[Cytogenetic analysis of childhood acute lymphoblastic leukemia].

OBJECTIVE: To characterize the genetic aberrations in pediatric acute lymphoblastic leukemia (ALL). METHODS: Ninety ALL cases were enrolled in the study from January 2009 to November 2011. Chromosome banding analysis and fluorescence in situ hybridization (FISH) were used to detect genetic aberrations. RESULTS: (1) Chromosome analysis: 35 (53.0%) of 66 cases who had metaphase were abnormal, and 24 cases had no metaphase. (2) FISH analysis: among the 31 cases who had normal karyotypes and 24 who had no metaphase detected by chromosome banding technique, 7 (22.6%) and 14 (58.3%) cases were abnormal detected by FISH, respectively. There were no statistically significant differences compared with chromosome analysis (P = 0.655). Among these 55 ALL cases TEL/AML1, bcr-abl and MLL fusion genes were observed in 16 (29.1%), 3(5.5%) and 2(3.6%) cases, respectively. (3) Cytogenetic aberration was observed in 56 of total 90 ALL cases (62.2%). CONCLUSIONS: Cytogenetic changes are common in childhood ALL. Conventional cytogenetic study could reliably detected chromosomal abnormalities for ALL with assessable metaphase. FISH should be used as a complementary method for ALL patients who have poor chromosomal morphology or no metaphase cells, and combination of both methods can improve the detection rate of genetic abnormalities in childhood leukemia.

Detecting 22q11.2 deletion in Chinese children with conotruncal heart defects and single nucleotide polymorphisms in the haploid TBX1 locus.

BACKGROUND: Conotruncal heart defects (CTDs) are present in 75-85% of patients suffering from the 22q11.2 deletion syndrome. To date, no consistent phenotype has been consistently correlated with the 22q11.2 deletions. Genetic studies have implicated TBX1 as a critical gene in the pathogenesis of the syndrome. The aim of study was to determine the incidence of the 22q11.2 deletion in Chinese patients with CTDs and the possible mechanism for pathogenesis of CTDs. METHODS: We enrolled 212 patients with CTDs and 139 unrelated healthy controls. Both karyotypic analysis and multiplex ligation-dependent probe amplification were performed for all CTDs patients. Fluorescence in situ hybridization was performed for the patients with genetic deletions and their relatives. The TBX1 gene was sequenced for all patients and healthy controls. The χ2 and Fisher's exact test were used in the statistical analysis. RESULTS: Thirteen of the 212 patients with CTDs (6.13%) were found to have the 22q11.2 deletion syndrome. Of the 13 cases, 11 presented with a hemizygous interstitial microdeletion from CLTCL1 to LZTR1; one presented with a regional deletion from CLTCL1 to DRCR8; and one presented with a regional deletion from CDC45L to LZTR1. There were eight sequence variants in the haploid TBX1 genes of the del22q11 CTDs patients. The frequency of one single nucleotide polymorphism (SNP) in the del22q11 patients was different from that of the non-del patients (P < 0.05), and the frequencies of two other SNPs were different between the non-del CTDs patients and controls (P < 0.05). CONCLUSIONS: CTDs, especially pulmonary atresia with ventricular septal defect and tetralogy of Fallot, are the most common disorders associated with the 22q11.2 deletion syndrome. Those patients with both CTDs and 22q11.2 deletion generally have a typical or atypical deletion region within the TBX1 gene. Our results indicate that TBX1 genetic variants may be associated with CTDs.