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Almut Nebel

Publications and source records attributed to Almut Nebel.

13 recordsLinked to original sources
PubMed2026

Genomic insights into preantibiotic osteomyelitis pathogens and their link to current resistant hospital strains.

OBJECTIVES: Osteomyelitis is a severe bone infection that was frequently fatal before the introduction of antibiotics and remains a significant healthcare burden today. Staphylococcus aureus is the most common cause, alongside other hospital-acquired pathogens. Despite their clinical importance, the evolutionary history of these bacteria remains poorly understood. We investigated historical osteomyelitis specimens to identify causative pathogens and characterise their genomes, virulence and antimicrobial resistance (AMR). METHODS: Seven osteomyelitis-affected bones from adults dating to 19th-20th century Germany were analysed using ancient DNA (aDNA) approaches. After sequencing and screening, candidate pathogens were prioritised based on authentic aDNA damage patterns, established association with osteomyelitis and exclusion as environmental contaminants. Identified species were characterised by phylogenetics, multilocus sequence typing and virulence/AMR profiling. RESULTS: In four patients, we detected authentic aDNA from Acinetobacter baumannii, S. aureus or Streptococcus pyogenes. Detected taxa in the remaining three patients did not fulfil the criteria for further analysis. Two patients carried A. baumannii genomes clustering closely with modern avian and freshwater isolates. Both harboured virulence genes, alongside intrinsic efflux pumps and β-lactamases. One patient carried an S. aureus strain belonging to the globally disseminated clonal complex 30, responsible for outbreaks since the 1950s. Molecular dating indicated that this strain diverged from the wider lineage around 1800, placing it among the earliest members of this group. It encoded multiple virulence genes, but no methicillin resistance genes. The fourth patient carried an S. pyogenes strain related to modern epidemic lineages from North America, encoding conserved virulence factors, but no AMR genes. CONCLUSIONS: These specimens provide a window into the evolution of osteomyelitis pathogens. Although modern developments such as widespread antibiotic use have intensified the global resistance crisis, our findings indicate that the genetic foundations for pathogenicity and resistance were already present more than 100 years ago.

Ancient DNA↗
PubMed2006

Host susceptibility to tuberculosis: CARD15 polymorphisms in a South African population.

Tuberculosis (TB) is one of the leading causes of death worldwide. The nucleotide-binding oligomerisation domain 2 protein (NOD2) has recently been recognised as a non-redundant recognition mechanism of Mycobacterium tuberculosis. The caspase recruitment domain-containing protein 15 gene (CARD15), which encodes the NOD2 protein, is a susceptibility gene for Crohn's disease (CD), a granulomatous, chronic inflammatory disorder. CARD15 was therefore investigated as a candidate gene in TB. We genotyped the R702W, G908R and 1007fs variants, previously associated with CD, in TB cases and controls from the admixed South African Coloured population. No statistically significant differences between cases and controls were observed for these variants. We determined that the CD-associated mutations occur at very low frequencies in this population. Our results indicate that CARD15 is not a major susceptibility gene for TB in the South African Coloureds.

Genetic Predisposition to Disease↗
PubMed2006

Allelic variation in the CNDP1 gene and its lack of association with longevity and coronary heart disease.

Carnosine, a cytoprotective dipeptide found at very high concentrations in skeletal muscle, heart and brain, is cleaved in blood by serum carnosinase which is encoded by the CNDP1 gene. We recently found that homozygosity of a 5-leucine variant in the leader peptide of this enzyme protects diabetes mellitus patients against nephropathy. Hypothesising that the same allele could also be associated with longevity or a reduced incidence of cardiovascular problems, we examined the frequency of CNDP1 alleles in German centenarians, patients with premature coronary heart disease, and matched controls. A total of 1382 individuals was investigated. The 5-leucine allele was the most common allele in all groups investigated. There was no difference in allele or genotype frequency between centenarians and their control group, or between cardiovascular patients and their control group. The recently identified functional carnosinase variant therefore does neither contribute to longevity nor protect against coronary heart disease in our probands. In addition to the known trinucleotide repeat alleles in the CNDP1 gene, we detected a rare 8-leucine allele, a rare duplication, p.L13_V15dup, and a more common frameshift deletion, L17fsX20. Homozygosity for L17fsX20, estimated to have a prevalence of approximately 1:20,000, would be expected to cause carnosinaemia, an autosomal recessive trait with uncertain clinical relevance.

Aged↗
PubMed2006

Aging at the interface of stem cell renewal, apoptosis, senescence, and cancer.

The aging-related research field has focused on the detection of genetic factors that affect the aging process, but more recently scientists have started to shift their attention to novel and more integrative ways of studying cellular and organismal function. Such approaches allow them to uncover and explore unexpected patterns and themes, resulting in a more comprehensive knowledge of the complex regulatory pathways and networks involved in aging and age-related diseases. Eventually, this knowledge will lead to a systems-level understanding of aging. The third "Functional Genomics of Aging" conference held in Palermo, Italy, in March/April 2006 highlighted some of the more exciting work in this area.

Aging↗
PubMed2005

Sirtuin 1 (SIRT1) sequence variation is not associated with exceptional human longevity.

The SIR2/Sirt1 gene has been demonstrated as regulating lifespan in many model organisms, including yeast, Caenorhabditis elegans and rodents. These findings render the human homologue, SIRT1, a very plausible candidate as a modifier of human life expectancy. We therefore sought to investigate whether common allelic variation in the SIRT1 gene was associated with human longevity. Five single nucleotide polymorphisms (SNPs), distributed across the entire gene, including the promoter region, were genotyped in our extensive DNA collections of 1573 long-lived individuals (centenarians and nonagenarians) and matched younger controls. Four of the markers were haplotype-tagging SNPs (htSNPs) that defined five common haplotypes. No evidence for an association was detected between any of the tested SNPs and the longevity phenotype at the allele, genotype or haplotype levels. These findings, based on an htSNP approach, suggest that there is no noteworthy influence of SIRT1 sequence variation on exceptional human longevity in the German population. However, this does not rule out the possibility that allelic variants in direct regulators or downstream substrates of SIRT1 could play critical roles in extending lifespan in humans.

Aged↗
PubMed2005

Allelic variation and human longevity.

Human longevity is a complex phenotype with a strong genetic contribution. The search for allelic variation that impacts on longevity often involves population-based association studies of long-lived individuals (centenarians and nonagenarians) and younger controls. A major methodological problem with this approach is that the cases and controls in these experiments are often born several generations apart. The inherent absence of "age matching" can lead to serious misinterpretations. For example, allele frequency differences between long-lived individuals and younger controls may not reflect an effect on longevity but rather a change in population structure over time or different gene-environment interactions across generations.

Aging↗
PubMed2005

No association between microsomal triglyceride transfer protein (MTP) haplotype and longevity in humans.

Human longevity is a multifactorial condition with a significant genetic contribution. A recent association study in two independent samples of long-lived U.S. Caucasians [long-lived individuals (LLI)] identified a SNP haplotype of the microsomal triglyceride transfer protein (MTP, 4q25) that was underrepresented among LLI when compared with younger controls. This suggested that variation in the MTP gene might modify human longevity. Because of its function in lipid metabolism, the MTP gene product could plausibly play a pivotal role in the physiology of aging. However, the association observed in the U.S. samples could not be replicated by the same authors in a larger French LLI sample. We have therefore investigated the MTP "risk" haplotype in our own collection of 1,589 German nonagenarians, centenarians, and appropriately matched controls. No statistically significant differences were observed between LLI and controls at the allele, genotype, or haplotype level. This indicates that a noteworthy influence of the respective MTP haplotype on human longevity in the German population is unlikely. Furthermore, in comparison with all other U.S. and European samples analyzed, the MTP "risk" haplotype was found to be overrepresented only in the U.S. controls. This implies that the putative association is more likely to reflect recent changes in the genetic structure of the U.S. Caucasian population as a whole, rather than genetic effects upon survival to old age. In our view, the original study therefore highlights potential problems that arise when the case-control design is used as a means to map longevity genes in humans.

Aged↗
PubMed2005

Y chromosome evidence for a founder effect in Ashkenazi Jews.

Recent genetic studies, based on Y chromosome polymorphic markers, showed that Ashkenazi Jews are more closely related to other Jewish and Middle Eastern groups than to their host populations in Europe. However, Ashkenazim have an elevated frequency of R-M17, the dominant Y chromosome haplogroup in Eastern Europeans, suggesting possible gene flow. In the present study of 495 Y chromosomes of Ashkenazim, 57 (11.5%) were found to belong to R-M17. Detailed analyses of haplotype structure, diversity and geographic distribution suggest a founder effect for this haplogroup, introduced at an early stage into the evolving Ashkenazi community in Europe. R-M17 chromosomes in Ashkenazim may represent vestiges of the mysterious Khazars.

Chromosomes, Human, Y↗
PubMed2004

GEHA--the pan-European "Genetics of Healthy Aging" project.

The pan-European "Genetics of Healthy Aging" (GEHA) consortium is undertaking a large study of long-lived individuals, which officially began on 22 May 2004. The consortium aims to identify genes that promote longevity and good health during the process of aging. The project will involve scientists working in multiple disciplines and using a variety of techniques.

Aged↗
PubMed2003

Genealogy and genes: tracing the founding fathers of Tristan da Cunha.

The island population of Tristan da Cunha has a well-documented genealogy that dates to its first permanent settlement in 1816. The current population is thought to have descended from only seven females and eight males. Today, there are seven family names in use, corresponding to the number of founding fathers with present-day male descendents. Y chromosome polymorphisms have previously been shown to be reliable tools for tracing patrilineal genealogies. Here, we studied Y chromosome polymorphisms in a sample from Tristan da Cunha together with genealogical records to (i) infer the haplotypes of the seven founders and (ii) test if the Y chromosome transmission is consistent with the documented patrilineal history of the island community. We observed nine Y chromosome haplotypes of which seven could be traced to the known ancestors. Of the two additional lineages, one probably evolved from a founder haplotype due to a single-step microsatellite mutation, while the other had an obvious non-island origin. Its introduction, however, is not reflected in the records. Four more instances of non-paternity were identified, with the "new" chromosomes matching other island haplotypes. The Y chromosome data presented here question the validity of some of the genealogical documentation and emphasise the value of genetic studies in tracing ancestry.

Atlantic Islands↗