A-TYPE AND B-TYPE LAMINS ARE DIFFERENTIALLY EXPRESSED IN NORMAL HUMANTISSUES

A selection of normal human tissues was investigated for the presence of lamins B1, B2, and A-type lamins, using a panel of antibodies speci fic for the individual lamin subtypes. By use of immunoprecipitation a nd two-dimensional immunoblotting techniques we demonstrated that thes e antibodies do not cross-react with other lamin subtypes and that a r ange of different phosphorylation isoforms is recognized by each antib ody. The lamin B2 antibodies appeared to decorate the nuclear lamina i n all tissues examined, except hepatocytes, in which very little lamin B2 expression was observed. In contrast to previous studies, which su ggested the ubiquitous expression of lamin B1 in mammalian tissues, we show that lamin B1 is not as universally distributed throughout norma l human tissues as was to be expected from previous studies. Muscle an d connective tissues are negative, while in epithelial cells lamin B1 seemed to be preferentially detected in proliferating cells. These res ults correspond well with those obtained for lamin B1 in chicken tissu es. The expression of A-type lamins is most prominent in well-differen tiated epithelial cells. Relatively undifferentiated and proliferating cells in epithelia showed a clearly reduced expression of A-type lami ns. Furthermore, most cells of neuroendocrine origin as well as most h ematopoietic cells were negative for A-type lamin antibodies.