Chapter 14: Maternal Fetal Conflict Flashcards
Robert Trivers parent offspring conflict
offspring are likely to be more selfish than parents desire.
potential conflict arises because:
Potential conflict arises because parents and offspring have shared but not identical genetic interests therefore, offspring are more selfish, and parents disagree because half their genes are different.
parents and offspring disagree over the level of:
parental investment.
what is parental investment.
PI is any parental expenditure that increases offspring fitness AND reduces a parent’s ability to invest in other offspring (must know this part of the term)
explain the HIGH cost of parental investment of Nazca boobies and the solution to decreasing the cost of reproduction.
Nazca boobies have the capacity to lay two eggs. If both are to survive, there is a 25% decrease in survival to the mother. to curb this low survival rate, usually the older sibling kills the younger sibling and now the mom only needs to take care of one sibling.
cost of reproduction
Greater investment in an offspring may reduce a parent’s ability to invest in future offspring
- Working too hard to take care of current offspirng results in your degeneration and reduced condition.
This present-future tradeoff is described as a cost of reproduction: more offspring now means fewer offspring in future
Natural selection is expected to maximize ___ ____ ___ (more or less)
Natural selection is expected to maximize lifetime reproductive success (more or less)
draw a reproductive success vs investment in current offspring curve. What is true reproductive success?
True reproductive success is an average between current reproductive success and future reproductive success.
This ____ ____ is the basis of offspring selfishness
This relatedness asymmetry is the basis of offspring selfishness. Parents are equally related (genetically) to all their offspring: an offspring, however, is more related to itself than its siblings (unless clonal)
Draw a fitness benefit/cost vs level of PI curve encapsulating the benefits, costs, and half costs, and where parent and offspring optimums are. What is net benefit?
net benefit: deduct cost from current benefit. Cost = lost future offspring.
The cost for offspring are less related to their future siblings than their parents are to their future children. Therefore, there is less of a cost of them to remain with their parents than it is for their parents to keep providing for them.
The cost for the parents are more because of the relatedness asymmetry
the optimal level of parental investment is going to maximize ____ ___, and the optimal level for offspring require higher ____ ____. What is the zone of conflict?
White arrow in this graph is the zone of conflict where the offspring optimum is where the fitness benefit to the PARENT DECREASES.
imprinted genes. How are they modified?
Imprinted genes: genes subject to be able to be turned on and off.
occurs via:
1) methylation. Adding a methyl group inhibits gene.
2) Histone modifications also turn the gene off.
One copy of the gene will be turned off depending on if it came from mother or father.
about 100 genes in the human genome are imprinted, meaning:
That is, their expression is conditional upon whether they were inherited from mother or father
An imprinted gene is turned off by methylation or histone modification
Instead of both alleles being active (diploid expression), only one gene is active (haploid expression)
kinship theory of genomic imprinting
the idea that patrigenes are expected to prefer greater PI than matrigenes, as the cost of selfishness is lower.
If dad is unlikely to mate with mother again, then dad’s genes have no interest in mother’s future offspring
For patrigenes, the future is now. They want HIGH PI, it doesn’t matter the cost to future offspring.
Genes from mother are more likely to be less selfish than genes from dad.
explain kinship theory of genomic imprinting in plants
In plants, the imprinted genes are associated with double fertilization in plants and the expression of dads genes in seed plants/flowering plants. The resources that go ointo a seed come from the mom (sporophyte). The genes that draw resources from maternal resources are actually male-donated genes.
Therefore, patrigenes have different optima for parental investment. In plants, patrigenes take more resources from mom. And mom is being more “tight” with reosurces because the kids she’s raising now is taking a lot from her and reducing her ability to make a future offspring. For the patrigenes, the future is now, they do not care about the future offspring but there are chances that the future kids will not be related to the patrigenes– it pays to just be more selfish now. Genes from mother are more likely to be less selfish than genes from dad.
Paternally active genes (maternally imprinted) should work to ____ investment in current offspring
Maternally active genes (paternally imprinted) should work to ____ investment in current offspring (in lieu of saving some resources to the future offspring.
Give an example
Paternally active genes (maternally imprinted) should work to increase investment in current offspring
Maternally active genes (paternally imprinted) should work to decrease investment in current offspring (in lieu of saving some resources to the future offspring
Ex/ IGFII (paternal gene)– gene that enhances the growth of the offspring and
H19 (female gene)– downregulates IGFII
How does gestational diabetes arise
Embryos favour a higher level of blood glucose than mother: embryos produce anti-insulin hormones and enzymes that degrade insulin
Embryo benefits from greater access to nutrients.
Caused by embryonic/fetal genes. The embryo produces hormones and enzymes that degrade insulin so that mom cannot regulate her blood glucose levels. Allows the embryo access to more resources. The developing embryo wants more and uses biochemical means to do so. Mothers who get gestational diabetes are more prone to developing type II diabetes in life. Dad’s genes in the fetal genes are at least partially responsible for this
High blood pressure during gestation
pre-elampsia
pre eclampsia is associated with ___ ____, which allows embryos to increase access to nutrients by increasing maternal blood pressure
SHALLOW PLACENTATION.
Placenta burrows into uterus wall. The deeper it burrows into uterus, the more access it has to the maternal blood supply and nutritients. The placenta is a partially foreign tissue that is contributed half by dad. The placenta will release chemicals to increase blood pressure in women to get better access to blood supply.
How can you modulate pre-eclampsia
The incidence of pre-elampsia negatively correlates with co-habitation time and even more importantly, the duration of unprotected sex.
Exposure to seminal fluid proteins primes the maternal immune system for immunotolerance of paternal antigens and reduces the incidence of pre-eclampsia
Why does assisted reproduction and the use of donor gametes increase the possibility of preeclampsia?
bc preeclampsia is a maternal-fetal conflict, and using a donor sperm and donor egg results in 0% relation to the maternal immune system. There is even more competition between dad genes and embryo genes against the mother.
What is the geographic variation in rates of pregnancy sickness.
The rate varies from about 1 in 4 women in rural Bangladesh and populations in sub-Saharan Africa, to more than 4 out of 5 women in Japan and Korea
severe morning sickness and causes
hyperemesis gravidarum.
- Can be fatal. Persistent until the last trimester, will last until fetus is born.
- Linked to over active thyroid: hyperthyroidism
morning sickness rises and falls with the amount of ___
HCG
2 forms of thyroid hormone. What is essential for the manufacturing of thyroid hormones? Secretion of the thyroid hormones are regulated by _____ ____ hromone (normally)
2 forms: thyroxine T4 and triiodothyronine, T3. Iodine is essential for the manufacture of thyroid hormone.
Secretion of the thyroid hormones are regulated by THYROID STIMULATING hormone (normally)
Normally, the secretion of thyroid hormone is regulated by TSH and is a ____ feedback loop
negative feedback loop. TSH= more thyroid hormone production, which causes TSH to downregulate afterwards.
Symptoms of hyper and hypothyroidism
Symptoms of hyperthyroidism (overactive thyroid):
- Irritability, insomnia,
- Sensitive to warm temperature
- Frequent bowel movements, diarrhea
Symptoms of hypothyroidism (underactive thyroid:
- Lethargy, chronic fatigue
- Sensitive to cold temperature
- Dry skin, coarse hair, constipation
An ABSENSE of pregnancy sickness (ie, NO thyroid hyperactivity), = higher likelihood of ____
miscarriage. Absence of pregnancy sickness= prone to spontaneous abortion
a higher likelihood of miscarriage that changes with maternal age too!
- For women under age 30, women without pregnancy sickness are 4x more likely to miscarry
- For women between 30 and 34, the risk is 6-fold greater
- For women 35 or older, the risk is 12-fold greater
T/F: the link between prenancy sickness and pregnancy outcome only holds for the first 20 weeks of gestation
true.
There is no correlation between pregnancy sickness and pregnancy losses that occur after 20 weeks
Losses due to pathogens (bacteria, viruses) generally occur after 20 weeks
Pregnancy losses before 20 weeks are usually due to genetic or epigenetic defects
Losses due to pathogens (bacteria, viruses) generally occur ____ 20 weeks
Pregnancy losses ____ 20 weeks are usually due to genetic or epigenetic defects
Losses due to pathogens (bacteria, viruses) generally occur after 20 weeks
Pregnancy losses before 20 weeks are usually due to genetic or epigenetic defects
Margie Profet hypothesis between pregnancy sickness and spontaneous abortion
Pregnancy sickness protects the mother and embryo and tends to cause food aversion, which carry a lot of pathogens. Avoiding these foods may allow mothers to avoid harmful pathogens and dietary toxins
Samuel Flaxman and Paul Sherman built on Margie Proffet’s hypothesis, creating the maternal and embryo protection hypothesis (MEPH), which sates:
1) embryos have an incomplete abiity to detoxify toxins and an incomplete immune system, leaving them vulnerable to some pathogens harmless to adults
2) mothers are immunocompromised during gestation because they have to dial down their immune system in order to deal with the foreign genes of the father. They too are vulnerable to pathogens harmeless to non pregnant adults.
Perhaps pregnancy sickness may protect mothers and embryos from dietary hazards
Why is Margie Profets, Samuel Flaxman and Paul Sherman’s hypothesis about the Maternal embryo protection hypothesis problematic?
Pathogen protection cannot be the reason behind sickness because pathogens affect abortion rates after the first 20 weeks, but PS occurs before the first 20 weeks.
3 lines of evidence for MEPH
- The link between pregnancy sickness and pregnancy outcome
- Food aversions associated with pregnancy sickness are plausibly protective
- The link between diet and pregnancy sickness in rural societies –> women in rural bangledesh had less sickness than meat eating countries
- Spontaneous abortion can be predicted at the time of implantation, before the onset of pregnancy sickness
- The great majority of spontaneous abortions are attributable to major ____ _____ present at conception
- Spontaneous abortion can be predicted at the time of implantation, before the onset of pregnancy sickness
- The great majority of spontaneous abortions are attributable to major chromosomal defects present at conception
High quality embryos produce more HCG, triggering _____ pregnancy sickness. Therefore, the link between pregnancy sickness and less miscarriages is because of the helth of the embryo.
High quality embryos produce more HCG, triggering more pregnancy sickness. Therefore, the link between pregnancy sickness and less miscarriages is because of the helth of the embryo. Pregnancy sickness is an index of embryo quality
Link between NVP (pregnancy sickness) and diet.
NVP is less common in societies where plants – especially corn – are the only food staples and more common when meat is a food staple.
Therefore, if NVP is indicative of embryo health where more NVP = healthier embryo, meat eating populations produce “healthier” embryos, where as corn-eating populations produce less healthy embryos.
Communities that eat cassava, sweet potato, soy, legumes, millet and cruciferous should have _____ pregnancy sickness
LESS. These foods are goitrogens - antithyroids. Antithyroid = hyPOthyroid = less pregnancy sickeness.
goitrogens are _____ glycosides. Consuming untreated bitter casava can result in paralysis.
CYANOGENIC GLYCOSIDES
Why are goitrogrens dangerous?
they impair thyroid functions. THey are associated with hypothyroidism. They IMPAIR IODINE UPtAKE, whch prevents the formation of T3 and T4 hormone. If you have adequate iodine consumption, goitrogen consumptions are fine.
We’ve long known that hyperemesis gravidarum is linked to _____thyroidism
We’ve long known that hyperemesis gravidarum is linked to hypERthyroidism. Therefore, vegetables that promote hypothyroidism will prevent pregnancy sickness, but may also be indicative of a less healthy fetus, since pregnancy sickness is also correlated with increased levels of HCG.
If pregnancy sickness is indued by HCG, how is pregnancy sickness linked to a mother’s thyroid function?
hCG and TSH are part of the same glycoprotein hormone family
hCG is secreted into the maternal bloodstream and interacts with the TSH receptor, activating the thyroid and resulting in potential hypERthyroidism. goitrogens prevent this interaction, resulting in hyPOthyroidism.
Hershman argued that ____ was a back-up system for the maternal thyroid stimulating hormone, but it did not fully evolve to perfection
___ is indeed a second control system, but not imperfect – it works just fine from the embryo’s point of view, but bad for the mother.
It induces mothers to produce thyroid hormone even when they don’t want to.
Parent-offspring conflict over thyroid function
Hershman argued that HCG was a back-up system for the maternal thyroid stimulating hormone, but it did not fully evolve to perfection
HCG is indeed a second control system, but not imperfect – it works just fine from the embryo’s point of view, but bad for the mother.
It induces mothers to produce thyroid hormone even when they don’t want to.
Parent-offspring conflict over thyroid function
_____ is a micronutrient key to cognitive development
iodine
___ ____ is the single greatest cause of preventable cognitive impairment
Iodine deficiency is the single greatest cause of preventable cognitive impairment. Distributing iodized salt to deficient population was the most cost effective health initiative ever
Why is iodine important to embryos? Where can you get sources of iodine?
Iodine is essential for the synthesis of two thyroid hormones (T4 and T3) necessary for skeletal maturation and neurological development
Thyroid hormones are key in mammalian brain maturation, affecting neural cell migration, differentiation, and signaling.
Among the important micronutrients it is unusual in that there is very little somatic storage: iodine losses need to be replenished from diet continuously
What are the key natural sources of iodine?
Seafood, eggs, dairy, meat ànd things that aren’t eaten because of morning sickness! –> mother doesn’t want to eat what the fetus needs to grow. Conflict.
Goiterbelts
Goiter belts; parts of the midwest. Severely iodic deficient populations. When provided iodized salt, they found that IQ rose a full standard deviation
How do gestational goiters occur?
Mothers need to protect their own thyroid status for future reproduction: iodine demands more than double during pregnancy
BUT: embryo demands for iodine may drain maternal somatic reserves.
this is a conflict. maternal genes want to retain iodine, but the embryo wants it. causes iodine deficiency in the mom.
In iodine deficient regions, maternal thyroid function deteriorates with successive pregnancies and can result in multinodular goiterGestational goiter is linked to thyroid disease later in life that reduces fertility and increases spontaneous abortion
Most plant foods are poor sources of dietary iodine; iodine content depends on iodine level in the soil: low in interior and montane regions
Therefore, iodine deficiency occurs where iodine is lacking in the earth’s crust. Coastal populations have____ access to iodine
Most plant foods are poor sources of dietary iodine; iodine content depends on iodine level in the soil: low in interior and montane regions
Iodine deficiency occurs where iodine is lacking in the earth’s crust: coastal populations have greater access to iodine
goitrogens are anti-nutrients that ____ iodine uptake
impair
Iodine demands ___ sharply during pregnancy due to embryo demands and increased renal clearance
Embryos cannot rely upon iodine-deficient mothers to deliver sufficient iodine
So they use take it from their mother
Iodine demands rise sharply during pregnancy due to embryo demands and increased renal clearance
Embryos cannot rely upon iodine-deficient mothers to deliver sufficient iodine
So they use take it from their mother
describe the link behind hypothyroidism (because goitrogens prevent thyroid function) and no pregnancy sickness
in iodine deficient or hypothyroid mothers, HCg production suppresses TSH, but DOES NOT INCREASE THYROID HORMONE PRODUCTION. Therefore, rT3 is low because the iodine levels are insufficient. If you don’t have rt3 you don’t have thyroid hormone. Thus no nausa/vomiting and pregnancy
____ is an index of thyroid hormone production and is the proximate trigger for pregnancy sickness.
rT3 (metabolite)
What is needed to induce pregnancy sickness?
- A high quality embryo (no major chromosomal defects) that can generate sufficient hCG to stimulate the maternal thyroid.
- if there are chromosomal defects (ex/ in older mothers), there is no pregnancy sickness. - A hyperthyroid mother that can respond to hCG stimulation and produce more thyroid hormone.
- if a mother is hypothyroid due to goitrogen consumption or iodine deficiency, there is no pregnancy sickness.
therefore, link between pregnancy sickness and outcome is larger in older mothers.
Link between diet and pregnancy sickness in traditional societies.
Most plants are poor sources of dietary iodine
Some plants are goitrogenic
plant-based diets more likely to be iodine deficient and goitrogen rich, inducing hypothyroidism in the mother.
in a study conducted by samuel flaxman and colleagues, staple foods in societies without pregnancy sickness (NVP) had a ___ iodine and ___goitrogen content.
Staple foods in societies without NVP had a low iodine and high goitrogen content.
The rate of pregnancy sickness clearly ____ with the iodine status of the population
The rate of pregnancy sickness clearly rises with the iodine status of the population. more iodine = maternal hyperthyroidism= more likely for pregnancy sickness.
Iodine nutrition is linked to the incidence of pregnancy sickness; and pregnancy sickness is not affordable under conditions of iodine deficiency.
Pregnancy sickness reduces dietary diversity. It induces aversions to foods rich in iodine and iron (meats, seafood, dairy, eggs) and can result in micronutrient deficiencies.
Therefore, a mechanism to reduce pregnancy sickness in iodine deficient environments benefits both mother and embryo. PS reduces dietary variation. You can do that in an iondine high environment, but not if you are low in iodine. If a woman is iodine deficient, she will be “allowed” to eat anything in order to obtain iodine.
Pregnancy sickness is linked to maternal-fetal conflict over ____ to ____ and appears to be induced by placental (embryonic) hormones
Pregnancy sickness is linked to maternal-fetal conflict over access to iodine and appears to be induced by placental (embryonic) hormones.
Embryo produces HCG, which stimulates thyroid hormone. You need iodine for this to work. if it works (you are hyperthyroid), the embryo will try and take the iodine and thyroid hormones you produce in order to develop itself.
If HCG doesn’t work because you are hypothyroid and iodine deficient, you will not get sick because there is nothing for the embryo to steal from you.
