title: Deficiency in APOBEC2 leads to a shift in muscle fiber type, diminished body mass, and myopathy.
abstract: The apoB RNA-editing enzyme, catalytic polypeptide-like (APOBEC) family of proteins includes APOBEC1, APOBEC3, and activation-induced deaminase, all of which are zinc-dependent cytidine deaminases active on polynucleotides and involved in RNA editing or DNA mutation. In contrast, the biochemical and physiological functions of APOBEC2, a muscle-specific member of the family, are unknown, although it has been speculated, like APOBEC1, to be an RNA-editing enzyme. Here, we show that, although expressed widely in striated muscle (with levels peaking late during myoblast differentiation), APOBEC2 is preferentially associated with slow-twitch muscle, with its abundance being considerably greater in soleus compared with gastrocnemius muscle and, within soleus muscle, in slow as opposed to fast muscle fibers. Its abundance also decreases following muscle denervation. We further show that APOBEC2-deficient mice harbor a markedly increased ratio of slow to fast fibers in soleus muscle and exhibit an approximately 15-20% reduction in body mass from birth onwards, with elderly mutant animals revealing clear histological evidence of a mild myopathy. Thus, APOBEC2 is essential for normal muscle development and maintenance of fiber-type ratios; although its molecular function remains to be identified, biochemical analyses do not especially argue for any role in RNA editing.
authors.affiliation: Department of Bioscience and Biotechnology, Graduate School of Agriculture, Kyushu University, Higashi-ku, Fukuoka 812-8581, Japan.
authors.forename: Yusuke
authors.initials: Y
authors.lastname: Sato
authors.forename: Hans Christian
authors.initials: HC
authors.lastname: Probst
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Tatsumi
authors.forename: Yoshihide
authors.initials: Y
authors.lastname: Ikeuchi
authors.forename: Michael S
authors.initials: MS
authors.lastname: Neuberger
authors.forename: Cristina
authors.initials: C
authors.lastname: Rada
mesh_terms: D000071478:APOBEC Deaminases; D000818:Animals; D001835:Body Weight; D002460:Cell Line; D003564:Cytidine Deaminase / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D003714:Denervation; D005260:Female; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018101:Mice, Inbred mdx; D018345:Mice, Knockout; D018656:Muscle Fibers, Fast-Twitch / Q000166:cytology / Q000378:metabolism*; D018657:Muscle Fibers, Slow-Twitch / Q000166:cytology / Q000378:metabolism*; D009124:Muscle Proteins / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D018482:Muscle, Skeletal / Q000166:cytology / Q000294:innervation / Q000378:metabolism; D009135:Muscular Diseases / Q000235:genetics* / Q000378:metabolism / Q000503:physiopathology; D055503:Protein Multimerization
chemical_list: D009124:Muscle Proteins; D000071478:APOBEC Deaminases; C485629:Apobec2 protein, mouse; D003564:Cytidine Deaminase