CRISPR screen for protein inclusion formation uncovers a role for SRRD in the regulation of intermediate filament dynamics and aggresome assembly

The presence of large protein inclusions is a hallmark of neurodegeneration, and yet the precise molecular factors that contribute to their formation remain poorly understood. Screens using aggregation-prone proteins have commonly relied on downstream toxicity as a readout rather than the direct formation of aggregates. Here, we combined a genome-wide CRISPR knockout screen with Pulse Shape Analysis, a FACS-based method for inclusion detection, to identify direct modifiers of TDP-43 aggregation in human cells. Our screen revealed both canonical and novel proteostasis genes, and unearthed SRRD, a poorly characterized protein, as a top regulator of protein inclusion formation. APEX biotin labeling reveals that SRRD resides in proximity to proteins that are involved in the formation and breakage of disulfide bonds and to intermediate filaments, suggesting a role in regulation of the spatial dynamics of the intermediate filament network. Indeed, loss of SRRD results in aberrant intermediate filament fibrils and the impaired formation of aggresomes, including blunted vimentin cage structure, during proteotoxic stress. Interestingly, SRRD also localizes to aggresomes and unfolded proteins, and rescues proteotoxicity in yeast whereby its N-terminal low complexity domain is sufficient to induce this affect. Altogether this suggests an unanticipated and broad role for SRRD in cytoskeletal organization and cellular proteostasis.

Body composition, gastrointestinal, and reproductive differences between broiler breeders fed using everyday or skip-a-day rearing programs

Broiler breeder feed restriction practices have intensified as broiler feed efficiency has been improved. Skip-a-day (SAD) rearing regimen has controlled breeder growth, although this practice has become questionable for the modern breeder. We compared everyday (ED) and SAD programs and evaluated their impact on pullet growth performance, body composition, gastrointestinal tract development, and reproduction. At d 0, Ross 708 (Aviagen) pullet chicks (n = 1,778) were randomly assigned to 7 floor pens. Three pens were fed using the ED and 4 pens with SAD program through wk 21 using a chain-feeder system. ED and SAD grower diets were formulated to be isonutritious, with the only difference that ED diets had more crude fiber. Pullets (n = 44 per pen) were moved to 16 hen pens by treatment at wk 21 with 3 YP males (Aviagen) in each pen. All birds were fed common laying diets. In addition to BW data, sampled pullets and hens were scanned using dual energy X-ray absorptiometry (DEXA) to obtain body bone density and composition. Hen performance and hatchery metrics were recorded through wk 60. ED birds were heavier with similar nutrient intake from wk 10 to 45 (P ≤ 0.013). Pullet uniformity was unaffected by feeding method (P ≥ 0.443). SAD pullets had less body fat at wk 19 (P = 0.034) compared to ED pullets, likely as a metabolic consequence of intermittent feeding. SAD birds had lower bone density at wk 7, 15, and 19 (P ≤ 0.026). At 4 wk of age, SAD pullets had less intestinal villi goblet cells compared to ED pullets (P ≤ 0.050), possibly explained by the effect that feed removal has on cell migration rates. Overall egg-specific gravity (P = 0.057) and hatch of fertile % (P = 0.088) tended to be higher in eggs from ED hens. Altogether, ED feeding increased young pullet intestinal goblet cells and increased both bone density and body fat at wk 19. ED program improved pullet feed conversion (2.6% less feed) and increased eggshell quality and hatch of fertile.

CRISPRing the Regulatory Genome, the Challenge Ahead

CRISPR saturation mutagenesis has the potential to dissect the functional landscape of noncoding regions, but is highly susceptible to false discovery and misinterpretation. As recently published, Canver et al. have now taken the first steps towards addressing these issues by increasing screening resolution and analyzing the effects of off targets on hit calling.

Pathogen-mediated NMDA receptor autoimmunity and cellular barrier dysfunction in schizophrenia

Autoantibodies that bind the N-methyl-D-aspartate receptor (NMDAR) may underlie glutamate receptor hypofunction and related cognitive impairment found in schizophrenia. Exposure to neurotropic pathogens can foster an autoimmune-prone environment and drive systemic inflammation leading to endothelial barrier defects. In mouse model cohorts, we demonstrate that infection with the protozoan parasite, Toxoplasma gondii, caused sustained elevations of IgG class antibodies to the NMDAR in conjunction with compromised blood-gut and blood-brain barriers. In human cohorts, NMDAR IgG and markers of barrier permeability were significantly associated with T. gondii exposure in schizophrenia compared with controls and independently of antipsychotic medication. Combined T. gondii and NMDAR antibody seropositivity in schizophrenia resulted in higher degrees of cognitive impairment as measured by tests of delayed memory. These data underscore the necessity of disentangling the heterogeneous pathophysiology of schizophrenia so that relevant subsets eligible for NMDAR-related treatment can be identified. Our data aid to reconcile conflicting reports regarding a role of pathological NMDAR autoantibodies in this disorder.

Deficiency in the mouse mitochondrial adenine nucleotide translocator isoform 2 gene is associated with cardiac noncompaction

The mouse fetal and adult hearts express two adenine nucleotide translocator (ANT) isoform genes. The predominant isoform is the heart-muscle-brain ANT-isoform gene 1 (Ant1) while the other is the systemic Ant2 gene. Genetic inactivation of the Ant1 gene does not impair fetal development but results in hypertrophic cardiomyopathy in postnatal mice. Using a knockin X-linked Ant2 allele in which exons 3 and 4 are flanked by loxP sites combined in males with a protamine 1 promoter driven Cre recombinase we created females heterozygous for a null Ant2 allele. Crossing the heterozygous females with the Ant2(fl), PrmCre(+) males resulted in male and female ANT2-null embryos. These fetuses proved to be embryonic lethal by day E14.5 in association with cardiac developmental failure, immature cardiomyocytes having swollen mitochondria, cardiomyocyte hyperproliferation, and cardiac failure due to hypertrabeculation/noncompaction. ANTs have two main functions, mitochondrial-cytosol ATP/ADP exchange and modulation of the mitochondrial permeability transition pore (mtPTP). Previous studies imply that ANT2 biases the mtPTP toward closed while ANT1 biases the mtPTP toward open. It has been reported that immature cardiomyocytes have a constitutively opened mtPTP, the closure of which signals the maturation of cardiomyocytes. Therefore, we hypothesize that the developmental toxicity of the Ant2 null mutation may be the result of biasing the cardiomyocyte mtPTP to remain open thus impairing cardiomyocyte maturation and resulting in cardiomyocyte hyperproliferation and failure of trabecular maturation. This article is part of a Special Issue entitled 'EBEC 2016: 19th European Bioenergetics Conference, Riva del Garda, Italy, July 2-6, 2016', edited by Prof. Paolo Bernardi.

Evidence that nitric oxide acts as an inhibitory neurotransmitter supplying taenia from the guinea-pig caecum

Nitric oxide synthase-containing nerve fibres are abundant within taenia of the guinea-pig caecum, but there is little previous evidence supporting a direct role for nitric oxide (NO) in responses to enteric inhibitory nerve stimulation. In this study we have attempted to identify an NO-dependent component of inhibitory transmission in isolated taenia coli. Isometric tension was recorded in the presence of atropine and guanethidine (both 1 microM). Tone was raised with histamine (1 microM), and intrinsic inhibitory neurons stimulated using either a nicotinic agonist (1,1-dimethyl-4-phenylpiperazinium iodide; DMPP) or electrical field stimulation (EFS). DMPP (1-100 microM) produced concentration-dependent biphasic relaxations, comprising an initial peak relaxation followed by a sustained relaxation. Responses to DMPP were antagonized by tetrodotoxin (1 microM) or apamin (0.3 microM) and abolished by hexamethonium (300 microM). L-nitro-arginine (L-NOARG; 100 microM) and oxyhaemoglobin (2%) both significantly reduced sustained relaxations produced by DMPP. EFS (5 Hz, 30 s) also produced biphasic relaxations. Both L-NOARG and an inhibitor of soluble guanylate cyclase (ODQ, 1-10 microM) reduced the sustained component of EFS responses. Two NO donors, sodium nitroprusside (SNP) and diethylenetriamine-nitric oxide adduct (DENO), produced concentration-dependent relaxations. Responses to SNP and DENO were antagonized by ODQ (1 microM) and by apamin (0.3 mM). These results suggest that NO contributes directly to a component of inhibitory transmission in guinea-pig taenia coli. The actions of NO appear to be mediated via cyclic GMP synthesis, and may involve activation of small conductance calcium activated K+ channels. A role for NO is most evident during sustained relaxations evoked by longer stimulus trains or chemical stimulation of intrinsic neurons.

Effects of a novel guanylate cyclase inhibitor on nitric oxide-dependent inhibitory neurotransmission in canine proximal colon

1. Previous studies suggested that nitric oxide (NO) may cause hyperpolarization and relaxation of canine colonic smooth muscle by both cGMP-dependent and cGMP-independent mechanisms. This hypothesis was tested using 1H-[1,2,4]oxadiazolo[4,3-a]quinoxaline-1-one (ODQ), a novel inhibitor of NO-stimulated guanylate cyclase. 2. In the presence of histamine (30 microM), atropine and indomethacin (both at 1 microM), electrical field stimulation of intrinsic neurons (EFS; 5 Hz) produced inhibition of phasic contractile activity that is due to NO synthesis. ODQ caused a concentration-dependent block of this response (10 nM to 10 microM). 3. Inhibitory junction potentials (IJPs) due to NO synthesis were recorded from muscle cells located near the myenteric border of the circular muscle layer, using intracellular microelectrodes. IJPs were abolished by ODQ (1-10 microM). 4. EFS (10-20 Hz) produced frequency-dependent inhibition of electrical slow waves recorded from cells located near the submucosal surface of the circular muscle layer. This inhibition is due to NO synthesis, and it was abolished by ODQ (1-10 microM). 5. Hyperpolarization and relaxation produced by an NO donor, sodium nitroprusside, were abolished by ODQ pretreatment (1-10 microM). In contrast, inhibitory responses to 8-Br-cGMP (1 mM) were unaffected by ODQ. 6. ODQ alone (1-10 microM) had no significant effect on spontaneous electrical or phasic contractile activity. In tissues pre-treated with L-NAME (300 microM), ODQ decreased the amplitude of spontaneous or histamine-stimulated phasic contractile activity. 7. These results suggest that electrical and mechanical effects of endogenously released and exogenously applied NO in canine colon are largely due to cGMP synthesis by ODQ-sensitive soluble guanylate cyclase. No evidence to support a direct (cGMP-independent) mechanism of NO action was found. ODQ also appears to cause a non-specific inhibition of muscle contractile activity; however, this effect does not contribute to block of NO-dependent effects.

Modification of acute focal ischemia in rabbits by poloxamer 188

We studied the effect of a synthetic copolymer surfactant, poloxamer 188, on cerebral blood flow in a rabbit model of focal cerebral ischemia. Following retro-orbital craniectomy, the parietal branch of the middle cerebral artery was occluded with bipolar current. Cerebral blood flow was measured by the hydrogen clearance technique using platinum-iridium electrodes placed within the parietal cortex. Ten rabbits were infused with 50 mg/kg poloxamer 188 in saline beginning 30 minutes after occlusion; 12 control rabbits received an equal volume of saline. Poloxamer 188 increased blood flow significantly in areas of severe or moderate ischemia but had little effect in areas with mild or no ischemia. The improvement in blood flow could not be accounted for by hemodilution, and the copolymer did not affect blood viscosity at any shear rate from 1 to 100 sec-1. We hypothesize that poloxamer 188 increases circulation in ischemic tissue by inhibiting adhesive interactions among proteins (fibrin and fibrinogen) and cells in the microcirculation.

CT-assisted stereotactic brain biopsy: value of intraoperative frozen section diagnosis

In 100 recent CT-guided brain biopsies, the value of intraoperative histologic examination using frozen section technique was evaluated. In 87 of these cases, the biopsy was performed stereotactically. In the remaining 13 cases, a CT-guided free hand technique was used. Of the 100 biopsies performed, adequate tissue for histopathologic diagnosis was obtained in 97, and in three the biopsy was nondiagnostic. In 61 procedures the initial biopsy specimen was adequate for diagnosis. Two specimens were required in 25 and in the remaining cases it was necessary to obtain three to four biopsy specimens before a definitive diagnosis could be made. Ultimately, the histologic diagnosis was made on frozen section examination in 93 of the cases. The lesions identified were neoplastic disease in 83 cases, vascular disease in seven, infectious disease in five, demyelinating disease in one, and radiation necrosis in one. Comparison between the frozen section diagnosis and the final diagnosis based on the permanent sections revealed that they matched in 89 cases (92%). Of the 83 cases of neoplasms the exact grade of malignancy was determined by frozen section to make a final diagnosis revealed that even if the specimen volume was less than 2 mm3, the biopsy was generally successful. The disadvantages of the small sample size obtained through needle biopsy are best overcome by careful targeting and assessment of sample quality by intraoperative frozen section examinations, which will give the definitive diagnosis in most of the cases without paraffin-embedded sections.

Pathophysiology of cerebrospinal fluid in head injury: Part 2. Biochemical markers for central nervous system trauma

Many substances are released into the cerebrospinal fluid after head injury. The study of these substances and their relationship to the severity and outcome of head trauma has lead to the search for biochemical markers to aid in the quantification of the severity of the lesion and serve as a prognostic guide. The authors review the potential usefulness of biochemical markers, qualities of an ideal marker, and several potential enzymes that may be utilized as markers in central nervous system trauma.

Pathophysiology of cerebrospinal fluid in head injury: Part 1. Pathological changes in cerebrospinal fluid solute composition after traumatic injury

After head injury, many complex neurochemical events occur locally, at the site of initial injury, and globally, as a result of secondary phenomena. Neurochemical alterations in the cerebrospinal fluid after injury can be utilized to reflect these events. The authors review the role of the cerebrospinal fluid in the treatment of head injury as it relates to the diagnosis, prognosis, and further elucidation of the pathophysiological manifestations of head injury at the cellular and biochemical level.