School of Medicine Publications and Presentations

Document Type

Article

Publication Date

9-2017

Abstract

Terrestrial opossums use their semiprehensile tail for grasping nesting materials as opposed to arboreal maneuvering. We relate the development of this adaptive behavior with ontogenetic changes in myosin heavy chain (MHC) isoform expression from 21 days to adulthood. Monodelphis domestica is expected to demonstrate a progressive ability to flex the distal tail up to age 7 mo, when it should exhibit routine nest construction. We hypothesize that juvenile stages (3-7 mo) will be characterized by retention of the neonatal isoform (MHC-Neo), along with predominant expression of fast MHC-2X and -2B, which will transition into greater MHC-1β and -2A isoform content as development progresses. This hypothesis was tested using Q-PCR to quantify and compare gene expression of each isoform with its protein content determined by gel electrophoresis and densitometry. These data were correlated with nesting activity in an age-matched sample of each age group studied. Shifts in regulation of MHC gene transcripts matched well with isoform expression. Notably, mRNA for MHC-Neo and -2B decrease, resulting in little-to-no isoform translation after age 7 mo, whereas mRNA for MHC-1β and -2A increase, and this corresponds with subtle increases in content for these isoforms into late adulthood. Despite the tail remaining intrinsically fast-contracting, a critical growth period for isoform transition is observed between 7 and 13 mo, correlating primarily with use of the tail during nesting activities. Functional transitions in MHC isoforms and fiber type properties may be associated with muscle "tuning" repetitive nest remodeling tasks requiring sustained contractions of the caudal flexors.

NEW & NOTEWORTHY Little is understood about skeletal muscle development as it pertains to tail prehensility in mammals. This study uses an integrative approach of relating both MHC gene and protein expression with behavioral and morphometric changes to reveal a predominant fast MHC expression with subtle isoform transitions in caudal muscle across ontogeny. The functional shifts observed are most notably correlated with increased tail grasping for nesting activities.

Comments

Copyright © 2017 the American Physiological Society. Original published version available at https://doi.org/10.1152/japplphysiol.00651.2016

Publication Title

Journal of Applied Physiology

DOI

10.1152/japplphysiol.00651.2016

Academic Level

faculty

Mentor/PI Department

Office of Human Genetics

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