Get access

Transcription and Motoneuron Size

Authors

  • Shoko Sato,

    1. Department of Physiology and Curriculum in Neurobiology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, U.S.A.
    Search for more papers by this author
    • The present address of Dr. S. Sato is Sugita Eye Hospital, Nagoya 460, Japan.

  • S. B. Burgess,

    1. Department of Physiology and Curriculum in Neurobiology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, U.S.A.
    Search for more papers by this author
  • D. L. McIlwain

    Corresponding author
    1. Department of Physiology and Curriculum in Neurobiology, University of North Carolina School of Medicine, Chapel Hill, North Carolina, U.S.A.
    Search for more papers by this author

Address correspondence and reprint requests to Dr. D. L. McIlwain at Department of Physiology, School of Medicine, University of North Carolina at Chapel Hill, Campus Box 7545, Chapel Hill, NC 27599, U.S.A.

Abstract

Abstract: Nuclear size and total RNA synthesis were compared in single lumbar motoneurons isolated from the grass frog. Transcription was found to correlate significantly, but not exclusively, with nuclear area or volume over a wide range of nuclear size, the largest nuclei having the highest mean transcriptional activity. Flow cytometric analysis of propidium iodide-stained nuclei excluded polyploidy or polyteny as an explanation for the increased transcription, but left open the possibility of a small increase in DNA with increasing nuclear size. Alternatively, motoneurons may increase transcription and nuclear size without increasing their DNA content, possibly by increasing the proportion of dispersed chromatin (euchromatin). These two mechanisms for size-related changes in RNA synthesis in motoneurons present an interesting contrast to mechanisms used by many other large animal cells.

Ancillary