Evidence for association with schizophrenia has been reported for NOTCH4, although results have been inconsistent. Previous studies have focused on polymorphisms in the 5 0 promoter region and first exon of NOTCH4. Our aim was to test the association of the entire genomic region of NOTCH4 in 218 families with at least two siblings affected by schizophrenia in Taiwan. We genotyped seven single nucleotide polymorphisms (SNPs) of this gene, with average intermarker distances of 5.3 kb. Intermarker linkage disequilibrium (LD) was calculated using GOLD software, and single-locus and haplotype association analyses were performed using TRANSMIT software. We found that the T allele of SNP rs2071285 (P 5 0.035) and the G allele of SNP rs204993 (P 5 0.0097) were significantly preferentially transmitted to the affected individuals in the single-locus association analysis. The two SNPs were in high LD (D 0 > 0.8). Trend for overtransmission was shown for the T-G haplotype of the two SNPs to affected individuals (P 5 0.053), with the A-A haplotype significantly undertransmitted (P 5 0.034). The associated region distributed across the distal portion of the NOTCH4 gene and overlapped with the genomic region of the G-protein signaling modulator 3 and pre-B-cell leukemia transcription factor 2. In summary, we found modest association evidence between schizophrenia and the distal genomic region of NOTCH4 in this Taiwanese family sample. Further replication for association with the distal genomic region of NOTCH4 is warranted.

To study the variation in spontaneous mutation frequencies in dierent chromosomal domains, a mini-Mu-kan-lacZ A transposable element was constructed to insert the lacZ A (Trp570 ® Opal) allele into many dierent loci in the Escherichia coli chromosome. Papillation on MacConkey lactose plates was used to screen for mini-Mu insertion mutants with elevated levels of spontaneous mutagenesis of lacZop ® LacZ + ; candidates were then screened for normal mutation frequencies in other genes. Two dierent insertion mutants with this enhanced mutagenesis phenotype were isolated from 14 000 colonies, and named plm-1 (preferential lacZ mutagenesis) and plm-2. The frequency of LacZ A ® LacZ + mutations in these plm mutants was over 400-fold higher than that in isogenic strains containing mini-Mu-kan-lacZop insertions at other loci. Six Lac + reversion (or suppression) mutations obtained from each of the two plm mutants were mapped by P1 transduction and all were found to be linked to the Kan r gene in the mini-Mu-kan-lacZop, suggesting that a localized mutagenic event is responsible for the preferential mutagenesis. Furthermore, both the LacZ + ® Lac-Z A and Kan r ® Kan s mutant frequencies of these Lac + revertants were in the range of 10 A3 to 10 A2 , indicating that this putative localized mutagenesis is neither allele nor gene speci®c. To identify the plm loci, the chromosomal regions¯anking the mini-Mu insertion sites were cloned and sequenced. A computer-assisted database search of homologous sequences revealed that the plm-1 locus is identical to the mutS gene; the mini-Mu insertion most probably results in the production of a truncated MutS protein. We suggest that the enhanced lacZ mutation frequency in plm-1 may be associated with an active process involving the putative truncated MutS protein. The DNA sequence of the plm-2 locus matched a putative malate oxidoreductase gene located at 55.5 min of the E. coli chromosome.