Biology subjects

Farah, M.

Publications and source records attributed to Farah, M..

3 recordsLinked to original sources

bioRxiv2026

Organizational principles governing synapse types in a whole-brain connectome

Neurons are classically viewed as polarized elements in which dendrites receive synaptic input and axons provide output. However, many neurons contain intermingled presynaptic and postsynaptic sites, enabling non-canonical forms of connectivity beyond axo-dendritic interactions. How such mixed polarity shapes connectivity across an entire nervous system remains unknown. Here, using the complete Drosophila connectome of an adult brain (approximately 140,000 neurons and >80 million synapses), we systematically mapped synapse types across neuronal compartments, cell types, and brain regions. We found that mixed polarity is widespread yet highly structured across neuronal populations. Approximately one third of synapses between polarized neurons are non-canonical, including axo-axonic, dendrodendritic, and dendro-axonic interactions. Remarkably, synapse type can be predicted from a simple axis of neuronal complexity derived from morphology and connectivity. Low-complexity neurons, which dominate early visual circuits, preferentially interact through dendrites, whereas larger and more highly connected neurons enriched in central brain regions preferentially interact through axons. Mixed polarity also strongly promotes reciprocal connectivity, which is dominated by non-canonical motifs. Finally, we identified postsynaptic terminals on presynaptic boutons as a widespread anatomical motif associated with local reciprocal and non-canonical interactions. Together, these findings reveal organizational principles linking neuronal architecture, synapse type, and circuit connectivity across a complete brain.

neuroscience↗

bioRxiv2025

Longitudinal TCR repertoires in ulcerative colitis patients show features distinguishing disease states

ABSTRACT AND KEY WORDSO_ST_ABSBackgroundC_ST_ABSUlcerative colitis (UC) affects an estimated 10 million people worldwide. The exact etiology of the disease is unknown, but T cell dysregulation and aberrant activation is associated with UC--prompting research into T cell receptor (TCR) repertoires in UC patients. However, few studies have compared UC patients TCR repertoires in flare (inflamed) and remission (uninflamed) states. Moreover, this is the first dataset to our knowledge examining multiple repertoires from UC patients over time, enabling longitudinal analyses. MethodsTCR repertoires were obtained for 21 patients across multiple timepoints, yielding a total of 58 samples. Repertoires clonality, diversity, overlap, and gene usage frequencies were compared across all patients. CDR3 sequences were split into K-mers (sequences of length K), and enriched K-mers in flare and remission states were identified using GLIPH2. ResultsAlthough repertoires vary across patients, there were significant differences in the usage of 20 V{beta} genes across flare and remission states. Moreover, calculating the overlap in repertoires with enriched K-mers showed higher overlap scores than when using full TCR sequences. 622 unique enriched K-mers were identified in flare states and 495 in remission states, with only 57 overlapping between the two states. ConclusionsOverall, these results highlight the importance of analyzing V{beta} gene usage and K-mer enrichment in TCR repertoires, particularly given the lack of public clones across patient cohorts. Future studies characterizing the specific antigenic targets associated with these features will pave the way for biomarker discovery in UC. KEY MESSAGESO_LIWhat is already known? UC is a chronic condition characterized by fluctuating periods of flares and remissions, as well as aberrant immune activity. C_LIO_LIWhat is new here? TCR repertoires were obtained from UC patients colonoscopies, with multiple timepoints per patient--enabling the analysis of repertoire characteristics within and across patients over time. C_LIO_LIHow can this study help patient care? Understanding the exact immune mechanisms in UC can pave the way for biomarker discovery and advance the state of care for patients, given that current treatments are non-specific and have adverse side effects. C_LI SummaryThis article presents an analysis of T cell receptor repertoires from ulcerative colitis patient samples collected during colonoscopies, identifying genes and motifs associated with patients flare (inflamed) and remission (uninflamed) states.

immunology↗

bioRxiv2020

Neuronal Hyperexcitability is a DLK-dependent Trigger of HSV-1 Reactivation that can be Induced by IL-1

Herpes Simplex Virus (HSV) establishes a latent infection in neurons and periodically reactivates to cause disease. The neuronal stimuli that trigger HSV reactivation have not been fully elucidated. Here we demonstrate that HSV reactivation can be induced by neuronal hyperexcitability. Neuronal stimulation-induced reactivation was dependent on voltage-gated ion and hyperpolarization-activated cyclic nucleotide-gated (HCN) channels, demonstrating that neuronal activity is required for reactivation. Hyperexcitability-induced reactivation was dependent on the neuronal pathway of DLK/JNK activation and progressed via an initial wave of viral gene expression that was independent of histone demethylase activity and linked to histone phosphorylation. IL-1{beta} induces neuronal hyperexcitability and is released under conditions of stress and fever; both known triggers of clinical HSV reactivation. IL-1{beta} induced histone phosphorylation in sympathetic neurons, and importantly HSV reactivation, which was dependent on DLK and neuronal excitability. Thus, HSV co-opts an innate immune pathway resulting from IL-1 stimulation of neurons to induce reactivation.

microbiology↗