Identification of new disease genes in xxxxcbskhvks：在xxxxcbskhvks新的疾病基因的鉴定.ppt

Gene identification in the “post-genomic” era:Microdeletion detection by whole genome array CGH Miranda Durkie 2009 Array CGH Hybridisation of patient and reference DNA (usually sex-matched) differentially labelled with 2 fluorophores DNA target sequences can be BACs, oligos, cDNA or SNPs Initial resolution for genome scan ~500kb-1Mb but tiling resolution (overlapping probes) commonly ~50-100kb but can be as low as 100bp Useful for detection of sub-microscopic microdeletions/microduplications Cannot detect balanced translocations No positional data Microdeletions/microduplications Microdeletion syndromes are due to haploinsufficiency for single genes e.g. RAI1 gene in Smith-Magenis syndrome (del 17p11.2) or UBE3A gene in Angelman Syndrome Microduplications can have novel effect e.g. PMP22 dup = CMT1A but PMP22 del = HNPP Or microduplications can have same effect as microdeletions e.g. HNPCC/FAP Can be gene dependant or population dependant e.g. Sotos syndrome – majority Caucasians have point mutations but majority Japanese have microdeletions Example of use of array CGH to identify new disease gene Vissers et al 2004 used a 1Mb BAC array to screen 2 individuals with CHARGE syndrome against normal reference DNA CHARGE = Coloboma, Heart defects, choanal Atresia, Retarded growth/development, Genital hypoplasia, Ear anomalies deafness (Sporadic malformation syndrome) Found ~5Mb deletion (3 clones) 8p12 in 1 individual with severe mental retardation Used BAC chrom 8 tiling array to further characterise region to 4.8Mb with 31 overlapping deleted clones CHARGE cont. 2nd individual with apparently balanced chrom 8 translocation also had 2 microdeletions on tiling array 1 overlapped with 1st case by 6 deleted clones Used FISH to confirm deletions Defined smallest region as 2.3Mb Screened 17 additional individuals with CHARGE using chrom 8 tiling array No additional copy number changes detected Array results a = 1Mb array CGH b = chrom 8 tiling array Search for c