Bettina Dunkelmann

Ferritin—a mediator of apoptosis?

Previously we have demonstrated an apoptosis inducing activity for a rat hepatocyte conditioned medium (CM) presumably mediated by acidic isoferritins. Here, we present support for this assumption since isoferritins purified from different rat hepatocyte CM significantly enhanced the frequency of apoptotic cells in primary rat hepatocytes, an effect completely inhibited by a neutralizing anti‐H‐ferritin antibody. The apoptosis induction appears to be related to a 43 kDa ferritin subunit contained in the isoferritins released from primary hepatocytes, presumably representing a ferritin heavy/light chain heterodimer. In addition, these isoferritins immunologically crossreact with antibodies raised against placental isoferritin p43‐PLF (which also contains a 43 kDa ferritin subunit) and melanoma‐derived H‐chain ferritin, representing ferritin isoforms which reveal immunomodulatory properties. Furthermore, p53 and FasL are upregulated upon isoferritin treatment in a time dependent mode, and apoptosis induction can be suppressed by neutralizing anti‐FasL antibodies. Proapoptotic Bid is upregulated too and translocated into mitochondria in primary hepatocytes exposed to the isoferritins purified from the CM. Finally, epidermal growth factor (EGF) and dexamethasone (DEX), which counteract proapoptotic mitochondrial signalling, almost completely abolished the proapoptotic effect of the hepatocyte derived isoferritins. In conclusion, our findings demonstrate that acidic isoferritins with homology to immunomodulatory ferritin isoforms (p43‐PLF, melanoma‐derived‐H‐chain ferritin) are released from hepatocytes in vitro, and are able to stimulate upregulation of p53 and mediate apoptosis involving Fas (CD95) signalling as well as addressing the intrinsic mitochondrial proapoptotic pathway. J. Cell. Physiol. 212: 157–164, 2007.

Elevated germline mutation rate in teenage fathers.

Men age and die, while cells in their germline are programmed to be immortal. To elucidate how germ cells maintain viable DNA despite increasing parental age, we analysed DNA from 24 097 parents and their children, from Europe, the Middle East and Africa. We chose repetitive microsatellite DNA that mutates (unlike point mutations) only as a result of cellular replication, providing us with a natural ‘cell-cycle counter’. We observe, as expected, that the overall mutation rate for fathers is seven times higher than for mothers. Also as expected, mothers have a low and lifelong constant DNA mutation rate. Surprisingly, however, we discover that (i) teenage fathers already set out from a much higher mutation rate than teenage mothers (potentially equivalent to 77–196 male germline cell divisions by puberty); and (ii) ageing men maintain sperm DNA quality similar to that of teenagers, presumably by using fresh batches of stem cells known as ‘A-dark spermatogonia’.

Yfiler® Plus amplification kit validation and calculation of forensic parameters for two Austrian populations

With the new 6-dye AmpFISTR(®) Yfiler(®) Plus amplification kit (Thermo Fisher Scientific, Waltham, MA, USA) a set of 25 Y-chromosomal short tandem repeat loci (Y-STRs), including seven rapidly mutating Y-STRs (RM Y-STRs), is now available for forensic DNA typing. In this study we present our validation data for the AmpFISTR(®) Yfiler(®) Plus amplification kit and show the results of Y-chromosomal typing of 425 unrelated male individuals from two Austrian populations (Salzburg and Upper Austria) with the AmpFISTR(®) Yfiler(®) Plus amplification kit. Forensic parameters were calculated and compared for four Y-STR marker sets. We also typed five brother pairs to evaluate the power of discrimination for related individuals. The AmpFISTR(®) Yfiler(®) Plus (Yfiler Plus) kit appeared to be unimpaired by typical inhibitors such as hematin and humic acid or by large amounts of female components. An upgrade of analyzed markers resulted in increased discrimination capacity that is crucial for forensic trace analysis.

An unusual case of identification by DNA analysis of siblings.

A badly decomposed body required identification by means of DNA analysis. A brother and sister of the deceased were available as reference subjects. Although investigation of Y-chromosomal markers established an exclusion condition, autosomal markers suggested a positive identification. In order to increase the reliability of the tests, X-chromosomal markers were also investigated. This analysis showed the body to have an XXY genotype (Klinefelters syndrome). A number of hypotheses were assessed using biostatistical methods, ultimately resulting in a definite identification. The special aspect of Klinefelters syndrome proved highly useful for biostatistical analysis.

Contamination incidents in the pre-analytical phase of forensic DNA analysis in Austria—Statistics of 17 years

Forensic DNA analyses have become more and more sensitive in the past years. With the ability to generate DNA profiles even from minute amounts of cellular material also the possibility to detect DNA on trace material that originates from persons not linked to the crime event, such as crime scene investigators, increases. The contamination of crime scene samples can lead to false positive results and misinterpretation that can cause deceptive investigations. In this work we continue a study of 2010 that compared the number of detected contamination incidents that were caused in the pre-analytical phase of forensic DNA analysis with the number of crime scene samples analyzed by our laboratory. Within the past 17 years we were able to detect a total of 347 contamination incidents caused by police officers in approximately 46,000 trace samples to their origin (0.75%). Additionally we demonstrate the usefulness of reference profile databases that contain DNA profiles of police officers to detect contamination incidents of trace material.