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J F Gusella

Publications and source records attributed to J F Gusella.

At least 55 records · Page 3Linked to original sources
PubMed1998

Huntingtin interacts with a family of WW domain proteins.

The hallmark neuropathology of Huntington's disease (HD) is due to elongation of a polyglutamine segment in huntingtin, a novel approximately 350 kDa protein of unknown function. We used a yeast two-hybrid interactor screen to identify proteins whose association with huntingtin might be altered in the pathogenic process. Surprisingly, no interactors were found with internal and C-terminal segments of huntingtin. In contrast, huntingtin's N-terminus detected 13 distinct proteins, seven novel and six reported previously. Among these, we identified a major interactor class, comprising three distinct WW domain proteins, HYPA, HYPB and HYPC, that bind normal and mutant huntingtin in extracts of HD lymphoblastoid cells. This interaction is mediated by huntingtin's proline-rich region and is enhanced by lengthening the adjacent glutamine tract. Although HYPB and HYPC are novel, HYPA is human FBP-11, a protein implicated in spliceosome function. The emergence of this class of proteins as huntingtin partners argues that a WW domain-mediated process, such as non-receptor signaling, protein degradation or pre-mRNA splicing, may participate in HD pathogenesis.

Amino Acid Sequence↗
PubMed1998

Loss of the NF2 gene and merlin occur by the tumorlet stage of schwannoma development in neurofibromatosis 2.

Loss of the neurofibromatosis 2 (NF2) gene-encoded protein merlin is a universal finding in sporadic and NF2-associated schwannomas. Certain NF2 patients may develop numerous minute Schwann cell tumorlets of the spinal nerve roots in addition to larger, frank schwannomas and thereby provide an opportunity to investigate the timing of NF2 gene/merlin loss in Schwann cell tumorigenesis. We studied an NF2 patient with a germline NF2 gene frameshift mutation who had many Schwann cell tumorlets and schwannomas. Loss of heterozygosity studies of DNA from microdissected specimens showed allelic loss of the NF2 region of chromosome 22q in tumorlets as well as schwannomas. Immunohistochemistry further demonstrated loss of merlin expression in tumorlets as well as schwannomas, with intact expression in adjacent nerve. Thus, loss of both NF2 alleles and merlin occur early in Schwann cell tumorigenesis, before the tumorlet stage. The study of tumorlets and schwannomas in such patients may also provide an opportunity to elucidate mechanisms responsible for the subsequent growth of Schwann cell lesions into symptomatic tumors.

Adult↗
PubMed1997

The Nf2 tumor suppressor gene product is essential for extraembryonic development immediately prior to gastrulation.

The neurofibromatosis type II (NF2) tumor suppressor encodes a putative cytoskeletal associated protein, the loss of which leads to the development of Schwann cell tumors associated with NF2 in humans. The NF2 protein merlin belongs to the band 4.1 family of proteins that link membrane proteins to the cytoskeleton and are thought to be involved in dynamic cytoskeletal reorganization. Beyond its membership in this family, however, the function of merlin remains poorly understood. In order to analyze the function of merlin during embryogenesis and to develop a system to study merlin function in detail, we have disrupted the mouse Nf2 gene by homologous recombination in embryonic stem cells. Most embryos homozygous for a mutation at the Nf2 locus fail between embryonic days 6.5 and 7.0, exhibiting a collapsed extraembryonic region and the absence of organized extraembryonic ectoderm. The embryo proper continues to develop, but fails to initiate gastrulation. These observations are supported by the expression patterns of markers of the extraembryonic lineage and the lack of expression of mesodermal markers in the mutant embryos. Mosaic studies demonstrate that merlin function is not required cell autonomously in mesoderm, and support the proposition that merlin function is essential for the development of extraembryonic structures during early mouse development.

Animals↗
PubMed1997

Rescue of a Drosophila NF1 mutant phenotype by protein kinase A.

The neurofibromatosis type 1 (NF1) tumor suppressor protein is thought to restrict cell proliferation by functioning as a Ras-specific guanosine triphosphatase-activating protein. However, Drosophila homozygous for null mutations of an NF1 homolog showed no obvious signs of perturbed Ras1-mediated signaling. Loss of NF1 resulted in a reduction in size of larvae, pupae, and adults. This size defect was not modified by manipulating Ras1 signaling but was restored by expression of activated adenosine 3', 5'-monophosphate-dependent protein kinase (PKA). Thus, NF1 and PKA appear to interact in a pathway that controls the overall growth of Drosophila.

Amino Acid Sequence↗
PubMed1997

Heterogeneous topographic and cellular distribution of huntingtin expression in the normal human neostriatum.

A striking heterogeneous distribution of topographic and cellular huntingtin immunoreactivity was observed within the human neostriatum using three distinct huntingtin antibodies. Patchy areas of low huntingtin immunoreactivity were present in both the caudate nucleus and putamen, surrounded by an intervening area of greater immunoreactivity. Comparison of huntingtin immunoreactivity with contiguous serial sections stained for enkephalin and calbindin D28k immunoreactivities showed that the topographic heterogeneity of huntingtin immunostaining corresponded to the patch (striosome) and matrix compartments within the striatum. Huntingtin immunoreactivity was confined primarily to neurons and neuropil within the matrix compartment, whereas little or no neuronal or neuropil huntingtin immunostaining was observed within the patch compartment. There was marked variability in the intensity of huntingtin immunolabel among medium-sized striatal neurons, whereas a majority of large striatal neurons were only faintly positive or without any immunoreactivity. Combined techniques for NADPH-diaphorase enzyme histochemistry and huntingtin immunocytochemistry, as well as double immunofluorescence for either nitric oxide synthase or calbindin D28k in comparison with huntingtin expression, revealed a striking correspondence between calbindin D28k and huntingtin immunoreactivities, with little or no colocalization between NADPH-diaphorase or nitric oxide synthase neurons and huntingtin expression. These observations suggest that the selective vulnerability of spiny striatal neurons and the matrix compartment observed in Huntington's disease is associated with higher levels of huntingtin expression, whereas the relative resistance of large and medium-sized aspiny neurons and the patch compartments to degeneration is associated with low levels of huntingtin expression.

Aged↗
PubMed1997

Frequent loss of chromosome 14 in atypical and malignant meningioma: identification of a putative 'tumor progression' locus.

Formation of meningiomas has been associated with the loss of genetic material on chromosome 22. To approach the additional chromosomal events that underlie progression of these tumors to malignancy, we have examined several other chromosomal regions for loss of heterozygosity (LOH) in these tumors. Fifty-eight tumors, comprising 43 benign meningiomas, 11 atypical meningiomas and four malignant meningiomas, were examined. While the loss of chromosome 22 was seen in approximately half of all these tumors, regardless of their malignancy, the most frequent chromosomal losses observed in the malignant and atypical tumors were on the long arm of chromosome 14. Thirty-nine tumors were informative for at least one of the three markers on chromosome 14 that we tested. Of these, 7/14 malignant and atypical tumors showed LOH in contrast to only 1/25 benign tumors. Other loci that showed LOH in malignant tumors, although at a much lower frequency, were on chromosomes 17p and 1p. The high frequency of LOH for loci on chromosome 14q in atypical and malignant tumors suggests the presence of a tumor progression gene at this locus. In one of the malignant meningiomas heterozygosity was lost at D14S13 and D14S16 but retained at the proximal marker D14S43 as well as the more distal marker D14S23. This suggests that an interstitial deletion occurred in this tumor which should be useful for further refining the position of the putative tumor progression locus.

Chromosome Deletion↗
PubMed1997

CAG repeat number governs the development rate of pathology in Huntington's disease.

We compared the number of CAG repeats, the age at death, and the severity of neuropathology in 89 Huntington's disease brains. We found a linear correlation between the CAG repeat number and the quotient of the degree of atrophy in the striatum (the brain region most severely affected in Huntington's disease) divided by age at death, with an intercept at 35.5 repeats. The largest CAG repeat length, therefore, at which no pathology is expected to develop is 35.5. These results imply that striatal damage in Huntington's disease is almost entirely a linear function of the length of the polyglutamine stretch beyond 35.5 glutamines multiplied by the age of the patient. Thus, it is predicted that the pathological process develops linearly from birth. Analysis of other measures of striatal function could test this hypothesis and might determine when treatment for CAG repeat diseases should start.

Adult↗
PubMed1997

Huntingtin immunoreactivity in the rat neostriatum: differential accumulation in projection and interneurons.

Huntington's disease is caused by a mutation of the gene encoding the protein huntingtin. Features of the human disease, characterized by selective loss of neurons from the neostriatum, can be replicated in rodents by administration of excitotoxins. In both affected individuals and the rodent model, there is massive loss of striatal projection neurons with selective sparing of interneurons. Furthermore, in the human disease the earliest evidence of striatal injury is found in striosomal regions of the striatum. The mRNA encoding huntingtin is known to be expressed by neurons throughout the brain, a distribution which does not account for the selective patterns of neuronal death which are observed. Using fluorescence immunocytochemistry and confocal microscopy with an antibody to huntingtin, we have observed that in rats a subset of striatal projection neurons contains dense accumulations of huntingtin immunoreactivity (HT-ir), while most neurons in the striatum contain much smaller amounts. The intensely stained neurons are concentrated within the striatal striosomes, as defined by calbindin-D28K staining. In the matrix regions, relatively few neurons contain dense accumulations of HT-ir, and these cells always lack perikaryal staining for calbindin-D28K. Striatal interneurons, identified by the presence of immunoreactivity for choline acetyltransferase, parvalbumin, calretinin, or neuronal nitric oxide synthase, exhibit little or no HT-ir. The paucity of HT-ir in striatal interneurons, as well as the prominence of staining in a subset of striosomal neurons, mirrors the selective vulnerability of these different types of cells in early stages of human Huntington's disease and in rodent excitotoxic models of the disorder. Our observations suggest that mechanisms which modulate the accumulation of huntingtin may play a central role in the neuronal degeneration of Huntington's disease.

Animals↗
PubMed1997

Exon trapping and sequence-based methods of gene finding in transcript mapping of human 4p16.3.

We have applied exon amplification, GRAIL2 exon prediction and EST database searching to a 2 Mb segment of chromosome 4p16.3. Experimental and computational methods of identifying exons were comparable in efficiency and apparent false positive rate, but were complementary in gene identification, revealing distinct overlapping sets of expressed sequences. EST searching was most powerful when we considered only those ESTs that show evidence of splicing relative to the genomic sequence. The combination of the three gene finding methods produced a transcription map of 30 loci in this segment of 4p16.3 that includes known human genes, homologs of loci identified in rodents and several anonymous transcripts, including a putative novel DNA polymerase and a gene related to Drosophila ash1. While most of the genes in the region have been found, our data suggest that even with the entire DNA sequence available, complete saturation of the transcript map will require additional, focused experimental effort.

Chromosome Mapping↗
PubMed1997

The early-onset torsion dystonia gene (DYT1) encodes an ATP-binding protein.

Early-onset torsion dystonia is a movement disorder, characterized by twisting muscle contractures, that begins in childhood. Symptoms are believed to result from altered neuronal communication in the basal ganglia. This study identifies the DYT1 gene on human chromosome 9q34 as being responsible for this dominant disease. Almost all cases of early-onset dystonia have a unique 3-bp deletion that appears to have arisen idependently in different ethnic populations. This deletion results in loss of one of a pair of glutamic-acid residues in a conserved region of a novel ATP-binding protein, termed torsinA. This protein has homologues in nematode, rat, mouse and humans, with some resemblance to the family of heat-shock proteins and Clp proteases.

ATP-Binding Cassette Transporters↗
PubMed1997

Huntingtin is required for neurogenesis and is not impaired by the Huntington's disease CAG expansion.

Huntington's disease (HD) is an autosomal-dominant neurodegenerative disorder caused by a CAG repeat expansion that lengthens a glutamine segment in the novel huntingtin protein. To elucidate the molecular basis of HD, we extended the polyglutamine tract of the mouse homologue, Hdh, by targetted introduction of an expanded human HD CAG repeat, creating mutant HdhneoQ50 and HdhQ50 alleles that express reduced and wild-type levels of altered huntingtin, respectively. Mice homozygous for reduced levels displayed characteristic aberrant brain development and perinatal lethality, indicating a critical function for Hdh in neurogenesis. However, mice with normal levels of mutant huntingtin did not display these abnormalities, indicating that the expanded CAG repeat does not eliminate or detectably impair huntingtin's neurogenic function. Thus, the HD defect in man does not mimic complete or partial Hdh inactivation and appears to cause neurodegenerative disease by a gain-of-function mechanism.

Alleles↗
PubMed1997

Reduced penetrance of the Huntington's disease mutation.

Controversy persists concerning the significance of Huntington disease (HD) alleles in the 36-39 repeat range. Although some clinically affected persons have been documented with repeats in this range, elderly unaffected individuals have also been reported. We examined 10 paternal transmissions of HD alleles of 37-39 repeats in collateral branches of families with de novo HD. All 10 descendants, including many who are elderly, are without symptoms of HD. Forty percent of the transmissions were unstable, although none varied by more than one repeat. The observation that individuals with alleles of 37-39 repeats may survive unaffected beyond common life expectancy supports the presence of reduced penetrance for HD among some persons with repeat sizes which overlap the clinical range. Non-penetrance may be increased in the collateral branches of de novo mutation families when compared to penetrance estimates from patient series. There was no CAA-->CAG mutation for the penultimate glutamine in either a de novo expanded 42 repeat allele or the corresponding non-penetrant 38 repeat allele in a family with fresh mutation to HD.

Adult↗
PubMed1997

Fine localization of the torsion dystonia gene (DYT1) on human chromosome 9q34: YAC map and linkage disequilibrium.

The DYT1 gene, which maps to chromosome 9q34, appears to be responsible for most cases of early-onset torsion dystonia in both Ashkenazic Jewish (AJ) and non-Jewish families. This disease is inherited in an autosomal dominant mode with reduced penetrance (30%-40%). The abnormal involuntary movements associated with this disease are believed to be caused by unbalanced neural transmission in the basal ganglia. Previous linkage disequilibrium studies in the AJ population placed the DYT1 gene in a 2-cM region between the loci D9S62a and ASS. A YAC contig has now been created spanning 600 kb of this region including D9S62a. The location of the DYT1 gene has been refined within this contig using several new polymorphic loci to expand the linkage disequilibrium analysis of the AJ founder mutation. The most likely location of the DYT1 gene is within a 150 kb region between the loci D9S2161 and D9S63.

Adult↗
PubMed1997

Universal absence of merlin, but not other ERM family members, in schwannomas.

NF2 (neurofibromatosis 2, encoding the merlin protein) gene mutations and chromosome 22q loss have been demonstrated in the majority of sporadic and NF2-associated schwannomas, but many schwannomas fail to demonstrate genetic evidence of biallelic NF2 gene inactivation. In addition, the role of the merlin-related ERM family members (ezrin, radixin, and moesin) remains unclear in these tumors. We therefore studied expression of NF2-encoded merlin as well as ezrin, radixin, and moesin in 22 vestibular and peripheral schwannomas that had been evaluated for NF2 mutations and chromosome 22q loss. Western blotting and immunohistochemistry with antibodies directed against the amino and carboxy termini of merlin demonstrated loss of merlin expression in all studied schwannomas, including 12 tumors lacking genetic evidence of biallelic NF2 gene inactivation. Western blotting with antibodies directed against ezrin, radixin, and moesin, however, showed expression of these proteins in all schwannomas. In addition, immunohistochemistry with an antibody to moesin revealed widespread expression in tumor and endothelial cells. These data indicate that the specific loss of merlin is universal to schwannomas and is not linked to loss of ezrin, radixin, or moesin expression.

Blood Proteins↗
PubMed1996

No association between alpha 1-antichymotrypsin and familial Alzheimer's disease.

Alzheimer's disease (AD) is the most common mid to late age-of-onset neurodegenerative disorder. AD has a strong and complex genetic etiology, and multiple genes, acting independently and/or interacting, likely affect the risk of developing AD. Several genes involved with AD already have been described, but only the APOE gene on chromosome 19q has been shown to affect the risk of the most common form of AD, occurring with onset over the age of 65. Because a substantial portion of late-onset AD is not explained by APOE, other genes affecting late-onset AD likely occur. These could act either independently or perhaps interact with APOE. alpha 1-Antichymotrypsin (ACT) is a major component of the amyloid plaques found in the brains of AD patients and may play a role in the pathophysiology of AD. It has been proposed that a specific polymorphism within the ACT gene interacts with APOE to increase the risk of developing AD. Our results do not confirm this finding.

Adult↗