Tuesday, February 17, 2015

Study group discussion: HNPCC (Lynch syndrome) and microsatellite instability

Just was mentioned in lecture: What is the cause of lynch syndrome (the specific cause)?

It's HNPCC. DNA mismatch repair affected.

Yes, a bit more specific! Which part of MMR?

I think it's micro satellite instability or MSH2.

Msh2 is one of them, correct!

MLH1 as well.

Mhmm. One more?

Donno any more T_T

Apparently MSH6 as well :)

Could you sum them all up? What is lynch syndrome..What are it's features?

Ovarian, Colon and Endometrial carcinoma are the features. You do the molecular talk!

Lynch syndrome (also known as HNPCC) increases the chance of colon cancer up to 80% along with increasing chances of other sorts of cancer.

It is caused by disruption of Mismatch Repair system due to mutations in 3 MMR factors : MSH2, MSH6, and MLH1

What about the microsatellite instability pathway? Which syndrome was that?

Oh I found out.. Microsatellite instability is found particularly in cells which are expressing mismatch repair defects. HNPCC is one of the of the most important syndromes where this happens. However its not an "exclusive feature" of MMR defects.

The microsatellite  instability is the evidence that the MMR isn't working properly and can't detect insertion-deletion loops that forms in the S phase. Googled and paraphrased.

Ah makes sense. Thanks!

Elaborate on the term microsatellite instability.

Umm it's kind of complex.. Usually you detect DNA by PCR, right?

Yup. You amplify the DNA!

So if while PCR, little microfragments of DNA split up which weren't there originally. They are called microsatellites. They were made during PCR. So if those are created, it means the fragment has microsatellite instability.

So these are abnormal?

They occur naturally.. But usually detected by MMR and dispatched if MMR doesn't work...
They will be present!

Yep!

Got it. Thanks!

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