MOLECULAR HETEROGENEITY OF CLASSICAL AND DUARTE GALACTOSEMIA - MUTATION ANALYSIS BY DENATURING GRADIENT GEL-ELECTROPHORESIS

Classical galactosemia is caused by one common missense mutation (Q188 R) and by several rare mutations in the galactose-1-phosphate uridyltr ansferase (GALT) gene. The most common variant of GALT, the Duarte var iant, occurs as two types, Duarte-1 (D-1) and Duarte-2 (D-2), both of which carry the sequence change N314D. D-1 increases, whereas D-2 decr eases GALT activity. To study the molecular genetics of classical and Duarte galactosemia, we analyzed the GALT mutations in 30 families wit h classical galactosemia, in 10 families with the D-2 variant and in 3 individuals carrying the D-l allele by denaturing gradient gel electr ophoresis (DGGE). DGGE detected 59 of the 60 classical galactosemia al leles. Q188R accounted for 60%, K285N accounted for 28% of these allel es. Eight novel candidate galactosemia mutations were found. On all D- 2 alleles N314D occurred in cis with two intronic sequence changes, on the D-1 alleles in cis with a neutral mutation in exon 7. We conclude that the mutations causing galactosemia are highly heterogeneous and that K285N is a second common galactosemia mutation in our population. (C) 1997 Wiley-Liss, Inc.