Biology subjects

Penney, J.

Publications and source records attributed to Penney, J..

6 recordsLinked to original sources

bioRxiv2026

DNA double-strand break signaling induces aberrant neuronal activity

Aberrant neuronal activity is an early pathological feature of numerous neurodegenerative disorders, including tauopathy, and is thought to play a role in disease progression. However, the mechanism underlying abnormal neuronal activity remains elusive. Here, we reveal a relationship between DNA double-strand break (DSB)/p53 pathway activation and aberrant neuronal activity. Activating p53 as part of the DNA damage response via DSB induction, or by preventing MDM2-mediated p53 degradation, causes aberrant activity in both mouse and human neurons. p53 activation induces the expression of genes regulating synaptic transmission, and p53-responsive gene upregulation is overrepresented in postmortem human Alzheimers disease neurons burdened with neurofibrillary tangles (NFTs). Using a human iPSC-based cerebral organoid model of frontotemporal dementia that exhibits relevant pathologies including elevated DSBs, aberrant neuronal activity, and NFTs, we show that inhibiting p53 transcriptional activity with a small molecule ameliorates aberrant calcium fluctuations in neurons. Together, our findings highlight p53 inhibition as a novel therapeutic strategy to counter aberrant neuronal activity in neurodegenerative diseases characterized by tauopathy.

neuroscience↗

bioRxiv2022

A CREBZF/Zhangfei isoform activates CHOP during prolonged cellular stress

The basic leucine zipper transcription factor CREBZF (Zhangfei or ZF) was identified through its interaction with Herpes Simplex Virus-1 related cellular protein HCF-1. CREBZF has been implicated in cellular stress responses through its interaction with other proteins, such as CREB3/Luman and ATF4. Here we investigated the production of four CREBZF isoforms, which arise from translational initiation of a downstream AUG at codon 83, and mRNA alternative splicing that adds an IFFFR pentapeptidyl tail to the C-terminus. We found that in addition to transcriptional activation, the short-tailed CREBZF (stZF) isoform was specifically induced by prolonged ER stress treatment. This stZF isoform is a potent transcriptional activator of the pro-apoptotic protein CHOP. Overexpression of stZF activates transcription of CHOP through a CCAAT enhancer binding protein (C/EBP)-ATF site, and promotes apoptosis. We propose that 1) CREBZF is a key component of the Integrated Stress Response (ISR); 2) stZF is essential for the role of CREBZF in inducing CHOP and promoting cell death upon prolonged cellular stress.

molecular biology↗

bioRxiv2022

Distinct effects of disease-associated TREM2 R47H/+ and T66M mutations on iPSC-derived microglia.

Genetic findings have highlighted key roles for microglia in the pathology of neurodegenerative conditions such as Alzheimers disease (AD). Distinct mutations in the microglial protein TREM2 (triggering receptor expressed on myeloid cells 2) are associated with different forms of neurodegeneration in humans; R47H/+ mutations increase AD risk, while loss-of-function mutations such as TREM2 T66M result in more severe forms of neurodegeneration. We employed gene editing and stem cell models to gain insight into the effects of these mutations on human iPSC-derived microglia. We found divergent effects of TREM2 R47H/+ and T66M mutations on gene expression, with R47H/+ cells exhibiting a pro-inflammatory gene expression signature. Both the TREM2 R47H/+ and T66M mutations caused similar impairments in microglial movement and the uptake of multiple substrates, while R47H/+ microglia were hyper-responsive to inflammatory stimuli, consistent with their gene expression signature. We developed an in vitro laser-induced injury model in neuron-microglia co-cultures, finding an impaired injury response by TREM2 R47H/+ microglia. Furthermore, in xenotransplantation experiments, mouse brains transplanted with TREM2 R47H/+ microglia exhibited reduced synaptic density. Consistently, we observed upregulation of multiple complement cascade components in TREM2 R47H/+ microglia, suggesting that inappropriate synaptic pruning may underlie the effect. Thus, these findings identify shared and distinct effects of these two TREM2 mutations on microglial gene expression and function. While the TREM2 T66M mutation impairs microglial movement and uptake processes, the TREM2 R47H/+ mutation additionally confers multiple potentially detrimental effects on human microglia, likely to underlie its association with AD.

neuroscience↗

bioRxiv2020

A cyclin-dependent kinase 5-derived peptide inhibits Cdk5/p25 activity and improves neurodegenerative phenotypes

Aberrant activity of cyclin-dependent kinase (Cdk5) has been implicated in various neurodegenerative diseases. This effect is mediated by pathological cleavage of the Cdk5 activator p35 to produce the truncated product p25, exhibiting increased stability and altered substrate specificity. The benefit of blocking p25 production has been demonstrated in various rodent and human neurodegenerative models. However, important Cdk5/p35 functions in the developing and adult brain have made it challenging to selectively target the detrimental effects of Cdk5/p25 while sparing the physiological functions of Cdk5/p35. Here, we report a 12-amino acid-long peptide fragment derived from Cdk5 (the Cdk5 inhibitory (Cdk5i) peptide) that shows a high binding affinity toward the Cdk5/p25 complex and can efficiently and selectively inhibit Cdk5/p25 kinase activity. Using cellular assays, mouse neurodegeneration models and human cerebral organoids generated from patient-derived iPSCs, we demonstrate beneficial effects of the Cdk5i peptide on various pathological phenotypes including gliosis, DNA damage, and Tau hyperphosphorylation.

neuroscience↗

bioRxiv2020

Probing the functions of microglial cyclin-dependent kinase 5 under physiological and pathological conditions

Cyclin dependent kinase 5 (Cdk5) regulates various developmental and physiological processes in the central nervous system. Deregulation of Cdk5 activity in neurons induces severe neurodegeneration and has been implicated in Alzheimers disease (AD) and other neurodegenerative conditions. A large fraction of AD risk genes are highly expressed in microglia, highlighting an important role for these cells in AD pathogenesis. While Cdk5 function in neurons is well characterized, our understanding of its roles in microglial function under physiological and neurodegenerative conditions remain rudimentary. Here, we investigate the roles of Cdk5 in microglia using myeloid-specific Cdk5 conditional knockout mice. Using microglia-specific transcriptome profiling, histological analyses, and behavioral assessments, we found that knockout of Cdk5 in microglia for 1 month induced transcriptional changes characterized by upregulation of cell cycle processes and type I interferon signaling genes in both physiological conditions and AD-related amyloidogenesis. In contrast to the robust transcriptional changes, conditional loss of microglial Cdk5 produced minimal effects on the density and morphology of microglia and their phagocytic activity toward myelin debris. Moreover, Cdk5cKO mice exhibited little change in synaptic density and tasks associated with locomotor, anxiety-like, and memory-related behaviors. Our findings indicate that the conditional loss of Cdk5 in microglia induces rapid alterations of microglial transcriptome with minimal or delayed effects on histological and behavioral responses.

neuroscience↗

bioRxiv2020

Phosphoproteomics identifies microglial Siglec-F inflammatory response during neurodegeneration

Alzheimers disease (AD) is characterized by the appearance of amyloid-{beta} plaques, neurofibrillary tangles, and inflammation in brain regions involved in memory. Using mass spectrometry, we have quantified the phosphoproteome of the CK-p25, 5XFAD, and Tau P301S mouse models of neurodegeneration. We identified a shared response involving Siglec-F which was upregulated on a subset of reactive microglia. The human paralog Siglec-8 was also upregulated on microglia in AD. Siglec-F and Siglec-8 were upregulated following microglial activation with interferon gamma (IFN{gamma}) in BV-2 cell line and human stem-cell derived microglia models. Siglec-F overexpression activates an endocytic and pyroptotic inflammatory response in BV-2 cells, dependent on its sialic acid substrates and immunoreceptor tyrosine-based inhibition motif (ITIM) phosphorylation sites. Related human Siglecs induced a similar response in BV-2 cells. Collectively, our results point to an important role for mouse Siglec-F and human Siglec-8 in regulating microglial activation during neurodegeneration. HighlightsO_LIPhosphoproteomics analysis of CK-p25, 5XFAD, and Tau P301S mouse models finds dysregulated signaling networks associated with Alzheimers disease pathologies. C_LIO_LIA phosphorylation site on Siglec-F is found to be upregulated across all three models of disease. C_LIO_LIExpression of Siglec-F and its human paralog Siglec-8 is increased in reactive microglia. C_LIO_LIOverexpression of Siglec-F and Siglec-8 in vitro drives an endocytic and pyroptotic inflammatory response. C_LI In BriefPhosphoproteome signaling changes associated with Alzheimers disease (AD) are poorly characterized. Here, Morshed et al. apply phosphoproteomics to mouse models of AD to uncover a novel microglial receptor, Siglec-F, that is upregulated on a subset of inflammatory microglia across models of neurodegeneration. The human paralog, Siglec-8 is also found to be upregulated in late-onset AD microglia. Overexpression of Siglec-F and related human Siglecs activates pro-inflammatory signaling responses in BV-2 cells.

neuroscience↗