Epigenetique 1.1: Empreinte parentale Flashcards
Define Empreinte parentale and relation with meiosis
On dit qu’un gène est sujet à l’empreinte parentale lorsque ses allèles paternel et
maternel ne sont pas transcrits de façon identique.
Par convention, on dit qu’un “gène a une empreinte paternelle” lorsque l’allèle paternel
est inhibé.
Cool thing abt meiosis:
l’empreinte est effacée dans les cellules germinales (méiose)
nouvelle marque selon le parent, plutôt que selon l’origine grand-parentale
IGF-2 vf H19?
Both IGF2 and H19 undergo a process called genomic imprinting, which means their activity depends on which parent they were inherited from.
For IGF2, only the copy inherited from a person’s father is active, while the copy inherited from the mother is not active1. For H19, only the maternal allele is expressed
IGF2 provides instructions for making a protein called insulin-like growth factor 2, which promotes the growth and division of cells. -> big baby, accelerator
H19 RNA expression might be to regulate the expression of IGF2. -> small baby, BREAKS
What is a Môles complètes, clinical relevance.
When the ovocyte contains 46 chromosomes, tous d’origine paternelle
Due to parental imprinting, we get important genes that are inhibited and other genes that will be overexpressed
Huge placenta
clinical relevance:
Only placenta without a baby -> Risque d’évolution en choriocarcinome (cancer)
What is Triploïdie paternelle (môle partielle)?
Similar to mole complete but less severe->
Faible risque d’évolution en cancer
46 paternels + 23 maternels
This is beacause there is a little break from the 23 maternal
What combination would give Placentas très hypoplasiques?
Triploïdie maternelle: 46 mat + 23 pat
because
—> Freins (H19) x 2,
Accélérateur (IGF2) x 1
papa wants to have big babies
mam wants to have small babies -> small placenta
Syndrome de Beckwith-Wiedemann
Describe what it is and what form is the worst?
Overexpression of IGF-2 in utero that leads to a form of gigantism
Increased probability of cancer
Worst form is disomie unipaternelle -> 2 paternal 11p15.5 -> OVEREXPRESSION OF IGF-2 with no BREAK-> more risk for cancer
Silver russel describe
Opposite of Beckwith-Wiedemann ->
surexpression H19 et inhibition IGF2
Leads to: Retard de croissance Retard développemental
L’hypothèse Knudson?
He was the one to say that on tp of conventional mutations, a cancer must also include epigenetic mutations!!!
Oncologie: Implications thérapeutiques given epigenetics?
You can use Inhibiteurs de DNMT et de HDAC
This is so that you can reactivate these molecules so that they can Réactivation des gènes suppresseurs de tumeurs (anti-oncogènes)
For example, p53 will lead to apoptosis if activated in a cancerous cell
What do we mean by cycle de krebs epigenetique?
Plusieurs points d’entrée (Facteurs de transcription inhibiteurs, Méthylation CG, DNMT, HDAC, MeCP, dsRNA, miRNAs, etc)
Lorsqu’un mécanisme est activé, il activera tous les autres mécanismes (double assurance)
