BAMAD no.56
Brit-Am
DNA and
Anthropology Updates
Updates in DNA studies along with Anthropological Notes of general interest with a particular emphasis on points pertinent to the study of Ancient Israelite Ancestral Connections to Western Peoples as explained in Brit-Am studies.
Brit-Am
Research
Revelation
Reconciliation
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BAMAD no. 56
Brit-Am Anthropology and DNA Update
23 July 2009, 2 Av 5769
Contents:
1. Most Aleut Male Ancestry is European!
2. Nordic Race merely a branch of the Mediterranean Racial Stock?
3. Different Parts of Body give Different DNA!!
(a) SNPs
in Non-Cancerous Tissue May Differ From Those In Blood, Study Finds
(b) DNA may differ between tissues
4. Human mtDNA
subject to selection by climate?
5. Distance from Africa explains within-population cranial variation better than
climate
1. Most Aleut Male Ancestry is
European!
Ann Hum Biol. 2009 Jul 8:1-16. [Epub ahead of print]
Mitochondrial DNA and Y-chromosome variation in five eastern Aleut
communities: Evidence for genetic substructure in the Aleut population.
Zlojutro M, Rubicz R, Crawford MH.
Since Russian contact in 1741, the Aleut communities of southwestern
Alaska have undergone a series of demographic upheavals stemming from
forced relocations, disease epidemics, population bottlenecks, and
pervasive admixture with European populations. This study
investigates the impact of key historical events on the genetic
structure of the Aleut population through analysis of mitochondrial
and Y-chromosome DNA variation in five eastern Aleut communities.
Results from HVS-I sequencing and Y-chromosome typing reveal patterns
of variability that exhibit east-west geographic differentiation for
the major Aleut haplogroups. This finding is underscored by SAMOVA
and Monmonier analyses that identify genetic discontinuities between
eastern and western Aleut populations. The majority of Aleut
Y-chromosomes were characterized to haplogroups of mostly Russian,
Scandinavian and Western European origin (approximately 85%), which
is in stark contrast to the 3.6% of Aleut mtDNA lineages identified
as non-Native American, and thus indicating a large degree of
asymmetrical gene flow between European men and Aleut women. Overall,
this study identifies a significant relationship between geography
and genetic variation in the Aleut population, with a distinct
substructure along an east-west axis that reflects the combined
effects of founder events in aggregate island communities,
male-biased gene flow from European populations, and the original
peopling of the Aleutian Archipelago.
2. Nordic Race merely a branch of the
Mediterranean Racial Stock?
http://racialreality.110mb.com/subraces.html
Corded Nordic: The Nordic race is
a partially depigmented branch of the greater Mediterranean racial stock.
It is probably a composite race made up
of two or more basic Mediterranean strains, depigmented separately or in
conjunction by a progressive evolutionary process. ...
Hallstatt
Nordic: This is the type associated with the Hallstatt Iron Age remains
in central Europe, and which probably did not enter Scandinavia much before the
middle of the first millennium B.C. [i.e. after ca.500 BCE] It has since been
largely replaced in central Europe, but has found a refuge in Sweden and in the
eastern valleys of southern Norway. In England this type is largely of
Anglo-Saxon and Danish inspiration.
Source:
Coon, Carleton S. The Races of Europe.
MacMillan,
1939
3. Different Parts of Body give
Different DNA!!
(a)
SNPs
in Non-Cancerous Tissue May Differ From Those In Blood, Study Finds
July 17, 2009
By Andrea Anderson
http://www.genomeweb.com/sequencing/
snps-non-cancerous-tissue-may-differ-
those-blood-study-finds
NEW YORK (GenomeWeb News): A new paper by Montreal researchers is providing
evidence that the gene variants found in some non-cancerous tissues may differ
from those present in blood samples from the same individual.
"The usual dogma is that your DNA is the same all over the place," senior author
Morris Schweitzer, an endocrinologist and lipidologist with McGill University
and the affiliated Lady Davis Institute for Medical Research at Montreal's
Jewish General Hospital, told GenomeWeb Daily News. But, he said, his team's
work suggests that isn't the case.
The researchers, who were studying a condition called abdominal aortic aneurysm,
or AAA, found that SNPs in a gene called BAK1 were different in aortic tissue
than in blood samples, even in samples taken from the same individuals. The work
appears in this month's issue of the journal Human Mutation. Based on the
findings, those involved in the study are urging caution in interpreting genetic
associations based on DNA from blood samples alone.
"Traditionally when we have looked for genetic risk factors for, say, heart
disease, we have assumed that the blood will tell us what's happening in the
tissue," lead author Bruce Gottlieb, a researcher affiliated with McGill and the
Lady Davis Institute for Medical Research, said in a statement. "It now seems
this is simply not the case."
AAA is a rare cardiovascular disease characterized by a ballooning of the
abdominal aorta, which provides blood for the abdomen and much of the lower
body. Although there are no obvious symptoms, the disease can lead increase the
risk of aortic ruptures, a potentially fatal event. AAA affects roughly five to
nine percent of the North American population ? particularly men over 60 years
old ? and is more common in individuals with cardiovascular risk factors such as
smoking, hypertension, or high cholesterol.
Because chronic apoptosis has been implicated in AAA, the researchers decided to
investigate a gene called BAK1, which codes for an apoptosis-activating protein,
in AAA patients. They used Sanger sequencing to sequence BAK1 cDNA from diseased
abdominal aortic tissue and matching blood samples from 31 AAA patients.
When they looked at these sequences, the researchers were surprised to find that
the BAK1 sequences in the aortic tissues differed from that in the matched blood
samples. The aortic tissue carried a version of the gene containing three SNPs
that are rare in the blood. In contrast, the matched blood samples contained a
version of BAK1 that did not contain any of the three SNPs found in the aortic
tissue samples.
On the other hand, when the team sequenced BAK1 cDNA from healthy aortic tissue
obtained from a Quebec transplant service, they found the same three SNPs as in
the aortic tissue from the AAA cases. The researchers verified their findings by
sequencing both strands of DNA and repeating the sequencing several times.
So far, Schweitzer said it's unclear whether these BAK1 differences in the blood
and aortic tissue are the consequence of RNA editing, which changes the
messenger RNA but not the gene, or DNA editing, which involves differences in
the gene itself.
Down the road, he and his team intend to use pyrosequencing to look at BAK1
sequences from healthy and diseased abdominal aortic tissues in more depth, an
approach that could provide insights into whether that tissue contains both
majority and minority BAK1 sequences. If that's the case, it would bolster the
idea that different genetic sequences can arise through selective pressures in
different tissue, Schweitzer added, "You may have different tissue selectivity
for different DNA phenotypes."
The team is also interested in investigating whether the pattern they detected
holds true in BAK1 sequences from genomic DNA and learning more about whether
there are differences in the expression or activity of different BAK1 variants.
Based on the evidence so far, Schweitzer believes the BAK1 differences his team
detected resulted from developmental rather than somatic DNA alterations. Such a
pattern may not hold true for all genes, he said, but the BAK1 story suggests
there could be other genes that vary slightly between blood and other tissues.
That, in turn, highlights the need to assess genetic profiles specifically in
tissues of interest, Schweitzer argued, though he noted that that is a lofty
goal given the fact that it is difficult or ethically impossible to collect some
types of tissue from living individuals.
He and his colleagues also suggested that their findings raise questions about
GWAS, many of which rely on DNA profiles obtained from blood samples.
"Genome-wide association studies were introduced with enormous hype several
years ago, and people expected tremendous breakthroughs," Gottlieb said in a
statement. "Unfortunately, the reality of these studies has been very
disappointing, and our discovery certainly could explain at least one of the
reasons why."
In an e-mail message to GenomeWeb Daily News, Navigenics Co-founder and Chief
Science Officer Dietrich Stephan said the team's work is interesting and
deserves further investigation.
"Differences between the germ-line genome and somatic cells is well established
in cancer. It is also well described that chimeras can result from early DNA
changes in early embryonic development that propagate to form regional
differences in the genome across the body," Stephan noted. "It is intriguing to
think that such mechanisms could result in common phenotypes, and is a topic
that warrants deeper study."
Even so, he does not believe the findings are a blow to the results or rationale
behind GWAS in general. Researchers have gained "incredible insight" into
disease mechanisms using GWAS over the past few years, Stephan said in his
message, adding, "It is much more likely that the missing heritability that we
are all searching for will be accounted for by rare DNA variants, copy number
variants, and heritable epigenetic modifications than by this mechanism."
(b) DNA may differ between tissues
http://www.the-scientist.com/blog/display/55827/
Extracts:
Recent findings may spell trouble for genome-wide association studies based on
DNA obtained through blood samples: Genetic material may vary between blood
cells and other tissues in a single individual, a study in the July issue of
Human Mutation reports.
The study "raises a very interesting question," Howard Edenberg, director of the
Indiana University School of Medicine's center for medical genomics, told The
Scientist. Many genome-wide association studies -- especially studies on
systemic diseases such as diabetes and atherosclerosis -- depend solely upon DNA
harvested from blood samples to identify genes associated with medical
conditions. But this study "suggests that looking only at blood, you may miss
some things."
Searching for the genes behind a fatal condition called abdominal aortic
aneurysm (AAA), researchers from McGill University in Montreal found that
complementary DNA from diseased abdominal aortic tissue did not match genomic
DNA from leukocytes in blood from the same patient. "We did not expect to find a
difference in the tissue [genes] compared to the leukocyte [genes]," said
endocrinologist Morris Schweitzer, who led the study.
Schweitzer and his team uncovered three single nucleotide polymorphisms (SNPs)
in samples of diseased tissue from 31 AAA patients that were not present in
matching blood samples. They also tested five aortic and blood samples from
normal individuals and found the same discrepancy. Schweitzer said that the
apparent genetic difference between different cells in the body may cast some
doubt on genome-wide association studies that only use DNA from blood samples to
infer disease states. "I think they may not be accurate because they might not
reflect what's in the tissue," he said, adding that researchers should look upon
such genetic results "very carefully and very trepidatiously"
4. Human
mtDNA
subject to selection by climate?
http://yannklimentidis.blogspot.
com/2009/07/human-mtdna-subject
-to-selection-by.html
Climate shaped the worldwide distribution of human mitochondrial DNA sequence
variation
Fran?is Balloux, Lori-Jayne Lawson Handley, Thibaut Jombart, Hua Liu and Andrea
Manica
Proceedings Royal Society B
Abstract: There is an ongoing discussion in the literature on whether human
mitochondrial DNA (mtDNA) evolves neutrally. There have been previous claims for
natural selection on human mtDNA based on an excess of non-synonymous mutations
and higher evolutionary persistence of specific mitochondrial mutations in
Arctic populations. However, these findings were not supported by the reanalysis
of larger datasets. Using a geographical framework, we perform the first direct
test of the relative extent to which climate and past demography have shaped the
current spatial distribution of mtDNA sequences worldwide. We show that
populations living in colder environments have lower mitochondrial diversity and
that the genetic differentiation between pairs of populations correlates with
difference in temperature. These associations were unique to mtDNA; we could not
find a similar pattern in any other genetic marker. We were able to identify two
correlated non-synonymous point mutations in the ND3 and ATP6 genes
characterized by a clear association with temperature, which appear to be
plausible targets of natural selection producing the association with climate.
The same mutations have been previously shown to be associated with variation in
mitochondrial pH and calcium dynamics. Our results indicate that natural
selection mediated by climate has contributed to shape the current distribution
of mtDNA sequences in humans.
5. Distance from Africa explains
within-population cranial variation better than climate
This paper is somewhat disappointingly deceptive (as Dienekes points out
nicely). They are actually looking at within-population variation in cranial
traits and how it varies across the globe. They could have put that in their
title.
To be fair, I haven't looked too closely at the paper, and it does look
interesting and informative as to the relative roles of demographic vs.
selection forces in shaping within-population variation.
Distance from Africa, not climate explains human variation.
http://yannklimentidis.blogspot.com/search?updated-max=2009-03-06T07%3A25%3A00-07%3A00
Lia Betti, Francis Balloux, William Amos, Tsunehiko Hanihara, Andrea Manica
Proc Roy Soc B Early online
Abstract: The relative importance of ancient demography and climate in
determining worldwide patterns of human within-population phenotypic diversity
is still open to debate. Several morphometric traits have been argued to be
under selection by climatic factors, but it is unclear whether climate affects
the global decline in morphological diversity with increasing geographical
distance from sub-Saharan Africa. Using a large database of male and female
skull measurements, we apply an explicit framework to quantify the relative role
of climate and distance from Africa. We show that distance from sub-Saharan
Africa is the sole determinant of human within-population phenotypic diversity,
while climate plays no role. By selecting the most informative set of traits, it
was possible to explain over half of the worldwide variation in phenotypic
diversity. These results mirror those previously obtained for genetic markers
and show that "bones and molecules" are in perfect agreement for humans.
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