Prion protein (PrP) is a glycoprotein constitutively expressed on the neuronal cell surface. A protease-resistant isoform of prion protein is implicated in the pathogenesis of a series of transmissible spongiform encephalopathies. We have developed a line of mice homozygous for a disrupted PrP gene in which the whole PrP-coding sequence is replaced by a drug-resistant gene. In keeping with previous results, we find that homozygous loss of the PrP gene has no deleterious effect on the development of these mice and renders them resistant to prion. The PrP-null mice grew normally after birth, but at about 70 weeks of age all began to show progressive symptoms of ataxia. Impaired motor coordination in these ataxic mice was evident in a rotorod test. Pathological examination revealed an extensive loss of Purkinje cells in the vast majority of cerebellar folia, suggesting that PrP plays a role in the long-term survival of Purkinje neurons.

We have cloned a cDNA for a novel member of the opioid receptor family, designated as ROR-C, from the rat cerebrum cDNA library using the probe derived from the dopioid receptor subtype cDNA. The deduced amino acid sequence of ROR-C shows high homology with those of ROR-A (rat S-opioid receptor subtype), ROR-B (rat ,&subtype) and ROR-D (rat K-subtype). RNA blot hybridization and in situ hybridization analysis revealed that ROR-C mRNA is expressed in discrete regions of the rat centraf nervous system.

The peptide nociceptin (also named orphanin FQ) acts in the brain to produce various pharmacological effects, including hyperalgesia and hypolocomotion. The nociceptin receptor uses guanine-nucleotide-binding proteins to mediate the inhibition of adenylyl cyclase, the activation of potassium channels and inhibition of calcium channels. It has been shown using knock-out mice that the nociceptin receptor is not required for regulation of nociceptive responses or locomotion activity, but modulates the auditory function. Here we show that mice lacking the nociceptin receptor possess greater learning ability and have better memory than control mice. Histological analysis revealed the expression of both the nociceptin precursor and the nociceptin receptor in the hippocampus, thought to take part in aspects of learning and memory. Moreover, the receptor-deficient mice showed larger long-term potentiation in the hippocampal CA1 region than control mice, without apparent changes in presynaptic or postsynaptic electrophysiological properties. These results show that the loss of the nociceptin receptor results in a gain-of-function mutation in both the memory process and the long-term potentiation mechanism in CA1, perhaps as a result of altered intracellular signal transduction systems in neurons.

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We identified a novel cDNA related to that of transcriptional enhancer factor-1 (TEF-1) during the course of isolation and characterization of cDNAs, whose mRNAs are preferentially expressed in the mouse neural precursor cells. The putative polypeptide, termed embryonic TEA domain-containing factor (ETF), deduced from the nucleotide sequence contains 445 amino acids and shares 66% amino acid identity with mouse and human TEF-1 proteins. The primary structure of the TEA domain, a probable DNA-binding domain, and the specific DNA binding activity to the GT-IIC motif of ETF are indistinguishable from those of the known vertebrate TEF-1 proteins. However, the expression of the ETF gene is strictly regulated in developing embryos and is limited to certain tissues, such as the hindbrain of a 10-day-old mouse embryo, in contrast to the ubiquitous expression pattern of the TEF-1 gene. These results suggest that ETF is a novel mammalian member of the TEA domain-containing transcription factor family and may be involved in the gene regulation of the neural development. We have discussed the possible existence of multiple subtypes of the mammalian TEF-1 family proteins, which may play different roles in cellular and development gene regulation.