Expression of the gene for the neuronal intermediate filament protein alpha-internexin coincides with the onset of neuronal differentiation in the developing rat nervous system.
While neurofilaments have long been considered early markers of neuronal differentiation, they cannot be detected in most newly postmitotic neurons of the developing central nervous system (CNS). Here we show that these neurons already express the neuronal intermediate filament protein alpha-internexin at high levels. alpha-internexin is expressed by most, if not all, neurons as they begin differentiation and shows no overlap with vimentin, whose expression in the CNS is restricted to mitotic neuronal precursors. In the adult, alpha-internexin is the only intermediate filament gene expressed by the cerebellar granule cells, the source of the thin-caliber parallel fibers; conversely, neurofilament proteins are highly expressed in large neurons, which express alpha-internexin at low levels. These data suggest that neuronal intermediate filaments may regulate axonal stability and/or diameter through changes not only in their number, but also in their subunit composition.
Fliegner
K H
KH
Department of Pathology, Columbia University College of Physicians and Surgeons, New York, New York 10032.
Kaplan
M P
MP
Wood
T L
TL
Pintar
J E
JE
Liem
R K
RK
D000818:Animals; D001369:Axons / Q000502:physiology; D002352:Carrier Proteins / Q000096:biosynthesis* / Q000235:genetics; D002454:Cell Differentiation / Q000502:physiology; D005260:Female; D015870:Gene Expression / Q000502:physiology*; D006651:Histocytochemistry; D017403:In Situ Hybridization; D007381:Intermediate Filament Proteins / Q000096:biosynthesis* / Q000235:genetics; D009046:Motor Neurons / Q000378:metabolism; D009420:Nervous System / Q000166:cytology / Q000196:embryology* / Q000378:metabolism; D009474:Neurons / Q000502:physiology*; D011247:Pregnancy; D015347:RNA Probes; D012333:RNA, Messenger / Q000096:biosynthesis; D051381:Rats; D017207:Rats, Sprague-Dawley; D013462:Sulfur Radioisotopes; D014746:Vimentin / Q000096:biosynthesis / Q000235:genetics
D002352:Carrier Proteins; D007381:Intermediate Filament Proteins; D015347:RNA Probes; D012333:RNA, Messenger; D013462:Sulfur Radioisotopes; D014746:Vimentin; C046643:alpha-internexin