what is a tissuespecific gene? transcription factors?

[naejjiv]

afte reading a bunch of papers i am getting more confused than ever.

tissue specificity is the level of expression of a gene in a certain type of cell, am i correct?
so a tissue-specific gene will only be expressed in that type of cell?
how do you decide if a gene is tissue specific? in my current work, i have a gene which is known to be tissue specific from previous researchers' work... when silenced, two organs completely do not develop at all. but these two organs are made from different tissue -- one forms from mesoderm, the other from ectoderm. so how is this gene considered tissue specific?

also, transcription factors are needed for the regulation of gene expression (for binding rna polymerase to dna), yes?
and transcription factors are proteins
proteins are a product of gene expression
so how did these genes which made the protein (TF) get expressed?

please advise.
thank you very much!

[canalon]

also, transcription factors are needed for the regulation of gene expression (for binding rna polymerase to dna), yes?
and transcription factors are proteins
proteins are a product of gene expression
so how did these genes which made the protein (TF) get expressed?

Think how cells are made.

[zerhos]

afte reading a bunch of papers i am getting more confused than ever.


........how do you decide if a gene is tissue specific?.............

a

you need to analyze the expression pattern by in situ-hybridizzation
or PCR,Q-PCR on cell lysate of each tissue

also, transcription factors are needed for the regulation of gene expression (for binding rna polymerase to dna), yes?
and transcription factors are proteins
proteins are a product of gene expression
so how did these genes which made the protein (TF) get expressed?

usually by external factors such as hormones, cytokines, etc.
each cell type will respond differently to the same external factor, through different receptors and activate different transcription pathways and therefore different tf
That was in addition to the action of epigenetics

[Martin11]

Without knowing the gene you are referring to, perhaps the gene product has two distinct functions at two different points in time possibly due to combinatorial effects by different cellular proteins at different stages of cell differentiation (my guess). So I guess zerhos's suggestion has some merit in terms of going about elucidating such interactions. But I think some sort of high throughput gene expression profiling should come first because that would let you see patterns of gene activity and possibly provide specific leads to investigate.
I also agree with zerho about the external factors directing early protein expression in cells