Mir-34 Deletion Case Study

Question and Answer

1. Paper reported that Olfm4 deletion induces colon adenocarcinoma in APCmin mice, so why after miR-34 deletion, olfm4 positive stem cell number was increased and tumor incidence was also increased?
Their research was working on the colon tumorigenesis, but we are working on the small intestine. Also in our model, colon tumor is very rare, could because of different genetic background. The function of Olfm4 may be also tissue specific.
2. Do these changes caused by the genetic modification, but not miR-34 deletion?
We also have the floxed control mice with the same genetic modification, but they did not show any difference to wild-type control mice. So for the crossing which will contain three genetic modified sites, we
An increased symmetric stem cell division was used to explain the increased number of stem cell after miR-34 deletion. But why the number of differentiated cell types (eg. Paneth cell and Goblet cell) also increased?
The increased symmetric stem cell division means the division rate of SS division was increased, however, there always an AS division at the same time. As the SS division could increase the stem cell number, but in order to keep the homeostasis of the crypt environment, the support cell (eg. Paneth cell) need also to be increased.
4. How about colon tumorigenesis?
In our model, colon tumor is rare, maybe is due to the different genetic background, so we focus on the tumorigenesis of the small intestine.
5. Paneth cell increasing and expansion are a primary response to miR-34 deletion or a response to bacterial invasion from a compromised intestinal epithelial barrier?
As in miR-34 ko mice, only expanded paneth cell was found, but not bacterial. Paneth cell increasing should be the primary response to miR-34 deletion. Further study may analyze the inducible miR-34 ko APCmin mice, at multiple time points after induced deletion. Check the paneth cell and bacterial status, and the expression level of involved
We have already used an RNA pool instead of single RNA sample from the same mouse to minimize the variation between the individual tumors. But to reduce the variation from the individual mouse need to increase the total mouse number. In the other hand, what we found from the sequencing results was the pattern throughout all the mice, this may indicate the direction for our further investigation.
11. How about the down-regulation pathways found in the bioinformatics? Do they have any connection to results?
The down-regulation pathways were mainly on immune reactions, which could be a mir-34 indirect effect. As the immune reactions also contribute to the bacterial defense, we suggest that it may be the other reason “mucosal defense defect” to explain the increased bacterial infiltration besides barrier defect.
12. Some of your interested genes were mainly expressed on stromal cells or were the extracellular matrix, how did these genes contribute to the regulations?
As miR-34 is a global regulator, it may also regulate the cellular signal transduction by its target genes not only between cancer cells but also between cancer cells and cancer-associated