Calpain 2 expression pattern and sub-cellular localization during mouse embryogenesis

Regulation of migration and proliferation by calpain has been shown in various cell types; however, no data are available concerning calpain 2 (CAPN2) localization in embryonic tissues. Here, we report the expression pattern of CAPN2 during mouse embryonic development. Expression of the capn2 gene is observed throughout embryonic development. From ES cells and the 8-cell stage to late neurulation stages, CAPN2 is expressed in the cytoplasm and nuclear compartments, with a clear co-localisation with chromatin. Whole-mount in situ hybridization analysis from E8.5 to 14.5 stages indicates high levels of capn2 expression in the nervous system, heart and mesodermal tissues. Up-regulation is maintained during later developmental stages in proliferating cells and in precursor cells involved in muscle (myoblasts) or bone formation (chondrocytes). At later developmental stages, elevated mRNA levels coincided with CAPN2 nuclear localization in these cell types, while differentiated cells maintained cytoplasmic expression. This detailed analysis reveals dynamic expression: nuclear localization was associated either with active cell mitosis in embryonic stem cells and early developmental stages or with precursor cells later during organogenesis. Thus, these data indicate that CAPN2 may represent a key factor in development from the first cell division.