NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
The G1 restriction point as critical regulator of neocortical neuronogenesisNeuronogenesis in the pseudostratified ventricular epithelium is the initial process in a succession of histogenetic events which give rise to the laminate neocortex. Here we review experimental findings in mouse which support the thesis that the restriction point of the G1 phase of the cell cycle is the critical point of regulation of the overall neuronogenetic process. The neuronogenetic interval in mouse spans 6 days. In the course of these 6 days the founder population and its progeny execute 11 cell cycles. With each successive cycle there is an increase in the fraction of postmitotic cells which leaves the cycle (the Q fraction) and also an increase in the length of the cell cycle due to an increase in the length of the G1 phase of the cycle. Q corresponds to the probability that postmitotic cells will exit the cycle at the restriction point of the G1 phase of the cell cycle. Q increases non-linearly, but the rate of change of Q with cycle (i.e., the first derivative) over the course of the neuronogenetic interval is a constant, k, which appears to be set principally by cell internal mechanisms which are species specific. Q also seems to be modulated, but at low amplitude, by a balance of mitogenic and antimitogenic influences acting from without the cell. We suggest that intracellular signal transduction systems control a general advance of Q during development and thereby determine the general developmental plan (i.e., cell number and laminar composition) of the neocortex and that external mitogens and anti-mitogens modulate this advance regionally and temporally and thereby produce regional modifications of the general plan.
Document ID
20040141975
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
External Source(s)
Authors
Caviness, V. S. Jr
(Massachusetts General Hospital, Harvard Medical School Boston 02114, United States)
Takahashi, T.
Nowakowski, R. S.
Date Acquired
August 22, 2013
Publication Date
April 1, 1999
Publication Information
Publication: Neurochemical research
Volume: 24
Issue: 4
ISSN: 0364-3190
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: NS33433
CONTRACT_GRANT: NS12005
Distribution Limits
Public
Copyright
Other
Keywords
NASA Discipline Cell Biology
Review, Tutorial
Non-NASA Center
Review

Available Downloads

There are no available downloads for this record.
No Preview Available