Disease relevance of Myo6

• Mutations of the unconventional myosins genes encoding myosin VI, myosin VIIA and myosin XV cause hearing loss and thus these motor proteins perform fundamental functions in the auditory system [1].
• 129/Sv x C57BL/6 mice with targeted deletion of the SAP gene spontaneously develop antinuclear autoantibodies and immune complex glomerulonephritis [2].
• SAP-deficient animals, created by backcrossing the 129/Sv SAP gene deletion into pure line C57BL/6 mice and studied here for the first time, also spontaneously developed broad spectrum antinuclear autoimmunity and proliferative immune complex glomerulonephritis but without proteinuria, renal failure, or increased morbidity or mortality [2].

High impact information on Myo6

• We show that sv encodes an unconventional myosin heavy chain, myosin VI, which is expressed within the sensory hair cells of the inner ear, and appears to be required for maintaining their structural integrity [3].
• Similar defects in basal synaptic transmission as well as presynaptic properties were observed in Myo6 and GIPC1 mutant mice [4].
• These results suggest that Myo6 plays a role in the clathrin-mediated endocytosis of AMPARs, and that its loss leads to alterations in synaptic structure and astrogliosis [5].
• Similarly, cultured sv/sv hippocampal neurons display decreased numbers of synapses and dendritic spines, and dominant-negative disruption of Myo6 in wild-type hippocampal neurons induces synapse loss [5].
• A role for myosin VI in postsynaptic structure and glutamate receptor endocytosis [5].

Biological context of Myo6

• These defects occur in a strain-independent manner, since neither rescue of the placental phenotype by aggregation of diploid 129/Sv EGFR mutant and tetraploid wild-type embryos, nor promotion of lung maturation by transplacental dexamethasone administration alters the course of neurodegeneration [6].
• Alternatively, the autoimmunity may be independent of SAP deficiency and caused by expression of 129/Sv chromosome 1 genes in the C57BL/6 background [2].
• Our results indicate that myosin VI is required in photoreceptor cells for normal retinal electrophysiology [7].

Anatomical context of Myo6

• Myo6-deficient (Snell's waltzer; sv/sv) hippocampus exhibits a decrease in synapse number, abnormally short dendritic spines, and profound astrogliosis [5].
• Whereas mutations in Myo6 cause inner-ear abnormalities in mice, as yet no human deafness has been found to the result of mutations in MYO6 [8].
• Myo6 participates in two steps of endocytic trafficking; it is recruited to both clathrin-coated pits and to ensuing uncoated endocytic vesicles (UCV) [9].
• Rescue experiments showed that fully functional myosin VI was able to restore Golgi complex morphology and protein secretion in Snell's waltzer cells to the same level as that observed in wild-type cells [10].
• In these cell lines, where myosin VI is absent, the Golgi complex is reduced in size by approximately 40% compared with wild-type cells [10].

Associations of Myo6 with chemical compounds

• The cells expressed several characteristic features of normal hair cells, including the transcription factor Brn3.1, a functional acetylcholine receptor composed of alpha9 subunits, and the cytoskeletal proteins myosin VI, myosin VIIa, and fimbrin [11].

References