"Rapid sizing of polymorphic microsatellite markers by capillary array electrophoresis"

Genetic mapping and DNA sequencing projects could potentially be completed more rapidly by using capillary array electrophoresis (CAE) systems running 48-96 capillaries simultaneously. Currently, multiplex polymerase chain reaction (PCR) and multicolor fluorescent dye-labeling strategies are used to generate DNA profiles containing 18-24 genotypes per sample. By using 4-color fluorescence detection and these multiplex PCR strategies, a CAE system has the capacity to generate up to 5.5 million genotypes per year. CAE offers extremely fast, high-resolution separation of DNA and more automated sample processing than conventional systems because the labor-intensive slab-gel pouring and sample-loading steps are eliminated. We used a prototype CAE system in an ongoing linkage analysis study of inherited deafness in Mediterranean families. CA-repeat markers linked to deafness susceptibility genes on chromosomes 7, 11 and 13 were analyzed and DNA profiles generated which contain 6 markers per color. Fragment sizes of over 28,000 short tandem repeat alleles and 3200 CA-repeat alleles have been determined by CAE. An average sizing precision of +/- 0.12 base pairs (bp) for fragments up to 350 bp was realized in 1-h runs. In addition, a versatile non-denaturing matrix was used to separate DNA sizing standards, restriction digests, and multiplex PCR samples. Application of this matrix to Duchenne muscular dystrophy exon deletion screening is also described. These CAE approaches should facilitate rapid genotyping of microsatellite markers and subsequent identification of disease-causing mutations

"Independent origins of cystic fibrosis mutations R334W, R347P, R1162X, and 3849+10KbC-T provide evidence of mutation recurrence in the CFTR gene."

Microsatellite analysis of chromosomes carrying particular cystic fibrosis mutations has shown different haplotypes in four cases: R334W, R347P, R1162X, and 3849 + 10kbC-->T. To investigate the possibility of recurrence of these mutations, analysis of intra- and extragenic markers flanking these mutations has been performed. Recurrence is the most plausible explanation, as it becomes necessary to postulate either double recombinations or single recombinations in conjunction with slippage at one or more microsatellite loci, to explain the combination of mutations and microsatellites if the mutations arose only once. Also in support of recurrence, mutations R334W, R347P, R1162X, and 3849 + 10kbC-->T involve CpG dinucleotides, which are known to have an increased mutation rate. Although only 15.7% of point mutations in the coding sequence of CFTR have occurred at CpG dinucleotides, approximately half of these CpG sites have mutated at least once. Specific nucleotide positions of the coding region of CFTR, distinct from CpG sequences, also seem to have a higher mutation rate, and so it is possible that the mutations observed are recurrent. G-->A transitions are the most common change found in those positions involved in more than one mutational event in CFTR