HMB321H1 Lecture Notes - Lecture 16: Chromatin Immunoprecipitation, Podlaska Wytwórnia Samolotów, Co-Adaptation

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8 Oct 2011

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16 MAR 2011
HMB321 L16: Imprinting in Human Diseases
Genomic Imprinting
-Depends on parent-of-origin
-Paternally imprinted = expressed only from maternally inherited allele
-Maternally imprinted = expressed only from paternally inherited allele
-I.e. Imprinting = turned off from parent n
-Imprinting in the germ line = imprint removal and then re-application by sex
-Imprinting maintains as it continues into development from child => adult
Why imprinting?
-Not confirmed, but there are many theories
-Conflict Theory
-Competing interests between mother and father’s resources, i.e. Paternal genes are
trying to draw resources from mother for this progeny; maternal genes are trying to
conserve resources for future pregnancies
Imprinting & Disease
-Imprinted regions are more vulnerable to disease
-I.e. If imprinted allele is normal + expressed is mutant = no homologous copy; no wt +
-E.g. If mother is affected for a maternally imprinted gene (paternal inherited copy expressed is
mutant) => will produce carriers because her copy will be imprinted anyways
-However, her sons will have affected children because they can inherit either a mutant
or wt allele, both of which are expressed because it is maternally imprinted and not
paternally imprinted + paternally re-set
Imprinting Domains
-6 imprinting domains on human chromosomes, associated with diseases (see slide for syndromes)
-11p15.5 (2 domains)
-Some individuals can get combinations of multiple domains due to hypermethylation (hyper-silencing)
15q11-13: Angelman & PRader-Willi Syndromes
-The two seem to be opposites in terms of phenotypes
-AS = hypotonic (underdeveloped; thin)
-PWS = hypertonic (overweight)
-See slides for clinical phenotypes
15q11-13 Imprinting Domain
-Preferentially paternally-imprinted area with some maternal > paternal regions
-A significant portion is also biallelic expression
-See slide for genes involved: MKRN3, etc
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