Wendy Hobbs

Minocycline inhibits caspase-1 and caspase-3 expression and delays mortality in a transgenic mouse model of Huntington disease

Huntington disease is an autosomal dominant neurodegenerative disease with no effective treatment. Minocycline is a tetracycline derivative with proven safety. After ischemia, minocycline inhibits caspase-1 and inducible nitric oxide synthetase upregulation, and reduces infarction. As caspase-1 and nitric oxide seem to play a role in Huntington disease, we evaluated the therapeutic efficacy of minocycline in the R6/2 mouse model of Huntington disease. We report that minocycline delays disease progression, inhibits caspase-1 and caspase-3 mRNA upregulation, and decreases inducible nitric oxide synthetase activity. In addition, effective pharmacotherapy in R6/2 mice requires caspase-1 and caspase-3 inhibition. This is the first demonstration of caspase-1 and caspase-3 transcriptional regulation in a Huntington disease model.

Genetic linkage of von Recklinghausen neurofibromatosis to the nerve growth factor receptor gene

von Recklinghausen neurofibromatosis (VRNF) is one of the most common inherited disorders affecting the human nervous system. VRNF is transmitted as an autosomal dominant defect with high penetrance but variable expressivity. The disorder is characterized clinically by hyperpigmented patches of skin (café au lait macules, axillary freckles) and by multiple tumors of peripheral nerve, spinal nerve roots, and brain (neurofibromas, optic gliomas). These tumors can cause disfigurement, paralysis, blindness, and death. We have determined the chromosomal location of the VRNF gene by genetic linkage analysis using DNA markers. The VRNF gene is genetically linked to the locus encoding nerve growth factor receptor, located on the long arm of chromosome 17 in the region 17q12----17q22. However, crossovers with the VRNF locus suggest that a mutation in the nerve growth factor receptor gene itself is unlikely to be the fundamental defect responsible for the VRNF phenotype.

Localization of the Huntington's disease gene to a small segment of chromosome 4 flanked by D4S10 and the telomere.

Huntingtons disease (HD) is an autosomal dominant neurodegenerative disorder of late onset, characterized by progressive motor disturbance, psychological manifestations, and intellectual deterioration. The HD gene has been genetically mapped by linkage to the DNA marker D4S10, but the exact physical location of the HD defect has remained uncertain. To delineate critical recombination events revealing the physical position of the HD gene, we have identified restriction fragment length polymorphisms for two recently mapped chromosome 4 loci, RAF2 and D4S62, and determined the pattern of segregation of these markers in both reference and HD pedigrees. Multipoint linkage analysis of the new markers with D4S10 and HD establishes that the HD gene is located in a very small physical region at the tip of the chromosome, bordered by D4S10 and the telomere. A crossover within the D4S10 locus orients this segment on the chromosome, providing the necessary information for efficient application of directional cloning strategies for progressing toward, and eventually isolating, the HD gene.

Linkage analysis in von Recklinghausen neurofibromatosis (NF1) with DNA markers for chromosome 17

The mutant gene causing von Recklinghausen neurofibromatosis (NF1) was recently shown to map to chromosome 17. We have used additional markers for chromosome 17 to narrow further the location of the gene defect. A preliminary multipoint linkage analysis suggests that the NF1 gene is located on the long arm of chroomsome 17, flanked by D17Z1 and NGFR. Linkage analysis with the human oncogene homolog erbA1, which maps to this region, suggests that this cancer-related gene is not the primary cause of NF1.

P301L tauopathy: confocal immunofluorescence study of perinuclear aggregation of the mutated protein

The clinical and neuropathological features in the P301L tauopathy have been described in several kindreds. In this study, we present findings in two previously unreported patients, evaluated both genetically, neuropathologically, and with multiparametric confocal immunofluorescence. The patients were female, with age 65 and 75 years old, respectively. Both exhibited clinical symptoms of frontotemporal dementia (FTD). Marked atrophy of the frontal and temporal lobes with moderate atrophy of the remaining cerebral and brain stem structures was present. The substantia nigra was pale. The atrophic neocortical regions exhibited neuronal loss, marked gliosis, status spongiosus, and occasional ballooned neurons. By light microscopy, the most striking findings were argyrophilic perinuclear rings, frequently with an attached small inclusion (mini Pick-like body), especially prominent in dentate granule cells, entorhinal and temporal cortices, and to a lesser extent in CA1. These structures were immunopositive for tau protein (Tau-2, AT-8, PHF-1, MC-1). Numerous astrocytic plaques, tuft-shaped astrocytes, coiled bodies, and dystrophic neurites were also present. Confocal immunofluorescence with a P301L-specific antibody directly demonstrated the presence of the mutated protein in the PHF-1 positive aggregates. The mutated tau protein (4-repeat tau) was detected in the mini Pick-like bodies, indicating an important biochemical difference between these inclusions and classical Pick bodies (3-repeat tau). Additionally, since 4-repeat tau protein is not normally present in dentate granule cells, this result also suggests an abnormality in the mRNA splicing mechanisms. The structural features of the involvement of proteolytic systems in this tauopathy were assessed by immunohistochemistry for the active form of calpain II (C-27) and ubiquitin. Colocalization of PHF-1 positive aggregates with C-27 points to the possible involvement of calpain in tau protein hyperphosphorylation. Absence of immunostaining for ubiquitin indicates possible dysfunction of the ubiquitin-proteasome system in this tauopathy.

Linkage of G8 (D4S10) in two Swedish families with Huntington's disease

Two Swedish families with Huntingtons disease (HD) have been investigated for linkage with G8 (D4S10). In one family from northern Sweden (Family 1) 48 family members were examined, and in another family from the southwestern part of Sweden (Family 2) 14 family members were examined. The lod scores were 1.531 for Family 1 and 2.057 for Family 2, and the combined lod score was 3.59. The HD gene was segregating with the haplotype C in Family 1 and with haplotype A in Family 2. The predictive value of the test was obvious. Before the testing with the G8 probe, 84.2% of the family members in Family 1 had a theoretical risk of 25% or 50% of having the HD gene. After the testing with the G8 probe, only 23.7% of the family members remained at the same risk, and it could also be certified that 63.2% had no or little risk of having the HD gene. Only one asymptomatic person was predicted to have HD.

Physical and genetic localization of quinonoid dihydropteridine reductase gene (QDPR) on short arm of chromosome 4

A portion of a cDNA clone corresponding to the 3′ end of the human quinonoid dihydropteridine reductase (QDPR) mRNA was used as a probe to physically map the QDPRgene by analysis of somatic cell hybrid lines. The provisional assignment of QDPRto chromosome 4, based on expression of the human enzyme in hybrids, was confirmed. The gene was further regionally localized on the short arm to 4p16.1→4p15.1. This physical localization places QDPRin the same area of the genome that contains the defect causing Huntingtons disease (HD). The QDPRprobe revealed a restriction fragment length polymorphism with the enzyme BanII, permitting determination of its genetic proximity to D4S10,an anonymous DNA marker tightly linked to HD. QDPRis only loosely linked to D4S10,excluding any primary role for the gene in HD.

DNA linkage analysis in Von Recklinghausen neurofibromatosis.

We have used DNA linkage analysis in 11 families with Von Recklinghausen neurofibromatosis (VRNF) in order to search for the chromosomal localisation of the defective gene causing this serious neurological disorder. Three groups of polymorphic DNA markers were used: (1) markers for chromosome 22, because of possible allelic genetic heterogeneity between VRNF and bilateral acoustic neurofibromatosis; (2) markers near the centromere of chromosome 4, since there was preliminary evidence for linkage between the VRNF gene and Gc; and (3) oncogenes and growth factors as possible candidate genes for VRNF. Our data exclude close linkage between any of these markers and the gene for VRNF.

Alterations in p53, p21, and MIB-1 Labeling Index in Primary Human Astrocytomas Following Radiation Therapy

SummaryLittle is known about the cellular and genetic changes that occur in human astrocytomas following radiation therapy (RT). Experimental studies would suggest that early effects include induction of p53 and p21 expression, cell cycle arrest, and selection of tumor cells with molecular changes that correlate with radiation resistance. Unfortunately, tissue sampling of primary human astrocytomas closely following radiation therapy is uncommon, hindering comparative assessment of primary human tumors. Through local databases, we were able to collect eight cases in which tissue was resected within 8 weeks of RT because of bulky residual disease: two patients with grade II diffuse astrocytomas (LGA) and 6 patients with high-grade astrocytomas (HGA; 1 anaplastic astrocytoma, 5 glioblastomas). Routine histopathologic sections, MIB-1 labeling index (LI), p53 and p21 expression, and EGFR expression were compared between the pre- and post-RT samples. Only one tumor (52d post-RT) showed prominent radiation-induced histopathologic changes. p53 expression was detected in two tumors pre-RT and in six tumors post-RT. In the four tumors in which p53 expression was induced, the post-RT LI was lower in each case, and p21 expression had increased in 3/4 of these cases. No change in LI was detected in tumors in which p53 expression was unchanged. EGFR expression was not altered following RT. The results of this unique series document that some primary human astrocytomas increase expression of p53 and p21 and decrease proliferation in response to RT. However, the small size of the series argues for further studies of radiation induced molecular changes in primary human astrocytoma tissue.

Genetic Linkage Analysis of Neurofibromatosis with DNA Markers

Peripheral neurofibromatosis (PNF), as described by von Recklinghausen, is one of the most common single-gene disorders affecting the nervous system. It is transmitted in an autosomal dominant fashion, with high penetrance but remarkably variable phenotype expression (for review see References 1 and 2). While multiple cell types can be affected, the most common abnormalities are in cells of neural crest origin, causing neoplasia or dysplasia. Typical clinical features include neurofibromas (disordered growth of Schwann cells) and cafk-au-lait spots (dysregulated growth of melanocytes).