Childhood-onset schizophrenia/autistic disorder and t(1;7) reciprocal translocation: identification of a BAC contig spanning the translocation breakpoint at 7q21.

Childhood-onset schizophrenia (COS) is defined by the development of first psychotic symptoms by age 12. While recruiting patients with COS refractory to conventional treatments for a trial of atypical antipsychotic drugs, we discovered a unique case who has a familial t(1;7)(p22;q21) reciprocal translocation and onset of psychosis at age 9. The patient also has symptoms of autistic disorder, which are usually transient before the first psychotic episode among 40-50% of the childhood schizophrenics but has persisted in him even after the remission of psychosis. Cosegregating with the translocation, among the carriers in the family available for the study, are other significant psychopathologies, including alcohol/drug abuse, severe impulsivity, and paranoid personality and language delay. This case may provide a model for understanding the genetic basis of schizophrenia or autism. Here we report the progress toward characterization of genomic organization across the translocation breakpoint at 7q21. The polymorphic markers, D7S630/D7S492 and D7S2410/D7S646, immediately flanking the breakpoint, may be useful for further confirming the genetic linkage for schizophrenia or autism in this region. Am. J. Med. Genet. (Neuropsychiatr. Genet.) 96:749-753, 2000. Published 2000 Wiley-Liss, Inc.

Prenatal lethality of a homozygous null mutation in the human glucocerebrosidase gene.

The complete spectrum of clinical phenotypes resulting from glucocerebrosidase deficiency continues to evolve. While most patients with Gaucher disease have residual glucocerebrosidase activity, we describe a fetus with severe prenatal lethal type 2 (acute neuronopathic) Gaucher disease lacking glucocerebrosidase activity. This 22-week fetus was the result of a first cousin marriage and had hydrops, external abnormalities, hepatosplenomegaly, and Gaucher cells in several organs. Fetal fibroblast DNA was screened for common Gaucher mutations, none of which was detected. Southern blot analysis using the restriction enzymes SstII and SspI ruled out a fusion gene, deletion, or duplication of either allele, and quantitative studies of SspI digested genomic DNA indicated that both alleles were present. Northern blot analysis of total RNA from fetal fibroblasts demonstrated no detectable transcription, although RT-PCR successfully amplified several exons, suggesting the presence of a very unstable mRNA. Direct PCR sequencing of all exons demonstrated a homozygous frameshift mutation (deletion of a C) on codon 139 in exon 5, thereby introducing a premature termination codon in exon 6. The absence of glucocerebrosidase protein was confirmed by Western analysis. This unique case confirms the essential role of glucocerebrosidase in human development and, like the null allele Gaucher mouse, demonstrates the lethality of a homozygous null mutation. The presence 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 disease.