Results of the 2003-2004 GEP-ISFG collaborative study on mitochondrial DNA: focus on the mtDNA profile of a mixed semen-saliva stain.
We report here a review of the seventh mitochondrial DNA (mtDNA) exercise undertaken by the Spanish and Portuguese working group (GEP) of the International Society for Forensic Genetics (ISFG) corresponding to the period 2003-2004. Five reference bloodstains from five donors (M1-M5), a mixed stain of saliva and semen (M6), and a hair sample (M7) were submitted to each participating laboratory for nuclear DNA (nDNA; autosomal STR and Y-STR) and mtDNA analysis. Laboratories were asked to investigate the contributors of samples M6 and M7 among the reference donors (M1-M5). A total of 34 laboratories reported total or partial mtDNA sequence data from both, the reference bloodstains (M1-M5) and the hair sample (M7) concluding a match between mtDNA profiles of M5 and M7. Autosomal STR and Y-STR profiling was the preferred strategy to investigate the contributors of the semen/saliva mixture (M6). Nuclear DNA profiles were consistent with a mixture of saliva from the donor (female) of M4 and semen from donor M5, being the semen (XY) profile the dominant component of the mixture. Strikingly, and in contradiction to the nuclear DNA analysis, mtDNA sequencing results yield a more simple result: only the saliva contribution (M4) was detected, either after preferential lysis or after complete DNA digestion. Some labs provided with several explanations for this finding and carried out additional experiments to explain this apparent contradictory result. The results pointed to the existence of different relative amounts of nuclear and mtDNAs in saliva and semen. We conclude that this circumstance could strongly influence the interpretation of the mtDNA evidence in unbalanced mixtures and in consequence lead to false exclusions. During the GEP-ISFG annual conference a validation study was planned to progress in the interpretation of mtDNA from different mixtures.
Crespillo
Manuel
M
Instituto Nacional de Toxicología y Ciencias Forenses, Servicio de Biología, Barcelona, Spain. manuel.crespillo@mju.es
Paredes
Miguel R
MR
Prieto
Lourdes
L
Montesino
Marta
M
Salas
Antonio
A
Albarran
Cristina
C
Alvarez-Iglesias
V
V
Amorin
Antonio
A
Berniell-Lee
Gemma
G
Brehm
Antonio
A
Carril
Juan C
JC
Corach
Daniel
D
Cuevas
Nerea
N
Di Lonardo
Ana M
AM
Doutremepuich
Christian
C
Espinheira
Rosa M
RM
Espinoza
Marta
M
Gómez
Felix
F
González
Alberto
A
Hernández
Alexis
A
Hidalgo
M
M
Jimenez
Magda
M
Leite
Fabio P N
FP
López
Ana M
AM
López-Soto
Manuel
M
Lorente
Jose A
JA
Pagano
Shintia
S
Palacio
Ana M
AM
Pestano
José J
JJ
Pinheiro
Maria F
MF
Raimondi
Eduardo
E
Ramón
M M
MM
Tovar
Florangel
F
Vidal-Rioja
Lidia
L
Vide
Maria C
MC
Whittle
Martín R
MR
Yunis
Juan J
JJ
Garcia-Hirschfel
Julia
J
D019411:Clinical Laboratory Techniques / Q000592:standards*; D016172:DNA Fingerprinting / Q000592:standards; D004272:DNA, Mitochondrial / Q000097:blood / Q000235:genetics*; D005260:Female; D006197:Hair / Q000737:chemistry; D006801:Humans; D008297:Male; D011786:Quality Control; D012463:Saliva / Q000737:chemistry*; D012661:Semen / Q000737:chemistry*; D017422:Sequence Analysis, DNA; D012955:Societies, Medical
D004272:DNA, Mitochondrial