This rough draft summarizing work completed in the Laboratory of Biochemical Genetics from 1987-1988 describes the latest
results from neuroblastoma research and the first year of work with Drosophila homeobox genes. The summary was authored as
part of a requirement for the justification of funding.
Item is a photocopy.
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2 (121,849 Bytes)
[Nirenberg, Marshall W.]
This item is in the public domain. It may be used without permission.
From Neuroblastoma to Homeobox Genes, 1976-1992
Annual Report of the Laboratory of Biochemical Genetics, October 1, 1987 - September 30, 1988 (September 1988)
Neuroblastoma and related lines of cultured cells were used as model systems for studies on synapse formation and other aspects
of neuronal development. Prolonged elevation of cyclic AMP levels of neuroblastoma cells has profound, long-lived, stimulatory
effects on the ability of the cells to form synapses and transmit information to other cells, which is due, in part, to the
appearance of functional voltage-sensitive calcium channels. cDNA and genomic DNA clones were obtained that correspond to
the alpha-subunit of L-type voltage-sensitive calcium channels of rat brain. In addition, seventeen cDNA clones were obtained
that correspond to species of RNA that increase in abundance when neuroblastoma-glioma hybrid cells are treated with dibutyryl
cAMP. Two of the cDNA clones were identified by nucleotide sequence analysis. Clone pNG-10 DNA corresponds to RNA transcribed
from the light strand of mitochondrial DNA that functions as an RNA primer needed for the initiation of synthesis of heavy
strand mitochondrial DNA. This species of RNA increases 40-fold in response to dibutyryl cAMP. Clone NG-32 DNA corresponds
to mRNA for ATP synthase subunit 6, which is transcribed from a heavy strand mitochondrial gene and codes for a protein that
is part of the H+ channel of the ATP synthase complex. This species of mRNA increases 8-fold in response to dibutyryl cAMP.
These results show that RNA transcripts from both light and heavy mitochondrial DNA strands increase in abundance when NG108-15
cells are treated with dibutyryl cAMP. The possibility that cAMP regulates the replication of mitochondrial DNA or the ability
of mitochondria to synthesize ATP are problems for future studies.
Four novel Drosophila homeobox genes were cloned and partially sequenced. The homeobox family of genes code for proteins
that regulate the expression of genes during development, and some Drosophila homeobox genes are known to regulate pathways
of differentiation. Three of the 4 new homeobox genes, NK-1, NK-3, and NK-4, were mapped to the 93 E region of the right
arm of the third chromosome. The fourth novel homeobox gene was mapped to the 2C region of the sex chromosome. The NK-1
gene is expressed in embryos 3 to 12 hours after fertilization. Nucleotide sequence analysis showed that the NK-1 gene has
3 exons, and that 1 of the 2 introns detected resides within the homeobox region. These genes provide an experimental system
that can be used to define the mechanisms that regulate the expression of these homeobox genes as well as the regulatory effects
of the homeobox protein products on the expression of other genes.