Progress toward a genotype/phenotype correlation in galactosemia
- Univ. of Southern California School of Medicine, Los Angeles, CA (United States)
Galactosemia is secondary to deficiency of the enzyme galactose-1-phosphate uridyl transferase (GALT). If untreated this condition results in severe neonatal symptoms and can be fatal. Most symptoms disappear upon the institution of a galactose-restricted diet. Therefore, most states in the US and many developed countries have implemented newborn screening programs for galactosemia. We have characterized thus far twelve disease-causing point mutations, four protein polymorphisms, one silent nucleotide substitution and a RFLP (restriction fragment length polymorphism) in over 200 patients. The most common galactosemia mutation, Q188R, is present on about 64% of Caucasian galactosemia alleles in the US. This mutation is present on 67% of {open_quotes}classic{close_quotes} Caucasian alleles with severe neonatal symptoms and undetectable crythrocytic GALT activity. Thus, Q188R almost defines the {open_quotes}classic{close_quotes} phenotype in Caucasian galactosemia patients. This mutation, however, is present on only 16% of the milder {open_quotes}variant{close_quotes} alleles and never in the homozygous state. Variant patients have up to 10% residual GALT activity in their red cells. Therefore, one or more as of yet uncharacterized mutations other than Q188R must be present in {open_quotes}variant{close_quotes} patients. The Q188R mutations is very rare in other ethnic and racial groups. Thus, Galactosemia is panethnic but the mutational basis of this disease differs among human populations. The frequency of Q188R is intermediate in Hispanic-American patients, probably reflecting the Spanish contribution to the gene pool in this population. We conclude that the Q188R mutation encodes the severe {open_quotes}classic{close_quotes}galactosemia phenotype in Caucasians and that other mutations produce the {open_quotes}variant{close_quotes} galactosemia phenotype.
- OSTI ID:
- 133434
- Report Number(s):
- CONF-941009-; ISSN 0002-9297; TRN: 95:005313-0162
- Journal Information:
- American Journal of Human Genetics, Vol. 55, Issue Suppl.3; Conference: 44. annual meeting of the American Society of Human Genetics, Montreal (Canada), 18-22 Oct 1994; Other Information: PBD: Sep 1994
- Country of Publication:
- United States
- Language:
- English
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