DEVELOPMENT OF A MODEL OF GLUTARIC ACIDEMIA

Glutaric acidemia (GA-I) is an inherited disorder of amino acid metabolism
that is characterized clinically by an extrapyramidal movement disorder in
childhood and pathologically by neuronal loss and gliosis in the caudate
and putamen. GA-I is caused by a deficiency of the enzyme glutaryl CoA
dehydrogenase (GCDH) and is one of few movement disorders whose genetic
basis is known. Over the past several years work in our center has led to
the isolation of the GCDH protein and cloning of human, murine and porcine
cDNAs. Work is ongoing to evaluate the phenotypic effects of specific
mutations in the human gene in patients with GA-I. As a means to further the understanding of the pathophysiologic mechanisms
involved in the development of the characteristic neuroanatomic and
clinical features of GA-I we propose to generate a mouse model of this
disease. Using the recently cloned murine cDNA we are now cloning the
murine GCDH gene in preparation for creating a targeting vector to
generate a null GCDH allele in embryonic stem (ES) cells via homologous
recombination. These mutated ES cells will then be used to generate a line
of mice that is heterozygous for the mutated GCDH allele. Subsequently,
these heterozygous animals will be used to evaluate the developmental
expression of GCDH using a marker gene which is incorporated into the
targeting vector. Such analysis will allow for a correlation of the
expression pattern of GCDH with the very characteristic neuropathology.
The heterozygous animals will also be crossed to generate animals
homozygous for the null GCDH allele. The homozygous animals will undergo
extensive biochemical, behavioral and neurochemical evaluation in order to
determine whether they are a good model of GA-I. If in fact they are a
model of GA-I, these animals can be used to test specific hypothesis
regarding pathophysiology and response to various treatment modalities.