what is a pluripotent stem cell?

Can someone please explain why C and not B is the answer to the attached MCQ?

According to my textbook RBC are produced from haematopoietic stem cells in bone marrow which are multipotent.

In previous edexcel mark schemes they define pluripotent stem cells as cells that can give rise to "many" / "most" cell types. This question uses the word "some".

Thanks a lot.

Original post by thomas.rhett

Can someone please explain why C and not B is the answer to the attached MCQ?

According to my textbook RBC are produced from haematopoietic stem cells in bone marrow which are multipotent.

In previous edexcel mark schemes they define pluripotent stem cells as cells that can give rise to "many" / "most" cell types. This question uses the word "some".

Thanks a lot.

Hmm, I think you're right to question this. Hæmatopœtic stem cells are immature multipotent cells, and not pluripotent, and give rise to a few different cell types.

I think the error is in the wording of the question: it should be 'Red blood cells are produced from multipotent stem cells found in bone marrow'. The answer then is 'C', which is correct.

Reply 2

Jpw1097

19

Original post by thomas.rhett

Can someone please explain why C and not B is the answer to the attached MCQ?

According to my textbook RBC are produced from haematopoietic stem cells in bone marrow which are multipotent.

In previous edexcel mark schemes they define pluripotent stem cells as cells that can give rise to "many" / "most" cell types. This question uses the word "some".

Thanks a lot.

As @Reality Check has said, haematopoietic stem cells are multipotent, not pluripotent. Haematopoietic stem cells give rise to red blood cells, as well as white blood cells and platelets. Pluripotent means that the cell is able to differentiate into any embryonic tissue (i.e. all cells within the body), whereas totipotent stem cells can also give rise to extraembryonic tissue (i.e. trophoblasts/placenta).

So in the list of options you have, A refers to totipotent, B refers to pluripotent, C to multipotent and D would be some erythroid progenitor.

(edited 2 years ago)

Reply 3

thomas.rhett

OP

10

Thank you both very much for your responses.

The question below is also from edexcel IAL (2017) but refers to stem cells in bone marrow as "pluripotent" but it doesn't refer specifically to hematopoietic stem cells.

I don't understand why it is wrong to say bone marrow cells are pluripotent because they can give rise to all cell types except cell types in extra-embryonic tissues.

Q/ Suggest why the stem cells in the bone marrow are considered to be pluripotent:
ANS: they can form many cell types
DO NOT ACCEPT ‘all cells types except {embryonic cells / embryonic-supporting cells / extra embryonic cells / totipotent cells}’

Examiner’s comments: Candidates have clearly been taught a definition of pluripotency in the context of the blastocyst but clearly do not realize there are pluripotent cells anywhere other than in the blastocyst. When you see the command word 'suggest' you must apply your knowledge to the context of the question and not just recall what you have been taught.

Reply 4

Reality Check

22

Original post by thomas.rhett

Thank you both very much for your responses.

The question below is also from edexcel IAL (2017) but refers to stem cells in bone marrow as "pluripotent" but it doesn't refer specifically to hematopoietic stem cells.

I don't understand why it is wrong to say bone marrow cells are pluripotent because they can give rise to all cell types except cell types in extra-embryonic tissues.

Q/ Suggest why the stem cells in the bone marrow are considered to be pluripotent:
ANS: they can form many cell types
DO NOT ACCEPT ‘all cells types except {embryonic cells / embryonic-supporting cells / extra embryonic cells / totipotent cells}’

Examiner’s comments: Candidates have clearly been taught a definition of pluripotency in the context of the blastocyst but clearly do not realize there are pluripotent cells anywhere other than in the blastocyst. When you see the command word 'suggest' you must apply your knowledge to the context of the question and not just recall what you have been taught.

I've done a bit more reading on this, and yes - HSCs are defined as pluripotent. This, from Cell Death Discovery (Nature Publishing) [Ng, A., Alexander, W. Haematopoietic stem cells: past, present and future. Cell Death Discov. 3, 17002 (2017). https://doi.org/10.1038/cddiscovery.2017.2]

Screen Shot 2021-12-08 at 08.03.18.png

I certainly thought that a HSC was multipotent, rather than pluripotent, so this is learning for me. @Jpw1097 - every day is a schoolday on TSR, it seems :smile:

Reply 5

Jpw1097

19

Original post by Reality Check

I've done a bit more reading on this, and yes - HSCs are defined as pluripotent. This, from Cell Death Discovery (Nature Publishing) [Ng, A., Alexander, W. Haematopoietic stem cells: past, present and future. Cell Death Discov. 3, 17002 (2017). ]https://doi.org/10.1038/cddiscovery.2017.2]

Screen Shot 2021-12-08 at 08.03.18.png

I certainly thought that a HSC was multipotent, rather than pluripotent, so this is learning for me. @Jpw1097 - every day is a schoolday on TSR, it seems :smile:

I always thought HSCs were the classic example of multipotent stem cells, but yes it seems that they are now considered pluripotent. Thanks for the update!

Reply 6

Reality Check

22

Original post by Jpw1097

I always thought HSCs were the classic example of multipotent stem cells, but yes it seems that they are now considered pluripotent. Thanks for the update!

No problem :smile:

As I say, it was news to me, too!

Reply 7

thomas.rhett

OP

10

Original post by Reality Check

No problem :smile:

As I say, it was news to me, too!

Thanks for the clarification. The first question I posted mixes up the definitions for pluripotent and multipotent which you clarified (this is from edexcel sample assessment). In the 2nd question I posted the examiner insists on one definition of pluripotency over the other. Do you have any thoughts on why that may be? I don't understand the examiner's comment.

(edited 2 years ago)

what is a pluripotent stem cell?

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