Isolation of a 40-kDa Huntingtin-associated protein

Huntington's disease is caused by an expanded CAG trinucleotide repeat coding for a polyglutamine stretch within the huntingtin protein. Currently, the function of normal huntingtin and the mechanism by which expanded huntingtin causes selective neurotoxicity remain unknown. Clues may come from the identification of huntingtin-associated proteins (HAPs). Here, we show that huntingtin copurifies with a single novel 40-kDa protein termed HAP40. HAP40 is encoded by the open reading frame factor VIII-associated gene A (F8A) located within intron 22 of the factor VIII gene. In transfected cell extracts, HAP40 coimmunoprecipitates with full-length huntingtin but not with an N-terminal huntingtin fragment. Recombinant HAP40 is cytoplasmic in the presence of huntingtin but is actively targeted to the nucleus in the absence of huntingtin. These data indicate that HAP40 is likely to contribute to the function of normal huntingtin and is a candidate for involvement in the aberrant nuclear localization of mutant huntingtin found in degenerating neurons in Huntington's disease.

SCA12 is a rare locus for autosomal dominant cerebellar ataxia: a study of an Indian family

Spinocerebellar ataxia 12 (SCA12) is an autosomal dominant cerebellar ataxia (ADCA) described in a single family with a CAG repeat expansion in the PPP2R2B gene. We screened 247 index cases, including 145 families with ADCA, for this expansion. An expanded repeat ranging from 55 to 61 triplets was detected in 6 affected and 3 unaffected individuals at risk in a single family from India. The association of the PPP2R2B CAG repeat expansion with disease in this new family provides additional evidence that the mutation is causative.

Widespread occurrence of intranuclear atrophin-1 accumulation in the central nervous system neurons of patients with dentatorubral-pallidoluysian atrophy

Dentatorubral-pallidoluysian atrophy (DRPLA) is an autosomal dominant neurodegenerative disorder caused by a CAG repeat expansion. In the present study of DRPLA, we have demonstrated immunohistochemically that diffuse accumulation of mutant atrophin-1 in the neuronal nuclei, rather than the formation of neuronal intranuclear inclusions (NIIs), was the predominant pathologic condition and involved a wide range of central nervous system regions far beyond the systems previously reported to be affected. In the neuronal nuclei harboring NIIs, promyelocytic leukemia protein (PML) nuclear bodies were redistributed into a single NII, and the CREB (cAMP-responsive element-binding protein)-binding protein was also recruited into NIIs. The results suggest that the novel lesion distribution revealed by the diffuse nuclear labeling may be responsible for a variety of clinical features, such as dementia and epilepsy in DRPLA, and that certain transcriptional abnormalities may be induced secondarily in neuronal nuclei with the formation of NIIs.

Current Australian practice in the prevention and management of corneal allograft rejection

PURPOSE

To determine current practices in the prevention and management of corneal allograft rejection in Australia.

METHODS

A questionnaire was circulated to attendees at the 1998 Eye Bank Meeting in Adelaide. Twenty-four responses were received and analysed.

RESULTS

All respondents used topical corticosteroids for routine prophylaxis and to treat established rejection episodes. Prednisolone acetate was the most frequently prescribed topical corticosteroid. Systemic non-steroidal immunosuppression was prescribed almost exclusively for high-risk grafts. Seventy-five per cent of surgeons used systemic antiviral agents for the treatment of graft rejection in patients with Herpes simplex keratitis.

CONCLUSION

There was a wide variation amongst surgeons in the choice of therapy for routine prophylactic immunosuppression as well as for the treatment of established corneal allograft rejection.

Atrophin-1, the dentato-rubral and pallido-luysian atrophy gene product, interacts with ETO/MTG8 in the nuclear matrix and represses transcription

Dentato-rubral and pallido-luysian atrophy (DRPLA) is one of the family of neurodegenerative diseases caused by expansion of a polyglutamine tract. The drpla gene product, atrophin-1, is widely expressed, has no known function or activity, and is found in both the nuclear and cytoplasmic compartments of neurons. Truncated fragments of atrophin-1 accumulate in neuronal nuclei in a transgenic mouse model of DRPLA, and may underlie the disease phenotype. Using the yeast two-hybrid system, we identified ETO/MTG8, a component of nuclear receptor corepressor complexes, as an atrophin-1-interacting protein. When cotransfected into Neuro-2a cells, atrophin-1 and ETO/MTG8 colocalize in discrete nuclear structures that contain endogenous mSin3A and histone deacetylases. These structures are sodium dodecyl sulfate-soluble and associated with the nuclear matrix. Cotransfection of ETO/MTG8 with atrophin-1 recruits atrophin-1 to the nuclear matrix, while atrophin-1 and ETO/MTG8 cofractionate in nuclear matrix preparations from brains of DRPLA transgenic mice. Furthermore, in a cell transfection-based assay, atrophin-1 represses transcription. Together, these results suggest that atrophin-1 associates with nuclear receptor corepressor complexes and is involved in transcriptional regulation. Emerging links between disease-associated polyglutamine proteins, nuclear receptors, translocation-leukemia proteins, and the nuclear matrix may have important repercussions for the pathobiology of this family of neurodegenerative disorders.

Gene identification using exon amplification on human chromosome 18q21: implications for bipolar disorder

We previously reported linkage between bipolar disorder and a region on human chromosome (HC) 18q21. To identify genes in this region, exon trapping was performed on cosmids isolated from an HC18-specific cosmid library (LL18NC02) using 47 sequence tagged site (STS) markers from 18q21 as hybridization probes. A total of 285 unique sequences (exons) were obtained from 850 sequenced clones. Homology searching of the databases using NCBI's BLAST algorithms revealed that 31 exons have identity to known genes and/or ESTs, seven are identical to regions of finished genomic sequences in the 18q21 region, 20 have significant similarity (>30% sequence identity) to genes from human and/or other species, 19 were repetitive sequences, and 208 sequences (72%) are novel. Seventy per cent of the trapped sequences were predicted to be derived from genes using library screening and RT-PCR analyses. This represents an initial stage in characterizing genes in a susceptibility region for further study in bipolar disorder or other diseases that map to this region.

Organization of the human synphilin-1 gene, a candidate for Parkinson's disease

We have recently identified a protein we called synphilin-1, which interacts in vivo with alpha-synuclein. Mutations in alpha-synuclein cause familial Parkinson's disease (PD). Alpha-synuclein protein is present in the pathologic lesions of familial and sporadic PD, and diffuse Lewy body disease, indicating an important pathogenic role for alpha-synuclein. Here we describe the structure of the human synphilin-1 gene (SNCAIP). The open reading frame of this gene is contained within ten exons. We have designed primers to amplify each SNCAIP exon, so these primers can now be used to screen for mutations or polymorphisms in patients with Parkinson's disease or related diseases. We found a highly polymorphic GT repeat within intron 5 of SNCAIP, suitable for linkage analysis of families with PD. We have mapped SNCAIP locus to Chromosome (Chr) 5q23.1-23.3 near markers WI-4673 and AFMB352XH5. In addition, using immunohistochemistry in human postmortem brain tissue, we found that synphilin-1 protein is present in neuropil, similar to alpha-synuclein protein. Because of its association with alpha-synuclein, synphilin-1 may be a candidate for involvement in Parkinson's disease or other related disorders.

Human huntingtin-associated protein (HAP-1) gene: genomic organisation and an intragenic polymorphism

The huntingtin-associated protein (HAP-1) interacts with the Huntington disease gene product, huntingtin. It is predominantly expressed in the brain and shows an increased affinity for mutant huntingtin. We have sequenced an 18,656bp genomic region encompassing the entire human HAP-1 gene and determined its genomic organisation, with 11 exons spanning 12.1kb. We have also found an intragenic polymorphism within intron 6 of HAP-1. We have recently shown that HAP-1 maps to a region of the genome which has been implicated in a variety of neurological conditions, including progressive supranuclear palsy (PSP), a late-onset atypical parkinsonian disorder. The detailed characterisation of the genomic organisation of HAP-1 and the presence of an intragenic polymorphism will be helpful in evaluating its role in different disorders, using candidate gene approaches.

Type 3 inositol 1,4,5-trisphosphate receptor modulates cell death

Mechanisms accounting for the cellular entry of calcium that mediates cellular proliferation and apoptosis have been obscure. Previously we reported selective augmentation of type 3 inositol (1,4,5) trisphosphate receptors (IP(3)R3) in lymphocytes undergoing programmed cell death, which was prevented by antisense constructs to IP(3)R3. We now report increases in mRNA and protein levels for IP(3)R3 associated with cell death in several apoptotic paradigms in diverse tissues. Elevations of IP(3)R3 occur during developmental apoptosis in early postnatal cerebellar granule cells, dorsal root ganglia, embryonic hair follicles, and intestinal villi. Neurotoxic damage elicited by the glutamate agonist kainate is also associated with IP(3)R3 augmentation. In chick dorsal root ganglia neurons undergoing apoptosis due to deprivation of nerve growth factor, levels of IP(3)R3 are selectively increased and cell death is selectively prevented by antisense oligonucleotides to IP(3)R3. Thus, IP(3)R3 appears to participate actively in cell death in a diversity of tissues.

Allelic distribution of CTG18.1 in Caucasian populations: association studies in bipolar disorder, schizophrenia, and ataxia

CTG18.1 is a highly polymorphic and unstable CTG repeat within an intron of the SEF2-1 gene. We tested the CTG18.1 repeat length in affective disorder, schizophrenia, and nonspecific ataxia; these diseases all have shown clinical evidence for anticipation. There was no difference in the allele frequencies comparing the controls and disease groups. The most common allele contains 11 CAGs (35%) followed by alleles with 14-17 CAGs (35%). There was no difference in the distribution of the alleles in the cases vs controls for ataxia (P = 0.11), affective disorders (P = 0.21), or schizophrenia (P = 0.26). The frequency of unstable CTG18.1 alleles was approximately 3% in a population of N. European descent and is not related to the phenotypes tested.

Decreased expression of striatal signaling genes in a mouse model of Huntington's disease

To understand gene expression changes mediated by a polyglutamine repeat expansion in the human huntingtin protein, we used oligonucleotide DNA arrays to profile approximately 6000 striatal mRNAs in the R6/2 mouse, a transgenic Huntington's disease (HD) model. We found diminished levels of mRNAs encoding components of the neurotransmitter, calcium and retinoid signaling pathways at both early and late symptomatic time points (6 and 12 weeks of age). We observed similar changes in gene expression in another HD mouse model (N171-82Q). These results demonstrate that mutant huntingtin directly or indirectly reduces the expression of a distinct set of genes involved in signaling pathways known to be critical to striatal neuron function.

Wild-type huntingtin protects from apoptosis upstream of caspase-3

Expansion of a polyglutamine sequence in the N terminus of huntingtin is the gain-of-function event that causes Huntington's disease. This mutation affects primarily the medium-size spiny neurons of the striatum. Huntingtin is expressed in many neuronal and non-neuronal cell types, implying a more general function for the wild-type protein. Here we report that wild-type huntingtin acts by protecting CNS cells from a variety of apoptotic stimuli, including serum withdrawal, death receptors, and pro-apoptotic Bcl-2 homologs. This protection may take place at the level of caspase-9 activation. The full-length protein also modulates the toxicity of the poly-Q expansion. Cells expressing full-length mutant protein are susceptible to fewer death stimuli than cells expressing truncated mutant huntingtin.

Developing low-cost clinical teaching tools

Nursing is an art as well as a science. Using artistic resources can help the nurse educator develop creative and low-cost teaching tools that are truly effective and realistic. According to Bowman, these inexpensive teaching tools assist in obtaining and maintaining attention of students, stimulate discussion, encourage questions, and provide a means of skill development.

Rate of caudate atrophy in presymptomatic and symptomatic stages of Huntington's disease

Previous research by our group demonstrated a longitudinal change in caudate volume for symptomatic subjects with Huntington's disease (HD), and suggested that volume of the caudate may be a useful outcome measure for therapeutic studies in symptomatic patients. The current study was designed to determine whether longitudinal change in caudate atrophy could be documented in presymptomatic carriers of the HD gene mutation, and to compare rate of change in these subjects with rate of change in mildly and moderately affected symptomatic patients. We measured caudate volumes on serial magnetic resonance image scans from 30 patients at three stages of HD: 10 presymptomatic; 10 with mild symptoms, as indicated by scores on the Quantified Neurological Exam (QNE) < or =35; and 10 with moderate symptoms (QNE >45). The mean interscan interval was 36 months. When analyzed separately, both symptomatic groups and the presymptomatic group demonstrated a significant change in caudate volume over time. Amount of change over time did not differ significantly among the three groups. We conclude that change in caudate volume may be a useful outcome measure for assessing treatment effectiveness in both presymptomatic and symptomatic subjects.

Synphilin-1 is present in Lewy bodies in Parkinson's disease

Alpha-synuclein is believed to play an important role in Parkinson's disease (PD). Mutations in the alpha-synuclein gene are responsible for familial forms of PD and alpha-synuclein protein is a major component of Lewy bodies in patients with sporadic PD. Synphilin-1 is a novel protein that we have previously found to associate in vivo with alpha-synuclein. We now show that synphilin-1 is present in Lewy bodies of patients with PD. Our data suggest that synphilin-1 could play a role in Lewy body formation and the pathogenesis of PD.

Building bridges to promote globalization in nursing: the development of a hermanamiento

The establishment of a hermanamiento (sister school) partnership between Duquesne University School of Nursing in Pittsburgh, Pennsylvania, United States, and the School of Nursing at the Polytechnic University in Managua, Nicaragua, is described. Also discussed is the Regis Group Model, under which the hermanamiento was developed, and suggestions of how to develop a similar international nursing partnership. One component of a comprehensive model for international partnership and collaboration is presented in detail. The activities and goals that were established and implemented by both schools of nursing provide a philosophic and transcultural backdrop on which the program was based.

Anticipation in schizophrenia: a review and reconsideration

There have been several reports on anticipation and schizophrenia, and the purpose of the present article is to review the literature and present data from an ongoing family study of schizophrenia. The published data find on average a 10-year difference in the age of onset between the parental and offspring generation in family sets that have been ascertained for a genetic linkage study. The biases inherent in such studies include the biases of ascertainment that were described by Penrose [1948]. Several investigators have searched for evidence of enlarged triplet repeats, and some find evidence consistent with expanded triplet repeats, whereas others do not. In any event the phenomenon of anticipation in schizophrenia appears to be consistently found and an explanation is needed. Data are presented from pairwise analyses using intergenerational pairs from 61 pedigrees with schizophrenia showing evidence of anticipation as well as the fertility bias. Anticipation was found in aunt:niece/nephew pairs (14.5 years) but not in uncle:niece/nephew pairs (0.5 years). The sex difference in age of onset was accentuated in uncles versus aunts (8.5 years), present in parents (4.5 years), but absent in the proband generation. Therefore, there appears to be an interaction within families between age of onset and sex that deserves further investigation. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 88:686-693, 1999.

Preparation of human cDNas encoding expanded polyglutamine repeats

At least eight neurodegenerative diseases result from expansions of polyglutamine tracts encoded by CAG trinucleotide repeats. Although polyglutamine diseases typically have onset after age 50 in humans, these diseases can be modeled in animals and in cell culture by using highly expanded repeats to accelerate the pathogenesis. Unfortunately, current methods for preparing recombinant constructs with large glutamine tracts either alter the coding region adjacent to the repeat or yield highly unstable pure CAG repeats. We have developed a technique for expanding repeats that results in a more stable mix of CAG and CAA glutamine codons. We expect this technique to allow rapid preparation of highly expand repeats suitable for stable animal and cell culture models for any of the polyglutamine repeat diseases.

Trinucleotide repeat expansion and neuropsychiatric disease

Trinucleotide, or triplet, repeats consist of 3 nucleotides consecutively repeated (e.g., CCG CCG CCG CCG CCG) within a region of DNA, a not uncommon motif in the genome of humans and other species. In 1991, a new type of genetic mutation was discovered, known as a dynamic or expansion mutation, in which the number of triplets in a repeat increases and the length becomes unstable. During the past decade, nearly 20 diseases-including Huntington disease, 2 forms of the fragile X syndrome, and myotonic dystrophy-caused by trinucleotide repeat expansions have been identified. The unstable nature of the expanded repeat leads to remarkable patterns of inheritance in these diseases, distinctly at odds with traditional notions of mendelian genetics. We review the clinical and genetic features of these disorders, with a particular emphasis on their psychiatric manifestations. We also critically examine the hypothesis that expansion mutations may have an etiologic role in psychiatric diseases such as bipolar disorder, schizophrenia, and autism.