. The findings are expected to provide reference for the further study of fur color formation in rabbits.