if you are specifically interested in ABO splicing I cannot help you. If instead your interest is in splicing mechanisms there are many other alternatively spliced messengers that could be used as a marker of splicing and in this case, to study several different messengers would be necessary since splicing can be somewhat specific for classes of splice sites.

One way to study biological role of particular splice variant is to use transgenic expression of your favorite splice form under tissue-specific inducible/repressible promoter in transgenic mice. I would suggest generating bi- tg mice using canonical Tet/Dox-responsive promoter. It is very convenient to use as presently there is a number of available mouse strains (commercially or though collaboration) expressing the reverse tetracycline-controlled transactivator (rtTA) protein under variety of tissue-specific promoters. Thus you will need to generate only one tg line with splice variant of your interest in Tet-responsive expression cassette and then you can cross it with various tissue-specific rtTA strains to study the effect expression on physiological function.

What I am interested in is to compare splicing in mice thymus wt vs KO.

I am not tied up with CD45 splicing. I can use other proteins but I want to use antibodies and flow cytometry because it allows us distinguish different cell types and allows quantitations.

I guess you might suggest me to do RNA seq. I am aware that this is the way to do the things (what many people do) but I would rather use something more at the protein level: MDM2 is spliced and there is at least one antibody that sees the different forms, by WB.

Anyway I might need to do RNAseq because this is the way to answer this questions.

THX to everybody