Creatine transporter (SLC6A8) knockout mice exhibit reduced muscle performance, disrupted mitochondrial Ca homeostasis, and severe muscle atrophy.

Creatine (Cr) is essential for cellular energy homeostasis, particularly in muscle and brain tissues. Creatine Transporter Deficiency (CTD), an X-linked disorder caused by mutations in the SLC6A8 gene, disrupts Cr transport, leading to intellectual disability, speech delay, autism, epilepsy, and various non-neurological symptoms. In addition to neurological alterations, Creatine Transporter knockout (CrT) mice exhibit severe muscle atrophy and functional impairments.

The Mechanism of Modulation of Cardiac Force by Temperature.

In maximally Ca-activated demembranated fibres from the mammalian skeletal muscle, the depression of the force by lowering the temperature below the physiological level (~35 °C) is explained by the reduction of force in the myosin motor. Instead, cooling is reported to not affect the force per motor in Ca-activated cardiac trabeculae from the rat ventricle. Here, the mechanism of the cardiac performance depression by cooling is reinvestigated with fast sarcomere-level mechanics.

An integrated picture of the structural pathways controlling the heart performance.

The regulation of heart function is attributed to a dual filament mechanism: i) the Ca-dependent structural changes in the regulatory proteins of the thin, actin-containing filament making actin available for myosin motor attachment, and ii) the release of motors from their folded (OFF) state on the surface of the thick filament allowing them to attach and pull the actin filament. Thick filament mechanosensing is thought to control the number of motors switching ON in relation to the systolic performance, but its molecular basis is still controversial. Here, we use high spatial resolution X-ray diffraction data from electrically paced rat trabeculae and papillary muscles to provide a molecular explanation of the modulation of heart performance that calls for a revision of the mechanosensing hypothesis.

Sarcomere level mechanics of the fast skeletal muscle of the medaka fish larva.

The medaka fish () is a vertebrate model used in developmental biology and genetics. Here we explore its suitability as a model for investigating the molecular mechanisms of human myopathies caused by mutations in sarcomeric proteins. To this end, the relevant mechanical parameters of the intact skeletal muscle of wild-type medaka are determined using the transparent tail at larval stage 40.