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Hoxa10 is a functional positional memory that governs stem cell function in adult skeletal muscle

ABSTRACT: Skeletal muscle is contractile tissue distributed throughout the body with functionally heterogeneous properties that may relate to region-specific pathophysiology of muscle diseases. Recent studies revealed that muscle stem cells (satellite cells) are a functional heterogeneous population in different muscles, dependent not only on fiber-types but also on embryonic origin. Homeobox (Hox) genes are key regulators of the embryonic body plan. Here, we showed that Hox-A cluster genes are robustly maintained in adult muscles and their associated satellite cells of both mice and humans in a body region-specific manner, whose distribution almost recapitulates their embryonic origin. The region-specific expression of Hox genes was linked to DNA hypermethylation status of Hox-A locus. Importantly, Hox gene expression is a functional memory; Hoxa10 inactivation in satellite cells led to genomic instability and mitotic catastrophe, resulting in a decline in the regionally specific regenerative ability of muscles in mice, even though Hox paralogs are known to be often functionally redundant. Thus, our results demonstrate that the topographic Hox gene expression profile could be a geotagging molecular signature that reflects the anatomical location and embryonic history of resident muscle stem cells, potentially contributing to regionally specific regulations of adult skeletal muscles.

ORGANISM(S): Mus musculus

PROVIDER: GSE154056 | GEO | 2021/04/16

REPOSITORIES: GEO

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Project description:Stimulation of the mouse hindlimb via the sciatic nerve was used to induce contractions for 4 hours to investigate acute muscle gene activation in a model of muscle phenotype conversion. Initial force production (1.6 + 0.1 g/g body weight) declined 45% within 10 min and was maintained for the remainder of the experiment. Force returned to initial levels upon completion of the study. An immediate-early growth response was present in the EDL (FOS, JUN, ATF3, MAFK) with a similar but attenuated pattern in the soleus. Transcript profiles showed decreased fast fiber specific mRNA (myosin heavy chains 2A, 2B; troponins T3, I; -tropomyosin, m-creatine kinase) and increased slow transcripts (myosin heavy chain slow/1, troponin C, tropomyosin 3) in the EDL. Histological analysis of the EDL revealed glycogen depletion without inflammatory cell infiltration or myofiber damage in stimulated vs. control muscles. Several fiber type specific transcription factors (EYA1, TEAD1, NFATc1 and c4, PPARG, PPARGC1 and β, BHLHB2) increased in the EDL along with transcription factors characteristic of embryogenesis (KLF4, SOX17, TCF15, PKNOX1, ELAV). No established in vivo satellite cell markers or the genes activated during our parallel studies of satellite cell proliferation in vitro (CYCLINS A2, B2, C, E1, MyoD) increased in the stimulated muscles. These data indicated that onset of fast to slow phenotype conversion occurred in the EDL within 4 hours of stimulation without satellite cell recruitment or muscle injury but was driven by phenotype specific transcription factors from resident fiber myonuclei including activation of nascent developmental transcriptional programs. Adult male Swiss Webster mice (30-35 g) were anesthetized, a bipolar electrode was implanted adjacent to the sciatic nerve and the hindlimb immobilized. The voltage-force relation was determined to establish supramaximal stimulation conditions and the length-tension relation was determined to set the resting length for maximum twitch tension. Contractions were induced by sciatic nerve stimulation (0.5 msec duration, 2-5 volts). The muscles were allowed to rest 15 minutes for full metabolic recovery at physiologic temperatures. Supramaximal stimulation was applied at a rate of 10 Hz for 4 hours. At the end of each experiment the soleus muscles were carefully dissected and flash frozen in liquid nitrogen for analysis of mRNA expression via microarray analysis. The contralateral, unstimulated Soleus provided a genetically matched, paired control for each specimen.

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Hoxa10 is a functional positional memory that governs stem cell function in adult skeletal muscle

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