Biology subjects

Halloran, M.

Publications and source records attributed to Halloran, M..

5 recordsLinked to original sources

bioRxiv2025

Inhibition of Cxcr4 chemokine receptor signaling improves habituation learning and increases cAMP-PKA signaling in a zebrafish model of Neurofibromatosis type 1

Neurofibromatosis type 1 (NF1) is a neurogenetic disorder caused by loss of function mutations in the gene neurofibromin 1 (NF1). NF1 encodes neurofibromin, a multifunctional tumor suppressing protein that regulates Ras, cAMP, and dopamine signaling. NF1 predisposes patients to a wide range of symptoms, including peripheral nerve tumors, brain tumors, and cognitive dysfunction. Despite considerable work using animal models to investigate the role of neurofibromin in behavior, translating research into treatment for NF1-associated cognitive dysfunction has not yet been successful. Here, we identify Cxcr4 chemokine receptor signaling as a regulator of habituation learning and modulator of cAMP-PKA signaling in nf1 mutant larval zebrafish. Combining a small-molecule drug screen and RNAseq analysis, we show that cxcr4b expression is increased in nf1 mutants and that pharmacological inhibition of Cxcr4 with AMD3100 (Plerixafor) improves habituation learning in nf1 mutants. We further demonstrate that Plerixafor treatment activates cAMP-PKA pathway signaling but has limited effects on Ras-Raf-MEK-ERK pathway signaling in the nf1 mutant brain. CXCR4 was previously identified as a potential therapeutic target for neurofibromin-deficient tumorigenesis. Our results provide evidence that Cxcr4 signaling also regulates neurofibromin-dependent cognitive function.

neuroscience↗

bioRxiv2021

KLC4 shapes axon arbors during development and mediates adult behavior

Development of elaborate and polarized neuronal morphology requires precisely regulated transport of cellular cargos by motor proteins such as kinesin-1. Kinesin-1 has numerous cellular cargos which must be delivered to unique neuronal compartments. The process by which this motor selectively transports and delivers cargo to regulate neuronal morphogenesis is poorly understood, although the cargo-binding kinesin light chain (KLC) subunits contribute to specificity. Our work implicates one such subunit, KLC4, as an essential regulator of axon branching and arborization pattern of sensory neurons during development. Using live imaging approaches in klc4 mutant zebrafish, we show that KLC4 is required for stabilization of nascent axon branches, proper microtubule (MT) dynamics, and endosomal transport. Furthermore, KLC4 is required for proper tiling of peripheral axon arbors: in klc4 mutants, peripheral axons showed abnormal fasciculation, a behavior characteristic of central axons. This result suggests that KLC4 patterns axonal compartments and helps establish molecular differences between central and peripheral axons. Finally, we find that klc4 mutant larva are hypersensitive to touch and adults show anxiety-like behavior in a novel tank test, implicating klc4 as a new gene involved in stress response circuits.

neuroscience↗

bioRxiv2020

Pregnancy associated plasma protein-aa regulates endoplasmic reticulum-mitochondria associations

The endoplasmic reticulum (ER) and mitochondria form close physical associations to facilitate calcium transfer, thereby regulating mitochondrial function and dynamics. For neurons with high metabolic demands, such as sensory hair cells, precise regulation of ER-mitochondria associations is especially critical for cell survival. We previously identified the secreted metalloprotease Pregnancy associated plasma protein-aa (Pappaa) as a novel regulator of mitochondrial function in zebrafish lateral line hair cells (Alassaf et al., 2019). Here, we show that pappaa mutant hair cells exhibit excessive and abnormally close ER-mitochondria associations, suggesting increased ER-mitochondria calcium transfer. Indeed, we find that pappaa mutant hair cells are more vulnerable to pharmacological induction of ER-calcium release. Additionally, pappaa mutant hair cells display ER stress and dysfunctional downstream processes of the ER-mitochondria axis including mitochondrial fragmentation and autophagy. Together our results support a model in which Pappaa regulates mitochondrial function, at least in part, by regulating ER-mitochondria associations.

cell biology↗

bioRxiv2019

Ex vivo expansion of skeletal muscle stem cells with a novel small compound inhibitor of eIF2α dephosphorylation

BACKGROUNDRegeneration of adult tissues requires the activity of rare, mitotically quiescent somatic stem cells. These features are illustrated by the muscle stem cell (MuSC), also known as the satellite cell for its satellite position underneath the basal lamina of the myofiber. Isolation of MuSCs results in their rapid activation of the myogenic program and their subsequent culture ex vivo leads to loss of stem cell regenerative capacity. These shortcomings make MuSCs difficult to study, manipulate and prevent cell based therapies. We have previously shown that muscle stem cells (MuSCs) require tightly regulated protein synthesis through the phosphorylation of eIF2. Sal003, an analog of salubrinal that blocks eIF2 dephosphorylation, promotes ex vivo expansion of MuSCs retaining regenerative capacity after engraftment into the Dmdmdx mouse model of Duchenne muscular dystrophy.\n\nMETHODSSince micromolar concentrations of sal003 (10M) are required to expand MuSCs ex vivo, we undertook a structure relations study to identify novel sal003 analogs with efficacy at lower concentrations. We demonstrate ex vivo expansion of MuSCs isolated from wild-type and mdx mice using new compounds, and use CRISPR/Cas9 genome editing tools to restore dystrophin expression in cultured MuSCs.\n\nRESULTSHere, we have synthesized and screened chemical analogs of sal003 to identify a novel compound promoting the ex vivo expansion of MuSCs. The novel compound expands wild-type and mdx MuSCs more efficiently than sal003 and also prolongs culture of primary myoblasts from isolated MuSCs.\n\nCONCLUSIONSWe identify a novel sal003 analog, C10, with increased potency at lower concentrations. Culture conditions including sal003 or C10 can extend culture of primary myoblasts from isolated MuSCs, which we predict will enable their further study, genetic manipulation and cell based therapies.

cell biology↗

bioRxiv2018

Modulating CRISPR gene drive activity through nucleocytoplasmic localization of Cas9 in S. cerevisiae

The bacterial CRISPR/Cas genome editing system has provided a major breakthrough in molecular biology. One use of this technology is within a nuclease-based gene drive. This type of system can install a genetic element within a population at unnatural rates. Combatting of vector-borne diseases carried by metazoans could benefit from a delivery system that bypasses traditional Mendelian laws of segregation. Recently, laboratory studies in fungi, insects, and even mice, have demonstrated successful propagation of CRISPR gene drives and the potential utility of this type of mechanism. However, current gene drives still face challenges including evolved resistance, containment, and the consequences of application in wild populations. In this study, we use an artificial gene drive system in budding yeast to explore mechanisms to modulate nuclease activity of Cas9 through its nucleocytoplasmic localization. We examine non-native nuclear localization sequences on Cas9 fusion proteins in vivo and demonstrate that appended signals can titrate gene drive activity and serve as a potential molecular safeguard.

synthetic biology↗