Transcript Slide 1

Genomic Definition of Self and Group Identity:
Implications for Biomedical Research
“2003 Summer Public Health Videoconference on Minority
Health - UNC ”
Charles N. Rotimi, Ph.D.
Director, Genetic Epidemiology
National Human Genome Center
College of Medicine, Howard University
UNC – June 10, 2003
Genome?
1. Only 1 percent of Americans can use the word
“genome”.
2. Genome: A person's entire set of genes.
3. Genome: All the DNA (genetic materials) contained
in an organism or a cell, which includes both the
chromosomes within the nucleus and the DNA in
mitochondria.
Holy Grail?
The human genome has been labeled the "Book of
Man" and its decoding likened to the search for the
Holy Grail.
Is our genome synonymous with our humanness?
Some view the genome as the core of our nature determining both our individuality and our species
identity.
Our Genome - Our Culture
Our Culture
Our
Genome
Co-evolution
Genes, Self and Group Identity
1. Genetic essentialism: Defining human identity in genetic
terms
2. The concept of self is reduced to a molecular entity
3. Human beings are equated, in all their social, historical, and
moral complexity, with their genes.
4. These new concepts profoundly challenge personal,
philosophical, cultural, legal, and political issues of identity.
5. These issues are described in more detail in The DNA
Mystique by Dorothy Nelkin and M. Susan Lindee
http://www.cnr.edu/home/Honors/syllabus/F1999/bio489.html
The Human Mosaic
A species is divided into races when it can
be regarded as an essentially discontinuous
set of individuals. Jonathan Marks
We maintain Complex relationships
We all have multiple identity
Genes, Self and Group Identity
Genetic Structure of Human Populations
Africa
Europe
Middle East
Central/
South Asia
East Asia
America
“the challenge of genetic studies of human history is to use the small
amount of genetic differentiation among populations to infer the history
of human migrations. Because most alleles are widespread, genetic
differences among human populations derive mainly from gradations in
allele frequencies rather than from distinctive diagnostic genotypes.”
Rosenberg et al Science 2002;298:2381-2385
Genetic Variation
Confusion
1.
Group identity is confused with group ancestry. For
example, the group identity “African Americans”
does not reflect a single path of ancestry.
2.
Self-identification is confused with more complex
tapestry of ancestry.
3.
Simplification of self and group identity. “If selfidentity is complex, group identity is infinitely more
complex.”
"Despite their long-term residence
in different countries -- most Jewish
populations were not significantly
different from one another at the
genetic level.” (M.F. Hammer, Proc.
Black Britons find their
African roots
http://news.bbc.co.uk
Nat'l Academy of Science, May 9, 2000)
DNA Testing to Determine
“Native American Identity”
DNA Analysis and the
Cultural Affiliation of the
Kennewick Man
Who gets to decide who is
a member of the group?
Black Southern African Bantuspeaking population who assert
Jewish ancestry: LEMBA men
NEIL BRADMAN AND MARK THOMAS
http://www.ucl.ac.uk/tcga/ScienceSpectra
House of artist and Oshun
priestess Suzanne Wenger,
Oshogbo
http://african.lss.wisc.edu/y
oruba
Suzanne Wenger in her Osogbo
home in 2000. Photo Marty Wong
http://www.friendsofnigeria.org/
Is a Diasporan African with genetic affinity to the
Yorubas more Yoruba than Suzanne Wenger, the
Austrian Anthropologist and Chief Priestess of the
Oshun Goddess, the keeper of Beaded Comb, in
Yoruba land even though she is white?
Genetic Variation
• How may we interpret data describing human
genetic variation today?
– Variation is not discontinuous.
– Pharmacogenomic differences can be 10 to more
than 40-fold between individual within an ethnic
group.
– Variation between ethnic groups is rarely more
than 2 to 3-fold
– Human populations exhibits considerable genetic
admixture
Pharmacogenomics
The study of how inherited genetic variations
affect an individual’s ability to response to a
drug and the use of that knowledge in drug
discovery and development.
Genetic Variation may explain why one person
may benefit from a drug while another person
may suffer toxic effects from the same dosage of
the same drug.
Variable Drug Response
• How do we interpret differential drug
response by “groups” when “group”
definition is imprecise, fluid and time
dependent?
• Can we tell how an individual will respond
based on group data?
• What is the acceptable error rate?
• Who decides this?
• Will error rate be higher for some groups
compared to others?
Variable Drug Response
• N-acetyltransferase 2 (NAT2)
– Enzyme involved in the detoxification of many
carcinogens and the metabolism of many
common drugs.
• NAT2 Variants
Slow acetylators
Rapid acetylators
• Slow acetylators
14% East Asia
34% African Americans
54% Caucasians
Anti-tuberculosis drug – isoniazid is inactivated by acetylation and the
capacity of individuals to inactivate the drug is dependent on their
genotype at the NAT2 locus
What we hear and read
• Racial differences in the response to
drugs – pointers to genetic differences.
N Engl J Med 2001 -----
The Medicalization of Race: Scientific Legitimization
of a Flawed Social Construct.
Serious negative consequences of a physician’s
assumptions about a patient’s race
Case 1: An 8-year-old boy, phenotypically European,
presented with acute abdominal pain and anemia
(hematocrit, 0.21). Although his body temperature was only
37.9 °C, surgery was considered. A technician found red
corpuscles with hemolytic characteristics on a smear.
Surgery was canceled after the results of a subsequent
sickle preparation were found to be positive, and the child
was treated for previously undiagnosed sickle cell anemia.
His parents were from Grenada and were of Indian,
northern European, and Mediterranean ancestry.
Ritchie Witzig – Ann Int Med 1996;125:675-679
The Medicalization of Race: Scientific Legitimization
of a Flawed Social Construct.
“---Ethnic boundaries are dynamic and imprecise, and it
is dangerous to assume that any person possesses a
certain health variable just because that person is a
member of a particular ethnic group. The common
thread between ethnicity and race is that both are social
constructs and subject to ethnocentric biases.
Ritchie Witzig – Ann Int Med 1996;125:675-679
Pharmacogenomics
Future use of drug therapy will not depend on the
imprecise indicators as race or ethnicity, but on the
individual patient’s genotype. The idea, then, is not to
eradicate or ignore differences but to redefine or
move beyond race to more precise categories of
difference with justification for establishing such
differences. M. Rothstein and P. Epps, Pharmacogenomics 2001,1:104-108
In this regard, pharmacogenomics may help deconstruct
the present concept of group definition including race. For
example, if you are defining a group with adverse reaction
to chloroquine-like drugs for the treatment of malaria, I
will not be in the same group as my mother.
Genomics, Health Disparity and the
Problem of Race
Genetic factors contribute to virtually every human
disease by way of increased
Susceptibility
Resistance
Affect the severity or progression of disease
Of all the forms of inequality, injustice in health is the most
shocking and the most inhuman.
The Rev. Martin Luther King – Chicago, March 25, 1966
Genomics and Health Disparity
• ---genetic explanation reifies racial and
ethnic classifications by reinforcing the
notion of biological difference rooted in
genetics. --- leads to stigmatization of racial
and ethnic minorities and to research
strategies that divert attention from
confronting the multidimensional ways in
which racism, not race, influence patterns of
disease.
•
Lundy Braun: Perspective in biology and medicine 2002
Can Genetic Variation Explain Health Disparity
----The historical, anthropological, and linguistic
definitions of “populations” with which genetic
findings are correlated represent superficial
understandings of the dynamic history of presentday ethnic populations and how these populations
were formed---
Current research emphasis on genetic explanation
for diseases disparities is problematic, since race
and ethnicity are social, not genetic, categories
comprised of individuals whose ancestry is highly
diverse.
Lundy Braun: Perspective in biology and medicine 2002.
Estimated European Ancestral Proportion of 11
populations of African Descent
Populations
Proportion
Charleston, SC
11.6±1.3
Philadelphia
12.7±1.5
Baltimore
15.5±2.6
Detroit
16.3±2.7
Houston
16.9±1.5
Maywood, IL
18.8±1.4
New York
19.8±2.1
New Orleans
22.5±1.6
Jamaica
6.8±1.3
Used 9 autosomal DNA markers; these are either population specific
alleles or show frequency difference > 45%; Para EJ Am J Hum
Genet 1998; 63:1839-51
Genomics and Health Disparity
“In America, race, ethnicity, and social class are so
confounded, and the reality of social class so firmly denied,
that it is easy to lose sight of the general setting of class
conflict out of which biological determinism arose. Biological
determinism, both in its literary and scientific forms, is part of
the legitimating ideology of our society, the solution offered to
our deepest social mystery, the analgesic for our most
recurrent social pain. In the words of Charles Darwin, quoted on
the title page of The Mismeasure of Man, “If the misery of our
poor be caused not by the laws of nature, but by our
institutions, great is our sin.”
In the book – It ain’t Necessarily So – The dream of the Human Genome and other
Illusions by Richard Lewontin pp18-19
Health Disparity
Has “Negro blood” become “black genes” (Wailoo 1997)
Prevalence of Diabetes by Mean BMI and Gender
in Populations of the African Diaspora
Men
14
Women
Prevalence of Diabetes
12
US
UK
UK
10
Caribbean
US
8
6
Caribbean
4
2
West Africa
West Africa
0
20
22
24
26
Body Mass Index
28
Cooper R, Rotimi C, Kaufman JS, et al., Diabetes Care 1997
30
32
Prevalence of Hypertension by Mean Body Mass
Index Among Populations of the African Diaspora
0.35
Maywood
North America
Percent Hypertensive
0.30
Barbados
St. Lucia
0.25
Caribbean
Jamaica
0.20
Cameroon
0.15
West Africa
Nigeria
0.10
22
23
Cooper R, Rotimi C. et al. AJPH. 1997
24
25
26
27
Body Mass Index
28
29
30
Prevalence of Hypertension (140/90 mmHg) by
Age in Rural and Urban Nigeria: Men and Women
.6
Urban
Prevalence
.5
.4
.3
Rural
.2
.1
0
25
35
45
55
65
Age in Years
75
85
Health Disparity and the Problem of Race
Health disparity is not new and is the result of
multiple factors with deep roots in social, political
and cultural practices.
It is not an American phenomenon but a global
one. Some of the largest disparity in health occur
among persons of similar ancestry living in the
same continent.
Epidemiological data coming out of Africa, Central
and South America are good examples.
The complex interwoven history of human species
The continuous interaction between human groups makes it very
unlikely to have genes or alleles that are population specific. Unlike
geographical separations, differences in allele frequencies are gradual,
without discontinuities between clusters
Figure is by Clayton Ryder- The Scientist 16[1]:16, Jan. 7, 2002 Ricki Lewis ([email protected])