LNA probes - questions on targets (Jan/11/2008 )

i have a very naive question about the use of LNA mirna probes in whole mount in situ hybridisation:
how do the probes just bind the mature miRNA in the cytoplasm and not the primary transcript too in the nucleus? What about the genomic complementary sequence? how come the LNA oligo doesnt detect or give a signal for that too?
is it possible to use LNA probes for miRNAs in southern blots to detect the copy number of a miRNA gene in the genome? if anyone has any experience on this i would be interested to read more..
Thanks in advance.

I'm not 100% certain, but I think you don't see any signal because the concentration is so low - both at the genomic DNA level and at precuror level, because precursors are rapidly processed to mature miRNAs.