Biology subjects

Guyon, A.

Publications and source records attributed to Guyon, A..

6 recordsLinked to original sources

bioRxiv2025

A Quest for a Histaminergic or Orexinergic Biomarker for Sudden Infant Death Syndrome

AimsThis study aimed to investigate the role of the Hypocretin/Orexin (Ox) and Histamine (HA) systems--two key regulators of wakefulness --in sudden infant death syndrome (SIDS), a condition characterized by impaired arousal responses during sleep. MethodsCerebrospinal fluid (CSF) Ox levels were measured in 61 healthy controls, 70 Sudden Unexpected Death Infants (SUDI) (38 SIDS cases and 32 explained deaths (ED). HA and its metabolite, tele-methylhistamine (t-MeHA), were analysed in an additional 46 SUDI (34 SIDS, 12 ED) and 42 controls. Immunocytochemistry was performed on hypothalamic tissue from 11 SIDS and 13 ED cases to assess the number of Ox and HA neurons, using markers for Orexin-A and histidine decarboxylase (HDC), respectively. ResultsOverall CSF Ox levels did not differ significantly between groups. However, while an age-related decline in Ox levels was observed in controls (0-2 vs. 2-6 months), this pattern was absent in deceased infants, resulting in relatively higher Ox concentrations in the 2-6 month age group. HA and t-MeHA levels were significantly elevated in both SIDS and ED cases, likely due to postmortem release. Immunohistochemical analysis revealed an increased number of Ox-immunoreactive neurons in the rostral and caudal dorsolateral hypothalamus in SIDS cases compared to EDs. No differences were observed in the number or morphology of HA neurons. ConclusionFindings suggest increased Ox activity in SIDS cases, potentially reflecting repeated exposure to stress or hypoxia prior to death. In contrast, HA neurons do not appear to play a role in the pathophysiology of SIDS. Further research is needed to identify more specific biomarkers for assessing SIDS risk.

neuroscience↗

bioRxiv2025

Mutualist-pathogen co-colonisation modulates phosphoinositide signatures at host intracellular interfaces

The host membrane that surrounds intracellular microbes forms a critical interface influencing whether interactions result in mutualism or pathogenesis. While phosphoinositide identities differ between pathogen and mutualist interface membranes, it is unclear if these are modulated during co-colonisation. To address this, we generated Nicotiana benthamiana plants expressing biosensors for PI4P and PI(4,5)P2 and imaged root colonisation by the pathogenic oomycete Phytophthora palmivora and the mutualistic fungus Funneliformis mosseae. Binary host-microbe interactions revealed distinct patterns: PI(4,5)P2 was tip-enriched at mutualist structures but evenly distributed around pathogen structures, while PI4P was absent from pathogen-associated membranes but present at mutualist interfaces. Strikingly, co-colonisation altered host membrane identity, triggering PI4P recruitment at pathogen haustoria, and enhanced resistance to P. palmivora. These findings reveal that phosphoinositide signatures distinguish pathogenic and mutualistic interfaces and are dynamically remodelled during co-colonisation, likely influencing interaction outcomes. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=105 SRC="FIGDIR/small/661106v1_ufig1.gif" ALT="Figure 1"> View larger version (27K): org.highwire.dtl.DTLVardef@9c0024org.highwire.dtl.DTLVardef@1cd5b98org.highwire.dtl.DTLVardef@138938dorg.highwire.dtl.DTLVardef@15f2633_HPS_FORMAT_FIGEXP M_FIG C_FIG

plant biology↗

bioRxiv2020

Base editing strategy allows insertion of the A673T mutation in APP gene to prevent the development of Alzheimer's disease

Amyloid precursor protein (APP), a membrane protein mostly found in neurons, is preferentially cut by the -secretase enzyme, however, abnormal cleavage by {beta}-secretase leads to the formation of {beta}-amyloid peptide plaque in the brains of Alzheimers patients. Genome analysis of an Icelandic population that did not appear to show symptoms of Alzheimers at advanced age led to the discovery of the A673T mutation, reducing {beta}-secretase cleavage by 40%. We hypothesized that the insertion of this mutation in a patients genome could be an effective and sustainable method to slow down or prevent the progression of familial and sporadic forms of Alzheimers disease. We have thus modified the APP gene in HEK293T cells and in SH-SY5Y neuroblastoma using a Cas9n-deaminase enzyme, which changes a cytosine into a thymine, thus converting the alanine codon to a threonine. Several Cas9n-deaminase variants were tested to compare their efficiency of conversion. The results were characterized and quantified by deep sequencing. We successfully modified the APP gene in up to 56.7% of the HEK293T cells. Our approach aimed to attest to the efficiency of base editing in the development of treatments against genetic diseases as well as provide a new strategy for the treatment of Alzheimers.

bioengineering↗

bioRxiv2020

Specific mutations in genes responsible for Alzheimer and for Duchenne Muscular Dystrophy introduced by Base editing and PRIME editing.

Base editing technique and PRIME editing techniques derived from the CRISPR/Cas9 discovery permit to modify selected nucleotides. We initially used the base editing technique to introduce in the APP gene the A673T mutation, which prevents the development of Alzheimers disease. Although the desired cytidine to thymidine mutation was inserted in up to 17% of the APP gene in HEK393T, there were also modifications of up to 20% of other nearby cytidines. More specific mutations of the APP gene were obtained with the PRIME editing technique. However, the best percentage of mutations was only 5.8%. The efficiency of the PRIME editing treatment was initially tested on the EMX1 gene. A single treatment produced the desired modification in 36% of the EMX1 gene. Three consecutive treatments increased the percentage of mutations to 50%. The PRIME editing technique was also used to insert specific point mutations in exons 9 and 35 of the DMD gene coding for the dystrophin gene and which is mutated in Duchenne Muscular Dystrophy (DMD). Up to 10% desired mutations of the DMD gene were obtained. Three repeated treatments increased the percentage of specific mutations to 16%. Given that there are thousands of nuclei inside a human muscle fiber and that the dystrophin nuclear domain is about 500 m, this level of modifications would be sufficient to produce a phenotype improvement in DMD patients.

genetics↗

bioRxiv2020

Protective mutation A673T as a potential gene therapy for most forms of APP Familial Alzheimer's Disease

The accumulation of plaque in the brain leads to the onset and development of Alzheimers disease. The Amyloid precursor protein (APP) is usually cut by -secretase, however an abnormal cleavage profile by {beta}-secretase (BACE1) leads to the accumulation of A{beta} peptides, which forms these plaques. Numerous APP gene mutations favor plaque accumulation, causing Familial Alzheimer Disease (FAD). However, a variant of the APP gene (A673T) in Icelanders reduces BACE1 cleavage by 40 %. A library of plasmids containing APP genes with 29 FAD mutations with or without the additional A673T mutation was generated and transfected in neuroblastomas to assess the effect of this mutation on A{beta} peptide production. In most cases the production of A{beta} peptides was decreased by the co-dominant A673T mutation. The reduction of A{beta} peptide concentrations for the London mutation (V717I) even reached the same level as A673T carriers. These results suggest that the insertion of A673T in the APP gene of genetically susceptible FAD patients may prevent the onset of, slow down, or stop the progression of the disease.

neuroscience↗

bioRxiv2018

CRISPR-induced deletion with SaCas9 restores dystrophin expression in dystrophic models in vitro and in vivo.

Duchenne Muscular Dystrophy (DMD), a severe hereditary disease, affecting 1 boy out of 3500, mainly results from the deletion of one or more exons leading to a reading frame shift of the DMD gene that abrogates dystrophin protein synthesis. We used the Cas9 of Staphylococcus aureus (SaCas9) to edit the human DMD gene. Pairs of sgRNAs were meticulously chosen to induce a genomic deletion to not only restore the reading frame but also produced a dystrophin protein with normally phased spectrin-like repeats. The formation of a dystrophin protein with spectrin-like repeats normally phased is not usually obtained by skipping or by deletion of complete exons. This can however be obtained in rare instances where the exon/intron borders of the beginning and the end of the complete deletion (patient deletion plus CRISPR-induced deletion are at similar positions in the spectrin-like repeat. We used pairs of sgRNAs, targeting exons 47 and 58 and a normal reading frame was restored in 67 to 86% of the resulting hybrid exons in myoblasts derived from muscle biopsies of 4 DMD patients with different exon deletions. The restoration of the DMD reading frame and restoration of the dystrophin expression was also obtained in vivo in the heart of the del52hDMD/mx. Our results provide a proof-of-principle that SaCas9 could be used to edit the human DMD gene and could be considered for the further development of a therapy for DMD.

molecular biology↗