The gene for the peripheral myelin protein PMP-22 is a candidate for Charcot-Marie-Tooth disease type 1A.

Charcot-Marie-Tooth disease type 1A (CMT1A) is an autosomal dominant peripheral neuropathy associated with a large DNA duplication on the short arm of human chromosome 17. The trembler (Tr) mouse serves as a model for CMT1A because of phenotypic similarities and because the Tr locus maps to mouse chromosome 11 in a region of conserved synteny with human chromosome 17. Recently, the peripheral myelin gene Pmp-22 was found to carry a point mutation in Tr mice.

A leucine-to-proline mutation in the putative first transmembrane domain of the 22-kDa peripheral myelin protein in the trembler-J mouse.

Peripheral myelin protein PMP-22 is a potential growth-regulating myelin protein that is expressed by Schwann cells and predominantly localized in compact peripheral myelin. A point mutation in the Pmp-22 gene of inbred trembler (Tr) mice was identified and proposed to be responsible for the Tr phenotype, which is characterized by paralysis of the limbs as well as tremors and transient seizures. In support of this hypothesis, we now report the fine mapping of the Pmp-22 gene to the immediate vicinity of the Tr locus on mouse chromosome 11.

Characterization of a novel peripheral nervous system myelin protein (PMP-22/SR13).

We have recently described a novel cDNA, SR13 (Welcher, A. A., U.

Trembler mouse carries a point mutation in a myelin gene.

The autosomal dominant trembler mutation (Tr), maps to mouse chromosome 11 (ref. 2) and manifests as a Schwann-cell defect characterized by severe hypomyelination and continuing Schwann-cell proliferation throughout life. Affected animals move clumsily and develop tremor and transient seizures at a young age.

The rat trk protooncogene product exhibits properties characteristic of the slow nerve growth factor receptor.

Two distinct nerve growth factor receptor (NGFR) complexes are present on NGF-responsive cell types; these correspond to 100 kDa and 158 kDa for the fast (fNGFR) and the slow (sNGFR) NGFRs, respectively. Previous studies indicate that each complex is derived from a separate gene product and that the sNGFR contains tyrosine kinase activity. The cDNA encoding the fNGFR has previously been cloned.

NGF/BDNF chimeric proteins: analysis of neurotrophin specificity by homolog-scanning mutagenesis.

Despite their extensive sequence identities at the amino acid level (approximately 55%), NGF and brain-derived neurotrophic factor (BDNF) display distinct neuronal specificity toward neurons of both the PNS and CNS. To explore which region(s) within these neurotrophic factors might determine their differential actions on various subpopulations of peripheral neurons, a systematic series (homolog-scanning mutagenesis) of chimeric NGF/BDNF molecules was prepared using PCR overlap-extension techniques. After expression in COS-7 cells, the chimeric proteins were tested for their biological activities in neurite outgrowth and neuronal survival assays.

Mutation of tryptophan-21 in mouse nerve growth factor (NGF) affects binding to the fast NGF receptor but not induction of neurites on PC12 cells.

By using in vitro DNA mutagenesis, we replaced the tryptophan residue at position 21 in mouse nerve growth factor (NGF) with either phenylalanine, leucine or serine. Yield, biological activity, immunological reactivity and receptor binding of the recombinant proteins were determined. All three mutants were produced at considerably lower yields than wild-type NGF, with the serine mutant being undetectable.

Two conserved domains in the NGF propeptide are necessary and sufficient for the biosynthesis of correctly processed and biologically active NGF.

The three members of the neurotrophin family (NGF, BDNF and NT-3) are synthesized as large precursor proteins which undergo proteolytic processing to yield biologically active, mature neurotrophic factors. We have used in vitro mutagenesis to examine the pro-region in the NGF precursor protein as a first step towards a general understanding of the role of propeptides in the biosynthesis of neurotrophins. Our results demonstrate that only two small domains within the NGF propeptide are required for the expression and secretion of properly processed and biologically active, recombinant mouse NGF in COS-7 cells.

A myelin protein is encoded by the homologue of a growth arrest-specific gene.

Striking features of the cellular response to sciatic nerve injury are the proliferation of Schwann cells in the distal nerve stump and the downregulation of myelin-specific gene expression. Once the axons regrow, the Schwann cells differentiate again to reform the myelin sheaths. We have isolated a rat cDNA, SR13, which is strongly downregulated in the initial phase after sciatic nerve injury.

Identification of transcriptionally regulated genes after sciatic nerve injury.

Mammalian peripheral nerve fibres can regenerate after injury. In an attempt toward a better understanding of the underlying molecular events, we have isolated novel and known rat cDNA sequences, the expression of which are regulated during sciatic nerve regeneration. For this purpose, cDNA libraries were constructed from either the nerve segment distal to the crush site or the corresponding contralateral uninjured nerve of the same animals.

Molecular approaches to nerve regeneration.

Current research into regeneration of the nervous system has focused on defining the molecular events that occur during regeneration. One well-characterized system for studying nerve regeneration is the sciatic nerve of rat. Numerous studies have characterized the sequence of events that occur after a crush injury to the sciatic nerve (Cajal 1928; Hall 1989).

The in vivo expression of type B CD23 mRNA in B-chronic lymphocytic leukemic cells is associated with an abnormally low CD23 upregulation by IL-4: comparison with their normal cellular counterparts.

We recently reported that the sera of chronic lymphocytic leukemia (CLL) patients contained 3-500 times more soluble CD23 (or IgE-BF) than the sera of patients with other lymphoproliferative diseases or normal individuals and that their B cells (B-CLLs) overexpressed CD23 Ag. In the present report, we extended these studies and showed that CD5+ B cells from all CLL patients (n = 15) co-express CD23 Ag. We next identified two additional major differences between B-CLLs and normal adult B cells.

Expression of human lymphocyte IgE receptor (Fc epsilon RII/CD23). Identification of the Fc epsilon RIIa promoter and its functional analysis in B lymphocytes.

Two species, Fc epsilon RIIa and Fc epsilon RIIb, of the human low-affinity receptor for IgE (Fc epsilon RII/CD23) have recently been described. They differ by only six amino acids in the cytoplasmic N-terminus and are generated by different cell-specific transcriptional start sites that lead to distinct 5'-leader sequences in the corresponding mRNA. In this study, we present the analysis of the promoter which is regulating the expression of the B cell-specific Fc epsilon RIIa.

Protein partitioning in two-phase aqueous polymer systems.

Theories of protein partitioning in two-phase polymer systems which account for the effects of different aspects of system composition-such as the choice of materials, protein size, polymer molecular weight, polymer concentration, salt concentration, and affinity ligands-are reviewed. Although the present models provide some information about specific aspects of partitioning, a comprehensive and fundamental theory which can be used to predict protein partitioning behavior has not yet been developed. Some recommendations for future work are given.

Human Fc epsilon R II and IgE-binding factors.

The low-affinity receptor for IgE (Fc epsilon R II) is mainly expressed on B lymphocytes, although it may also be found on some monocytes, eosinophils, and platelets. The presence of Fc epsilon R II on T cells is still controversial, but our results demonstrate that it is expressed on some HTLV-I-transformed T lymphocytes, and they strongly suggest that it may be found on a small proportion of normal T cells. Fc epsilon R II is a 45-KD glycoprotein containing one N-linked carbohydrate of complex type, O-linked carbohydrates, and sialic acid residues.

T-cell-derived IgE-binding factors. II. Purification and characterization of IgE-binding factors produced by human T cell leukemia/lymphoma virus-1-transformed T lymphocytes.

We previously described human T cell leukemia/lymphoma virus-1-transformed T cell clones expressing surface molecules binding to monoclonal antibodies against lymphocyte Fc epsilon receptor (Fc epsilon R) and releasing soluble factors binding to both IgE and to monoclonal antibody to lymphocyte Fc epsilon R. In this study, one such clone (HE1-11) was tested for the presence of mRNA hybridizing with a cDNA probe coding for Fc epsilon R on B cells. Northern blot analysis revealed the presence of the same 1.

Molecular structure of the gene and the 5'-flanking region of the human lymphocyte immunoglobulin E receptor.

Overlapping clones which contain the complete gene encoding the human lymphocyte IgE receptor (MW:45kd; identical with CD23), were isolated from human genomic lambda-libraries. The gene spans approximately 13kb and comprises 11 exons. The 5'-end of the mRNA was mapped by primer extension and S1-mapping, revealing two initiation sites for transcription.

Cloning and expression of the cDNA coding for a human lymphocyte IgE receptor.

Low-affinity receptors (Fc epsilon R) and secreted factors (IgE-BF) which bind to immunoglobulins of the IgE isotype play a key role in the regulation of human IgE synthesis. We report here the cloning of a cDNA coding for the Fc epsilon R of the human B-lymphoblast cell line RPMI 8866. The nucleotide sequence of this cDNA predicts a polypeptide with 321 amino acids and a mol.