The phosphatidylinositol 3' kinase (PI3'K) pathway, which regulates cell survival, is antagonized by the PTEN tumor suppressor. The regulation of PTEN is unclear. A genetic screen of Drosophila gain-of-function mutants identified DJ-1 as a suppressor of PTEN function. In mammalian cells, DJ-1 underexpression results in decreased phosphorylation of PKB/Akt, while DJ-1 overexpression leads to hyperphosphorylation of PKB/Akt and increased cell survival. In primary breast cancer samples, DJ-1 expression correlates negatively with PTEN immunoreactivity and positively with PKB/Akt hyperphosphorylation. In 19/23 primary non-small cell lung carcinoma samples, DJ-1 expression was increased compared to paired nonneoplastic lung tissue, and correlated positively with relapse incidence. DJ-1 is thus a key negative regulator of PTEN that may be a useful prognostic marker for cancer.

Mutations of the DJ-1 (PARK7) gene are linked to familial Parkinson's disease. We used gene targeting to generate DJ-1-deficient mice that were viable, fertile, and showed no gross anatomical or neuronal abnormalities. Dopaminergic neuron numbers in the substantia nigra and fiber densities and dopamine levels in the striatum were normal. However, DJ-1؊͞؊ mice showed hypolocomotion when subjected to amphetamine challenge and increased striatal denervation and dopaminergic neuron loss induced by 1-methyl-4-phenyl-1,2,3,6-tetrahydropyrindine. DJ-1؊͞؊ embryonic cortical neurons showed increased sensitivity to oxidative, but not nonoxidative, insults. Restoration of DJ-1 expression to DJ-1؊͞؊ mice or cells via adenoviral vector delivery mitigated all phenotypes. WT mice that received adenoviral delivery of DJ-1 resisted 1-methyl-4-phenyl-1,2,3,6-tetrahydropyrindine-induced striatal damage, and neurons overexpressing DJ-1 were protected from oxidative stress in vitro. Thus, DJ-1 protects against neuronal oxidative stress, and loss of DJ-1 may lead to Parkinson's disease by conferring hypersensitivity to dopaminergic insults. P arkinson's disease (PD) is a neurodegenerative disorder characterized by tremor, rigidity, akinesia, and postural instability (1). The cause of PD remains unknown, but epidemiological and genetic studies have suggested that the observed loss of dopaminergic neurons in PD is due to defects in common intracellular signaling pathways (2). Genes linked to familial PD include ␣-synuclein (3), Parkin (4), UCH-L1 (5), PINK1 (6), and dardarin (7). Proteins encoded by these genes are thought to be involved in protein aggregation and proteasome function, processes which, when disrupted in model systems, can also result in noninherited forms of PD (8). Recently, loss-of-function mutations in the DJ-1 locus were found in families with autosomal recessive early-onset PD (9). Additional studies have confirmed other DJ-1 mutations in various PD cohorts (10). DJ-1 was initially cloned as a putative oncogene (11) and as part of an RNA-binding complex (12). DJ-1 is highly expressed by normal astrocytes (13) and has been implicated in fertilization (14) and tumorigenesis (15,16). Studies of the crystal structure of DJ-1 (17) suggest that a particular DJ-1 mutation (L166P) reduces DJ-1 protein stability (18)(19)(20), resulting in degradation through the ubiquitin-proteasome system (21, 22). However, the physiological function of DJ-1 remains largely unknown.Motor impairments in PD patients result from inhibition of the nigrostriatal motor pathway. This inhibition is due to the loss of dopaminergic neurons in the substantia nigra pars compacta (SNc) (8). The cause of the dopaminergic neuron loss remains unknown, but oxidative stress leading to apoptotic neuronal death has been implicated (23). Various neurotoxic paradigms have been studied in an effort to reproduce oxidative stress leading to neuronal loss in the SNc. Of these, administration of the well characterized meperidine analogue 1-methyl-4-phenyl-1,2,3,6-te...

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The standard of care for first-tier clinical investigation of the aetiology of congenital malformations and neurodevelopmental disorders is chromosome microarray analysis (CMA) for copy-number variations (CNVs), often followed by gene(s)-specific sequencing searching for smaller insertion–deletions (indels) and single-nucleotide variant (SNV) mutations. Whole-genome sequencing (WGS) has the potential to capture all classes of genetic variation in one experiment; however, the diagnostic yield for mutation detection of WGS compared to CMA, and other tests, needs to be established. In a prospective study we utilised WGS and comprehensive medical annotation to assess 100 patients referred to a paediatric genetics service and compared the diagnostic yield versus standard genetic testing. WGS identified genetic variants meeting clinical diagnostic criteria in 34% of cases, representing a fourfold increase in diagnostic rate over CMA (8%; P value=1.42E−05) alone and more than twofold increase in CMA plus targeted gene sequencing (13%; P value=0.0009). WGS identified all rare clinically significant CNVs that were detected by CMA. In 26 patients, WGS revealed indel and missense mutations presenting in a dominant (63%) or a recessive (37%) manner. We found four subjects with mutations in at least two genes associated with distinct genetic disorders, including two cases harbouring a pathogenic CNV and SNV. When considering medically actionable secondary findings in addition to primary WGS findings, 38% of patients would benefit from genetic counselling. Clinical implementation of WGS as a primary test will provide a higher diagnostic yield than conventional genetic testing and potentially reduce the time required to reach a genetic diagnosis.

An accurate diagnosis is an integral component of patient care for children with rare genetic disease. Recent advances in sequencing, in particular whole‐exome sequencing (WES), are identifying the genetic basis of disease for 25–40% of patients. The diagnostic rate is probably influenced by when in the diagnostic process WES is used. The Finding Of Rare Disease GEnes (FORGE) Canada project was a nation‐wide effort to identify mutations for childhood‐onset disorders using WES. Most children enrolled in the FORGE project were toward the end of the diagnostic odyssey. The two primary outcomes of FORGE were novel gene discovery and the identification of mutations in genes known to cause disease. In the latter instance, WES identified mutations in known disease genes for 105 of 362 families studied (29%), thereby informing the impact of WES in the setting of the diagnostic odyssey. Our analysis of this dataset showed that these known disease genes were not identified prior to WES enrollment for two key reasons: genetic heterogeneity associated with a clinical diagnosis and atypical presentation of known, clinically recognized diseases. What is becoming increasingly clear is that WES will be paradigm altering for patients and families with rare genetic diseases.

Growing evidence highlights a role for mitochondrial dysfunction and oxidative stress as underlying contributors to Parkinson's disease (PD) pathogenesis. DJ-1 (PARK7) is a recently identified recessive familial PD gene. Its loss leads to increased susceptibility of neurons to oxidative stress and death. However, its mechanism of action is not fully understood. Presently, we report that DJ-1 deficiency in cell lines, cultured neurons, mouse brain and lymphoblast cells derived from DJ-1 patients display aberrant mitochondrial morphology. We also show that these DJ-1-dependent mitochondrial defects contribute to oxidative stress-induced sensitivity to cell death since reversal of this fragmented mitochondrial phenotype abrogates neuronal cell death. Reactive oxygen species (ROS) appear to play a critical role in the observed defects, as ROS scavengers rescue the phenotype and mitochondria isolated from DJ-1 deficient animals produce more ROS compared with control. Importantly, the aberrant mitochondrial phenotype can be rescued by the expression of Pink1 and Parkin, two PD-linked genes involved in regulating mitochondrial dynamics and quality control. Finally, we show that DJ-1 deficiency leads to altered autophagy in murine and human cells. Our findings define a mechanism by which the DJ-1-dependent mitochondrial defects contribute to the increased sensitivity to oxidative stress-induced cell death that has been previously reported.

Multiple differing surgical techniques are currently utilized to perform total knee arthroplasty (TKA). We compared knee arthroplasties performed using either a measured resection or gap balancing technique to determine if either operative technique provides superior coronal plane stability as measured by assessment of the incidence and magnitude of femoral condylar lift-off. We performed 40 TKA using a measured resection technique (20 PCLretaining and 20 PCL-substituting) and 20 PCL-substituting TKA were implanted using gap balancing. All subjects were analyzed fluoroscopically while performing a deep knee bend. The incidence of coronal instability (femoral condylar lift-off) was then determined using a 3-D model fitting technique. The incidence of lift-off greater than 0.75 mm was 80% (maximum, 2.9 mm) and 70% (maximum, 2.5 mm) for the PCL-retaining and substituting TKA groups performed using measured resection versus 35% (maximum, 0.88 mm) for the gap-balanced group. Lift-off greater than 1 mm occurred in 60% and 45% of the PCL-retaining and -substituting TKA using measured resection versus none in the gap-balanced group. Rotation of the femoral component using a gap balancing technique resulted in better coronal stability which we suggest will improve functional performance and reduce polyethylene wear.

Mutations in several genes, including Parkin, PTEN-induced kinase 1 (Pink1) and DJ-1, are associated with rare inherited forms of Parkinson's disease (PD). Despite recent attention on the function of these genes, the interplay between DJ-1, Pink1 and Parkin in PD pathogenesis remains unclear. In particular, whether these genes regulate mitochondrial control pathways in neurons is highly controversial. Here we report that Pink1-dependent Parkin translocation does occur in mouse cortical neurons in response to a variety of mitochondrial damaging agents. This translocation only occurs in the absence of antioxidants in the neuronal culturing medium, implicating a key role of reactive oxygen species (ROS) in this response. Consistent with these observations, ROS blockers also prevent Parkin recruitment in mouse embryonic fibroblasts. Loss of DJ-1, a gene linked to ROS management, results in increased stress-induced Parkin recruitment and increased mitophagy. Expression of wild-type DJ-1, but not a cysteine-106 mutant associated with defective ROS response, rescues this accelerated Parkin recruitment. Interestingly, DJ-1 levels increase at mitochondria following oxidative damage in both fibroblasts and neurons, and this process also depends on Parkin and possibly Pink1. These results not only highlight the presence of a Parkin/Pink1-mediated pathway of mitochondrial quality control (MQC) in neurons, they also delineate a complex reciprocal relationship between DJ-1 and the Pink1/Parkin pathway of MQC.