pH-temperature Responsive Hydrogel-Mediated Delivery of Exendin-4 Encapsulated Chitosan Nanospheres for Sustained Therapeutic Efficacy in Type 2 Diabetes Mellitus

Type 2 Diabetes Mellitus (T2D) is a chronic, obesity-related, and inflammatory disorder characterize by insulin resistance, inadequate insulin secretion, hyperglycemia, and excessive glucagon secretion. Exendin-4 (EX), a clinically established antidiabetic medication that acts as a glucagon-like peptide-1 receptor agonist, is effective in lowering glucose levels and stimulating insulin secretion while significantly reducing hunger. However, the requirement for multiple daily injections due to EX's short half-life is a significant limitation in its clinical application, leading to high treatment costs and patient inconvenience. To address this issue, an injectable hydrogel system is developed that can provide sustained EX release at the injection site, reducing the need for daily injections. In this study, the electrospray technique is examine to form EX@CS nanospheres by electrostatic interaction between cationic chitosan (CS) and negatively charged EX. These nanospheres are uniformly dispersed in a pH-temperature responsive pentablock copolymer, which forms micelles and undergoes sol-to-gel transition at physiological conditions. Following injection, the hydrogel gradually degraded, exhibiting excellent biocompatibility. The EX@CS nanospheres are subsequently released, maintaining therapeutic levels for over 72 h compared to free EX solution. The findings demonstrate that the pH-temperature responsive hydrogel system containing EX@CS nanospheres can be a promising platform for the treatment of T2D.

A novel injectable pH-temperature sensitive hydrogel containing chitosan-insulin electrosprayed nanosphere composite for an insulin delivery system in type I diabetes treatment

A novel insulin composite delivery system was prepared and characterized. The composite consisted of a pH- and temperature-sensitive hydrogel, which is an oligomer serine-b-poly(lactide)-b-poly(ethylene glycol)-b-poly(lactide)-b-oligomer serine (OS-PLA-PEG-PLA-OS) pentablock copolymer, as matrix and chitosan-insulin electrosprayed nanospheres (CIN) as constituent materials. The properties of the OS-PLA-PEG-PLA-OS pentablock copolymer and the chitosan-insulin nanoparticles were characterized. The chitosan-insulin nanospheres uniformly distributed in the matrix had a reinforcing effect on the mechanical properties and prolonged the degradation time of the hydrogel depot under body conditions. The composite solutions accommodating different concentrations of the chitosan-insulin nanospheres were subcutaneously injected into induced diabetic BALB/c mice to study the in vivo insulin-release profile. The result showed that insulin concentrations in blood plasma were maintained at a steady-state level. Furthermore, the bio-properties of the insulin were retained and it showed a blood glucose level reducing effect for more than 60 hours after injection to a streptozotocin (STZ)-induced diabetic mouse model. The results suggested that this injectable pH-temperature sensitive hydrogel containing chitosan-insulin electrosprayed nanosphere composites has promising potential applications for type 1 diabetes treatment.

Self-Assemblable Polymer Smart-Blocks for Temperature-Induced Injectable Hydrogel in Biomedical Applications

Self-assembled temperature-induced injectable hydrogels fabricated via self-assembly of polymer smart-blocks have been widely investigated as drug delivery systems and platforms for tissue regeneration. Polymer smart-blocks that can be self-assembly play an important role in fabrication of hydrogels because they can self-assemble to induce the gelation of their copolymer in aqueous solution. The self-assembly occurs in response to an external stimulus change, such as temperature, pH, glucose, ionic strength, light, magnetic field, electric field, or their combination, which results in property transformations like hydrophobicity, ionization, and conformational change. The self-assembly smart-block based copolymers exist as a solution in aqueous media at certain conditions that are suitable for mixing with bioactive molecules and/or cells. However, this solution turns into a hydrogel due to the self-assembly of the smart-blocks under exposure to an external stimulus change in vitro or injection into the living body for a controllable release of loaded bioactive molecules or serving as a biomaterial scaffold for tissue regeneration. This work reports current scenery in the development of these self-assembly smart-blocks for fabrication of temperature-induced injectable physically cross-linked hydrogels and their potential application as drug delivery systems and platforms for tissue engineering.

Polyurethane/polycaprolactone membrane grafted with conjugated linoleic acid for artificial vascular graft application

Constructing satisfied small-diameter vascular graft (diameter less than 6 mm) remains an unsolvable challenge in vascular tissue engineering. This study described the fabrication of electrospun polyurethane/polycaprolactone (PU/PCL) membranes chemically grafted with various densities of conjugated linoleic acid (CLA) - an antithrombotic fatty acid - for making small-diameter blood vessel. Differences in mechanical, antithrombotic properties and biocompatibility of the membranes resulting from the CLA-grafting procedure were the focus of the study. Investigation of mechanical properties relevant to vascular graft application revealed that these properties of the membranes remained unaffected and satisfied clinical criteria following the CLA graft. Blood-membrane interaction assays showed that the CLA-grafted membranes mitigated the adhesion of blood cells, as well as preventing blood coagulation. These effects were also commensurate with increasing density of CLA, suggesting an effective approach to improve antithromboticity. Cellular tests suggested that CLA has an optimal density at which it promoted cell proliferation on the surface of the membranes; however, excessive presence of CLA might cause undesirable inhibition on cells. In conclusion, PU/PCL membrane grafted with CLA could be a prospective material for vascular tissue engineering with further development and investigation.

Facile and Scalable Fabrication of Porous Polystyrene Fibers for Oil Removal by Centrifugal Spinning

The demand for an efficient oil sorbent with high sorption capacity, low cost, scalable fabrication, and high selectivity for the cleanup of spreading oil on water is increasingly urgent due to the frequent occurrence of oil spill accidents in seawater all over the world. In this study, porous polystyrene (PS) fibers with high hydrophobicity and superoleophilicity were directly fabricated by a centrifugal spinning method (CS). The effect of solvents, tetrahydrofuran (THF), and dimethylformamide (DMF) on the morphology and porous structure of the polystyrene fibers was evaluated by using scanning electron microscopy and nitrogen adsorption-desorption experiments. The formation mechanism for the porous structure on the fibers was also evaluated. The oil sorption capacities of the PS fibers for silicon oil, pump oil, and vegetable oil were investigated. The highest oil sorption capacity was found in PS fibers fabricated from PS solution with a THF/DMF weight ratio of 1/3, which exhibited the highest specific surface area, pore volume, and porosity. The high productivity and highly porous structure of PS fibers indicate that CS is a promising method to fabricate porous fibers for the cleanup of oil spills.

Centrifugally Spun Recycled PET: Processing and Characterization

Centrifugal spinning, which is a high-productivity fiber fabrication technique, was used to produce a value-added product from recycled poly(ethylene terephthalate) (rPET). In the present study, rPET fibers, with fiber diameters ranging from submicron to micrometer in scale, were fabricated by spinning a solution of rPET in a mixture of dichloromethane and trifluoroacetic acid. The influence of the polymer solution concentration (the viscosity), the rotational speed of the spinneret, and the inner diameter of the needles on the formation and morphology and mechanical properties of the fibers were examined through scanning electron microscopy and using a tensile testing machine. The thermal behaviors of fibrous mats with various average diameters were also investigated through differential scanning calorimetry. The smoothest and smallest fibers, with an average diameter of 619 nm, were generated using an rPET solution of 10 wt % under a rotation speed of 15,000 rpm using needles having an inner diameter of 160 μm. The fibrous mats have an average tensile strength and modulus of 4.3 MPa and 34.4 MPa, respectively. The productivity and the mechanical properties indicate that centrifugal spinning is an effective technique to fabricate high-value product from rPET.

Fabrication and photochromic properties of Forcespinning® fibers based on spiropyran-doped poly(methyl methacrylate)

Photochromic PMMA micro/nanofibers were fabricated using a Forcespinning™ apparatus of our own design.

Engineering highly swellable dual-responsive protein-based injectable hydrogels: the effects of molecular structure and composition in vivo

Highly swellable, dual-responsive bovine serum albumin (BSA)-based injectable hydrogels that exhibit sol-to-gel phase transitions in response to the physiological pH and temperature have been developed.

Intraarterial gelation of injectable cationic pH/temperature-sensitive radiopaque embolic hydrogels in a rabbit hepatic tumor model and their potential application for liver cancer treatment

Radiopaque embolic solutions employing cationic poly(amino ester urethane)-based copolymers are injected into a rabbit hepatic tumor artery and form hydrogels in response to local temperature and pH for chemoembolization.

Screening for mutations in synaptotagmin XI in Parkinson's disease

Parkinson's disease (PD) is characterized by selective degeneration of neurons in the substantia nigra and subsequent dysfunction of dopaminergic neurotransmission. Genes identified in familial forms of PD encode proteins that are linked to the ubiquitin-proteasome system indicating the pathogenic relevance of disturbed protein degradation in PD. Some of them, i.e. alpha-synuclein, parkin and synphilin-1, have been implicated in presynaptic neurotransmission based on their localization in synaptic vesicles. Synaptotagmin XI is linked to the pathogenesis of PD based on its identification as a substrate of the ubiquitin-E3-ligase parkin. Moreover synaptotagmin XI is involved in the maintainance of synaptic function and represents a component of Lewy bodies (LB) in brains of PD patients. Therefore, we performed a detailed mutation analysis of the synaptotagmin XI gene in a large sample of 393 familial and sporadic PD patients. We did not find any disease causing mutations arguing against a major role of mutations in the synaptotagmin XI gene in the pathogenesis of PD.

Differential expression and tissue distribution of parkin isoforms during mouse development

Mutations of the parkin gene are a cause of autosomal recessive juvenile parkinsonism. Although the parkin gene has been isolated from mouse, rat, and human, little is known about its expression in neural and nonneural tissues during development. In this study, we used a polyclonal antibody to a peptide downstream of the parkin ubiquitin domain to investigate (1) the differential expression of parkin isoforms in protein extracts from fetal and adult mouse tissues, and (2) the distribution of parkin in mouse fetal tissues at different developmental stages and in adult CNS tissues. By Western blot analyses, at least three isoforms of parkin of 22, 50, and 55 kDa were differentially expressed in mouse tissues. The p22 and p50 isoforms were found in fetal and adult mouse CNS tissues, while the p55 isoform was found only in adult tissues. The p50 isoform is the predominant form in both fetal and adult tissues. Immunolocalization in mouse fetuses showed that parkin was expressed only after neuronal differentiation. Although parkin was localized throughout the cytoplasm, the highest level of parkin was found in the neurites of both fetal and adult neurons.

Identification and expression of a mouse ortholog of A2BP1

Human ataxin-2 contains a polyglutamine repeat that is expanded in patients with spinocerebellar ataxia type 2 (SCA2). Ataxin-2 is highly conserved in evolution with orthologs in mouse, Caenorhabditis elegans, and Drosophila melanogaster. It interacts at its C-terminus with ataxin-2 binding protein 1, A2BP1. This study presents a highly conserved mouse ortholog of A2BP1, designated A2bp1. The amino acid sequence of the human and mouse protein is 97.6% identical. This remarkable degree of conservation supports the fact that these proteins have an important basic function in development and differentiation. Sequence analysis reveals the existence of RNA binding motifs. The A2bp1 transcript was found in various regions of the CNS including cerebellum, cerebral cortex, brain stem, and thalamus/hypothalamus. The A2bp1 protein was detected by immunocytochemistry in the CNS and connective tissue of the mouse embryo starting at stage E11, as well as in the heart at all stages. Mouse embryos showed varying expression of A2bp1 at all stages. Previous studies in other model systems had implicated the orthologs of ataxin-2 and A2BP1 in development. This study suggests a role for A2bp1 in embryogenesis as well as in the adult nervous system, possibly mediated by a function in RNA distribution or processing.

Cellular distribution of torsin A and torsin B in normal human brain

BACKGROUND

Early-onset torsion dystonia is a hyperkinetic movement disorder caused by a deletion of 1 glutamic acid residue in torsin A protein, a novel member of the AAA family of adenosine triphosphatases. No mutation has been found so far in the closely related torsin B protein. Little is known about the molecular basis of the disease, and the cellular functions of torsin proteins remain to be investigated.

OBJECTIVE

To study the regional, cellular, and subcellular distribution of the torsin A and torsin B proteins.

METHODS

Expression of torsin proteins in the central nervous system was analyzed by Western blot analysis and immunohistochemistry in human postmortem brain tissues.

RESULTS

We generated polyclonal antipeptide antibodies directed against human torsin A and torsin B proteins. In Western blot analysis of normal human brain homogenates, the antibodies specifically recognized 38-kd endogenous torsin A and 62-kd endogenous torsin B. Absorption controls showed that labeling was blocked by cognate peptide used for immunization. Immunolocalization studies revealed that torsin A and torsin B were widely expressed throughout the human central nervous system. Both proteins displayed cytoplasmic distribution, although torsin B localization in some neurons was perinuclear. Strong labeling of neuronal processes was detected for both proteins.

CONCLUSIONS

Torsin A and torsin B have similar distribution in the central nervous system, although their subcellular localization is not identical. Strong expression in neuronal processes points to a potential role for torsin proteins in synaptic functioning.

Learning deficits, but normal development and tumor predisposition, in mice lacking exon 23a of Nf1

Neurofibromatosis type 1 (NF1) is a commonly inherited autosomal dominant disorder. Previous studies indicated that mice homozygous for a null mutation in Nf1 exhibit mid-gestation lethality, whereas heterozygous mice have an increased predisposition to tumors and learning impairments. Here we show that mice lacking the alternatively spliced exon 23a, which modifies the GTPase-activating protein (GAP) domain of Nf1, are viable and physically normal, and do not have an increased tumor predisposition, but show specific learning impairments. Our findings have implications for the development of a treatment for the learning disabilities associated with NF1 and indicate that the GAP domain of NF1 modulates learning and memory.

Parkin is associated with actin filaments in neuronal and nonneural cells

Inactivating mutations of the gene encoding parkin are responsible for autosomal recessive juvenile parkinsonism (AR-JP). However, little information is known about the function and distribution of parkin. We generated antibodies to two different peptides of parkin. By Western blot analysis and immunohistochemistry, we found that parkin is a 50-kd protein that is expressed in neuronal processes and cytoplasm of selected neurons in the basal ganglia, midbrain, cerebellum, and cerebral cortex. Unlike ubiquitin and alpha-synuclein, parkin labeling was not found in Lewy bodies of four sporadic Parkinson disease brains. Parkin was colocalized with actin filaments but not with microtubules in COS1 kidney cells and nerve growth factor-induced PC12 neurons. These results point to the importance of the cytoskeleton and associated proteins in neurodegeneration.

Nuclear localization or inclusion body formation of ataxin-2 are not necessary for SCA2 pathogenesis in mouse or human

Instability of CAG DNA trinucleotide repeats is the mutational mechanism for several neurodegenerative diseases resulting in the expansion of a polyglutamine (polyQ) tract. Proteins with long polyQ tracts have an increased tendency to aggregate, often as truncated fragments forming ubiquitinated intranuclear inclusion bodies. We examined whether similar features define spinocerebellar ataxia type 2 (SCA2) pathogenesis using cultured cells, human brains and transgenic mouse lines. In SCA2 brains, we found cytoplasmic, but not nuclear, microaggregates. Mice expressing ataxin-2 with Q58 showed progressive functional deficits accompanied by loss of the Purkinje cell dendritic arbor and finally loss of Purkinje cells. Despite similar functional deficits and anatomical changes observed in ataxin-1[Q80] transgenic lines, ataxin-2[Q58] remained cytoplasmic without detectable ubiquitination.

The neurofibromatosis 2 tumor suppressor protein interacts with hepatocyte growth factor-regulated tyrosine kinase substrate

The neurofibromatosis 2 tumor suppressor protein schwannomin/merlin is commonly mutated in schwannomas and meningiomas. Schwannomin, a member of the 4.1 family of proteins, which are known to link the cytoskeleton to the plasma membrane, has little known function other than its ability to suppress tumor growth. Using yeast two-hybrid interaction cloning, we identified the HGF-regulated tyrosine kinase substrate (HRS) as a schwannomin interactor. We verified the interaction by both immunoprecipitation of endogenous HRS with endogenous schwannomin in vivo as well as by using bacterially purified HRS and schwannomin in vitro. We narrowed the regions of interaction to include schwannomin residues 256-579 and HRS residues from 480 to the end of either of two HRS isoforms. Schwannomin molecules with a L46R, L360P, L535P or Q538P missense mutation demonstrated reduced affinity for HRS binding. As HRS is associated with early endosomes and may mediate receptor translocation to the lysosome, we demonstrated that schwannomin and HRS co-localize at endosomes using the early endosome antigen 1 in STS26T Schwann cells by indirect immunofluorescence. The identification of schwannomin as a HRS interactor implicates schwannomin in HRS-mediated cell signaling.

A novel protein with RNA-binding motifs interacts with ataxin-2

Spinocerebellar ataxia type 2 (SCA2) is caused by expansion of a polyglutamine tract in ataxin-2, a protein of unknown function. Using the yeast two-hybrid system, we identified a novel protein, A2BP1 (ataxin-2 binding protein 1) which binds to the C-terminus of ataxin-2. Northern blot analysis showed that A2BP1 was predominantly expressed in muscle and brain. By immunocfluorescent staining, A2BP1 and ataxin-2 were both localized to the trans -Golgi network. Immunocytochemistry showed that A2BP1 was expressed in the cytoplasm of Purkinje cells and dentate neurons in a pattern similar to that seen for ataxin-2 labeling. Western blot analysis of subcellular fractions indicated enrichment of A2BP1 in the same fractions as ataxin-2. Sequence analysis of the A2BP1 cDNA revealed an RNP motif that is highly conserved among RNA-binding proteins. A2BP1 had striking homology with a human cDNA clone, P83A20, of unknown function and at least two copies of A2BP1 homologs are found in the Caenorhabditis elegans genome database. A2BP1 and related proteins appear to form a novel gene family sharing RNA-binding motifs.

Expression of ataxin-2 in brains from normal individuals and patients with Alzheimer's disease and spinocerebellar ataxia 2

Spinocerebellar ataxia type 2 (SCA2) is caused by expansion of a CAG trinucleotide repeat located in the coding region of the human SCA2 gene. The SCA2 gene product, ataxin-2, is a basic protein with two domains (Sm1 and Sm2) implicated in RNA splicing and protein interaction. However, the wild-type function of ataxin-2 is yet to be determined. To help clarify the function of ataxin-2, we produced antibodies to three antigenic peptides of ataxin-2 and analyzed the expression pattern of ataxin-2 in normal and SCA2 adult brains and cerebellum at different developmental stages. These studies revealed that (1) both wild-type and mutant forms of ataxin-2 were synthesized; (2) the wild-type ataxin-2 was localized in the cytoplasm in specific neuronal groups with strong labeling of Purkinje cells; (3) the level of ataxin-2 increased with age in Purkinje cells of normal individuals; and (4) ataxin-2-like immunoreactivity in SCA2 brain tissues was more intense than in normal brain tissues, and intranuclear ubiquitinated inclusions were not seen in SCA2 brain tissues.

The mouse SCA2 gene: cDNA sequence, alternative splicing and protein expression

Spinocerebellar ataxia type 2 (SCA2) is caused by expansion of a CAG trinucleotide repeat located in the coding region of the human SCA2 gene. Sequence analysis revealed that SCA2 is a novel gene of unknown function. In order to provide insights into the molecular mechanisms of pathogenesis of SCA2 and to identify conserved domains, we isolated and characterized the mouse homolog of the SCA2 gene. Sequence and amino acid analysis revealed 89% identity at the nucleotide and 91% identity at the amino acid level. However, there was no extended polyglutamine tract in the mouse SCA2 cDNA, suggesting that the normal function of SCA2 is not dependent on this domain. Northern blot analysis of different mouse tissues indicated that the mouse SCA2 gene was expressed in most tissues, but at varying levels. Alternative splicing seen in human SCA2 was conserved in the mouse. By northern blot analysis, SCA2 was expressed during embryogenesis as early as day 8 of gestation (E8). Immunohistochemical staining using affinity-purified antibodies demonstrated that ataxin 2 was expressed in the cytoplasm of Purkinje cells as well as in other neurons of the CNS.

Neurofibromatosis 2 tumour suppressor schwannomin interacts with betaII-spectrin

NF2 is the most commonly mutated gene in benign tumours of the human nervous system. The NF2 protein, called schwannomin or merlin, is absent in virtually all schwannomas, and many meningiomas and ependymomas. Using the yeast two-hybrid system, we identified betaII-spectrin (also known as fodrin) as a schwannomin-binding protein. Interaction occurred between the carboxy-terminal domain of schwannomin isoform 2 and the ankyrin-binding region of betaII-spectrin. Isoform 1 of schwannomin, in contrast, interacted weakly with betaII-spectrin, presumably because of its strong self-interaction. Thus, alternative splicing of NF2 may regulate betaII-spectrin binding. Schwannomin co-immunoprecipitated with betaII-spectrin at physiological concentrations. The two proteins interacted in vitro and co-localized in several target tissues and in STS26T cells. Three naturally occurring NF2 missense mutations showed reduced, but not absent, betaII-spectrin binding, suggesting an explanation for the milder phenotypes seen in patients with missense mutations. STS26T cells treated with NF2 antisense oligonucleotides showed alterations of the actin cytoskeleton. Schwannomin itself lacks the actin binding sites found in ezrin, radixin and moesin, suggesting that signalling to the actin cytoskeleton occurs via actin-binding sites on betaII-spectrin. Thus, schwannomin is a tumour suppressor directly involved in actin-cytoskeleton organization, which suggests that alterations in the cytoskeleton are an early event in the pathogenesis of some tumour types.

Neuronal expression and intracellular localization of presenilins in normal and Alzheimer disease brains

The expression patterns of presenilin 1 (PS1) and presenilin 2 (PS2) in human normal and Alzheimer disease (AD) brains were investigated using antibodies to specific N-terminal peptides of PS1 (Alzh14A and Alzh14B) and PS2 (Alzh1A-AB). The antibodies to peptides Alzh14A (Alzh14A-AB) and Alzh14B (Alzh14B-AB) detected the full-length protein (approximately 63 kDa) and the N-terminal-processed fragment (36 kDa) of PS1, while the Alzh1A-AB detected mainly the N-terminal-processed fragment (36 kDa) of PS2. Immunofluorescent staining detected by confocal microscopy suggested that both native PS1 and PS2 are localized mainly in the Golgi/ER apparatus. Immunohistochemical studies of human temporal lobes from 2 normal and 5 sporadic Alzheimer brains revealed high levels of PS1 and PS2 expression in the granule cell layer and pyramidal neurons of the hippocampus. Strong immunoreactivity was found in reactive astrocytes and neurofibrillary tangles of all 5 Alzheimer brains. In contrast, only 2 sporadic Alzheimer brains showed presenilin-positive neuritic plaques. These observations suggest that presenilins may be involved in the pathology of some cases of sporadic AD.

Immunohistochemical detection of schwannomin and neurofibromin in vestibular schwannomas, ependymomas and meningiomas

In addition to schwannomas, patients with neurofibromatosis type 2 (NF2) frequently develop meningiomas and occasionally, ependymomas. Using DNA and protein analyses, we have shown NF2 gene mutations and lack of the gene product schwannomin in 29 schwannomas, 10 meningiomas, and in 7 ependymomas. We have raised antibodies (ABs) to peptides from the C-terminal (5990-AB) and N-terminal (5991-AB) domains of schwannomin. The ABs specifically detected a 65 kDa protein in a Schwann cell line and recognized schwannomin in the cytoplasm of Schwann cells (SCH), perineurial cells, and vestibular ganglion neurons. None of the 29 schwannomas were stained by the 5990-AB. Only 4 schwannomas were stained by the 5991-AB, indicating that most truncated schwannomins were unstable or not expressed in schwannomas. Seven of 10 meningiomas, including 3 tumors from NF2 patients, were not stained by either 5990-AB or 5991-AB. Only 2 of 7 ependymomas lacked schwannomin. Complete lack of schwannomin in these tumors supports a tumor suppressor function for schwannomin in some meningiomas and ependymomas. All tumors showed staining with an antibody to a C-terminal peptide of neurofibromin, confirming that full-length neurofibromin is present in these vestibular schwannomas, meningiomas, and ependymomas. The presence of schwannomin in some meningiomas and in the majority of ependymomas indicates that additional genes are likely to play a role in tumorigenesis of these tumors.

Characterization and expression of presenilin 1 in mouse brain

The expression pattern of presenilin 1 (PS-1) in adult mouse brain was investigated using antibodies to specific peptides of PS-1. One antibody, Alz14A, specifically detected a 53 kDa protein in retinoic acid-treated P19 cells and mouse brain protein extracts consistent with the predicted PS-1 molecular weight. Immunohistochemical staining revealed that PS-1 was localized predominantly in large neurons in areas that were known to be affected by Alzheimer disease (AD) such as the hippocampal formation, entorhinal cortex and the subiculum. Selected neurons in other regions not known to be directly affected by AD, such as thalamic nuclei, Purkinje cells, large neurons in the brainstem and the gray matter of the spinal cord, and the dorsal root ganglion, also expressed PS-1. These observations suggest that other as yet identified factors might interact with mutated presenilins to cause neurodegeneration in AD-affected areas.

Expression of neurofibromatosis 2 transcript and gene product during mouse fetal development

Neurofibromatosis 2 (NF2) is an autosomal dominant inherited disorder that predisposes to benign tumors of the nervous system as well as a variety of ocular abnormalities. In contrast to NF1, NF2 is associated with only minor developmental abnormalities. The human NF2 gene encodes a tumor suppressor protein, termed schwannomin or merlin, which is a member of a superfamily of proteins thought to link cytoskeletal elements to cell membrane components. To determine the pattern of NF2 gene expression in mouse embryos, we sequenced the mouse NF2 gene and used in situ hybridization and antischwannomin antibodies to determine the developmental expression of the NF2 gene. Schwannomin was detected in most differentiated tissues but was undetectable in undifferentiated tissues. In particular, schwannomin was not detectable in mitotic neuroepithelial cells, the perichondrium, the liver, the neocortex, and the ventricular zone of the developing cerebral cortex. In the heart, expression was observed in all developmental stages beginning on embryonic day 8. In the eye, which shows developmental abnormalities in NF2 patients, expression was detected in the cells of the lens and in the pigment epithelium but weakly detected in retinal neurons. The most striking example of tightly regulated NF2 expression was observed in cells migrating from the ventricular zone to the cortical plate on embryonic days 15 and 16. Only cells in the intermediate zone expressed schwannomin, indicating that schwannomin may play an important role in cellular migration.

Neurofibromatosis 2 antisense oligodeoxynucleotides induce reversible inhibition of schwannomin synthesis and cell adhesion in STS26T and T98G cells

Mutations in the neurofibromatosis 2 (NF2) gene are the predominant cause in the development of sporadic schwannomas and are also involved in the pathogenesis of meningiomas and ependymomas. The product of the NF2 gene, termed merlin or schwannomin, is thought to act as a tumor suppressor protein. Although its protein sequence shows homology to proteins that are known to link the cytoskeleton to the cell membrane, no direct evidence for this function has been obtained. We used antisense phosphorothioate oligodeoxynucleotides (pODNs) complementary to the human NF2 cDNA sequence and transfected them into Schwann-like STS26T cells permeabilized by streptolysin 0. Changes in cell morphology and attachment were observed at 12 to 24 h and continued up to 48 h post transfection. Cells were rounded and easily dislodged from the substratum at 12-24 h. These changes were reversible and cells became bipolar with thin protrusions and began to reattach to the substratum after 48 h. Normal morphology and adhesion were observed at 72 h post transfection. Morphological changes were due to suppression of schwannomin synthesis. Immunoprecipitations with antischwannomin antibodies showed schwannomin to be almost absent 3 h after treatment with antisense pODNs and to be significantly suppressed up to 12 h post transfection whereas beta-actin levels remained unchanged. The morphological changes were not the result of cell death, but resulted in increased cell proliferation. These data demonstrate that antisense oligonucleotides can be successfully employed to suppress schwannomin synthesis and indicate that schwannomin may belong to a class of tumor suppressor genes that provide a link between cell adhesion and tumorigenesis.

Alternative transcripts in the mouse neurofibromatosis type 2 (NF2) gene are conserved and code for schwannomins with distinct C-terminal domains

Mutations in the neurofibromatosis type 2 (NF2) gene predispose individuals to the development of nervous system tumors and ocular abnormalities. The NF2 gene product, schwannomin, is a member of a superfamily of proteins thought to link cytoskeletal elements to cell membrane components. These proteins share significant homologies in the N-terminal and alpha-helical domains, but diverge in the C-terminus. During our efforts to characterize mouse NF2 transcripts, we identified four different transcripts by cDNA analysis and reverse-transcribed PCR that contained different sequences in the 3' end of the coding sequences. In human cell lines three isoforms encoding two distinct schwannomins were detected. The mouse and human transcripts containing 61 and 60 bp inserts, respectively, have not been previously described. The isoforms encode schwannomins with significantly altered C-termini and were expressed at different relative levels in adult mouse tissues and during mouse embryogenesis. These results suggest that schwannomin isoforms have distinct functional roles and predict the existence of human mutations involving the C-terminus of schwannomin.

Mutations of the neurofibromatosis type 2 gene and lack of the gene product in vestibular schwannomas

Schwannomas are common tumors of the nervous system and are frequently found in patients with neurofibromatosis (NF) 2. Although loss of heterozygosity in NF2 tumors suggests that the NF2 gene functions as a tumor suppressor gene, the NF2 gene shows amino acid sequence homology to structural proteins in one of which dominantly acting mutations have been described. We performed a mutational analysis in 30 vestibular schwannomas and examined the effect of mutations on the NF2 protein. We detected 18 mutations in 30 vestibular schwannomas of which seven contained loss or mutation of both NF2 alleles. Most mutations were predicted to result in a truncated protein. Mutational hot spots were not identified. Immunocytochemical studies using antibodies to the NF2 protein showed complete absence of staining in tumor Schwann cells, whereas staining was observed in normal vestibular nerve. These data indicate that loss of NF2 protein function is a necessary step in schwannoma pathogenesis and that the NF2 gene functions as a recessive tumor suppressor gene.

Differential expression and tissue distribution of type I and type II neurofibromins during mouse fetal development

Mutations in the NF1 gene may cause developmental abnormalities and the formation of a variety of tumors of neural crest origin in humans. The NF1 gene codes for a large protein, neurofibromin (nf), which is structurally and functionally related to yeast and human ras-GTPase-activating proteins (ras-GAPs). Recently, two transcripts coding for type I and type II nf with different ras-GAP activity have been identified. Since ras proteins do not appear to be significantly regulated during mouse development, we examined if differential expression of neurofibromins may provide evidence for a role of nfs in regulating ras-mediated cell proliferation and differentiation. Nfs were expressed as early as E8. At E11 a marked increase of NF1 transcripts occurred and was associated with expression of nfs in all tissues. Type I and type II nfs each showed a different time course of expression and tissue localization, with type II nf present mainly from E8 through E10, although in the heart type II nf was present at E12. In some tissues such as heart and dorsal root ganglia rapid increases and decreases of nfs were detected related to differentiation of these tissues. These results are consistent with a role of nfs in regulating ras-mediated cell proliferation and differentiation during development and support distinct functional roles for type I and type II nfs.

Expression of neurofibromin, the neurofibromatosis 1 gene product: studies in human neuroblastoma cells and rat brain

Neurofibromatosis type 1 (NF1) is one of the most frequent Mendelian disorders in man and one of the most common autosomal dominant disorders affecting the nervous system. The NF1 gene has recently been cloned, and shows homology to the GTPase activating protein. In order to characterize the NF1 gene product, now called neurofibromin, we raised polyclonal antibodies against C- and N-terminal regions of neurofibromin and analyzed the protein by Western blot analysis and immunohistochemical studies of rat brain.