Archiv der Kategorie: Genetics

Virus reactivation

16.09.2021 admin

A recent Nature study showed Ebola reactivation in a previously infected patient:

The 2021 lineage shows considerably lower divergence than would be expected during sustained human-to-human transmission, which suggests a persistent infection with reduced replication or a period of latency.

The most recent viral genome shared 10 substitutions that evolved during the previous epidemic making it unlikely that there was a new animal spillover event. I always wondered how second & third wave of COVID-19 started in Germany. Was it really a new spread or just a reactivation? A Frontiers review concluded from the existing literature that

our study, consisting more than a total of 113,715 patients, indicates that the RP-SARS-CoV-2 scenario occurs plausibly due to reactivation, reinfection, viral shedding, or testing errors.

So far, there are 240 documented COVID-19 cases of reinfection reported worldwide according to the reinfection tracker. In the case of Ebola there is a known viral persistence in semen while transmission through milk and cervicovaginal fluid is also possible (similar for COVID-19 although neuronal persistence seems to be more relevant). Maybe we need more immunological studies particular in long COVID if there is a continuous or intermittent antigenic stimulation due to persistence of an antigenic reservoir.

The fourth wave in Germany is caused by the delta variant, reactivation of alpha is certainly not a major factor. So we will only know in the next few years if reactivation is responsible for small regional outbreaks in unvaccinated communities.

Allergy, Genetics

A new hypothesis why atopic dermatitis and asthma may be linked by vitamin D

16.12.2020 admin

We had a major discussion before our 2010 paper where I argued that rare variants should have been included. Ten years after there is a nice paper using massive exome sequencing that finally includes them. The respiratory tract isn’t so much influenced by rare variants but there is a strong effect in the immune system.

Qanli Wang https://www.biorxiv.org/content/10.1101/2020.12.13.422582v1, posted December 13, 2020.

And there is another interesting fact.

Surveying the contribution of rare variants to the genetic architecture of human disease through exome sequencing of 177,882 UK Biobank participants …if we look at the …. European population who are carriers of a filaggrin (FLG) PTV, we find those carriers have significantly higher risk for well-known associations, such as dermatitis … and asthma … Concomitant increases in vitamin D levels suggest risk of melanoma and basal cell carcinoma in FLG PTV carriers could be attributable to increased sensitivity to ultraviolet B radiation.

So far, I have only assumed some asthma/allergy priming effect of oral vitamin D in the newborn gut.

This paper now argues for an increased vitamin D sensitivity in the skin of FLG dermatitis patients which is interesting given the largely contradictory data of serum vitamin D and atopic dermatitis. Maybe dermatologists should focus their research more on local vitamin D turnover?

Allergy, Genetics

IL4 and asthma

10.09.2020 admin

A new Cell paper on “The Polygenic and Monogenic Basis of Blood Traits and Diseases” now highlights the association of IL4 and asthma.

Unfortunately we know that already for 27 years. Is genomic science suffering already from amnesia?

Allergy, Genetics

New England Journal of Medicine Retractions

7.03.2020 admin

Retraction Watch says on Jan 30, 2020 that

Until yesterday the New England Journal of Medicine had retracted only 24 papers. Now that tally is 25.

While the retracted paper has been cited 190 times, here are inaccuracies in another NEJM paper that has been cited 1961 times.

Full details are at PubPeer.

Is it justified to speak of a “protective” effect just by a negative association?

In addition to the problems with the math, I don’t get the point – farming should be leading to a generally reduced capacity for numerous pleiotropic cytokines?

There are even reports that LPS induces TH2 dependent senstization which is exactly the opposite of what this paper wants us to believe by some cryptic smoother applied to a heterogenous population.

Genetics

What does shared genetics mean?

3.03.2020 admin

On Feb 7,2020 I had the chance to hear a talk of Luke Jostins-Dean about Irritable Bowel Syndrome (IBS) and Inflammatory Bowel Disease (IBD). While IBS had a substantial overlap of polygeneic risk scores with psychological features, IBD did not. Sounds logical but does this prove anything?

Two new medRxiv preprints [Wendt and Marees ] throroughly examine also possible genetic correlates. Although I am quite sceptical that SES correlates should be tested at all (and also think that GWAS are not hypothesis free) here is the Marees explanation of the three possibilities we do have: PRS, MTAG, mtCOJO.

First, polygenic risk scoring (PRS) is a tempting approach; but PRS using mental health/disease to predict the same or different phenotypes from an independent dataset often explain very little variance in the outcome phenotype. PRS also cannot detect specific biology underlying each phenotype.
Second is multi-trait analysis of GWAS (MTAG), which jointly analyses GWAS summary statistics and adjusts per-SNP effect estimates and association p-values using the strength of the genetic correlation between phenotypes. Genetic correlations between EDU/SES and related phenotypes have, however, demonstrable biases from environmental confounders….
To disentangle the complex genetic overlaps between EDU/SES and mental health, we therefore used multi-trait conditioning and joint analysis (mtCOJO), which generates conditioned GWAS summary statistics for each phenotype of interest after correcting for the per-SNP effects of another phenotype). The mtCOJO approach is not based on genetic correlation; it is based on the causal relationship between trait pairs inferred by Mendelian randomization (MR).

mtCOJO seems the way to go although the usual restrictions apply.

Genetics, Joke

Fastest ever data transfer: 126 Petabyte per second

21.01.2020 admin

1 x ejaculation expells 250,000,000 sperm at a speed of 500 cm/s. Each sperm contains 3,088,000,000 base pairs = bits ~ 368 megabyte of genomic DNA

Each base pair takes 2 bits (you can use 00, 01, 10, and 11 for T, G, C and A). … And remember, you have to go from bits to bytes to get to an answer in megabytes. A bit is just a single unit of digital information, but a byte is a sequence of bits (usually 8). And because computers work in binary math, 1 kilobyte = 1024 (i.e. 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 x 2 = 1024). 1 gigabyte = 1024 megabytes = 1048576 kilobytes = 1073741824 bytes. So you take the 3,088,000,000 bits and divide it by 8 to get 750,000,000 bytes. Divide that by 1024 and you get 376,953 kilobytes. Divide it by 1024 once more and you’re left with 368 megabytes.

Add 30,000 CpG islands x 8 bytes ~ 0,2 Megabyte
Also add 75 mitochondria x 16,569,000 base pairs ~ 148 Megabyte
So in total 516,2 Megabyte per sperm

250,000,000 x 51,2 Megabyte / 1024 = 126,000,000 Gigabyte = 126,000 Terabyte = 126 Petabyte

Genetics

Polygenic risk scores – dead end of human genetics

15.01.2020 admin

Eric Topol will agree on the fact that

the practice of utilizing the DNA of an individual to predict disease has been judged to provide little to no useful information.

but they nevertheless the group tried to rescue the concept by combining clinical risk factors plus low/medium/high polygenic risk. As a pragmatic approach this may work for some diseases but it will not explain any genetic pathhway.

More recently Richardson et al. tried another approach using the UK Biobank data where they analysed 162 PRS and 551 heritable traits from 334,398 individuals. Using their web application for my search term “asthma” I did not find anything useful that hasn’t been known for ages.

Jan 15, 2020 http://mrcieu.mrsoftware.org/PRS_atlas

So lets have a look at an example published last November in Cell “Screening Human Embryos for Polygenic Traits Has Limited Utility”. The outcome is sobering: If an IVF embryo would be profiled with polygenic scores for traits such as height or IQ

the top-scoring embryo is expected to be about 2.5 cm or about 2.5 IQ points above the average. The adult trait value of the top-scoring embryo would remain widely distributed.

I wouldn’t have even run this analysis for being pointless.

Genetics, Philosophy

Makroskopische Anatomie (Bewusstseinsmodelle VI)

10.01.2020 admin

Währen des Updates eines früheren Blogeintrages über “social pain” fiel mir ein Artikel über die anatomische Basis des “Selbst” aus dem Jahr 2018 in die Hand. Die Lokalisation hier war in der Insula bzw anteriorem Gyrus cingulus, damit also Brodmann-Areale 24, 32 und 33, alles Areale die seit langem auch mit der Schizophrenie in Verbindung gebracht werden.

Viele Menschen lokalisieren ihr “bewusstes Selbst” irgendwo zwischen den Augen hinter der Glabella, die in der Mythologie oft auch als drittes Auge (chakra) bezeichnet wird. In der Wissenschaft des post Phrenologie Zeitalter ist in die Lokalisation allerdings “frustriend vage” (“frustratingly diaphanous“). In meiner kleinen Umfrage gaben einige auch eine Lokalisation im oberen Brustbereich mit Atmung/Herzschlag an; andere hatten keine permanente , Kinder und eine (blinde) Person überhaupt keine Lokalisation.

Mehr zu dem “verkörperten Bewusstsein” bei Thomas Fuchs oder auch bei Goethe “Nichts ist drinnen, nichts ist draußen; denn was innen, das ist außen“. Irritierend bleibt jedenfalls wie leicht die Selbstwahrnehmung gestört werden kann, sei es durch Schlaf, LSD oder Datenbrille [1, 2]

Vielleicht müsste man auch besser nach der anatomischen Selbstlokalisation von “Seele” oder “Mind” suchen? Zumindest für die historische Klärung würde das weiter führen. Immerhin , Leonardo lokalisierte auch für oberhalb des Chiasma opticum.

TBC

Genetics

Does smoking kill by accumulation of mutations or by repeated exposure until the final crack?

7.12.2019 admin

We have a new paper at Sci Rep online “High degree of polyclonality hinders somatic mutation calling in lung brush samples of COPD cases and controls“.

It took a long time from my initial grant application at Sander Stiftung in Dec 2009 (where it was rejected), to the field work within the scope of the EvA study (where the PI Loems Ziegler-Heitbrock already retired). Followed by some first analysis together with Francesc at CNAG in Barcelona the final publication now appeared – my gratulations to Gian-Andri and Ivo Gut for their hard work!

Chronic obstructive pulmonary disease (COPD) is induced by cigarette smoking and characterized by inflammation of airway tissue. Since smokers with COPD have a higher risk of developing lung cancer than those without, we hypothesized that they carry more mutations in affected tissue.
We called somatic mutations in airway brush samples from medium-coverage whole genome sequencing data from healthy never and ex-smokers (n=8), as well as from ex-smokers with variable degrees of COPD (n=4). Owing to the limited concordance of resulting calls between the applied tools we built a consensus, a strategy that was validated with high accuracy for cancer data.
However, consensus calls showed little promise of representing true positives due to low mappability of corresponding sequence reads and high overlap with positions harbouring known genetic polymorphisms. A targeted re-sequencing approach suggested that only few mutations would survive stringent verification testing and that our data did not allow the inference of any difference in the mutational load of bronchial brush samples between former smoking COPD cases and controls.

So we would have probably needed a higher genome coverage on our brush sample mix. Or should we have sequenced more single cells as discussed in the paper?

At least, we now know, that sequencing at rather low coverage rate is not a screening tool for expected cancer development. Are there less pre-malignant lesions than expected? When looking at some other papers (Cancer Genome Atlas, esophagus, and more recently colon samples, I can only confirm what Iñigo Martincorena wrote

this study emphasizes how little we know about somatic evolution within normal tissues, a fundamental process that is likely to take place to varying degrees in every tissue of every species.

Somatic mutations accumulates with age. There may be even more mutations in the aging esophagus than in sun-exposed human skin. Lee-Six estimates 43.6 mutations /year, while I still have a gut feeling that there is no gradually accumulation of mutations (until the second hit) but a clonal expansion of a single

Martincorena 2018 https://science.sciencemag.org/content/362/6417/911

bronchial cell, hit by a single smoke stream. With this hypothesis, smoking would not kill by accumulation of deleterious mutations, but by the never ending re-exposure until the ultimate deleterious mutation occurs.

Many more of these timeline studies will be necessary to explain why the lung cancer risk drops immediately after you stop smoking.

Genetics, Vitamins

Is the Loomis Hypothesis wrong?

2.12.2019 admin

I remember an old vitamin D book – I believe it was Feldman’s Vitamin D – that argues that if we are going down the Transsahara Route (Algier-Lagos) human skin color gets always darker towards Tamanrasset due to increased solar power- also known known as the Loomis hypothesis (Science 1967).

So , let’s have a look at three maps. Solar power first.

1. Solar power. Source: https://upload.wikimedia.org/wikipedia/commons/1/1e/Global_Map_of_Global_Horizontal_Radiation.png

Second, skin tones – the Tamanrasset observation is correct but the overall picture does not match the Loomis hypothesis.

2. Skin tone. Source https://science.sciencemag.org/content/358/6365/867.full For full details see the original paper

Neither does the new vitamin D map published last week in the Lancet.

3. Vitamin D map. Source: https://linkinghub.elsevier.com/retrieve/pii/S2214109X19304577 For full details see the original paper

Maps are still patchy but let me already believe that the Loomis hypothesis is wrong.

Genetics

Doubling time

18.11.2019 admin

I always had the impression that whenever a scientific work group is growing too quickly, it is difficult to keep ethical and scientific standards. Maybe that’s even true on macroscopic scale? The paper “Age, Aging and Age Structure in Science” by Robert Merton & Harriet Zuckerman summarizes in 1972 (on p 498 of Merton’s collected works “Sociology of Science”) that

the population of scientists, with a doubling time of about fifteen years, is far outrunning the acceleration rate of increase in the general population.

and he quotes Derek Price “Little science, big science” p 19 that we

will soon have two scientists for every man, woman, child and dog.

Genetics

The science and art of scientific presentations

17.11.2019 admin

I always recommend Edward Tufte’s book The Visual Display of Quantitative Information” and what he says about data ink

Above all else show data.
Maximize the data-ink ratio.
Erase non-data-ink.
Erase redundant data-ink.
Revise and edit.

Genetics

Instrumentalisierte Wissenschaft

9.11.2019 admin

BR24 berichtet über ein fünfteiliges Maßnahmen-Paket zu multiresistente Keimen über das der Landtag gestern diskutiert hat.

In Teil vier dieses Pakets geht es auch um Homöopathie. In der Hauptsache soll eine Studie veranlasst werden, die untersucht, wie man mit weniger Antibiotika auskommt. Dabei soll eine mögliche “positive Rolle von gegebenenfalls ergänzend verabreichten homöopathischen Präparaten” beleuchtet werden, um so den Einsatz von Antibiotika zu verringern oder teilweise ersetzen zu können.
In der Antragsbegründung heißt es, dass laut einer bereits veröffentlichten Studie, eine zusätzliche homöopathische Behandlung bei schwer an Blutvergiftung erkrankten Menschen “nützlich” sein kann. In dem Antrag wird des Weiteren für möglich gehalten, dass eine homöopathische Behandlung Antibiotika zum Teil ersetzen oder reduzieren kann und “in manchen Fällen ebenso heilsam” sei.

Ich vermute mal, so eine Studie geht über keine Ethik-Kommission, so dass sich die Aufregung bald wieder legen wird. Blamiert haben sich aber schon einige Parteien.

Allerdings sollte damit aber jedem Wissenschaftler klar sein, dass man nur so lange gefragt ist, wie es zu dem jeweiligen Weltbild passt.

https://mobile.twitter.com/spasskultur/status/1192515797853319168

Das deutsche Ärzteblatt zeigt die Schwierigkeit, dass sich nun kaum eine deutsche Universität mit der Seidenath-Studie blamieren will.

Ich verstehe die Aufregung nicht“, sagt hingegen der CSU-Politiker Bernhard Seidenath. „Jeder keilt sich an dem Thema Homöopathie fest.“ Dieses komme nur am Rande vor und sei Teil eines größeren Maßnahmenpaketes, mit dem multiresistente Keime bekämpft werden sollen. Der Landtagsabgeordnete aus Dachau hatte daran federführend mitgewirkt. Seidenath betonte, man wolle „versuchen, alle Register zu ziehen, um die Wirksamkeit von Antibiotika zu erhalten und Resistenzen zu vermeiden“. Dafür dürfe nichts unversucht und nichts ununtersucht bleiben. Er hält das Geld für die Studie – Seidenath geht von rund 300.000 bis 400.000 Euro Kosten aus – für „sinnvoll investiert“.

30.11.2019
dto Stefan Rahmstorf

Schlägt die Politik wissenschaftliche Beratung zu oft in den Wind?
Rahmstorf: Mein Eindruck im Wissenschaftlichen Beirat war leider: Wenn wir einen Rat gegeben haben, der der Regierung gepasst hat, dann wurde er gerne aufgegriffen; andernfalls wurde es eher ignoriert.

Die ultimative Zusammenfassung zur homöopathischen Datenlage im übrigen im Laborjournal.

Genetics, Theology

Genetische Ausnahmslosigkeit?

3.11.2019 admin

Peter Dabrock im Deutschen Ärzteblatt

Die Keimbahn als solche ist nicht sakrosankt. Das mag auf den ersten Eindruck erstaunen, weil viele Menschen die Keimbahn als etwas Besonderes einschätzen. Aber der Mensch geht in seiner Keimbahn nicht auf – das wäre eine ethisch unstatthafte Biologisierung menschlichen Daseins.

Die Keimbahn sakrosankt? Es ist ein klassische Strohmann Argument hier: irgendetwas behaupten, widerlegen und einen Schluss zu ziehen, der nicht gerechtfertigt ist.

Ohne hier einen genetischen Exzeptionalismus zu vertreten, ist die Keimbahn natürlich etwas Besonderes – der individuelle Code des Lebens, der Blueprint von drei Milliarden Basenpaaren anhand derer sich durch einen mehrfach abgesicherten Mechanismen jeder Mensch entwickelt hat. Und zwar indivduell, jeder Mensch einzigartig, als Kind seiner Eltern, das schätzen die meisten Menschen auch völlig richtig ein.

In der Keimbahn geht der Mensch nicht auf, er entwickelt sich daraus. Hier ist dann auch noch Ursache und Wirkung vertauscht, um das vernichtende Argument abzugeben – ethisch unstatthaft – mit entsprechenden Konsequenzen.

Die Menschwerdung ist etwas Besonderes, wie es Karl Eibl es wunderbar einmal beschrieben hat.

Und Gott der HERR machte den Menschen aus einem Erdenkloß, und blies ihm ein den lebendigen Odem in seine Nase. Und also ward der Mensch eine lebendige Seele.” (1. Mose 2,7). Diese alte Geschichte gibt knapp und schmeichelhaft Auskunft über die Stellung des Menschen in der Natur, aber sie wird in der Regel nur am Sonntag erzählt. Die andere, neuere und werktagsgeeignete Geschichte trägt so unangenehm plärrende Titel wie “Der nackte Affe” oder “Der dritte Schimpanse” oder “Von Menschen und anderen Tieren”. Sie hat zwar einige Plausibilität, wenn wir das Verhalten unserer Mitmenschen ansehen, aber uns selbst und ein paar Freunde würden wir gerne ausnehmen, sprechen deshalb lieber von Bewusstsein, Emanzipation von Naturzwängen, Emergenz und ähnlichen schwer definierbaren Kostbarkeiten, die uns letzten Endes doch eine Sonderstellung im Kosmos sichern sollen. Dagegen ist auch gar nichts einzuwenden. Auch der Elefant ist nicht irgendein Dahergelaufener, und wenn er sprechen könnte, würde er uns vielleicht ärgerlich versichern, dass auch er eine Sonderstellung im Kosmos hat. Eigentlich ist jede Gattung oder Art etwas Besonderes, sonst könnten wir sie ja nicht von anderen unterscheiden. Die Frage ist eher, ob das Besondere des Menschen ein besonders Besonderes, ein ganz Anderes ist.

Allergy, Genetics

A new research route for fighting allergy?

1.11.2019 admin

Sci Immunol today shows an incomplete genetic reconstitution of B cell pools after measles infection.

Using B cell receptor (BCR) sequencing of human peripheral blood lymphocytes before and after MeV infection, we identified two immunological con- sequences from measles underlying immunosuppression: (i) incomplete reconstitution of the naïve B cell pool leading to immunological immaturity and (ii) compromised immune memory to previously encountered pathogens due to depletion of previously expanded B memory clones.

This “immune amnesia” is noteworthy as sensitivity to D pter was observed less frequent in children with a history of measles than in those without.