ICln is essential for cellular and early embryonic viability

pICln is a 26-kDa protein that is ubiquitously expressed and highly conserv ed from Xenopus laevis to Homo sapiens. The physiological functions of pICl n remain to be established. To address this question, we disrupted the ICln gene in embryonic stem cells. We found that murine embryos lacking ICln di e early in gestation (between stages E3.5 and E7.5). Furthermore, we found that ICln is essential for embryonic stem cell viability. Previously, we sh owed that pICln interacts directly with a homolog of a yeast protein that b inds a PAK-like kinase and participates in the regulation of cell morpholog y and cell cycling. pICln also forms a complex with several core spliceosom al proteins, and this interaction may play a role in the regulation of spli ceosomal biogenesis. Collectively, these data strongly suggest that pICln p articipates in critical cellular pathways, including regulation of the cell cycle find RNA processing.