Absence of somatic mosaicism in 17 families with hemophilia B: an analysis with a sensitivity 10- to 1000-fold greater than that of sequencing gels.
Most estimates of germ-line mosaicism have been derived from families in which there has been transmission of a mutated allele to two or more children by an unaffected individual. Previously, analyses for somatic mosaicism detected five such individuals by PCR-based sequencing and haplotype analysis at a sensitivity of approximately 1 mutant per 10 wild-type alleles. To determine whether mutations that occur later in embryogenesis also give rise to somatic mosaicism, we analyzed leukocyte DNA from 17 individuals in whom a mutation in the factor IX gene was known to have originated. Methods capable of detecting 1 mutant allele in 100-10,000 were utilized, and no further examples of somatic mosaicism were detected. If confirmed by future studies, the paucity of somatic mosaicism with mutant:wild-type allele frequencies ranging from 1:10 to 1:1000 (relative to the 11% of somatic mosaicism detected with mutant:wild-type allele frequencies of 1:1 to 1:10) may reflect a higher mutation rate and/or germ-line lineage allocation very early in embryogenesis.
Knöll
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Mayo Clinic/Foundation, Department of Biochemistry and Molecular Biology, Rochester, MN 55905, USA.
Ketterling
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RP
Sommer
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D000483:Alleles; D005260:Female; D002836:Hemophilia B / Q000196:embryology / Q000235:genetics*; D006801:Humans; D008297:Male; D009030:Mosaicism / Q000235:genetics*; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D015183:Restriction Mapping; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA; D013094:Spermatozoa