The Research About Copy Number Variations Associated With Mental Retardation/Brain Development Retardation

ObjectiveThe cause of mental retardation/brain development retardation (MR/BDR) is complication,between 65% and 80% for unknown reasons, while,the routine clinical test, such as karyotyping, multiplex ligation-dependent probe amplification (MLPA) and fluorescent in situ hybridization (FISH) cannot fine mapping the region of copy number variations (CNVs),and it is difficult to get a definitive diagnosis only to rely on phenotype as well as to analysis the relationship between phenotype and genotype, which is disadvantage to study genetic disease in-depth continuously, also for a challenge to afford a genetic counsel. Using array-based single nucleotide polymorphisms comparative genomic hybridization (SNP-aCGH) to detect and fine mapping CNVs in children with unexplained MR/BDR or angelman syndrome (AS) then analysing the CNVs to find pathogenic region or disease candidate gene, to clear genetic diagnosis and afford genetic counseling, finally to discuss the application of SNP -aCGH in genetic diagnosis about MR/BDR.MethodsPART ??To recruit 92children with unexplained MR/BDR. ?Using SNP-aCGH to get CNVs from the whole genome-wide,to analysis the correlation of CNVs and phenotype, try to definit disease genes or pathogenic fragment. ?Applying statistics to analysis the common phenotype between positive case (case with CNVs) and negative case.PART ??To recruit 11 children whose manifestation meets international standard about Angelman syndrome.?Arranging examination of Electroencephalogram (EEG) and Intelligence Quotient (IQ) evaluation for 11 cases diagnosed as Angelman syndrome clinically. Gesell scares is chosen as the evaluation criterion of IQ. The screening techniques was methylation PCR (MS-PCR), Then SNP-aCGH was used to make genetic diagonosis and analysis the correlation about phenotype and genotype.ResultPART ? ?The CNVs were detected in 10 cases with a detection rate of 10.86%, from which, the cases with subtelomeric aberration were 8, without subtelomeric aberrationwere 5, rate was 8.7%,5.4% respectively. The CNVs relate with MR/BDR involved 10different subtelomeric regions (9p,21q,3p,2p,15q,4p,12p,22q,16p,17p), and 7 different regions without subtelomeric (1p,4q,2p,14q,15q,12q,22q). The deletions involved 11 zones (size:1.05 Mb-8.8Mb), and duplications refer to 8 zones(size:1.33 Mb-31.25 Mb).?Diagnosed a case of 9P duplication syndrome, for candidate genes: DOCK8, VLDLR. A case detected with a gene fracture (CRBN). A cases was diagnosed with Coffin-Siris syndrome combined with a deletion of 15q26.3-qter, for candidate genes:SOX11 and LZMS1,repectively. A case about 12p13.3 deletion syndrome, for candidate genes:ELKS, ERC1. A case diagnosed as 22q13 deletion syndrome, for candidate genes:SHANK3. Two cases diagnosed as ATR-16 syndrome with 17p13.3 deletion syndrome, their candidate genes:SOX8 for the former, LIS1, YWHAE for the latter.? It was statistically significant (p<0.05) to compare positive cases with the negatives about growth delay, internal organs deformity, low birth weight infant (LBW) and premature infant.PART ? ?11 cases of AS was confirmed, for detail:1 case was UPD (uniparental disomy),10 cases were type of deletion, from which 6 cases were deletion(?),4 cases were deletion(?).?The copy number variations was detected in the region of 15q 11-q 13, which contains genes as MKRN3, MAGEL2, NDN,SNRPN,SNURF,GABRB3,GABRA5,GABRG3,UBE3A, OCA2, ATP10A.To search OMIM (Online Mendelian Inheritance In man), genes above were correlated to AS manifestation.?All cases of deletion were 3-5 standard deviation (SD) in weight and hight to normal children with same age and sex, while UPD was below 1.5 SD. Gesell scares shows that the deletion (?) was the most serious in MR, deletion (?) was moderate, and the UPD was mild. EEG reveals that 1 case of deletion (?) and the UPD were spike occasionally, another one deletion (?) was limit electroencephalogram. The rest cases displayed slow and spike waves paroxysmally with amplitude of medium or high,2.5-3.0HZ.8 cases are hypopigmentation, for one was the UPD.Conclusions?PART I:All the positive cases perform not only MR/BDR in different degrees, but growth delay, most of them with internal organs deformity, low birth weight infant and premature infant.subtelomeric aberrations is related to MR/BDR, while, the submicroscopic rearrangement in regions without subtelomeric are suspicious to be pathogenic, need to be further studied.?PART ?:manifestation of the deletion is more serious than UPD,and the deletion(?), more serious than deletion(?).?SNP-aCGH can fine mapping the region of CNVs by high resolution from the whole genome-wide, which do contribute to limit the zones for finding pathogenic region and candidate genes, as well as to afford a technology platform for investigating about the correlation of phenotype and genotype.