The SAC1 domain in synaptojanin is required for autophagosome maturation at presynaptic terminals

Presynaptic terminals are metabolically active and accrue damage through continuous vesicle cycling. How synapses locally regulate protein homeostasis is poorly understood. We show that the presynaptic lipid phosphatase synaptojanin is required for macroautophagy, and this role is inhibited by the Parkinson's disease mutation R258Q. Synaptojanin drives synaptic endocytosis by dephosphorylating PI(4,5)P₂, but this function appears normal in Synaptojanin^RQ knock‐in flies. Instead, R258Q affects the synaptojanin SAC1 domain that dephosphorylates PI(3)P and PI(3,5)P₂, two lipids found in autophagosomal membranes. Using advanced imaging, we show that Synaptojanin^RQ mutants accumulate the PI(3)P/PI(3,5)P₂‐binding protein Atg18a on nascent synaptic autophagosomes, blocking autophagosome maturation at fly synapses and in neurites of human patient induced pluripotent stem cell‐derived neurons. Additionally, we observe neurodegeneration, including dopaminergic neuron loss, in Synaptojanin^RQ flies. Thus, synaptojanin is essential for macroautophagy within presynaptic terminals, coupling protein turnover with synaptic vesicle cycling and linking presynaptic‐specific autophagy defects to Parkinson's disease.     

Incidence and Characteristics of Total Stroke in the United States

Background and Purpose  

Stroke, increasingly referred to as a "brain attack", is one of the leading causes of death and the leading cause of adult disability in the United States. It has recently been estimated that there were three quarters of a million strokes in the United States in 1995. The aim of this study was to replicate the 1995 estimate and examine if there was an increase from 1995 to 1996 by using a large administrative claims database representative of all 1996 US inpatient discharges.     

Evaluating whether velar lobe size indicates food limitation among larvae of the marine gastropod Crepidula fornicata

Disproportionately large feeding structures have been used to infer food limitation in some marine invertebrate larvae, but few studies have investigated whether other factors alter larval morphology in similar ways. In this study, larvae of Crepidula fornicata were reared either at five different food concentrations of Isochrysis galbana (clone T-ISO) at a single temperature (22 degrees C) (Experiments I and II); or on three different phytoplankton species (Isochrysis galbana, Dunaliella tertiolecta, and Pavlova lutheri) at both high and low concentrations at a single temperature (22 degrees C) (Experiment III); or at high and low concentrations of Isochrysis galbana at four different temperatures between 16 and 25 degrees C (Experiment IV). Shell lengths and velar lobe dimensions were determined for individual larvae at intervals to monitor relative rates of velar and shell growth. In addition (Experiment V), fast growing and slow growing larvae in Experiment I were examined separately to determine whether velar lobes developed at similar rates (relative to shell growth) for fast and slow growing larvae within individual cultures. In general, velar lobes grew significantly larger, relative to shell length, when larvae were reared at low food concentrations (P<0.0001); for larvae of similar shell length, the velar lobes of those fed 1x10(4) cells ml(-1) were on average 17.7% larger than those of larvae fed 18x10(4) cells ml(-1) of T-ISO. In contrast, larvae fed different phytoplankton species at equivalently high food concentrations did not differ in relative velum size (P=0.2666), even though shell growth rates differed significantly for larvae raised on the different diets, indicating substantial variation in food quality. We also found that relative rates of velum and shell growth differed among fast and slow growing individuals within treatments. Temperature had no significant effect on relative rates of velar and shell growth within the 16-25 degrees C range tested (P=0.121), but may have altered the relationship between food concentration and relative velar growth. These results indicate that dramatically reduced food concentration induces disproportionate growth in the velar lobes of C. fornicata, but that interpretation of data from field-collected individuals of this species will be made difficult by the potentially confounding effects of temperature, food quality, and differences in individual growth potential. Assessments of food limitation using morphological measurements for field-collected larvae will need to be supplemented with other indicators before convincing conclusions about the extent of food limitation in C. fornicata can be drawn.     

ALS2/Alsin regulates Rac-PAK signaling and neurite outgrowth

Rac and its downstream effectors p21-activated kinase (PAK) family kinases regulate actin dynamics within growth cones to control neurite outgrowth during development. The activity of Rac is stimulated by guanine nucleotide exchange factors (GEFs) that promote GDP release and GTP binding. ALS2/Alsin is a recently described GEF that contains a central domain that is predicted to regulate the activities of Rac and/or Rho and Cdc42 activities. Mutations in ALS2 cause some recessive familial forms of amyotrophic lateral sclerosis (ALS) but the function of ALS2 is poorly understood. Here we demonstrate that ALS2 is present within growth cones of neurons, in which it co-localizes with Rac. Furthermore, ALS2 stimulates Rac but not Rho or Cdc42 activities, and this induces a corresponding increase in PAK1 activity. Finally, we demonstrate that ALS2 promotes neurite outgrowth. Defects in these functions may therefore contribute to motor neuron demise in ALS.     

Patterns of differentiation and hybridization in North American wolflike canids, revealed by analysis of microsatellite loci

Genetic divergence and gene flow among closely related populations are difficult to measure because mutation rates of most nuclear loci are so low that new mutations have not had sufficient time to appear and become fixed. Microsatellite loci are repeat arrays of simple sequences that have high mutation rates and are abundant in the eukaryotic genome. Large population samples can be screened for variation by using the polymerase chain reaction and polyacrylamide gel electrophoresis to separate alleles. We analyzed 10 microsatellite loci to quantify genetic differentiation and hybridization in three species of North American wolflike canids. We expected to find a pattern of genetic differentiation by distance to exist among wolflike canid populations, because of the finite dispersal distances of individuals. Moreover, we predicted that, because wolflike canids are highly mobile, hybrid zones may be more extensive and show substantial changes in allele frequency, relative to nonhybridizing populations. We demonstrate that wolves and coyotes do not show a pattern of genetic differentiation by distance. Genetic subdivision in coyotes, as measured by theta and Gst, is not significantly different from zero, reflecting persistent gene flow among newly established populations. However, gray wolves show significant subdivision that may be either due to drift in past Ice Age refugia populations or a result of other causes. Finally, in areas where gray wolves and coyotes hybridize, allele frequencies of gray wolves are affected, but those of coyotes are not. Past hybridization between the two species in the south-central United States may account for the origin of the red wolf.      

Mutagenicity of the mycotoxin diacetoxyscirpenol on somatic and germ cells of mice

Genotoxicity of diacetoxyscirpenol (DAS) was studied on laboratory mice after intraperitoneal injection with single and repeated doses. DAS was administrated at three different dose levels (0.5, 0.75, and 1.0 mg/kg body weight). The study was conducted on both somatic and germ cells additional to the sperm morphology analysis. DAS treatment resulted in a significant reduction (P<0.01) in mitotic activity at all levels of doses tested, confirming that DAS is a potent protein and DNA synthesis inhibitor. At somatic cells (bone marrow) both structural and numerical chromosome abnormalities were observed. Single dose treatment showed significant abnormalities only with high dose treatment. In contrast, at repeated dose similar abnormalities were also observed with some significance but no systematic relation between the administrated dose and abnormalities ratio could be settled. In germ cells (testicles), structural and numerical abnormalities were also observed. In general, the frequencies of scored abnormalities at germ cells were lower than that the somatic cells. Sperm count test revealed a decrease in the number of released sperm after toxin treatment. Abnormalities of sperm shape (head and tail) were observed, confirming the positive correlation between cytogenetic damage and sperm abnormality. The results also proved that DAS is a very toxic mycotoxin, in addition to inducing chromosomal abnormalities, it causes a severe inhibition of DNA synthesis which subsequently affects the cell cycle and cell division. A good system for good harvesting practice and good food technology can lower the risk for the consumers.