Biology subjects

Sohail, A.

Publications and source records attributed to Sohail, A..

5 recordsLinked to original sources

bioRxiv2026

Climate change drives contrasting redistribution patterns in endemic and endangered Himalayan Gentiana

O_LIRapid climate warming threatens mountain biodiversity, particularly species with narrow climatic niches and limited dispersal capacity. Mountain ecosystems are especially vulnerable because steep environmental gradients restrict opportunities for species redistribution. The Kashmir Himalaya, a globally important biodiversity hotspot experiencing accelerated warming, has already undergone an increase of approximately 0.8 {degrees}C during the 20th century and is projected to warm by 2.5-2.8 {degrees}C by the 2050s. Despite climatic changes, future persistence of many threatened plants remains poorly understood. C_LIO_LIHere, we evaluate present and future habitat suitability for two Himalayan taxa, Gentiana cachemirica, an endemic species, and Gentiana kurroo, a critically endangered species. Specifically, we quantify how climate change and topographic variability influence species distribution and persistence under multiple emission scenarios. C_LIO_LIWe applied species distribution models (SDMs) to presence data of both species and forecasted habitat suitability under four Shared Socioeconomic Pathways (SSP126, SSP245, SSP370, and SSP585). We hypothesized that G. cachemirica, a narrow-niche, low-dispersal species, is expected to lose habitat due to thermal sensitivity, while G. kurroo may persist or expand under favorable scenarios because of broader tolerance and higher dispersal. We also expected microclimatic refuges to buffer populations, whereas extreme warming would accelerate habitat decline. C_LIO_LIThe predictions of our SDMs under current conditions indicate a highly restricted and fragmented habitat for G. cachemirica, covering 651 km{superscript 2}, but a broader suitable area (2,452 km{superscript 2}) for G. kurroo. In agreement with our hypotheses, our forecasts indicate severe habitat contraction (55-70%) for G. cachemirica across all SSPs, but scenario-dependent responses for G. kurroo, including modest expansion under low-emission scenarios and severe declines under high-emission scenarios. Centroid analyses suggest pronounced climate-driven range shifts, with G. kurroo projected to migrate up to 33 km toward the east-southeast by 2100, while G. cachemirica is projected to display limited dispersal capacity. C_LIO_LISynthesis. Our findings suggest that climatic niche breadth, dispersal limitation, and topographic buffering strongly mediate species responses to warming in mountain ecosystems. Endemic specialists are projected to experience disproportionate habitat fragmentation and range restriction, highlighting the importance of conserving climatic refugia and elevational connectivity under rapid environmental change. C_LI

ecology↗

bioRxiv2024

A novel membrane stress-response that blocks chromosomal replication by targeting the DnaA initiator via the ClpP protease

In Escherichia coli, membrane-stress due to interrupted lipoprotein (Lpp) maturation impairs DNA replication and arrests cell growth. How the two disparate processes of Lpp maturation and DNA replication are connected remains unclear. We demonstrate that upon membrane-stress the Rcs stress-response pathway is activated and the replication initiator DnaA is lost, which explains the replication block. However, the Lon protease, a key regulator of the Rcs pathway, is not required for the DnaA loss. We further ruled out the involvement of (p)ppGpp, one of the major mediators of stress-response in bacteria. However, upon deletion of the ClpP protease gene, DnaA was stable, replication initiated, and there was no cell-growth arrest. In wildtype cells, overexpression of DnaA was lethal even without the membrane-stress apparently from hyper-initiation. The hyper-initiation was restrained in {Delta}crp cells, and overexpression of DnaA was able to overcome the growth-arrest. {Delta}fis cells, which were earlier found resistant to the membrane-stress, showed DnaA stability and normal replication upon induction of the membrane-stress. We conclude that DnaA loss suffices to explain the growth-arrest upon the membrane-stress. The stress-response pathway described here appears novel because of its independence from Lon and (p)ppGpp, which have been implicated in other stress-responses that block DNA replication. SignificanceThe seminal observation that DNA replication-stress can block cell division in E. coli (SOS response), introduced the concept of checkpoint control in the cell cycle. Here, we describe a novel checkpoint control that functions in the opposite direction: membrane-stress causing replication block. We show how two apparently unrelated outcomes of reducing a membrane phospholipid, accumulation of a precursor lipoprotein (pLpp) and block of replication initiation, could be linked. The pLpp accumulation stresses the membrane that causes a response culminating in activating the ClpP protease that blocks replication by targeting the initiator DnaA. DnaA being vital and highly conserved, the detail understanding of the response pathway is likely to open new avenues to treat bacterial infection.

microbiology↗

bioRxiv2024

Evidence for direct control of neurovascular function by circulating platelets in healthy older adults

Platelets play a vital role in preventing haemorrhage through haemostasis, but complications arise when platelets become overly reactive, leading to pathophysiology such as athero-thrombosis. Elevated haemostatic markers are linked to dementia and predict its onset in long-term studies. Despite epidemiological evidence, the mechanism linking haemostasis with early brain pathophysiology remains unclear. Here, we aimed to determine whether a mechanistic association exists between platelet function and neurovascular function in 52 healthy mid- to older-age adults. To do this we combined, for the first time, magnetic resonance imaging (MRI) of neurovascular function, peripheral vascular physiology, and in vitro platelet assaying. We show a direct association between platelet reactivity and neurovascular function that is both independent of vascular reactivity and mechanistically specific: Distinct platelet signalling mechanisms (Adenosine 5-diphosphate, Collagen-Related Peptide, Thrombin Receptor Activator Peptide 6) were directly associated with different physiological components of the haemodynamic response to neural (visual) stimulation (full-width half-maximum, time to peak, area under the curve), an association that was not mediated by peripheral vascular effects. This finding challenges the previous belief that systemic vascular health determines the vascular component of neurovascular function, highlighting a specific link between circulating platelets and the neurovascular unit. Since altered neurovascular function marks the initial stages of neurodegenerative pathophysiology, understanding this novel association becomes now imperative, with the potential to lead to a significant advancement in our comprehension of early dementia pathophysiology. Key points summaryO_LIHaemostasis (platelet function) has been linked to the early stages of dementia, but the precise mechanisms are not well understood. C_LIO_LIThis study asks whether a causal mechanism exists through athero-thrombotic effects on the vasculature which can in turn affect brain health, or through direct platelet effects on brain physiology. C_LIO_LIHere we show that elevated platelet reactivity is associated with blunted (delayed, shorter, and smaller) blood flow responses to neural activation in healthy middle-aged and older adults. C_LIO_LIHowever, the association between platelet reactivity and neurovascular function was not mediated by systemic vascular reactivity. C_LIO_LIThis finding challenges the previous belief that systemic vascular health determines the vascular component of neurovascular function, highlighting a specific link between circulating platelets and the neurovascular unit in early dementia pathophysiology. C_LI

neuroscience↗

bioRxiv2021

Itaconate and derivatives reduce interferon responses and inflammation in influenza A infection

Itaconate has recently emerged as a metabolite with immunomodulatory properties. We evaluated effects of endogenous itaconate and exogenous itaconate, dimethyl-, and 4-octyl-itaconate on host responses to influenza A virus infection. Infection induced ACOD1 (the enzyme catalyzing itaconate synthesis) mRNA in monocytes and macrophages, which correlated with viral replication and was abrogated by itaconate treatment. Pulmonary inflammation and weight loss were greater in Acod1-/- than wild-type mice, and ectopic synthesis of itaconate in human epithelial cells reduced infection-induced inflammation. The compounds induced different recruitment programs in infected human macrophages, and transcriptome profiling revealed that they reversed infection-triggered interferon responses and modulated inflammation in cell lines, PBMC, and lung tissue. Single-cell RNA sequencing of PBMC revealed that infection induced ACOD1 exclusively in monocytes, whereas treatment silenced IFN-responses in monocytes, lymphocytes, and NK cells. Viral replication did not increase under treatment despite the dramatically repressed IFN responses, but 4-octyl itaconate inhibited viral transcription in PBMC. The results reveal dramatic reprogramming of host responses by itaconate and derivatives and their potential as adjunct treatments for hyperinflammation in viral infection.

immunology↗

bioRxiv2020

Prediction Of Eye, Hair And Skin Color In Admixed Populations Of Latin America

We report an evaluation of prediction accuracy for eye, hair and skin pigmentation based on genomic and phenotypic data for over 6,500 admixed Latin Americans (the CANDELA dataset). We examined the impact on prediction accuracy of three main factors: (i) The methods of prediction, including classical statistical methods and machine learning approaches, (ii) The inclusion of non-genetic predictors, continental genetic ancestry and pigmentation SNPs in the prediction models, and (iii) Compared two sets of pigmentation SNPs: the commonly-used HIrisPlex-S set (developed in Europeans) and novel SNP sets we defined here based on genome-wide association results in the CANDELA sample. We find that Random Forest or regression are globally the best performing methods. Although continental genetic ancestry has substantial power for prediction of pigmentation in Latin Americans, the inclusion of pigmentation SNPs increases prediction accuracy considerably, particularly for skin color. For hair and eye color, HIrisPlex-S has a similar performance to the CANDELA-specific prediction SNP sets. However, for skin pigmentation the performance of HIrisPlex-S is markedly lower than the SNP set defined here, including predictions in an independent dataset of Native American data. These results reflect the relatively high variation in hair and eye color among Europeans for whom HIrisPlex-S was developed, whereas their variation in skin pigmentation is comparatively lower. Furthermore, we show that the dataset used in the training of prediction models strongly impacts on the portability of these models across Europeans and Native Americans.

genetics↗