Biology subjects

Chaudhry, B.

Publications and source records attributed to Chaudhry, B..

4 recordsLinked to original sources

bioRxiv2025

Remodelling of supernumerary leaflet primordia leads to bicuspid aortic valve (BAV) caused by loss of primary cilia

AimsBicuspid aortic valve (BAV), where two valve leaflets are found instead of the usual three, affects 1-2% of the general population and is associated with significant morbidity and mortality. Despite its frequency, the majority of cases remain unexplained. This is, at least in part, because there are two types of valve leaflet primordia: endocardial cushions and intercalated valve swellings (ICVS). Moreover, multiple progenitors make distinct contribution to the formation of these primordia. Genomic studies in mouse and human have suggested a correlation between BAV and malfunctional primary cilia. However, the precise requirement for cilia during early embryonic valvulogenesis remains unknown. Methods and resultsHere, we disrupted primary cilia by deleting the ciliary gene Ift88 in the main progenitor cells forming the aortic valve using specific Cre drivers: Wnt1-Cre for neural crest cells, Isl1-Cre for second heart field cells (SHF); Tie2-Cre for endocardial-derived cells and Tnnt2-Cre for direct-differentiating SHF in the ICVS. Loss of Ift88, and thus primary cilia, from neural crest cells and endocardium did not impact aortic valve formation. However, primary cilia are essential in SHF cells for aortic valve leaflet formation, with over half of Ift88f/f;Isl1-Cre mutants presenting with BAV. As the valve leaflets are forming, 50% of the Ift88f/f;Isl1-Cre mutants have two small leaflets in the position of the usual posterior leaflet, meaning that at this stage the aortic valve is quadricuspid, which then remodels to BAV by E15.5. Mechanistic studies demonstrate premature differentiation of SHF cells as the ICVS form, leading to the formation of a broadened ICVS that forms two posterior leaflet precursors. This abnormality in the formation of the ICVS is associated with disruption of Notch-Jag1 signalling pathway, with Jag1f/f;Isl1-Cre mutants presenting with a similar phenotype. ConclusionsThese data show that primary cilia, via the Notch-Jag1 signalling pathway, regulate differentiation of SHF cells in the aortic valve primordia. Additionally, we identify a mechanistic link between the developmental basis of quadricuspid and bicuspid arterial valve leaflets. Translational PerspectiveSeveral genomic studies in human and mouse have suggested that disruption of cilia-related genes may be a significant cause of CHD. Although there is limited data from animal models to suggest a link between cilia and bicuspid aortic valve (BAV), the mechanisms underpinning BAV formation during early valvulogenesis have not been described. Here, we established a potential mechanism underpinning BAV formation, highlighting a role for primary cilia in a subset of valve interstitial cells (VIC) derived from second heart field progenitors. Loss of cilia altered VIC differentiation and valvulogenesis. This study confirms that disruption of cilial formation and/or function can lead to arterial valve defects and could pave the way to finding therapies for patient benefit.

developmental biology↗

bioRxiv2025

The diversity of cellular systems involved in carbonate precipitation by Escherichia coli

Climate change is increasing the need to limit levels of anthropogenic CO2 released into the atmosphere. One approach being investigated is to generate products based on microbially induced carbonate precipitation (MICP), which can trap CO2 as CaCO3. We recently identified a novel MICP pathway in bacteria that is initiated by Ca2+ toxicity in cells, causing extracellular CO2 to be trapped as CO 2- by Escherichia coli, although the yield of precipitated CaCO remained low (in the milligram range). In this work, we used the E. coli Keio gene knock-out library to identify 54 genes involved in MICP in E. coli, which could be broadly characterized into four groups: central metabolism, iron metabolism, cell architecture, and transport. The role of central metabolism appears to be crucial in maintaining alkaline conditions surrounding the cell that promote CaCO3 precipitation. The role of iron metabolism was less clear, although the results suggest that growth rate influences the initiation of MICP. While the impact of repeating polymeric structures on cell surfaces promoting MICP is well established, our results suggest that other structural features may play a role, including fimbriae and flagella. Finally, the results confirmed that Ca2+ transport is central to MICP under calcium stress. The results further suggest that the ZntB efflux pump may play a previously unidentified role in Ca2+ transport in E. coli. By overexpressing some of these genes, our work suggests that there are several previously unidentified cellular mechanisms that could serve as a target for enhanced MICP in E. coli. By incorporating these processes into MICP pathways in E. coli, it may be possible to increase the volume of CO2 fixed using this pathway and yield potentially new products that can replace CO2 intensive products, such as precipitated calcium carbonates (PCCs) for industry.

microbiology↗

bioRxiv2024

Zebrafish arterial valve development occurs through direct differentiation of second heart field progenitors

AimsBicuspid Aortic Valve (BAV) is the most common congenital heart defect, affecting at least 2% of the population. The embryonic origins of BAV remain poorly understood, limiting the identification of assays for validating patient variants and ultimately causative genes for BAV. In both human and mouse, the left and right leaflets of the arterial valves arise from the outflow tract cushions, with interstitial cells originating from neural crest cells and endocardial-to-mesenchymal transition (EndoMT). In contrast, an EndoMT-independent mechanism of direct differentiation by cardiac progenitors from the second heart field (SHF) is responsible for the formation of the anterior and posterior leaflets. Defects in either of these developmental mechanisms can result in BAV. Although zebrafish have been suggested as a model for human variant testing, their naturally bicuspid arterial valve has not been considered suitable for understanding human arterial valve development. Here, we have set out to investigate to what extent the processes involved in arterial valve development are conserved in zebrafish and ultimately, whether functional testing of BAV variants could be carried out in zebrafish. Methods and ResultsUsing a combination of live imaging, immunohistochemistry and Cre-mediated lineage tracing, we show that the zebrafish arterial valve primordia develop directly from undifferentiated SHF progenitors with no contribution from EndoMT or neural crest, in keeping with the human and mouse anterior and posterior leaflets. Moreover, once formed, these primordia share common subsequent developmental events with all three mammalian arterial valve leaflets. ConclusionsOur work highlights a conserved ancestral mechanism of arterial leaflet formation from the SHF and identifies that development of the zebrafish arterial valve is distinct from that of the atrioventricular valve. Crucially, this confirms the utility of zebrafish for understanding the development of specific BAV subtypes and arterial valve dysplasia, offering potential for high-throughput variant testing. Translational PerspectiveLarge genomic studies of patients with Bicuspid Aortic Valve (BAV) have identified numerous variants predicted to be causative, yet due to a lack of suitable, in vivo functional assays, advancement of genetic testing, discussion of risk to family members and accurate prognosis is not yet widely possible. Here, we show that zebrafish demonstrate a high level of conservation in arterial valve development with the intercalated leaflets in human, establishing zebrafish as a suitable in vivo model that can begin to overcome the disconnect between clinical genetics and developmental biology.

developmental biology↗

bioRxiv2019

An alternatively spliced zebrafish jnk1a transcript has an essential and non-redundant role in development of the first heart field derived proximal ventricular chamber.

Alternative splicing is a ubiquitous mechanism for producing different mRNA species from a single gene, resulting in proteomic diversity. Despite potential for regulating embryogenesis, its developmental role remains under-investigated. The Jun kinase (Jnk) genes, considered downstream effectors of the non-canonical Wnt planar cell polarity pathway, utilise extensive and evolutionarily-conserved alternative splicing. Although many PCP members are associated with heart malformation, the role of Jnk genes in cardiac development, and specifically which alternatively spliced transcripts orchestrate these processes, remain unknown. In this study we exploit the jnk1 duplication and subspecialisation found in zebrafish to reveal an essential and non-redundant requirement for jnk1a in cardiac development. We characterise alternatively spliced jnk1a/jnk1b transcripts and demonstrate that hypoplasia of the proximal ventricular component, which corresponds to human hypoplastic left ventricle, can only be rescued by the jnk1a Ex7 Lg transcript. These studies highlight the importance of Jnk signalling and alternative splicing in heart development

developmental biology↗