PRENATAL LETHALITY OF A HOMOZYGOUS NULL MUTATION IN THE HUMAN GLUCOCEREBROSIDASE GENE

The complete spectrum of clinical phenotypes resulting from glucocereb rosidase deficiency continues to evolve, While most patients with Gauc her disease have residual glucocerebrosidase activity, we describe a f etus with severe prenatal lethal type 2 (acute neuronopathic) Gaucher disease lacking glucocerebrosidase activity, This 22-week fetus was th e result of a first cousin marriage and had hydrops, external abnormal ities, hepatosplenomegaly, and Gaucher cells in several organs, Fetal fibroblast DNA was screened for common Gaucher mutations, none of whic h was detected, Southern blot analysis using the restriction enzymes S stII and SspI ruled out a fusion gene, deletion, or duplication of eit her allele, and quantitative studies of SspI digested genomic DNA indi cated that both alleles were present, Northern blot analysis of total RNA from fetal fibroblasts demonstrated no detectable transcription, a lthough RT-PCR successfully amplified several exons, suggesting the pr esence of a very unstable mRNA. Direct PCR sequencing of all exons dem onstrated a homozygous frameshift mutation (deletion of a C) on codon 139 in exon 5, thereby introducing a premature termination codon in ex on 6, The absence of glucocerebrosidase protein was confirmed by Weste rn analysis. This unique case confirms the essential role of glucocere brosidase in human development and, like the null allele Gaucher mouse , demonstrates the lethality of a homozygous null mutation, The presen ce of this novel mutation and the resulting unstable mRNA accounts for the severity of the phenotype observed in this fetus, and contributes to the understanding of genotype/ phenotype correlation in Gaucher di sease. (C) 1997 Wiley-Liss, Inc.