Project Number: Z01 HL 00011-02 LBG
Period Covered: July 1, 1975 through June 30, 1976.
Title of Project: The Development of Chick Embryo Retina
Names, Laboratory and Institute Affiliations, and Titles of Principal Investigations and All Other Professional Personnel Engaged on the Project:
PI: F.G. DeMello, Visiting Associate, LBG NHLI
Marshall Nirenberg, Chief, LBG, LBG NHLI
Cooperating Units (if any): None
Lab/Branch: Laboratory of Biochemical Genetics
Section: Section on Molecular Biology
Institute and Location: NHLI, NIH, Bethesda, Maryland 20014
Total Man Years: 1.2
Professional: 1.2
Other: 0
Summary of Work:  Some biochemical aspects of chick embryo retina differentiation were studied:  1) An alternate route for GABA synthesis was characterized in the retina; which depends upon the conversion of putrescine to GABA.   2) Glutamic acid decarboxylase specific activity in the retina, increased during the course of embryonic development, either when measured in ovo or in aggregate cultures.  3) The presence of GABA in the culture medium prevented the development of glutamic acid decarboxylase activity in aggregate cultures.   4) The proposed course of this project is to attempt to correlate the biochemical changes observed, with synaptogenesis in the retina.
Project Description:
Objectives:  The objective of the project is to study the biochemical step required for synaptogenesis in chick embryo retina.
Major Findings: Two pathways for gamma-aminobutyric acid synthesis were found in chick embryo retina.  The first pathway depends upon the conversion of putrescine to ornithine decarboxylase and the subsequent conversion of ornithing to gamma-aminobutyric acid.  The second route of synthesis is dependent upon the conversion of glutamic acid to gamma-aminobutyric acid, catalyzed by glutamic acid decarboxylase.  Elevation of cAMP levels in neuroblastoma cells was shown to induce ornithine decarboxplase activity.  Thus, in the developing embryo, neurotransmitters which affect cAMP levels may regulate ornithine decarboxylase activity and thereby control the rate of GABA synthesis from ornithine.
Proposed Course:  To determine the effect of retina neurotransmitters and other compounds on retina synaptogenesis.
Publications:
1.  DeMello, F. G., Bachrach, U. and Nirenberg, M.: Ornithine and glutamic acid decarboxylase activities in the developing retina.  J. Neurochem. In Press.