Biology subjects

Guiraud, A.

Publications and source records attributed to Guiraud, A..

3 recordsLinked to original sources

bioRxiv2021

The myotendinous junction marker collagen XXII enables zebrafish postural control learning and optimal swimming performance through its force transmission activity

Although the myotendinous junction (MTJ) is essential for skeletal muscle integrity, its contribution to skeletal muscle function remains largely unknown. Here, we show that CRISPR-Cas9-mediated gene ablation of the MTJ marker col22a1 in zebrafish identifies two distinctive phenotypic classes: class 1 individuals reach adulthood with no overt muscle phenotype while class 2 display severe movement impairment and eventually dye before metamorphosis. Yet mutants that are unequally affected are all found to display defective force transmission attributed to a loss of ultrastructural integrity of the MTJ and myosepta, though with distinct degrees of severity. The behavior-related consequences of the resulting muscle weakness similarly reveal variable phenotypic expressivity. Movement impairment at the critical stage of swimming postural learning eventually causes class 2 larval death by compromising food intake while intensive exercise is required to uncover a decline in muscle performance in class 1 adults. By confronting MTJ gene expression compensation and structural, functional and behavioral insights of MTJ dysfunction, our work unravels variable expressivity of col22a1 mutant phenotype. This study also underscores COL22A1 as a candidate gene for myopathies associated with dysfunctional force transmission and anticipates a phenotypically heterogeneous disease.

developmental biology↗

bioRxiv2020

SH3KBP1 scaffolds endoplasmic reticulum and controls skeletal myofibers architecture and integrity

The building block of skeletal muscle is the multinucleated muscle fiber, formed by the fusion of hundreds of mononucleated precursor cells, myoblasts. In the normal course of muscle fiber development or regeneration, myonuclei are actively positioned throughout muscular development and adopt special localization in mature fibers: regular spacing along muscle fibers periphery, raising the notion of MyoNuclear Domains (MNDs). There is now growing support for a direct connection between myonuclear positioning and normal function of muscles, but how myonuclei affects muscle function remains poorly characterized. To identify new factors regulating forces applied on myonuclei in muscles fibers, we performed a siRNA screen and identified SH3KBP1 as a new factor controlling myonuclear positioning in early phases of myofibers formation. Depletion of SH3KBP1 induces a reset of MNDs establishment in mature fibers reflected by a dramatic reduction in pairwise distance between myonuclei. We show that SH3KBP1 scaffolds Endoplasmic Reticulum (ER) in myotubes that in turn controls myonuclei velocity and localization and thus myonuclear domains settings. Additionally, we show that in later phases of muscle maturation, SH3KBP1 contributes to the formation and maintenance of Sarcoplasmic Reticulum (SR) and Transverse-tubules (T-tubules). We also demonstrate that in muscle fibers, GTPase dynamin-2 (DNM2) binds to SH3 domains of SH3KBP1. Interestingly, we observed that Sh3kbp1 mRNA is up regulated in a mouse model harboring the most frequent mutation for Autosomal Dominant CentroNuclear Myopathy (AD-CNM): Dnm2+/R465W. SH3KBP1 thus appears as a compensation mechanism in this CNM model since its depletion contributes to an increase of CNM-like phenotypes (reduction of muscle fibers Cross-section Areas (CSA) and increase in slow fibers content). Altogether our results identify SH3KBP1 as a new regulator of myonuclear domains establishment in the early phase of muscle fibers formation through ER scaffolding and later in myofibers integrity through T-tubules scaffolding/maintenance. SummaryMyonuclei are actively positioned throughout muscular development. Guiraud, Christin, Couturier et al show that SH3KBP1 scaffolds the ER through Calnexin interaction and controls myonuclei motion during early steps of muscle fibers formation. Besides SH3KBP1 participates in cell fusion and T-tubules formation/maintenance in mature skeletal muscle fibers and contributes to slow-down CNM-like phenotypes.

cell biology↗

bioRxiv2019

Muscle MACF1 maintains myonuclei and mitochondria localization through microtubules to control muscle functionalities

Skeletal muscle is made from multinuclear myofiber, where myonuclei are positioned at the periphery or clustered below neuromuscular junctions (NMJs). While mispositioned myonuclei are the hallmark of numerous muscular diseases, the molecular machinery maintaining myonuclei positioning in mature muscle is still unknown. Here, we identified microtubule-associated protein MACF1 as an evolutionary conserved regulator of myonuclei positioning, in vitro and in vivo, controlling the \"microtubule code\" and stabilizing the microtubule dynamics during myofibers maturation, preferentially at NMJs. Specifically, MACF1 governs myonuclei motion, mitochondria positioning and structure and acetylcholine receptors (AChRs) clustering. Macf1-KO in young and adult mice decreases muscle excitability and causes evolutionary myonuclei positioning alterations in adult mice, paralleled with high mitochondria content and improved resistance to fatigue. We present MACF1 as a primary actor of the maintenance of synaptic myonuclei and AChRs clustering, peripheral myonuclei positioning and mitochondria organization through the control of microtubule network dynamics in muscle fibers.

cell biology↗