Biology subjects

Wahedi, A.

Publications and source records attributed to Wahedi, A..

5 recordsLinked to original sources

bioRxiv2022

Transcriptomic analyses reveal neuronal specificity of Leigh syndrome associated genes

Leigh syndrome (subacute necrotising encephalomyelopathy) is a rare inherited, complex, and typically early onset mitochondrial disorder with clinical and genetic heterogeneity. It owes its heterogeneous nature to the complex nature of mitochondrial genetics and the significant interactions that occur between the mitochondrial and nuclear genomes. Stepwise developmental regression is a classical feature of patients with Leigh syndrome, but other neurological features include ataxia, tremor, seizures, and occasionally psychiatric manifestations. To date the involvement of more than 100 genes has been identified in patients with Leigh syndrome. Despite this, the pathophysiology of Leigh syndrome remains unknown, although it is thought to be due to primary mitochondrial dysfunction. Here, we sought to determine the cellular specificity of all Leigh syndrome associated genes within the brain and investigate a potential common genetic mechanism between Leigh syndrome and other disorders with overlapping clinical features. We utilized co-expression network analyses constructed using existing UK Brain Expression Consortium (UKBEC) data from 10 brain regions to identify regions of the brain where our genes of interest were enriched. Next, expression weighted cell type enrichment (EWCE) was employed to determine the cellular specificity of Leigh syndrome associated genes. Association with pre-or post-synaptic structures was identified using synaptic gene ontology (SynGO) analysis. Finally, heritability analysis was performed on the co-expression network modules demonstrating enrichment of Leigh syndrome associated genes to investigate potential genetic relationships with Parkinson disease, epilepsy, and schizophrenia. Co-expression network analyses reveal that genes encoding oxidative phosphorylation subunits and assembly factors exhibit the highest levels of expression in brain regions most affected on MRI and neuropathology in Leigh syndrome. Further, over two thirds of the genes were found to be enriched within the substantia nigra and 19 genes appeared to cluster, with selective enrichment in the putamen, substantia nigra, medulla and thalamus. EWCE analyses of single cell RNA-Seq data from mouse brain revealed significant enrichment of Leigh syndrome associated genes in hippocampal and somatosensory pyramidal neurones and interneurons of the brain. SynGO analysis demonstrated that expression of these genes is preferentially associated with pre-synaptic structures. Heritability studies suggested that some modules in which Leigh syndrome associated genes were enriched were also enriched for Parkinson disease and epilepsy. In conclusion, our findings suggest a primary mitochondrial dysfunction as the underlying basis of Leigh syndrome with causative genes primarily expressed in neuronal cells, explaining the relative sparing of glial cells observed in neuropathological studies.

genetics↗

bioRxiv2022

Functional insight and cell-specific expression of the adipokinetic hormone/corazonin-related peptide in the human disease vector mosquito, Aedes aegypti

The adipokinetic hormone/corazonin-related peptide (ACP) is an insect neuropeptide structurally intermediate between corazonin (CRZ) and adipokinetic hormone (AKH). Unlike the AKH and CRZ signaling systems that are widely known for their roles in the mobilization of energy substrates and stress responses, respectively, the main role of ACP and its receptor (ACPR) remains unclear in most arthropods. The current study aimed to localize the distribution of ACP in the nervous system and provide insight into its physiological roles in the disease vector mosquito, Aedes aegypti. Immunohistochemical analysis and fluorescence in situ hybridization localized the ACP peptide and transcript within a number of cells in the central nervous system, including two pairs of laterally positioned neurons in the protocerebrum of the brain and a few ventrally localized neurons within the pro- and mesothoracic regions of the fused thoracic ganglia. Further, extensive ACP-immunoreactive axonal projections with prominent blebs and varicosities were observed traversing the abdominal ganglia. Given the prominent enrichment of ACPR expression within the abdominal ganglia of adult A. aegypti mosquitoes as determined previously, the current results indicate that ACP may function as a neurotransmitter and/or neuromodulator facilitating communication between the brain and posterior regions of the nervous system. In an effort to elucidate a functional role for ACP signaling, biochemical measurement of energy nutrients in female mosquitoes revealed a reduction in abdominal glycogen stores in response to ACP that matched the actions of AKH, but interestingly, a corresponding hypertrehalosaemic effect was only found in response to AKH since ACP did not influence circulating carbohydrate levels. Comparatively, both ACP and AKH led to a significant increase in haemolymph carbohydrate levels in male mosquitoes while both peptides had no influence on their glycogen stores. Neither ACP nor AKH influenced circulating or stored lipid levels in both male and female mosquitoes. Collectively, these results reveal ACP signaling in mosquitoes may have complex sex-specific actions, and future research should aim to expand knowledge on the role of this understudied neuropeptide.

zoology↗

bioRxiv2020

Characterization of mitochondrial health from human peripheral blood mononuclear cells to cerebral organoids derived from induced pluripotent stem cells

Mitochondrial health plays a crucial role in human brain development and diseases. However, the evaluation of mitochondrial health in the brain is not incorporated into clinical practice due to ethical and logistical concerns. As a result, the development of targeted mitochondrial therapeutics remains a significant challenge due to the lack of appropriate patient-derived brain tissues. To address these unmet needs, we developed cerebral organoids (COs) from induced pluripotent stem cells (iPSCs) derived from human peripheral blood mononuclear cells (PBMCs) and monitored mitochondrial health from the primary, reprogrammed and differentiated stages. Our results show preserved mitochondrial genetics, function and treatment responses across PBMCs to iPSCs to COs, and measurable neuronal activity in the COs. We expect our approach will serve as a model for more widespread evaluation of mitochondrial health relevant to a wide range of human diseases using readily accessible patient peripheral (PBMCs) and stem-cell derived brain tissue samples.

neuroscience↗

bioRxiv2019

An anti-diuretic hormone receptor in the human disease vector, Aedes aegypti: identification, expression analysis and functional deorphanization

Insect CAPA neuropeptides, which are homologs of mammalian neuromedin U, have been described in various insect species and are known to influence ion and water balance by regulating the activity of the Malpighian renal tubules (MTs). A number of diuretic hormones have been shown to increase primary fluid and ion secretion by the insect MTs and, in the adult female mosquito, a calcitonin-related peptide (DH31) also known as mosquito natriuretic peptide, increases sodium secretion at the expense of potassium to remove the excess salt load acquired upon blood-feeding. An endogenous mosquito anti-diuretic hormone was recently described, having inhibitory activity against select diuretic factors and being particularly potent against DH31-stimulated diuresis. In the present study, we have functionally deorphanized, both in vitro and in vivo, a mosquito anti-diuretic hormone receptor (AedaeADHr). Expression analysis by quantitative PCR indicates the receptor is highly enriched in the MTs, and fluorescent in situ hybridization confirms expression within principal cells. Characterization using a heterologous system demonstrated the receptor was highly sensitive to mosquito CAPA peptides. In adult females, AedaeADHr transcript knockdown using RNAi led to the abolishment of CAPA-peptide induced anti-diuretic control of DH31-stimulated MTs. The neuropeptidergic ligand is produced within a pair of neurosecretory cells in each of the six abdominal ganglia, whose axonal projections innervate the abdominal neurohaemal organs (known as the perivisceral organs), where these neurohormones are released into the open circulatory system of the insect. Furthermore, pharmacological inhibition of PKG/NOS signalling abolished the anti-diuretic activity of AedaeCAPA-1, which collectively confirms the role of cGMP/PKG/NOS in this anti-diuretic signalling pathway.\n\nSignificanceInsects are by far the most successful and abundant group of organisms on earth. As a result of their small size, insects have a relatively large surface area to volume ratio, raising the potential for rapid gain or loss of water, ions and other molecules including toxins - a phenomenon that applies to insects living in both aquatic and terrestrial environments. In common with many other organisms, hormones are key regulators of the excretory system in insects, and numerous factors control the clearance of excess water and ions (i.e. diuretics) or retention of these elements (i.e. anti-diuretics). Here we characterized an endogenous anti-diuretic hormone receptor in the human disease vector, Aedes aegypti, demonstrating its expression is highly enriched in the Malpighian renal tubules and is necessary for eliciting anti-diuretic control of this key component of the mosquito excretory system.

physiology↗

bioRxiv2019

Insight into mosquito GnRH-related neuropeptide receptor specificity revealed through analysis of naturally occurring and synthetic analogs of this neuropeptide family

Adipokinetic hormone (AKH), corzazonin (CRZ) and the AKH/CRZ-related peptide (ACP) are peptides considered homologous to the vertebrate gonadotropin-releasing hormone (GnRH). All three Aedes aegypti GnRH-related neuropeptide receptors have been characterized and functionally deorphanized, which individually exhibit high specificity for their native ligands, which prompted us to investigate the contribution of ligand structures in conferring receptor specificity. In the current study, we designed a series of analogs based on the native ACP sequence in A. aegypti and screened them against the ACP receptor using a heterologous system to identify critical residues required for receptor activation. Specifically, analogs lacking the carboxy-terminal amidation, replacing aromatic residues, as well as truncated analogs were either completely inactive or had very low activities even at high concentration. The next most critical residues were the polar threonine in position 3 and the blocked amino-terminal pyroglutamate, with activity of the latter partially recovered using an alternatively blocked analog. ACP analogs with alanine substitutions at position 2 (valine), 5 (serine), 6 (arginine) and 7 (aspartic acid) positions were less detrimental as were replacements of charged residues. Interestingly, replacing asparagine with an alanine at position 9, creating a C-terminal WAA-amide, resulted in a 5-fold more active analog which may be useful as a lead superagonist compound. Similarly, we utilized this high-throughput approach against an A. aegypti AKH receptor (AKHR-IA) testing a number of mostly naturally-occurring AKH analogs from other insects to determine how substitutions of specific amino acids in the AKH ligand influences receptor activation. AKH analogs having single substitutions compared to the endogenous A. aegypti AKH revealed position 7 (serine) was well tolerated whereas changes to position 6 (proline) had pronounced effects, with receptor activity compromised nearly ten-fold. Substitution of position 3 (threonine) or analogs with combinations of substitutions were quite detrimental with a significant decrease in AKHR-IA activation. Interestingly, analogs with an asparagine residue at position seven displayed improved receptor activation compared to the native mosquito AKH. Collectively, these results advance our understanding of how two GnRH-related systems in A. aegypti sharing the most recent evolutionary origin sustain independence of function and signalling despite their relatively high degree of ligand and receptor homology.

physiology↗