Maternal DNA Analysis IDs Fetal Gene Microdeletions

Noninvasive analysis of maternal plasma DNA can identify fetal chromosomal microdeletion

WEDNESDAY, Nov. 9 (HealthDay News) -- Fetal chromosomal microdeletion can be identified by noninvasive analysis of maternal plasma DNA, according to a letter published in the Nov. 10 issue of the New England Journal of Medicine.

David Peters, Ph.D., from the University of Pittsburgh Medical Center, and colleagues assessed whether maternal plasma DNA analysis has the potential for noninvasive diagnosis of common fetal aneuploidies in a couple presenting for prenatal genetic counseling. The couple previously had a child with developmental delay and dysmorphic features in whom a paternally inherited 4.2-Mb deletion on chromosome 12 between bands 12p11.22 and 12p12.1 was diagnosed. The same heterozygous deletion in the male fetus was detected, based on amniocentesis at week 21 of gestation and microarray-based comparative genomic hybridization. Plasma DNA was extracted without further enrichment from a maternal blood sample at 35 weeks of gestation. Reference libraries were made by sequencing seven maternal plasma samples in which both the mother and fetus had known diploid chromosomes 12 and 14. A pair-wise comparison was made with each of the reference libraries to determine whether the maternal sample (PL565) was diploid in each of 22 nonoverlapping 4-Mb regions on chromosomes 12 and 14.

The investigators found that all seven pair-wise comparisons with the reference libraries showed a 4-Mb depletion in DNA copy number on chromosome 12p in PL565. All seven pair-wise comparisons showed nonsignificant adjusted P values for all other 21 regions tested.

"We have shown proof of concept that a fetal chromosomal microdeletion can be identified by means of noninvasive analysis of DNA in maternal plasma," the authors write.

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