HETEROZYGOS ELETION OF β-CATENIN IN EARLY CARDIOGENESIS ATTENUATED THE HEART GROWTH AND AFFECTED ON CANONICAL WNT KINETICSAim. In our present work, we have analyzed newborn and embryonic heart under the β-catenin haploinsufficiency. Methods. Beta-catenin conditional knockout mice were bred with α-MHC-Cre transgenic mice. In such way we generate the β-catenin haploinsufficient new born (P1-2) and embryonic hearts (E12,5 an E14,5) With rtPCR using we analyze the canonical WNT signalling kinetics in embryonic and newborn hearts. Namely we have analyzed the level of TСF-4, Axin2, c-Fos and CyclinD2 genes expression .Beside of this we have studied the γ-catenin gene expression under normal and β-catenin haploinsufficient conditions. Results. Cardiac β-catenin knockout leads attenuated newborn heart growth and associated with γ-catenin expression up-regulation. Canonical Wnt signalling activated in later cardiogenesis (E12,5-14,5) in WT heart and downregulated in newborns. Conclusions. We have shown the importance of canonical Wnt during later cardiogenesis. Thus β-catenin haploinsufficiency leads to violation of WNT kinetic in latter embryos and attenuated the heart growth.