Biology subjects

Appaix, F.

Publications and source records attributed to Appaix, F..

4 recordsLinked to original sources

bioRxiv2025

The metabolic kinase LKB1 shapes the enteric nervous system bymitigating the oxidative stress and p53 activity

The enteric nervous system (ENS) comprises ganglia of neurons and glial cells derived from migratory multipotent neural crest cells. While the molecular mechanisms of ENS development are well-studied, the involvement of metabolic processes has received less attention. We previously showed that the tumor suppressor kinase LKB1 is essential for the trophic maintenance of postnatal ENS. Here we examined LKB1s role in ENS formation using a genetically engineered mouse model that conditionally inactivates Lkb1 in neural crest progenitors during gut invasion. We conducted a comprehensive phenotyping of the ENS through histology and 3D imaging of cleared tissue, combining lightsheet microscopy with adaptive optics confocal microscopy. We found that Lkb1 loss impairs early neuronal differentiation, followed by glial degeneration, leading to hypoganglionosis and compromised digestive tissue integrity. Metabolite profiling of digestive tracts revealed an increase of oxidative stress upon Lkb1 ablation. In vitro, Lkb1 knockdown induced oxidative stress in neural crest progenitors and their glial derivatives, causing DNA damage and p53 activation. Ablation of p53 rescued glial specification under these conditions. In vivo, hyperphosphorylation of p53 was also observed; however, deletion of p53 alleles in Lkb1 mutants did not restore enteric neurons number. Instead, it improved axonal fiber organization and partially rescued digestive tissue integrity. These findings establish LKB1 as a key metabolic regulator on both the development and maintenance of the ENS, suggesting that aberrant LKB1 signaling may contribute to human enteric glioneuropathies. HighlightsO_LILKB1 loss in enteric progenitors results in extensive hypoganglionosis and disrupts gut tissue homeostasis. C_LIO_LIDuring embryogenesis, LKB1 shapes enteric ganglia by sequentially regulating neuronal differentiation and preserving glial cells, partly by limiting oxidative stress and p53 activity. C_LIO_LIThese findings establish LKB1 as a critical regulator of neural crest cell formation, highlighting its multifaceted roles and potential pathological implications in digestive neuropathies. C_LI

developmental biology↗

bioRxiv2024

Early alterations of motor learning and corticostriatal network activity in a Huntington's disease mouse model

Huntingtons disease (HD) is a neurodegenerative disorder that presents motor, cognitive and psychiatric symptoms as it progresses. Prior to motor symptoms onset, alterations and dysfunctions in the corticostriatal projections have been described along with cognitive deficits, but the sequence of early defects of brain circuits is largely unknown. There is thus a crucial need to identify early alterations that precede symptoms and that could be used as potential early disease markers. Using an HD knock-In mouse model (HdhCAG140/+) that recapitulates the human genetic alterations and that show a late and progressive appearance of anatomical and behavior deficits, we identified early alterations in the motor learning abilities of young mice, long before any motor coordination defects. In parallel, ex vivo two-photon calcium recordings revealed that young HD mice have altered basal activity patterns in both dorsomedial and dorsolateral parts of the striatum. In addition, while wild-type mice display specific reorganization of the activity upon motor training, network alterations present in the basal state of non-trained mice are not affected by motor training of HD mice. Our results thus identify early behavioral deficits and network alterations that could serve as early markers of the disease.

neuroscience↗

bioRxiv2024

Somatostatin interneurons select dorsomedial striatal representations of the initial learning phase

The dorsomedial striatum (DMS) is an associative node involved in the adaptation of ongoing actions to the environmental context and in the initial formation of motor sequences. In early associative or motor learning phases, DMS activity shows a global decrease in neuron firing, eventually giving rise to a select group of active cells, whose number is correlated with animal performance. Unveiling how those representation emerge from DMS circuits is crucial for understanding plasticity mechanisms of early adjustments to learning a task. Here, we hypothesized that inhibitory microcircuits formed by local interneurons are responsible for the genesis of early DMS representation and associated task performance. Despite the low density of somatostatin (SOM)-positive cells, we observed that selective manipulation of SOM cells disrupted reorganization of DMS activity and modulated initial phases of learning in two behavioral contexts. This effect was cell-specific as manipulation of parvalbumin-positive interneurons had no significant effect. Finally, we identified the high plasticity of SOM innervation in the DMS as a key modulator of the SPN excitability and firing activity. Hence, SOM interneurons set the pace of early learning by actively controlling the remapping of DMS network activity.

neuroscience↗

bioRxiv2023

Sperm motility restoration in mice suffering from oligo-astheno-teratozoospermia by in vivo injection and electroporation of naked mRNA

Oligo-astheno-teratozoospermia (OAT), a recurent cause of male infertility, is the most frequent disorder of spermatogenesis with a probable genetic cause. Patients and mice bearing mutations in the ARMC2 gene have a decreased sperm concentration, and individual sperm show multiple morphological defects and a lack of motility - a canonical OAT phenotype. Intracytoplasmic sperm injection (ICSI) is required to treat such a condition but it is associated with a small increase in birth defects in comparison to pregnancies not involving assisted conception. Consequently, new targeted treatments are needed to restore fertility. Here, a combination of in vivo injection and electroporation of capped and poly-A-tailed naked mRNA is tested as a strategy to treat ARMC2-related infertility in mouse. mRNAs coding for several reporter genes are tested and the efficiency and the kinetic of expression are assessed using in vivo and in vitro 2D and 3D imaging experiments. We show that mRNA-coded reporter proteins are detected for up to 3 weeks in germ cells, making the use of mRNA possible to treat infertility. We compare these results with those obtained with a non-integrative plasmid Enhanced Episomal Vector (EEV), which induces low and transient expression in spermatogenic cells. Consequently, injection and electroporation of naked mRNA-Armc2 into the testes of Armc2-deficient males were performed and we show the presence of normal and motile sperm in the epididymis. These motile sperm were able to produce embryos by IVF and ICSI. This study demonstrates, for the first time, that mRNA electroporation can restore sperm motility and partially fertilizing ability, providing a proof-of-concept for mRNA-based strategies to correct monogenic causes of male infertility and opening new avenues for male infertility treatment.

molecular biology↗