Journal of Neuroscience, Vol 5, 1965-1971, Copyright © 1985 by Society for Neuroscience
Localized survival of ciliary ganglionic neurons identifies neuronotrophic factor bands on nitrocellulose blots
TB Carnow, M Manthorpe, GE Davis and S Varon
A novel and sensitive method has been developed to identify ciliary
neuronotrophic factors (CNTFs) from tissue extracts after blotting to
nitrocellulose paper. The CNTF proteins are required for the in vitro
survival of embryonic chick ciliary ganglionic neurons. Tissue extracts
containing such CNTFs are electrophoresed using sodium dodecyl sulfate-
polyacrylamide gel electrophoresis and transferred to nitrocellulose paper.
Purified ciliary ganglionic neurons are seeded on the surface of the
nitrocellulose blot, and the culture is incubated for 24 hr in medium
lacking CNTF. CNTF can be localized on the blot because it retains its
ability to support the survival of the neurons cultured on the
nitrocellulose. A band of viable neurons, easily visualized by staining
with a vital dye, is supported by the blotted CNTF polypeptide. The number
of neurons surviving on the blotted CNTF is related to the amount of CNTF
originally loaded on the electrophoretic gel. As little as 2 ng (16 trophic
units) of CNTF protein contained in crude tissue extracts can be loaded on
the sodium dodecyl sulfate gel and still be recognized by the cultured
neurons. This method was used to identify CNTF polypeptides from extracts
of adult rat nerve (24,000 and 19,000 daltons) and from tissue found near
experimentally induced adult rat brain lesions (24,000 daltons). The
electrophoretic mobilities of these peptides are distinct from the
previously purified chick eye CNTF polypeptide (20,400 daltons).