Josephine Purps

Validation of a combined autosomal/Y-chromosomal STR approach for analyzing typical biological stains in sexual-assault cases

DNA testing is an established part of the investigation and prosecution of sexual assault. The primary purpose of DNA evidence is to identify a suspect and/or to demonstrate sexual contact. However, due to highly uneven proportions of female and male DNA in typical stains, routine autosomal analysis often fails to detect the DNA of the assailant. To evaluate the forensic efficiency of the combined application of autosomal and Y-chromosomal short tandem repeat (STR) markers, we present a large retrospective casework study of probative evidence collected in sexual-assault cases. We investigated up to 39 STR markers by testing combinations of the 16-locus NGMSElect kit with both the 23-locus PowerPlex Y23 and the 17-locus Yfiler kit. Using this dual approach we analyzed DNA extracts from 2077 biological stains collected in 287 cases over 30 months. To assess the outcome of the combined approach in comparison to stand-alone autosomal analysis we evaluated informative DNA profiles. Our investigation revealed that Y-STR analysis added up to 21% additional, highly informative (complete, single-source) profiles to the set of reportable autosomal STR profiles for typical stains collected in sexual-assault cases. Detection of multiple male contributors was approximately three times more likely with Y-chromosomal profiling than with autosomal STR profiling. In summary, 1/10 cases would have remained inconclusive (and could have been dismissed) if Y-STR analysis had been omitted from DNA profiling in sexual-assault cases.

Y-chromosomal analysis identifies the skeletal remains of Swiss national hero Jörg Jenatsch (1596-1639).

Jörg Jenatsch was a Swiss defender of independence and a fighter for liberty in the 17th century. With the help of three living male members of the Jenatsch family, we successfully identified a skeleton exhumed from Chur cathedral as the remains of Jörg Jenatsch. Our conclusion was based upon complete Y-STR and Y-SNP profiles that could be generated by replicate analyses of a bone sample available to us. The skeleton and the three living family members carried the same Y-SNP haplogroup, but were discordant at three of 23 Y-STR loci. This notwithstanding, conservative biostatistical evaluation of the data suggests that the Chur skeleton is at least 20 times more likely than not to be Jörg Jenatsch.

Refining the Y chromosome phylogeny with southern African sequences

The recent availability of large-scale sequence data for the human Y chromosome has revolutionized analyses of and insights gained from this non-recombining, paternally inherited chromosome. However, the studies to date focus on Eurasian variation, and hence the diversity of early-diverging branches found in Africa has not been adequately documented. Here, we analyze over 900xa0kb of Y chromosome sequence obtained from 547 individuals from southern African Khoisan- and Bantu-speaking populations, identifying 232 new sequences from basal haplogroups A and B. We identify new clades in the phylogeny, an older age for the root, and substantially older ages for some individual haplogroups. Furthermore, while haplogroup B2a is traditionally associated with the spread of Bantu speakers, we find that it probably also existed in Khoisan groups before the arrival of Bantu speakers. Finally, there is pronounced variation in branch length between major haplogroups; in particular, haplogroups associated with Bantu speakers have significantly longer branches. Technical artifacts cannot explain this branch length variation, which instead likely reflects aspects of the demographic history of Bantu speakers, such as recent population expansion and an older average paternal age. The influence of demographic factors on branch length variation has broader implications both for the human Y phylogeny and for similar analyses of other species.

A Novel MCPH1 Isoform Complements the Defective Chromosome Condensation of Human MCPH1-Deficient Cells

Biallelic mutations in MCPH1 cause primary microcephaly (MCPH) with the cellular phenotype of defective chromosome condensation. MCPH1 encodes a multifunctional protein that notably is involved in brain development, regulation of chromosome condensation, and DNA damage response. In the present studies, we detected that MCPH1 encodes several distinct transcripts, including two major forms: full-length MCPH1 (MCPH1-FL) and a second transcript lacking the six 3′ exons (MCPH1Δe9–14). Both variants show comparable tissue-specific expression patterns, demonstrate nuclear localization that is mediated independently via separate NLS motifs, and are more abundant in certain fetal than adult organs. In addition, the expression of either isoform complements the chromosome condensation defect found in genetically MCPH1-deficient or MCPH1 siRNA-depleted cells, demonstrating a redundancy of both MCPH1 isoforms for the regulation of chromosome condensation. Strikingly however, both transcripts are regulated antagonistically during cell-cycle progression and there are functional differences between the isoforms with regard to the DNA damage response; MCPH1-FL localizes to phosphorylated H2AX repair foci following ionizing irradiation, while MCPH1Δe9–14 was evenly distributed in the nucleus. In summary, our results demonstrate here that MCPH1 encodes different isoforms that are differentially regulated at the transcript level and have different functions at the protein level.

Genetic research at a fivefold children's burial from medieval Berlin

Berlin originated from the two twin cities Berlin and Cölln, which both were founded at the beginning of the 13th century. However the real date of their foundation as well as the origin of the first settlers is still unknown. On the Berlin site the historic city center is still visible in the Nikolaiviertel, but the medieval origin of Cölln disappeared almost completely. In 2007 a large scale excavation, which comprised an area of about 1700m(2) of the historical center of the St. Peters church, recovers the remains of Cöllns first citizens and span a period of 500 years of medieval population. Here we present the first genetic analysis of a fivefold childrens burial from excavations in Berlin. The genetic data unveiled next to ancestry and eye color data also the kinship and the gender of the five individuals. Together with the archeological context the new gained information help to shed more light on the possible reasons for this burial.

Das Y-chromosom als forensischer und genealogischer marker

DNA markers on the human Y chromosome are used as an investigative tool in crime labs all over the world. Especially in sexual assault cases the Y chromosome provides essential evidence. Because male relatives share for several generations an identical Y chromosome profile and paternal relatives tend to live in the geographic and cultural territory of their ancestors, the Y chromosome analysis can also infer the probable geographic origin of an unknown male DNA.

Genetic structure and sex-biased gene flow in the history of southern African populations

Abstract Objectives We investigated the genetic history of southern African populations with a special focus on their paternal history. We reexamined previous claims that the Y‐chromosome haplogroup E1b1b (E‐M293) was brought to southern Africa by pastoralists from eastern Africa, and investigated patterns of sex‐biased gene flow in southern Africa. Materials and methods We analyzed previously published complete mtDNA genome sequences and ∼900u2009kb of NRY sequences from 23 populations from Namibia, Botswana, and Zambia, as well as haplogroup frequencies from a large sample of southern African populations and 23 newly genotyped Y‐linked STR loci for samples assigned to haplogroup E1b1b. Results Our results support an eastern African origin for Y‐chromosome haplogroup E1b1b (E‐M293); however, its current distribution in southern Africa is not strongly associated with pastoralism, suggesting more complex demographic events and/or changes in subsistence practices in this region. The Bantu expansion in southern Africa had a notable genetic impact and was probably a rapid, male‐dominated expansion. Our finding of a significant increase in the intensity of the sex‐biased gene flow from north to south may reflect changes in the social dynamics between Khoisan and Bantu groups over time. Conclusions Our study shows that the population history of southern Africa has been complex, with different immigrating groups mixing to different degrees with the autochthonous populations. The Bantu expansion led to heavily sex‐biased admixture as a result of interactions between Khoisan females and Bantu males, with a geographic gradient which may reflect changes in the social dynamics between Khoisan and Bantu groups over time.