ORCID Profile
0000-0002-9914-7859
Current Organisation
University of South Australia
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Publisher: Cold Spring Harbor Laboratory
Date: 12-04-2023
DOI: 10.1101/2023.04.11.536495
Abstract: Mutations in the KCNT1 potassium channel cause severe forms of epilepsy which are resistant to current treatments. In vitro studies have shown that KCNT1- epilepsy mutations are gain of function, significantly increasing K + current litudes. To investigate if Drosophila can be used to model human KCNT1 epilepsy, we generated Drosophila melanogaster lines carrying human KCNT1 with the patient mutation G288S, R398Q or R928C. Expression of each mutant channel in GABAergic neurons gave a seizure phenotype which was sensitive to drugs currently used to treat patients with KCNT1 -epilepsy. Cannabidiol showed the greatest reduction of the seizure phenotype while some drugs increased the seizure phenotype. Our study shows that Drosophila can be used to model human KCNT1 -epilepsy and potentially used as a tool to assess new treatments for KCNT1 epilepsy.
Publisher: Springer Science and Business Media LLC
Date: 14-09-2017
DOI: 10.1038/S41598-017-11613-2
Abstract: Tumors frequently fail to pass on all their chromosomes correctly during cell ision, and this chromosomal instability (CIN) causes irregular aneuploidy and oxidative stress in cancer cells. Our objective was to test knockdowns of metabolic enzymes in Drosophila to find interventions that could exploit the differences between normal and CIN cells to block CIN tumor growth without harming the host animal. We found that depleting by RNAi or feeding the host inhibitors against phosphoenolpyruvate carboxykinase (PEPCK) was able to block the growth of CIN tissue in a brat tumor explant model. Increasing NAD+ or oxidising cytoplasmic NADH was able to rescue the growth of PEPCK depleted tumors, suggesting a problem in clearing cytoplasmic NADH. Consistent with this, blocking the glycerol-3-phosphate shuttle blocked tumor growth, as well as lowering ROS levels. This work suggests that proliferating CIN cells are particularly vulnerable to inhibition of PEPCK, or its metabolic network, because of their compromised redox status.
Publisher: MDPI AG
Date: 09-05-2023
Abstract: Aneuploidy, or having a disrupted genome, is an aberration commonly found in tumours but rare in normal tissues. It gives rise to proteotoxic stress as well as a stereotypical oxidative shift, which makes these cells sensitive to internal and environmental stresses. Using Drosophila as a model, we investigated the changes in transcription in response to ongoing changes to ploidy (chromosomal instability, CIN). We noticed changes in genes affecting one-carbon metabolism, specifically those affecting the production and use of s-adenosyl methionine (SAM). The depletion of several of these genes has led to cell death by apoptosis in CIN cells but not in normal proliferating cells. We found that CIN cells are particularly sensitive to SAM metabolism at least partly because of its role in generating polyamines. Feeding animals spermine was seen to rescue the cell death caused by the loss of SAM synthase in CIN tissues. The loss of polyamines led to decreased rates of autophagy and sensitivity to reactive oxygen species (ROS), which we have shown to contribute significantly to cell death in CIN cells. These findings suggest that a well-tolerated metabolic intervention such as polyamine inhibition has the potential to target CIN tumours via a relatively well-characterised mechanism.
Publisher: Springer Science and Business Media LLC
Date: 30-07-2012
Publisher: MDPI AG
Date: 12-2022
Abstract: KCNT1 (K+ channel subfamily T member 1) is a sodium-activated potassium channel highly expressed in the nervous system which regulates neuronal excitability by contributing to the resting membrane potential and hyperpolarisation following a train of action potentials. Gain of function mutations in the KCNT1 gene are the cause of neurological disorders associated with different forms of epilepsy. To gain insights into the underlying pathobiology we investigated the functional effects of 9 recently published KCNT1 mutations, 4 previously studied KCNT1 mutations, and one previously unpublished KCNT1 variant of unknown significance. We analysed the properties of KCNT1 potassium currents and attempted to find a correlation between the changes in KCNT1 characteristics due to the mutations and severity of the neurological disorder they cause. KCNT1 mutations identified in patients with epilepsy were introduced into the full length human KCNT1 cDNA using quick-change site-directed mutagenesis protocol. Electrophysiological properties of different KCNT1 constructs were investigated using a heterologous expression system (HEK293T cells) and patch cl ing. All mutations studied, except T314A, increased the litude of KCNT1 currents, and some mutations shifted the voltage dependence of KCNT1 open probability, increasing the proportion of channels open at the resting membrane potential. The T314A mutation did not affect KCNT1 current litude but abolished its voltage dependence. We observed a positive correlation between the severity of the neurological disorder and the KCNT1 channel open probability at resting membrane potential. This suggests that gain of function KCNT1 mutations cause epilepsy by increasing resting potassium conductance and suppressing the activity of inhibitory neurons. A reduction in action potential firing in inhibitory neurons due to excessively high resting potassium conductance leads to disinhibition of neural circuits, hyperexcitability and seizures.
Publisher: Elsevier BV
Date: 08-2012
DOI: 10.1016/J.GENE.2012.05.038
Abstract: Bovine spongiform encephalopathy (BSE) is a neurodegenerative prion protein misfolding disorder of cattle. BSE is of two types, classical BSE and atypical BSE which in turn is of two types, H-type BSE and L-type BSE. Both H-type BSE and L-type BSE are primarily sporadic prion disorders. However, one case of H-type BSE has recently been associated with E211K polymorphism in the prion protein gene (PRNP). Two polymorphisms in the bovine PRNP are also associated with susceptibility to classical BSE: a 23 bp insertion/deletion (indel) in the PRNP promoter region and a 12 bp indel in the first intron. No information regarding BSE susceptibility in Pakistani cattle is available. The present study aimed at achieving this information. A total of 236 cattle from 7 breeds and 281 buffaloes from 5 breeds were screened for E211K polymorphism and 23 bp and 12 bp indels employing triplex PCR. The E211K polymorphism was not detected in any of the animals studied. The 23 bp insertion allele was underrepresented in studied cattle breeds while the 12 bp insertion allele was overrepresented. Both 23 bp and 12 bp insertion alleles were overrepresented in studied buffalo breeds. Almost 90% of alleles were insertion alleles across all studied buffalo breeds. The average frequency of 23 bp and 12 bp insertion alleles across all studied cattle breeds was found to be 0.1822 and 0.9407, respectively. There were significant differences between Pakistani and worldwide cattle in terms of allele, genotype and haplotype frequencies of 23 bp and 12 bp indels. The higher observed frequency of 12 bp insertion allele suggests that Pakistani cattle are relatively more resistant to classical BSE than European cattle. However, the key risk factor for classical BSE is the dietary exposure of cattle to contaminated feedstuffs.
Publisher: Georg Thieme Verlag KG
Date: 05-2015
Abstract: Chromosomal instability (CIN) is a common feature of tumours that leads to increased genetic ersity in the tumour and poor clinical outcomes. There is considerable interest in understanding how CIN comes about and how its contribution to drug resistance and metastasis might be counteracted. In the last decade a number of CIN model systems have been developed in Drosophila that offer unique benefits both in understanding the development of CIN in a live animal as well as giving the potential to do genome wide screens for therapeutic candidate genes. This review outlines the mechanisms used in several Drosophila CIN model systems and summarizes some significant outcomes and opportunities that they have produced.
Publisher: MDPI AG
Date: 19-12-2022
DOI: 10.3390/BIOM12121902
Abstract: Cancer metabolic reprogramming is essential for maintaining cancer cell survival and rapid replication. A common target of this metabolic reprogramming is one-carbon metabolism which is notable for its function in DNA synthesis, protein and DNA methylation, and antioxidant production. Polyamines are a key output of one-carbon metabolism with widespread effects on gene expression and signaling. As a result of these functions, one-carbon and polyamine metabolism have recently drawn a lot of interest for their part in cancer malignancy. Therapeutic inhibitors that target one-carbon and polyamine metabolism have thus been trialed as anticancer medications. The significance and future possibilities of one-carbon and polyamine metabolism as a target in cancer therapy are discussed in this review.
Publisher: Bentham Science Publishers Ltd.
Date: 05-01-2016
DOI: 10.2174/1389450116666150126111055
Abstract: The production of reactive oxygen species is a normal part of cell physiology, but many internal and external stimuli are able to trigger the production of excess levels of oxidants that are potentially damaging. The threat of oxidative damage is particularly significant to DNA, as damaged bases can interfere with replication to generate lasting mutations. Signalling through the JNK pathway is a key cellular response to oxidative damage. Depending on the intensity and duration of the damage signal, JNK signalling can lead to distinct alternative responses including DNA repair, anti-oxidant production or cell death. These responses are highly relevant to cancer therapy, as tumours are often under oxidative stress that produces elevated JNK levels and therapy often involves inducing DNA damage with the intention of driving cell death. In this review we examine the causes and consequences of JNK activation that relate to oxidative DNA damage, with a focus on the potential therapeutic implications.
Publisher: Wiley
Date: 02-11-2022
DOI: 10.1111/APA.16580
Abstract: Sudden infant death syndrome (SIDS) occurs more often in male than in female infants, suggesting involvement of the X‐chromosome. Histopathological studies have suggested that altered expression of the Neurokinin‐1 receptor may also play a role in the pathogenesis of SIDS. It was hypothesised that genetic variants in three X‐chromosome‐encoded microRNA (miRNA/miR), known to down‐regulate expression of the Neurokinin‐1 receptor, may contribute to SIDS. To identify sequence variants in the miRNAs within a study cohort (27 cases of SIDS and 28 controls) and determine if there was a difference in the frequencies in male and female SIDS infants. Genomic DNA prepared from stored blood spots was lified and sequenced to identify genetic variants in miR500A, miR500B and miR320D2. No novel variants in the miRNAs were identified in our study cohort. We identified one known single‐nucleotide polymorphism (SNP) in miR320D2: rs5907732 G/T, in both cases and controls. No significant difference in the SNP frequency was observed between male and female SIDS cases. This pilot study suggests that sequence variants in three miRNAs do not contribute to the reported higher prevalence of SIDS in male infants and do not contribute to the pathogenesis of SIDS in our cohort.
Publisher: Springer Science and Business Media LLC
Date: 27-10-2015
DOI: 10.1038/ONC.2014.344
Abstract: Chromosomal INstability (CIN), a hallmark of cancer, refers to cells with an increased rate of gain or loss of whole chromosomes or chromosome parts. CIN is linked to the progression of tumors with poor clinical outcomes such as drug resistance. CIN can give tumors the ersity to resist therapy, but it comes at the cost of significant stress to tumor cells. To tolerate this, cancer cells must modify their energy use to provide adaptation against genetic changes as well as to promote their survival and growth. In this study, we have demonstrated that CIN induction causes sensitivity to metabolic stress. We show that mild metabolic disruption that does not affect normal cells, can lead to high levels of oxidative stress and subsequent cell death in CIN cells because they are already managing elevated stress levels. Altered metabolism is a differential characteristic of cancer cells, so our identification of key regulators that can exploit these changes to cause cell death may provide cancer-specific potential drug targets, especially for advanced cancers that exhibit CIN.
No related grants have been discovered for Rashid Hussain.