Array-based comparative genomic hybridization in 190 Korean patients with developmental delay and/or intellectual disability: a single tertiary care university center study.

PURPOSE: This study analyzed and evaluated the demographic, clinical, and cytogenetic data [G-banded karyotyping and array-based comparative genomic hybridization (array CGH)] of patients with unexplained developmental delay or intellectual disability at a single Korean institution. MATERIALS AND METHODS: We collected clinical and cytogenetic data based on retrospective charts at Ajou University Medical Center, Suwon, Korea from April 2008 to March 2012. RESULTS: A total of 190 patients were identified. Mean age was 5.1±1.87 years. Array CGH yielded abnormal results in 26 of 190 patients (13.7%). Copy number losses were about two-fold more frequent than gains. A total of 61.5% of all patients had copy number losses. The most common deletion disorders included 22q11.2 deletion syndrome, 15q11.2q12 deletion and 18q deletion syndrome. Copy number gains were identified in 34.6% of patients, and common diseases among these included Potocki-Lupski syndrome, 15q11-13 duplication syndrome and duplication 22q. Abnormal karyotype with normal array CGH results was exhibited in 2.6% of patients; theses included balanced translocation (n=2), inversion (n=2) and low-level mosaicism (n=1). Facial abnormalities (p<0.001) and failure to thrive were (p<0.001) also more frequent in the group of patients with abnormal CGH findings. CONCLUSION: Array CGH is a useful diagnostic tool in clinical settings in patients with developmental delay or intellectual disability combined with facial abnormalities or failure to thrive.

Mutation spectrum of NF1 and clinical characteristics in 78 Korean patients with neurofibromatosis type 1.

Neurofibromatosis type 1 (NF1) is one of the most common autosomal dominant disorders in humans. NF1 is caused by mutations of the NF1 gene. Mutation detection is complex owing to the large size of the NF1 gene, the presence of pseudogenes, and the great variety of mutations. Also, few probable genotype-phenotype correlations have been found in NF1. In this study 78 Korean patients from 60 families were screened for NF1 mutations. Mutation analysis of the entire coding region and flanking splice sites was carried out and included the use of a combination of reverse transcription polymerase chain reaction, multiplex ligation probe amplification, or fluorescence in situ hybridization. Mutation spectrum and genotype-phenotype relationship were assessed. Fifty-two distinct NF1 mutations were identified in 60 families. The mutations included 30 single base substitutions (12 missense and 18 nonsense), 11 missplicing mutations, seven small insertion or deletions, and four gross deletions. Sixteen (30.8%) mutations were novel; c.1A>G, c.2033_2034insC, c.2540T>C, c.4537C>T, c.5546G>A, c.6792C>A, and c.6792C>G were recurrently identified. The mutations were evenly distributed across exon 1 through intron 47 of NF1, and no mutational hot spots were found. A genotype-phenotype analysis suggests that there is no clear relationship between specific mutations and clinical features. This analysis revealed a wide spectrum of NF1 mutations in Korean patients. As technologies advance in molecular genetics, the mutation detection rate will increase. Considering that 30.8% of detected mutations were novel, exhaustive mutation analysis of NF1 may be an important tool in early diagnosis and genetic counseling.

Mutation spectrum of the TYR and SLC45A2 genes in patients with oculocutaneous albinism.

Oculocutaneous albinism (OCA) is a group of inherited disorders characterized by defective melanin biosynthesis. OCA1, the most common and severe form, is caused by mutations in the tyrosinase (TYR) gene. OCA4, caused by mutations in the SLC45A2 gene, has frequently been reported in the Japanese population. To determine the mutational spectrum in Korean OCA patients, 12 patients were recruited. The samples were first screened for TYR mutations, and negative samples were screened for SLC45A2 mutations. OCA1 was confirmed in 8 of 12 (66.7%) patients, and OCA4 was diagnosed in 1 (8.3%) patient. In the OCA1 patients, a total of 6 distinct TYR mutations were found in 15 of 16 (93.8%) alleles, all of which had been previously reported. Out of the 6 alleles, c.929insC was the most frequently detected (31.3%), and was mainly associated with OCA1A phenotypes. Other TYR mutations identified included c.1037-7T>A/c.1037-10delTT, p.D383N, p.R77Q and p.R299H. These largely overlapped with mutations found in Japanese and Chinese patients. The SLC45A2 gene analysis identified 1 novel mutation, p.D93N, in 1 patient. This study has provided information on the mutation spectrum in Korean OCA patients, and allows us to estimate the relative frequencies of OCA1 and OCA4 in Korea.

Chromosomal Alterations in Hepatocellular Carcinoma Cell Lines Detected by Comparative Genomic Hybridization.

PURPOSE: There have only been a few cytogenetic studies of hepatocellular carcinoma (HCC), and so far, no consistent specific chromosomal abnormalities have been described. Here, we have used comparative genomic hybridization (CGH), a powerful molecular cytogenetic technique for detecting changes of the copy number throughout the genome, to screen for genetic alterations in HCC cell lines. The CGH results were compared with those derived from G-banding and chromosome painting. MATERIALS AND METGODS: Conventional cytogenetic analyses were performed on five HCC cell lines, SNU-354, SNU-368, SNU-387, SNU-449 and SNU-475, using a G- banding staining technique. In CGH, equal amounts of differently labeled DNA from the cell lines, and normal reference DNA, were hybridized simultaneously to normal metaphase chromosomes. They were visualized by different fluorochromes, and the signal intensities quantified separately as gray levels along the single chromosomes. The over- and under-represented DNA segments were determined by computation of ratio images and average ratio profiles. To confirm the CGH results, florescence in situ hybridization (FISH), with chromosome specific painting, was performed using indirectly labeled chromosome specific paints. RESULTS: Complex unbalanced chromosomal aberrations, which could not be identified reliably by conventional cytogenetics in HCC cell lines, were successfully resolved by CGH analysis. CGH results were validated using FISH with chromosome specific probes. In HCC cell lines, gains in DNA copy number were more common than losses. The most prominent changes were gains of 1q12- qter (80% of cases), 1q41-qter (100%), 7 (80%), 8q12-qter (60%), 8q23-qter (80%) and 20q12-qter (60%). Recurrent losses were mapped on 4q13-qter (60%), 16q12-qter (60%), 16q21-qter (80%), 13q12-q14.2 (60%) and Yq11.2 (100%). All four male HCC cell lines showed loss or rearrangement of the Y chromosome. CONCLUSION: Conventional cytogenetics, CGH and FISH using painting probes, represent complementary approaches that, when employed in combination, could greatly facilitate the comprehensive analysis of chromosomal imbalances in HCC cell lines. Our results suggest the existence of an oncogene, or protooncogenes, on chromosome 1q41-qter, and the tumor suppressor genes on Yq11.2, that play a role in the development and/or progression of hepatocellular carcinogenesis.