Biology subjects

Sheikh, S.

Publications and source records attributed to Sheikh, S..

8 recordsLinked to original sources

bioRxiv2025

The core MICOS complex subunit Mic60 has been substituted by two cryptic mitofilin-containing proteins in Euglenozoa

Cristae enclose respiratory chain complexes, making them the bioenergetic subcompartments of mitochondria. The MICOS complex is among the inducers of membrane curvature needed for crista formation. Resembling the respiratory chain complexes, MICOS is organized around a core protein, the mitofilin-domain bearing Mic60, that was inherited from the alphaproteobacterial progenitor of mitochondria. Extant alphaproteobacteria express Mic60 to form their own bioenergetic subcompartments, demonstrating the permeance of Mic60s form and function during prokaryotic and eukaryotic evolution. Yet, unlike virtually all aerobic eukaryotes, Mic60 is not encoded within the genomes of the multifarious protists that comprise the phylum Euglenozoa, including trypanosomes. Here, we show that Mic60 has been replaced in euglenozoans by two cryptic mitofilin domain-containing MICOS subunits, Mic34 and Mic40. Contrasting alphaproteobacterial and mitochondrial Mic60, these are not integral membrane proteins. Mic34 and Mic40 are as diverged from each other as both are to canonical Mic60. Reverse genetics revealed they are intertwined with the oxidative protein folding pathway required for mitochondrial-and crista-biogenesis, veiling a potential membrane remodeling role. Nevertheless, Mic34 binds phospholipid bilayers in vitro. Mic34 and Mic40 heterologous expression remodels gammaproteobacterial cytoplasmic membranes, like Mic60. Unexpectedly, Mic34 overexpression elaborates the simplified tubular mitochondrion of a Trypanosoma brucei life cycle stage with repressed oxidative phosphorylation. Furthermore, this activity was ablated by mutations to Mic34s mitofilin domain that correspond to essential motifs found in yeast Mic60s mitofilin domain. Thus, the mitofilin protein family is more diverse than originally supposed, with two of its structurally most divergent members altering the core of euglenozoan MICOS.

molecular biology↗

bioRxiv2023

Fertilizer and cultivar affect the barley rhizobiome, while domestication age only affects growth at low nutrient levels

Modern plant breeding has provided barley cultivars that produce high yields when supplied with ample amounts of mineral fertilizer. This narrow selection criterion may have reduced key traits facilitating vital microbiome-plant interactions. Here, we investigated the performance of three old and four modern barley cultivars grown at different fertilizer regimes and assessed the root microbiome composition using 16s rRNA amplicon sequencing. The objectives were to investigate: i) nutrient availability effects on nutrient uptake and biomass production and, ii) how domestication age, cultivar, and fertilizer treatment affect the root microbiome. Without fertilizer, old cultivars outperformed modern ones in terms of biomass and had higher leaf concentration of nitrogen, potassium, sulphur, iron, zinc, and copper. This suggests that older barley cultivars retained the ability of their wild ancestor to collaborate with the soil microbiome resulting in improved nutrient acquisition in low-input systems. Interestingly, domestication age did not significantly affect the diversity of the rhizo-microbiome, which was instead dependent on individual cultivar and fertilizer treatment. HighlightOlder barley cultivars outperform the modern ones in terms of biomass at low nutrient availability. However, the rhizo-microbial diversity depended on the individual cultivar and fertilizer regime.

plant biology↗

bioRxiv2023

Hypoxia-sensing by the Histone Demethylase UTX (KDM6A) Controls Colitogenic CD4+ T cell Fate and Mucosal Inflammation

Hypoxia is a feature of inflammatory conditions [e.g., inflammatory bowel disease (IBD)] and can exacerbate tissue damage in these diseases. To counteract hypoxias deleterious effects, adaptive responses have evolved which protect against hypoxia-associated tissue injury. To date, much attention has focused on hypoxia-activated HIF (hypoxia-inducible factor) transcription factors in these responses. However, recent work has identified epigenetic regulators that are also oxygen-sensitive, but their role in adaptation to hypoxic inflammation is currently unclear. Here, we show that the oxygen-sensing epigenetic regulator UTX is a critical modulator of colitis severity. Unlike HIF transcription factors that act on gut epithelial cells, UTX functions in colitis through its effects on immune cells. Hypoxia results in decreased CD4+ T cell IFN-{gamma} production and increased CD4+ regulatory T cells, and these findings are recapitulated by T cell-specific UTX deficiency. Hypoxia impairs the histone demethylase activity of UTX, and loss of UTX function leads to accumulation of repressive H3K27me3 epigenetic marks at IL12/STAT4 pathway genes (Il12rb2, Tbx21, and Ifng). In a colitis mouse model, T cell-specific UTX deletion ameliorates colonic inflammation, protects against weight loss, and increases survival. Together these findings implicate UTXs oxygen-sensitive histone demethylase activity in mediating protective, hypoxia-induced pathways in colitis.

immunology↗

bioRxiv2023

CoVar: A generalizable machine learning approach to identify the coordinated regulators driving variational gene expression

Network inference is used to model transcriptional, signaling, and metabolic interactions among genes, proteins, and metabolites that identify biological pathways influencing disease pathogenesis. Advances in machine learning (ML)-based inference models exhibit the predictive capabilities of capturing latent patterns in genomic data. Such models are emerging as an alternative to the statistical models identifying causative factors driving complex diseases. We present CoVar, an inference framework that builds upon the properties of existing inference models, to find the central genes driving perturbed gene expression across biological states. We leverage ML-based network inference to find networks that capture the strength of regulatory interactions. Our model first pinpoints a subset of genes, termed variational, whose expression variabilities typify the differences in network connectivity between the control and perturbed data. Variational genes, by being differentially expressed themselves or possessing differentially expressed neighbor genes, capture gene expression variability. CoVar then creates subnetworks comprising variational genes and their strongly connected neighbor genes and identifies core genes central to these subnetworks that influence the bulk of the variational activity. Through the analysis of yeast expression data perturbed by the deletion of the mitochondrial genome, we show that CoVar identifies key genes not found through independent differential expression analysis.

genetics↗

bioRxiv2022

Aberrant miR-29 is a predictive feature of severe phenotypes in pediatric Crohn's disease

Crohns disease (CD) is a chronic inflammatory gut disorder. Molecular mechanisms underlying the clinical heterogeneity of CD remain poorly understood. MicroRNAs (miRNAs) are important regulators of gut physiology and several have been implicated in the pathogenesis of adult CD. However, there is a dearth of large-scale miRNA studies for pediatric CD. We hypothesized that specific miRNAs uniquely mark pediatric CD. We performed small RNA-sequencing of patient-matched non-inflamed colon and ileum biopsies from treatment-naive pediatric patients with CD (n=169) and a control cohort (n=108). Comprehensive miRNA analysis revealed 58 miRNAs altered in pediatric CD. Notably, multinomial logistic regression analysis revealed that index levels of ileal miR-29 are strongly predictive of severe inflammation and stricturing. Transcriptomic analyses of transgenic mice overexpressing miR-29 show a significant reduction of the tight junction protein gene Pmp22 and classic Paneth cell markers. The dramatic loss of Paneth cells was confirmed by histologic assays. Moreover, we also found that pediatric CD patients with elevated miR-29 exhibit significantly lower Paneth cell counts, increased inflammation scores, and reduced levels of PMP22. These findings strongly indicate that miR-29 up-regulation is a distinguishing feature of pediatric CD, highly predictive of severe phenotypes, and associated with inflammation and Paneth cell loss.

genomics↗

bioRxiv2022

The development of intracytoplasmic membranes in alphaproteobacteria involves the conserved mitochondrial crista-developing Mic60 protein

Mitochondrial cristae expand the surface area of respiratory membranes and ultimately allow for the evolutionary scaling of respiration with cell volume across eukaryotes. The discovery of Mic60 homologs among alphaproteobacteria, the closest extant relatives of mitochondria, suggested that cristae might have evolved from bacterial intracytoplasmic membranes (ICMs). Here, we investigated the predicted structure and function of alphaproteobacterial Mic60, and a protein encoded by an adjacent gene Orf52, in two distantly related purple alphaproteobacteria, Rhodobacter sphaeroides and Rhodopseudomonas palustris. In addition, we assessed the potential physical interactors of Mic60 and Orf52 in R. sphaeroides. We show that the three -helices of mitochondrial Mic60s mitofilin domain, as well as its adjacent membrane-binding amphipathic helix, are present in alphaproteobacterial Mic60. The disruption of Mic60 and Orf52 caused photoheterotrophic growth defects, which are most severe under low light conditions, and both their disruption and overexpression led to enlarged ICMs in both studied alphaproteobacteria. We also found that alphaproteobacterial Mic60 physically interacts with BamA, the homolog of Sam50, one of the main physical interactors of eukaryotic Mic60. This interaction, responsible for making contact sites at mitochondrial envelopes, has been conserved in modern alphaproteobacteria despite more than a billion years of evolutionary divergence. Our results suggest a role for Mic60 in photosynthetic ICM development and contact site formation at alphaproteobacterial envelopes. Overall, we provide support for the hypothesis that mitochondrial cristae evolved from alphaproteobacterial ICMs, and therefore have improved our understanding of the nature of the mitochondrial ancestor.

evolutionary biology↗

bioRxiv2022

Delimiting the cryptic diversity and host preferences of Sycophila parasitoid wasps associated with oak galls using phylogenomic data

Cryptic species diversity is a major challenge for the species-rich community of parasitoids attacking oak gall wasps due to a high degree of sexual dimorphism, morphological plasticity, small size, and poorly known biology. As such, we know very little about the number of species present, nor the evolutionary forces responsible for generating this diversity. One hypothesis is that trait diversity in the gall wasps, including the morphology of the galls they induce, has evolved in response to selection imposed by the parasitoid community, with reciprocal selection driving diversification of the parasitoids. Using a rare, continental-scale data set of Sycophila parasitoid wasps reared from 44 species of cynipid galls from 18 species of oak across the US, we combined mitochondrial DNA barcodes, Ultraconserved Elements (UCEs), morphological, and natural history data to delimit putative species. Using these results, we generate the first large-scale assessment of ecological specialization and host association in this species-rich group, with implications for evolutionary ecology and biocontrol. We find most Sycophila target specific subsets of available cynipid host galls with similar morphologies, and generally attack larger galls. Our results suggest that parasitoid wasps such as Sycophila have adaptations allowing them to exploit particular host trait combinations, while hosts with contrasting traits are resistant to attack. These findings support the tritrophic niche concept for the structuring of plant-herbivore-parasitoid communities.

evolutionary biology↗

bioRxiv2020

Increased Colonic Expression of ACE2 Associates with Poor Prognosis in Crohn's disease

Background and AimsThe host receptor for SARS-CoV-2, angiotensin-converting enzyme 2 (ACE2), is highly expressed in small intestine. Our aim was to study colonic ACE2 expression in Crohns disease (CD) and non-inflammatory bowel disease (non-IBD) controls. We hypothesized that the colonic expression levels of ACE2 impacts CD course. MethodsWe examined the expression of colon ACE2 using RNA-seq and quantitative (q) RT-PCR from 69 adult CD and 14 NIBD control patients. In a subset of this cohort we validated ACE2 protein expression and localization in formalin-fixed, paraffin-embedded matched colon and ileal tissues using immunohistochemistry. The impact of increased ACE2 expression in CD for the risk of surgery was evaluated by a multivariate regression analysis and a Kaplan-Meier estimator. To provide critical support for the generality of our findings, we analyzed previously published RNA-seq data from two large independent cohorts of CD patients. ResultsColonic ACE2 expression was significantly higher in a subset of adult CD patients (ACE2-high CD). IHC in a sampling of ACE2-high CD patients confirmed high ACE2 protein expression in the colon and ileum compared to ACE2-low CD and NIBD patients. Notably, we found that ACE2-high CD patients are significantly more likely to undergo surgery within 5 years of diagnosis, with a Cox regression analysis finding that high ACE2 levels is an independent risk factor (OR 2.18; 95%CI, 1.05-4.55; p=0.037). ConclusionIncreased intestinal expression of ACE2 is associated with deteriorated clinical outcomes in CD patients. These data point to the need for molecular stratification that may impact CD disease-related outcomes.

genomics↗