Prenatal diagnosis of the isodicentric chromosome 22 associated with cat eye syndrome by multiplex ligation-dependent probe amplification

Cat eye syndrome (CES) is a very rare chromosomal syndrome characterized by various malformations such as anal atresia, preauricular malformation, coloboma of the iris, and congenial heart and renal defects. This genetic disorder is caused by partial duplication of chromosome 22, mostly as a result of a supernumerary isodicentric marker chromosome idic(22)(q11.2). Various congenital abnormalities and extreme phenotypic variability in CES patients have been reported, which have made prenatal diagnosis of CES difficult. We report the first case diagnosed with CES prenatally by multiplex ligation-dependent probe amplification in a woman who was referred to our hospital, for a fetus presenting with heart anomaly.

Carrier screening for (CGG)n repeat expansion of FMR1 gene in Korean women

PURPOSE: We examined the prevalence and CGG/AGG repeat structure of expanded alleles of the FMR1 gene in preconceptional and pregnant Korean women. MATERIALS AND METHODS: The CGG repeats in the FMR1 genes of 1,408 women were analyzed by polymerase chain reaction and Southern blot analysis. To estimate the prevalence of expansion alleles, the individuals were divided into low risk and high risk group. RESULTS: Within this population, 98.4% had normal alleles and 1.6% had abnormal alleles including intermediate (0.6%), premutation (0.5%), full mutation (0.1%), and hemizygous (0.4%) alleles. There were 2 premutation alleles (1:666, 95% confidence interval [CI] 1:250-1,776) in the low risk group and 5 premutation alleles (1:15, 95% 1:6-36) in the high risk group. There were 8 intermediate alleles (1:167, 95% CI 1:130-213) in the low risk group and 1 intermediate alleles (1:76, 95% CI 1:11-533) in the high group. Six of the 7 premutation alleles did not contain AGG interruptions within the repeats and 1 had a single AGG interruption. Four of the 9 intermediate alleles contained 2-3 AGG, 4 had a single AGG, and 1 had no AGG interruptions. CONCLUSION: Our study demonstrates the prevalence and CGG/AGG structure of expansion alleles in Korean women. The identified premutation prevalence is higher than that of other Asian populations and lower than that of Caucasian populations. Although our study is limited by size and population bias, our findings could prove useful for genetic counseling of preconceptional or pregnant women.

Pseudoisodicentric X chromosome in a female with primary amenorrhea

A 24-year-old female with primary amenorrhea was referred for a chromosome study. The karyotype of the patient was 46,X,der(X) under initial GTG-banding analysis. Fluorescence in situ hybridization (FISH) analysis with an LSI Kallmann (KAL) region probe [probes for Xp22.3(KAL) and CEP(X) for control] was carried out. The abnormal chromosome was KAL- and CEP(X)x2. In addition, interphase FISH analysis revealed the patient to be mosaic for two different cell lines: 90% of cells had three signals and 10% of the cells had only one signal for CEP(X). Based on these results, the karyotype of the patient was 45,X/46,X,psu idic(X)(p22.1), which is partial trisomy for Xqter-->Xp22.1 and partial monosomy for Xpter-->Xp22.1. This karyotype was considered a variant of Turner syndrome. In summary, Idic(X) and low-level mosaicism was successfully characterized by FISH analysis with a CEP(X) probe.

p53 Mutation and Functional Analyses by Using Yeast Functional Assay / 대한암학회지

PURPOSE: Mutation of the p53 tumor suppressor gene is the most common genetic defect in all human tumors. Because of the widespread mutations and polymorphism in the p53 gene, the conventional screening methods cannot distinguish between polymorphisms or functionally silent mutations and inactivating mutations. It is well known that plasmids can be generated by homologous recombination in vivo in the yeast by cotransforming the PCR product with a linearized yeast expression vector encoding part of a gene and a selectable marker gene. The aim of this study is to develop more easy and reliable method for functional assay of p53 mutation. MATERIALS AND METHODS: We constructed a gap vector which can reliably and conveniently be used to screen p53 mutations in a simple yeast growth assay. The gap vector was constructed as follows: About 100 bp DNA fragments containing parts of N- and C- terminal portion of p53 were cloned into XbaI/SmaI and HindIII/XhoI sites of yeast expressing vector, respectively. The gap vector was obtained by double cutting with SmaI and HindIII followed by gel elution. Yeast was transformed with the reporter vector containing three tandem copies of the consensus p53 binding site by lithium acetate-mediated method. RT-PCR amplification of p53 transcripts from cell lines or tumor tissues was carried out. To investigate whether p53 gene is mutated or not, yeast containing reporter gene was cotransformed with PCR product and linearized gap vector, plated on SD medium minus histidine, and incubated for 3 days. The colonies on selective media were isolated and characterized. RESULTS: The tumor tissues examined were one hepatocellular carcinoma, three breast cancers, two stomach cancers and two colon cancers. One hepatocellular carcinoma tissue had mutation in both alleles of the p53 gene, and 7 cancer tissues had heterozygous mutations in the p53 gene. The result of functional assay was well correlated with mutational analysis by sequencing. CONCLUSION: p53 functional assay system might be easy and reliable method for functional screening of p53 on tumor tissues and this might be used for screening of other mutated gene. This technique, FASAY, requires only a few steps, can be automated readily and should permit screening for germline or somatic heterozygous mutations in any gene whose function can be monitored in yeast.