Biology subjects

Hammond, B.

Publications and source records attributed to Hammond, B..

5 recordsLinked to original sources

bioRxiv2026

The meiotic synaptonemal complex is assembled from independently regulated gene programmes

Synaptonemal complex (SC) proteins assemble a highly specialised chromosome structure during meiosis and are considered products of a coordinated germline programme that is silenced in somatic cells. Here, we show that this binary model does not describe the regulation of the eight core mammalian SC genes. Despite assembling into a single molecular complex, SC genes follow distinct regulatory trajectories from meiotic entry through SC disassembly. Their activation is staggered, transcripts and proteins persist with different kinetics after SC disassembly begins in late pachytene, and RNA abundance generally fails to predict protein abundance, revealing extensive regulation between transcription and protein accumulation. Integrating promoter state, nascent transcription, RNA and translational measurements identified gene-specific regulatory strategies rather than a shared SC regulatory mechanism. This independence extends beyond the germline and explains how cancers can express individual SC genes. In cancer cells, individual SC loci occupy distinct transcriptional states, including conventional promoter activation, alternative promoter usage, cell-cycle-dependent transcription and promoter competence without detectable productive transcription. DNA methylation can repress individual SC promoters but does not define a common somatic OFF state, while related transcriptional inputs produce different downstream RNA outputs between SC genes. Unexpectedly, single-cell transcriptomes across healthy mouse and human tissues reveal that somatic SC expression is not restricted to cancer: individual SC genes show reproducible associations with specific cell populations, including fibroblasts, myeloid cells, Schwann cells and progenitors. Thus, SC proteins are neither expressed nor silenced as an obligately coupled gene set. We propose that SC identity emerges from the temporally restricted convergence and assembly of independently regulated genes and proteins during meiosis, while their regulatory autonomy permits individual components to be retained or redeployed in normal somatic cells and cancer. The SC therefore represents an emergent molecular state: its components retain distinct regulatory identities, while their transient convergence during meiotic prophase generates a structure and function that none defines individually.

cell biology↗

bioRxiv2026

Cell-matrix mechanosensing and cellular metabolic demand are linked through SKT and mTORC2

Integrin-based adhesion complexes mediate cell adhesion to the extracellular matrix and enable the cell to interpret and respond to both biochemical and mechanical cues. Such cues can affect a cells metabolic rate; however, how mechanical signals are converted into metabolic rate changes is not clear. We identified an uncharacterised protein; Sickle Tail Protein Homolog (KIAA1217), SKT to be enriched in cell-matrix adhesion complexes in stiff microenvironments. Low SKT expression correlates with an improved prognosis in pancreatic ductal adenocarcinoma (PDAC), suggesting an important role for SKT in extracellular matrix dependent tumour progression. Here, we show that SKT interacts with the mechanistic target of rapamycin complex 2 (mTORC2), a pivotal signalling complex in glucose metabolism, cell growth, and survival. SKT recruits mTORC2 to cell-matrix adhesions in a mechanoresponsive manner. SKT mediated mTORC2 signalling from adhesions is required for maintaining glycolytic flux and control of adhesion dynamics. Our findings show that SKT serves as a rheostat that controls metabolic adaptation of cells to their matrix microenvironment. Collectively, our research provides insights into the molecular mechanisms and interplay between cell adhesion and metabolic signalling in complex and stiff tumour microenvironments. The novel functions identified for SKT in cell-matrix adhesions, mTORC2 signalling and glycolysis unveils a signalling axis between the tumour microenvironment and cellular metabolism that are required for PDAC growth and invasion.

cell biology↗

bioRxiv2025

Asynchronous firing and off-states in working memory maintenance

Persistent spiking activity and activity-silent mechanisms have been proposed as neural correlates of working memory. To determine their relative contribution, we recorded neural activity from the lateral prefrontal and posterior parietal cortex of two male macaques using high-density microelectrode probes. We found that, when averaged across all neurons, persistent delay activity was observable throughout the duration of single trials in populations of prefrontal neurons with silent periods that did not deviate significantly from chance. However, temporal fluctuations in activity-dependent mnemonic information were present and weakly correlated between the prefrontal and posterior parietal cortices, suggesting at least partial, long-distance synchronization of off-states. Decoding accuracy of neurons recorded simultaneously was also reduced relatively to pseudo-populations constructed by splicing different trials together. Our results support an asynchronous state of working memory, maintained by the distributed pattern of persistent discharges across cortical neurons, which is subject to widely distributed fluctuations in information representation fidelity.

neuroscience↗

bioRxiv2025

Expanded adaptive NKG2C+ NK cells exhibit potent ADCC and functional responses against HBV-infected hepatoma cell lines

BackgroundHepatitis B virus (HBV) infection remains a significant global health challenge, leading to chronic liver disease and hepatocellular carcinoma (HCC). Natural killer (NK) cells play an important role in the clearance of HBV-infected cells, but their efficacy is often compromised during chronic infection. Adaptive NK cells, characterised by NKG2C expression and enhanced functional responses, represent a promising therapeutic avenue for enhancing anti-HBV immunity and responses to HBV-driven cancers. MethodsWe applied an established protocol, involving K562-HLA-E expressing feeder cells and cytokines (IL-2), for the expansion of adaptive NK cells from cryopreserved T- and B cell depleted peripheral blood mononuclear cells (PBMCs) derived from donors with chronic HBV infection alone or with Human Immunodeficiency Virus (HIV) co-infection. We evaluated the adaptive profile of expanded NK cells, their antibody-dependent cellular cytotoxicity (ADCC) capacity and functional responses against hepatoma cell lines in the presence or absence of HBV infection. ResultsExpanded NK cells achieved >97% purity, with the NKG2C positive population exhibiting a mean 100-fold expansion. These cells demonstrated a predominantly adaptive phenotype with high surface expression of NKG2C and cytotoxic potential (Granzyme B). They maintained high levels of CD16 surface expression and upregulated CD2, essential for ADCC. Functionally, expanded adaptive NK cells showed enhanced ADCC capacity and functional responses to K562 targets, naive, HBV integrant-expressing, and de novo infected hepatoma cell lines. TGF-{beta} preconditioning induced tissue-resident features (CD103, CD49a) in expanded adaptive NK cells, while preserving their adaptive phenotype and functionality, enhancing their potential for liver targeted immunotherapy. Further, expanded adaptive NK cells demonstrated minimal reactivity against autologous activated T cells, suggesting limited off-target effects. ConclusionsOur study demonstrates the first successful expansion of adaptive NK cells with robust functional responses from donors with chronic viral infection. This approach creates opportunities for NK cell-based therapies alone or in combination with monoclonal antibodies contributing to HBV functional cure strategies and the treatment of HBV-driven cancers.

immunology↗

bioRxiv2024

Distinct Mechanisms of T3SS Recognition Control LTB4 Synthesis in Neutrophils versus Macrophages

Leukotriene B4 (LTB4) is critical for initiating the inflammatory cascade in response to infection. However, Yersinia pestis colonizes the host by inhibiting the timely synthesis of LTB4 and inflammation. Here, we show that the bacterial type 3 secretion system (T3SS) is the primary pathogen associated molecular pattern (PAMP) responsible for LTB4 production by leukocytes in response to Yersinia and Salmonella, but synthesis is inhibited by the Yop effectors during Yersinia interactions. Moreover, we unexpectedly discovered that T3SS-mediated LTB4 synthesis by neutrophils and macrophages require two distinct host signaling pathways. We show that the SKAP2/PLC signaling pathway is essential for LTB4 production by neutrophils but not macrophages. Instead, phagocytosis and the NLRP3/CASP1 inflammasome are needed for LTB4 synthesis by macrophages. Finally, while recognition of the T3SS is required for LTB4 production, we also discovered a second unrelated PAMP-mediated signal independently activates the MAP kinase pathway needed for LTB4 synthesis. Together, these data demonstrate significant differences in the signaling pathways required by macrophages and neutrophils to quickly respond to bacterial infections. SignificanceThe production of inflammatory lipid mediators by the host is essential for timely inflammation in response to invasion by bacterial pathogens. Therefore, defining how immune cells recognize pathogens and rapidly produce these lipids is essential for us to understand how our immune system effectively controls infection. In this study, we discovered that the host signaling pathways required for leukotriene B4 (LTB4) synthesis differ between neutrophils and macrophages, highlighting important differences in how immune cells respond to infection. Together, these data represent a significant improvement in our understanding of how neutrophils and macrophages rapidly react to bacteria and provide new insights into how Yersinia pestis manipulates leukocytes to evade immune recognition to cause disease.

immunology↗