Use of X-linked short tandem repeats loci to confirm mutations in parentage caseworks.
BACKGROUND
Analysis of short tandem repeats (STRs) has become wide-spread in routine for parentage test. However, the accuracy of STR is sometimes interfered by the presence of microsatellite mutations. Analysis of other DNA markers such as the HV1 and HV2 hypervariable regions of mitochondrial DNA or the Y-STR becomes essential to settle the noncongruence. Owing to the time-consuming nature of these tests, we explored here the use of X-chromosome STR (X-STR) to resolve the paternity and maternity disputes.


METHODS
At first, the autosomal STR mutation frequencies among 4758 Taiwanese were analyzed. Population data were obtained from randomly selected 99 females and 101 males to setup the X-STR database. Two families with a mismatch of one allele in autosomal STR analysis were subjected to the X-STR test to explore its clinical application.


RESULTS
The STR mutations occurred in all 15 autosomal STR loci with the exception of TH01 and TPOX. The mutation rates could reach as high as 0.106% for the loci of D8S1179 and D18S51. As to the X-STR frequencies, the probability values of exact tests for Hardy-Weinberg equilibrium were 0.1471, 0.0019, 0.0025, 0.1427, and 0.1167 for the loci of DXS7132, DXS981, DXS6789, DXS101, and HPRTB, respectively. In addition, 33 and 34 different haplotypes were revealed for DXS101-DXS6789 and DXS7132-DXS981, respectively. Furthermore, two cases with one allele mismatch in routine parentage test were resolved by performing X-STR analysis.


CONCLUSIONS
Typing of X-STR markers is recommended for parentage test when 1 or 2 alleles mismatch is present or when the samples are difficult to be analyzed.
Chen
Ding-Ping
DP
Department of Laboratory Medicine, Chang Gung Memorial Hospital, Taoyuan County, Taiwan, ROC.
Tseng
Ching-Ping
CP
Tsai
Shu-Hui
SH
Wang
Mei-Chia
MC
Lu
Shu-Chuan
SC
Wu
Tsu-Lan
TL
Chang
Pi-Yueh
PY
Sun
Chien-Feng
CF
D041321:Chromosomes, Human, X / Q000235:genetics*; D005260:Female; D053803:Forensic Genetics / Q000379:methods*; D006801:Humans; D008297:Male; D018895:Microsatellite Repeats / Q000235:genetics*; D009154:Mutation; D010334:Paternity