Lecture 15 Imprinting (II) Flashcards
Peg3 gene?
Paternally expressed gene 3.
Maternal copy is imprinted to be silenced.
Expressed in maternal hypothalamus, placenta and foetal hypothalamus.
Regulates maternal behaviour and physiology.
imprinted inheritance, so requires paternal inheritance.
Peg3 effect on behaviour
maternal care, milk release.
suckling in pup.
Peg3 KO in mother
maternal care impaired - time spent retrieving pups increases.
latency of nest building increases.
latency of crouching over pups increases.
impacts litter growth, weight decreases in KO litter. delayed growth, puberty onset and adult reproduction.
Peg3 KO pups
Impaired placental growth
Impaired hormonal priming for maternal care and milk let-down.
Delayed growth, puberty onset and adult reproduction
Peg3 KO overall effects
The convergent actions of Peg3 in mother and foetus illustrate its functional co-adaptation for the hypothalamus and placenta
Peg3 in males
can’t detect estrus cycle.
80:1 likelihood of finding a fertile female.
mice estrus cycle?
estrus - when progesterone low ready to be fertilised.
high they are in diestrus state, can’t be fertilised.
if males can detect, pheromones, advantage.
peg3 generational?
even if silenced will still be carried to next gen
turner syndrome
one x chromosome.
random, not hereditary.
turner chromosome karyotype
70% X maternal
30% X paternal
23rd (sexual) chromosome only one X.
nondisjunction during meiosis II. don’t split normally, some cells end up with too few/many X.
when fertilisation occurs, can lead to 1 X.
Turner
X chromosome contains approx. 900 genes, while the Y chromosome contains 60 genes.
To maintain relative gene dose equivalence between 46,XY men and 46,XX women, one X chromosome is typically inactivated in women in any given somatic cell.
In Turner Syndrome girls, all cells contain an X chromosome with the same parental origin.
turner phenotype
short height.
cardiac abnormalities.
Ovarian failure, therefore no production of sexual steroids.
Absent secondary sexual characteristics during puberty.
May exhibit behavioural abnormalities, including higher prevalence of autism.
turner treatment
no cure.
female hormone replace therapy, helps height, can get pregnant.
growth hormone therapy.
regular health checks of heart, kidneys etc.
Life expectancy is slightly reduced.
turner cognitive features.
week 15 in gestation, overian failure occurs due to lack of sex steroids.
Executive function is affected, with impairments in attention, working memory, cognitive flexibility and abstract reasoning.
Moderate social impairments including core deficits in recognition of emotional affect, particularly fear and impaired detection of non-verbal cues such as eye gaze.
don’t occur in those with ovarian failure, therefore these cognitive features are likely X-linked in origin.
turner girls v boys
girls special education needs higher, also social cognition worse.
Some genes involved in behavioural and social cognitive skills are paternally imprinted.
Hypothesis is that in maternal X, these genes are silenced.
A search is underway to find those genes in the X chromosome.
These data suggest that there are primary (non-hormonal) factors contributing to the difference between the sexes.
