Biomedical subjects

Paul Lockhart

Publications and source records attributed to Paul Lockhart.

4 recordsLinked to original sources

PubMed2007

Polyalanine expansion mutations in the X-linked hypopituitarism gene SOX3 result in aggresome formation and impaired transactivation.

Polyalanine expansion mutations have been identified in eight transcription factors that are associated with a range of congenital disorders. While some of these mutant proteins have been shown to generate cellular aggregates in heterologous cell lines, little is known about the mechanism by which these aggregates cause disease. Here we examine the aggregation and functional properties of the two known polyalanine expansion mutations associated with X-linked Hypopituitarism (XH), SOX3(22Ala) and SOX3(26Ala), which contain an additional seven and eleven alanine residues, respectively. SOX3(22Ala) and SOX3(26Ala) proteins form cytoplasmic aggregates and nuclear inclusions in transiently transfected COS-7 and CHO K1 cells, and in transfected explant cultures of chick neural epithelium. SOX3(26Ala) exhibits a more potent aggregation phenotype, resulting in significantly more cells with dispersed cytoplasmic and large perinuclear aggregates. SOX3(22Ala) and SOX3(26Ala) protein aggregates exhibit the key properties of aggresomes including vimentin redistribution, colocalisation with the Microtubule Organising Centre and sensitivity to microtubule disruption. This is the first time that aggresomes have been implicated in the aetiology of a polyalanine expansion disorder, suggesting that XH and protein conformation disorders may become manifest through similar pathological mechanisms. Further, we show that mutant SOX3 proteins have impaired transcriptional activity and reduced capacity to inhibit beta-catenin/TCF-mediated transcription. These data suggest that deregulation of SOX3 target genes and inappropriate canonical Wnt signaling in central nervous system (CNS) progenitors may also contribute to dysfunction of the hypothalamic-pituitary axis in XH patients.

Animals↗

PubMed2004

Quantitative proteomic analysis of mitochondrial proteins: relevance to Lewy body formation and Parkinson's disease.

The mechanisms underlying Parkinson's disease (PD) and Lewy body (LB) formation, a pathological hallmark of PD, are incompletely understood; however, mitochondrial dysfunction is likely to be at least partially responsible. To study the processes that might be related to nigral neurodegeneration and LB formation, we employed nonbiased quantitative proteomics with isotope-coded affinity tag (ICAT) to compare the mitochondrial protein profiles in the substantia nigra (SN) between controls and mice treated chronically with 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP), a potent mitochondrial toxicant, and an adjuvant, probenecid (prob), for 5 weeks, which produced selective nigrostriatal neurodegeneration with formation of LB-like cytoplasmic inclusions in the remaining nigral neurons. This method identified a total of more than 300 proteins; of these proteins, more than 100 displayed significant changes in relative abundance in the MPTP/prob-treated mice compared to the controls. We validated one of these proteins, DJ-1, whose mutation has been implicated in familial PD, with Western blot analysis, followed by immunohistochemical studies of its distribution in the SN in relation to cytoplasmic inclusions in mice, as well as in classical LBs in PD patients. The results demonstrated that DJ-1 was not only colocalized with alpha-synuclein in dopaminergic neurons but also to cytoplasmic inclusions in mice treated with MPTP/prob. In addition, DJ-1 was present in the halo but not in the core of classical LBs in patients with PD. Our findings suggested that DJ-1 might play an important role in mitochondrial dysfunction, as well as LB formation in PD.

Animals↗

PubMed2003

The PARK8 locus in autosomal dominant parkinsonism: confirmation of linkage and further delineation of the disease-containing interval.

Recently, a new locus (PARK8) for autosomal dominant parkinsonism has been identified in one large Japanese family. Linkage has been shown to a 16-cM centromeric region of chromosome 12, between markers D12S1631 and D12S339. We tested 21 white families with Parkinson disease and an inheritance pattern compatible with autosomal dominant transmission for linkage in this region. Criteria for inclusion were at least three affected individuals in more than one generation. A total of 29 markers were used to saturate the candidate region. One hundred sixty-seven family members were tested (84 affected and 83 unaffected). Under the assumption of heterogeneity and through use of an affecteds-only model, a maximum multipoint LOD score of 2.01 was achieved in the total sample, with an estimated proportion of families with linkage of 0.32. This LOD score is significant for linkage in a replication study and corresponds to a P value of.0047. Two families (family A [German Canadian] and family D [from western Nebraska]) reached significant linkage on their own, with a combined maximum multipoint LOD score of 3.33, calculated with an affecteds-only model (family A: LOD score 1.67, P=.0028; family D: LOD score 1.67, P=.0028). When a penetrance-dependent model was calculated, the combined multipoint LOD score achieved was 3.92 (family A: LOD score 1.68, P=.0027; family D: LOD score 2.24, P=.0007). On the basis of the multipoint analysis for the combined families A and D, the 1-LOD support interval suggests that the most likely disease location is between a CA repeat polymorphism on genomic clone AC025253 (44.5 Mb) and marker D12S1701 (47.7 Mb). Our data provide evidence that the PARK8 locus is responsible for the disease in a subset of families of white ancestry with autosomal dominant parkinsonism, suggesting that it could be a more common locus.

Chromosome Mapping↗

PubMed2003

SCA2 may present as levodopa-responsive parkinsonism.

Some kindreds with familial parkinsonism exhibit genetic anticipation, suggesting possible involvement of trinucleotide repeat expansion. Recent reports have shown trinucleotide repeat expansions in the spinocerebellar ataxia 2 (SCA2) gene in patients with levodopa-responsive parkinsonism. We tested 136 unrelated patients with familial parkinsonism for SCA2 mutations. Two probands had borderline mutations; the rest were normal. ( or=36 is pathogenic). The expanded allele segregated with neurological signs in one kindred. The absence of borderline mutations in the normal population, and the co-segregation of the expanded allele with neurological signs in one kindred suggest that SCA2 mutations may be responsible for a subset of familial parkinsonism.

Adult↗