Pantothenate kinase-associated neurodegeneration is not a synucleinopathy

Aims: Mutations in the pantothenate kinase 2 gene (PANK2) are responsible for the most common type of neurodegeneration with brain iron accumulation (NBIA), known as pantothenate kinase-associated neurodegeneration (PKAN). Historically, NBIA is considered a synucleinopathy with numerous reports of NBIA cases with Lewy bodies and Lewy neurites and some cases reporting additional abnormal tau accumulation. However, clinicopathological correlations in genetically proven PKAN cases are rare. We describe the clinical, genetic and neuropathological features of three unrelated PKAN cases. Methods: All three cases were genetically screened for the PANK2 gene mutations using standard Sanger polymerase chain reaction sequencing. A detailed neuropathological assessment of the three cases was performed using histochemical and immunohistochemical preparations. Results: All cases had classical axonal swellings and Perls' positive iron deposition in the basal ganglia. In contrast to neuroaxonal dystrophies due to mutation of the phospholipase A2, group VI (PLA2G6) gene, in which Lewy body pathology is widespread, no α-synuclein accumulation was detected in any of our PKAN cases. In one case (20-year-old male) there was significant tau pathology comprising neurofibrillary tangles and neuropil threads, with very subtle tau pathology in another case. Conclusions: These findings indicate that PKAN is not a synucleinopathy and, hence the cellular pathways implicated in this disease are unlikely to be relevant for the pathomechanism of Lewy body disorders.

Genetic characterization of two gain-of-function alleles of the effector caspase DrICE in Drosophila

Caspases are the executioners of apoptosis. Although much is known about their physiological roles and structures, detailed analyses of missense mutations of caspases are lacking. As mutations within caspases are identified in various human diseases, the study of caspase mutants will help to elucidate how caspases interact with other components of the apoptosis pathway and how they may contribute to disease. DrICE is the major effector caspase in Drosophila required for developmental and stress-induced cell death. Here, we report the isolation and characterization of six de novo drICE mutants, all of which carry point mutations affecting amino acids conserved among caspases in various species. These six mutants behave as recessive loss-of-function mutants in a homozygous condition. Surprisingly, however, two of the newly isolated drICE alleles are gain-of-function mutants in a heterozygous condition, although they are loss-of-function mutants homozygously. Interestingly, they only behave as gain-of-function mutants in the presence of an apoptotic signal. These two alleles carry missense mutations affecting conserved amino acids in close proximity to the catalytic cysteine residue. This is the first time that viable gain-of-function alleles of caspases are described in any intact organism and provides a significant exception to the expectation that mutations of conserved amino acids always abolish the pro-apoptotic activity of caspases. We discuss models about how these mutations cause the gain-of-function character of these alleles.

Preliminary investigation of the area under the L-lactate concentration-time curve (LACArea) in critically ill equine neonates

BACKGROUND

A variety of measures of L-lactate concentration ([LAC]) in the blood of critically ill neonatal foals have shown utility as prognostic indicators. These measures, evaluating either the severity of hyperlactatemia or the duration of exposure to hyperlactatemia, perform fairly well and have correctly classified 75-80% of foals examined in several studies. The area under the L-lactate concentration versus time curve (LACArea) encompasses both severity and duration of hyperlactatemia and should improve correct classification of patient survival.

HYPOTHESIS/OBJECTIVES

LACArea is larger in nonsurviving critically ill neonatal foals.

ANIMALS

Forty-nine foals admitted for critical illness to 1 of 4 referral hospitals.

METHODS

Whole blood was obtained at admission and 6, 12, 18, and 24 hours after admission for measurement of L-lactate using a handheld lactate meter. LACArea was calculated for: admission-6, 6-12, 12-18, 18-24 hours, and admission-24 hours using the trapezoidal method and summing the 6-hours interval areas to determine total 24 hours area. Differences between survivors and nonsurvivors were determined using robust regression and Kruskal-Wallis testing, P < .05.

RESULTS

LACArea was significantly larger in nonsurviving foals (n = 9) than in surviving foals (n = 40) at all time periods examined.

CONCLUSIONS AND CLINICAL IMPORTANCE

Differences in LACArea between surviving and nonsurviving critically ill neonatal foals are large and support further investigation of this method as an improved biomarker for survival in critically ill neonatal foals is indicated.

Mesenteric lymphatic vessels adapt to mesenteric venous hypertension by becoming weaker pumps

Lymphangions, the segments of lymphatic vessels between two adjacent lymphatic valves, actively pump lymph. Acute changes in transmural pressure and lymph flow have profound effects on lymphatic pump function in vitro. Chronic changes in pressure and flow in vivo have also been reported to lead to significant changes in lymphangion function. Because changes in pressure and flow are both cause and effect of adaptive processes, characterizing adaptation requires a more fundamental analysis of lymphatic muscle properties. Therefore, the purpose of the present work was to use an intact lymphangion isovolumetric preparation to evaluate changes in mesenteric lymphatic muscle mechanical properties and the intracellular Ca(2+) in response to sustained mesenteric venous hypertension. Bovine mesenteric veins were surgically occluded to create mesenteric venous hypertension. Postnodal mesenteric lymphatic vessels from mesenteric venous hypertension (MVH; n = 6) and sham surgery (Sham; n = 6) animals were isolated and evaluated 3 days after the surgery. Spontaneously contracting MVH vessels generated end-systolic active tension and end-diastolic active tension lower than the Sham vessels. Furthermore, steady-state active tension and intracellular Ca(2+) concentration levels in response to KCl stimulation were also significantly lower in MVH vessels compared with those of the Sham vessels. There was no significant difference in passive tension in lymphatic vessels from the two groups. Taken together, these results suggest that following 3 days of mesenteric venous hypertension, postnodal mesenteric lymphatic vessels adapt to become weaker pumps with decreased cytosolic Ca(2+) concentration.

Pathways to Alzheimer's disease

Recent trials of anti-amyloid agents have not produced convincing improvements in clinical outcome in Alzheimer's disease; however, the reason for these poor or inconclusive results remains unclear. Recent genetic data continue to support the amyloid hypothesis of Alzheimer's disease with protective variants being found in the amyloid gene and both common low-risk and rare high-risk variants for disease being discovered in genes that are part of the amyloid response pathways. These data support the view that genetic variability in how the brain responds to amyloid deposition is a potential therapeutic target for the disease, and are consistent with the notion that anti-amyloid therapies should be initiated early in the disease process.

Meta-analysis of 74,046 individuals identifies 11 new susceptibility loci for Alzheimer's disease

Eleven susceptibility loci for late-onset Alzheimer's disease (LOAD) were identified by previous studies; however, a large portion of the genetic risk for this disease remains unexplained. We conducted a large, two-stage meta-analysis of genome-wide association studies (GWAS) in individuals of European ancestry. In stage 1, we used genotyped and imputed data (7,055,881 SNPs) to perform meta-analysis on 4 previously published GWAS data sets consisting of 17,008 Alzheimer's disease cases and 37,154 controls. In stage 2, 11,632 SNPs were genotyped and tested for association in an independent set of 8,572 Alzheimer's disease cases and 11,312 controls. In addition to the APOE locus (encoding apolipoprotein E), 19 loci reached genome-wide significance (P < 5 × 10(-8)) in the combined stage 1 and stage 2 analysis, of which 11 are newly associated with Alzheimer's disease.

Genome-wide association study of obsessive-compulsive disorder

Obsessive-compulsive disorder (OCD) is a common, debilitating neuropsychiatric illness with complex genetic etiology. The International OCD Foundation Genetics Collaborative (IOCDF-GC) is a multi-national collaboration established to discover the genetic variation predisposing to OCD. A set of individuals affected with DSM-IV OCD, a subset of their parents, and unselected controls, were genotyped with several different Illumina SNP microarrays. After extensive data cleaning, 1465 cases, 5557 ancestry-matched controls and 400 complete trios remained, with a common set of 469,410 autosomal and 9657 X-chromosome single nucleotide polymorphisms (SNPs). Ancestry-stratified case-control association analyses were conducted for three genetically-defined subpopulations and combined in two meta-analyses, with and without the trio-based analysis. In the case-control analysis, the lowest two P-values were located within DLGAP1 (P=2.49 × 10(-6) and P=3.44 × 10(-6)), a member of the neuronal postsynaptic density complex. In the trio analysis, rs6131295, near BTBD3, exceeded the genome-wide significance threshold with a P-value=3.84 × 10(-8). However, when trios were meta-analyzed with the case-control samples, the P-value for this variant was 3.62 × 10(-5), losing genome-wide significance. Although no SNPs were identified to be associated with OCD at a genome-wide significant level in the combined trio-case-control sample, a significant enrichment of methylation QTLs (P<0.001) and frontal lobe expression quantitative trait loci (eQTLs) (P=0.001) was observed within the top-ranked SNPs (P<0.01) from the trio-case-control analysis, suggesting these top signals may have a broad role in gene expression in the brain, and possibly in the etiology of OCD.

Adaptation of mesenteric lymphatic vessels to prolonged changes in transmural pressure

In vitro studies have revealed that acute increases in transmural pressure increase lymphatic vessel contractile function. However, adaptive responses to prolonged changes in transmural pressure in vivo have not been reported. Therefore, we developed a novel bovine mesenteric lymphatic partial constriction model to test the hypothesis that lymphatic vessels exposed to higher transmural pressures adapt functionally to become stronger pumps than vessels exposed to lower transmural pressures. Postnodal mesenteric lymphatic vessels were partially constricted for 3 days. On postoperative day 3, constricted vessels were isolated, and divided into upstream (UP) and downstream (DN) segment groups, and instrumented in an isolated bath. Although there were no differences between the passive diameters of the two groups, both diastolic diameter and systolic diameter were significantly larger in the UP group than in the DN group. The pump index of the UP group was also higher than that in the DN group. In conclusion, this is the first work to report how lymphatic vessels adapt to prolonged changes in transmural pressure in vivo. Our results suggest that vessel segments upstream of the constriction adapt to become both better fluid conduits and lymphatic pumps than downstream segments.

Transmitter deficits in Alzheimer's disease

The pattern of neurotransmitter pathway losses in Alzheimer's disease are reviewed. Deficits of the cholinergic pathway from the nucleus basalis, the noradrenergic pathway from the locus coeruleus and the serotoninergic pathway from the raphe nuclei are established. Cortical somatostatin interneurons are affected and dopaminergic neurons may be affected although these may be late or secondary phenomena in the disease process. Other neuronal systems, particularly in the hippocampus and temporal cortex, are also damaged. However, the disease is not one of generalised neuronal atrophy since some neurons are selectively spared. The established pathway-specific losses are discussed in relation to the clinical symptomatology and the pathology of the disorder. The biochemical and histological findings are compared with similar measurements made on tissues from other dementing disorders in an attempt to trace features common to dementias. Finally, as an addendum, a hypothesis is briefly outlined which attempts to explain the common features of the affected neurons and the pathogenesis of the disorder.