We have serendipitously established a mouse that expresses an N-terminal human huntingtin (htt) fragment with an expanded polyglutamine repeat (Ϸ120) under the control of the endogenous human promoter (shortstop). Frequent and widespread htt inclusions occur early in shortstop mice. Despite these inclusions, shortstop mice display no clinical evidence of neuronal dysfunction and no neuronal degeneration as determined by brain weight, striatal volume, and striatal neuronal count. These results indicate that htt inclusions are not pathogenic in vivo. In contrast, the full-length yeast artificial chromosome (YAC) 128 model with the identical polyglutamine length and same level of transgenic protein expression as the shortstop demonstrates significant neuronal dysfunction and loss. In contrast to the YAC128 mouse, which demonstrates enhanced susceptibility to excitotoxic death, the shortstop mouse is protected from excitotoxicity, providing in vivo evidence suggesting that neurodegeneration in Huntington disease is mediated by excitotoxic mechanisms.Huntington disease ͉ mouse models ͉ excitotoxicity ͉ aggregates ͉ fragment H untingtin (htt), the protein product encoded by the gene mutated in Huntington disease (HD), forms aggregates and inclusion bodies in the presence of a pathogenic expanded polyglutamine (polyQ) repeat. Htt protein inclusions are a hallmark of HD and are present in brains of human patients (1), in HD mouse models (2, 3), and in cell culture models of HD (4). It is still controversial whether htt inclusions are pathogenic (2), benign biomarkers (5), or neuroprotective (4, 6). The distinction between these hypotheses is clinically relevant, because much therapeutic research has focused on screening compounds for their ability to inhibit inclusion formation (7,8). A decrease in inclusion formation has been interpreted as a positive outcome in preclinical therapeutic trials with mouse models (9, 10).Increasing evidence in vitro in cell culture models supports the hypothesis that htt inclusions are not pathogenic (5, 11). In a recent study, Arrasate et al. (4) discovered that in their cell culture system, neurons with inclusions had an increased likelihood of survival compared with neurons without inclusions. However, because these results were obtained in a cell culture system, the question of whether htt inclusions are toxic in vivo during the lifespan of an organism and therefore clinically relevant for patients with HD remains unanswered.Examinations of inclusions in brains from HD patients are limited due to the inability to sample inclusions over the natural history of the disease, and, therefore, studies of mouse models of HD can be useful in determining the role of htt inclusions in vivo. The yeast artificial chromosome (YAC) 128 model of HD, which expresses full-length mutant htt, forms intranuclear inclusions 12 months after the onset of behavioral changes measured by rotarod and 6 months after striatal neuronal degeneration (3).During the development of the full-length YAC mouse models, a m...

Partial amino acid sequences of rabbit C-reactive protein, a peptide derived from human C-reactive protein by cyanogen bromide cleavage, and the Cit subcomponent of the human complement component CI have been determined. Extensive sequence homology between these proteins establish their evolutionary relationships. In addition, examination of C-reactive proteins by negative-stain electron microscopy revealed that the protein is composed of five subunits arranged in cyclic symmetry. This structure is similar to that reported for both Cit and the amyloid P-component. The extensive structural relationship suggests similar or overlapping functions and the term pentraxin is proposed to describe these homologous proteins.Activation of the primary complement (C) pathway is one of the principle biological activities of immunoglobulins. The C pathway sequence is initiated via an interaction between the Fc region of certain immunoglobulins and the C1 macromolecular complex, which leads to an internal activation of C1 and the generation of its proteolytic activity (1). During recent years several alternative mechanisms for the activation of the C system have been described. Most of these activators operate through one or another of the complex maze of interactions known as the properdin or alternative pathway (2). However, one of these agents, C-reactive protein (CRP), would appear to act in a manner entirely analogous to immunoglobulin. It has been found that upon interaction with a variety of substances, CRP can activate the C cascade and initiate both the opsonic and lytic potentials of this system through an activation of the primary C pathway (3-6). CRP has been described as being comprised of probably identical subunits, ca 23,000 daltons, noncovalently linked to form an oligomer of molecular weight 120,000-140,000 (7,8 During preliminary presentations (15, 16) of some of the data described here, an extensive amino acid-sequence homology (ca 50%) between CRP and Cit was noted. Although there are no a priori reasons to preclude such an extensive homology between an activator of C1 and one of its subcomponents, this was unexpected. We report here partial amino acid sequences of human and rabbit CRP and human Cit that establish the evolutionary relatedness of these proteins. In addition, we present a detailed ultrastructural analysis of both human and rabbit CRP by negative stain electron microscopy that shows it to be assembled as a cyclic pentamer, in a manner similar to both Cit and amyloid P-component. The term pentraxin (Greek. revrE, five and 'pat, berry) is proposed to describe these related proteins.MATERIALS AND METHODS C-Reactive Proteins. Human CRP was isolated by affinity chromatography of human serous fluids on agarose beads (Bio-Gel A-15m) to which pneumococcal C-polysaccharide was covalently linked (5). Subunits and aggregates of CRP were removed from the native protein by gel filtration in Trisbuffered saline on Bio-Gel A-0.5m. The purity of such preparations of CRP has been previously established...

Huntington disease (HD) is an inherited progressive neurodegenerative disorder, characterized by motor, cognitive, and psychiatric deficits as well as neurodegeneration and brain atrophy beginning in the striatum and the cortex and extending to other subcortical brain regions. The genetic cause is an expansion of the CAG repeat stretch in the HTT gene encoding huntingtin protein (htt). Here, we generated an HD transgenic rat model using a human bacterial artificial chromosome (BAC), which contains the full-length HTT genomic sequence with 97 CAG/CAA repeats and all regulatory elements. BACHD transgenic rats display a robust, early onset and progressive HD-like phenotype including motor deficits and anxiety-related symptoms. In contrast to BAC and yeast artificial chromosome HD mouse models that express full-length mutant huntingtin, BACHD rats do not exhibit an increased body weight. Neuropathologically, the distribution of neuropil aggregates and nuclear accumulation of N-terminal mutant huntingtin in BACHD rats is similar to the observations in human HD brains. Aggregates occur more frequently in the cortex than in the striatum and neuropil aggregates appear earlier than mutant htt accumulation in the nucleus. Furthermore, we found an imbalance in the striatal striosome and matrix compartments in early stages of the disease. In addition, reduced dopamine receptor binding was detectable by in vivo imaging. Our data demonstrate that this transgenic BACHD rat line may be a valuable model for further understanding the disease mechanisms and for preclinical pharmacological studies.

Huntington's disease (HD) is caused by an expanded CAG repeat leading to the synthesis of an aberrant protein and to the formation of polyglutamine (polyQ)-containing inclusions and aggregates. Limited information is available concerning the association of neuropathological markers with the development of behavioral markers in HD. Using a previously generated transgenic rat model of HD (tgHD rat), we performed association studies on the time-course of behavioral symptoms (motor function, learning, anxiety) and the appearance of striatal atrophy, 1C2 immunopositive aggregates and polyQ recruitment sites, a precursor to these aggregates. At the age of 1 month, tgHD rats exhibited reduced anxiety and improved motor performance, while at 6 months motor impairments and at 9 months cognitive decline occurred. In contrast, polyQ recruitment sites appeared at around 6-9 months of age, indicating that HD-like behavioral markers preceded the appearance of currently detectable neuropathological markers. Interestingly, numerous punctate sites containing polyQ aggregates were also seen in areas receiving afferents from the densely recruiting regions suggesting either transport of recruitment-competent aggregates to terminal projections where initially 1C2 positive aggregates were formed or different internal properties of neurons in different regions. Furthermore, striatal atrophy was observed at the age of 12 months. Taken together, our findings support the hypothesis of a dynamic process leading to region- and age-specific polyQ recruitment and aggregation. The dissociation of onset between behavioral and neuropathological markers is suggestive of as yet undetected processes, which contribute to the early phenotype of these HD transgenic rats.