The thesis is devoted to the analysis of the role of the genes of the adherin complex: Cdh2, Ctnnb1 and Ctnna1 and their products in cardiogenesis and adult heart functioning, the study of the participation of Ctnnb1 and Ctnna1 genes in the regulation of the activity of cardiomyocyte signaling systems and, accordingly, their participation in control of proliferative activity and terminal differentiation of neonatal cardiomyocytes.
It has been shown for the first time that homozygous knockout of the Cdh2 gene in embryo cardiomyocytes causes a violation of the formation of myocardial tissue, delayed embryo development and leads to lethality of embryos (E10.5 - E12.5) due to the violation of the adhesive function of its product N-cadherin.
The study has established that cytoplasmic partners of N-cadherin, β-catenin and α-E-catenin are involved in the formation of intercellular adhesion and in controlling of the size and proliferative activity of myocytes. Thus, the homozygous knockout of the Ctnnb1 gene enduced lethality of the mutant embryos in late gestation and in newborn animals (P1-3). Both the hetero- and homozygous knockout of the Ctnnb1 gene caused the inhibition of proliferative activity of neonatal cardiomyocytes, an increase in their size and a decrease in the size of the hearts in newborn animals (P1-2). The inhibition of terminal differentiation of cardiomyocytes caused the knockout of the Ctnna1 gene and the Ctnnb1 gene.
It has been found that homozygous knockout of the Ctnnb1 gene leads to inhibition of the activity of the canonical Wnt cascade in the hearts of newborn (P1-2) animals. The heterozygous knockout of the Ctnnb1 gene also causes a malfunction of the Wnt / β-catenin cascade, in particular in the hearts of newborn mice, increased content of skeletal proteins APC and Axin1. Also, with the Ctnnb1 knockout and suppression of Wnt / β-catenin signaling, increased activity of Pi3K / Akt signaling and MAPC signaling was observed in the hearts of adult animals.
We have specified the function of the canonic Wnt cascade in the formation of a hypertrophic response, using the Meta-analysis, revealed a relationship between expression of β-catenin and hypertrophy. Using the model of chronic hypertension (AngII infusion) and athletic myocardium, it has been shown that the activation of the signaling function of β-catenin is a necessary condition for adaptation of the heart to endurance training and occurs in the early stages of remodeling.
It has been shown for the first time that heterozygous knockout Ctnnb1 causes delayed athletic myocardial development during prolonged physical activity.
The present study has demonstrated for the first time that the knockout of the Ctnnb1 gene results in an increase in the expression of its homologue γ-catenin (Jup) in the myocardium of newborn mice. The latter is able to participate in the regulation of the activity of the canonical Wnt signaling cascade (regulates the expression of Axin2 and c-Myc).
It has been shown that both heterozygous and homozygous cardiac-specific knockout Ctnna1 causes the activation of the Wnt / β-catenin signaling cascade, both in cardiomyocytes of newborn (P1-2) and adult (10 months) of animals. Also, the product of Ctnna1 gene (α-E-catenin protein) in modulating the transcriptional activity of the main mediator of the Hippo signaling pathway-Yap has been established. Increased expression of the target genes of Yap: Aurka, Ctgf, Il1rl1, Tnfrsf1b with Ctnna1 knockout was shown.
It has been demonstrated for the first time that the knockout of Ctnna1 in cardiogenesis results in the development of heart failure, and as a consequence, premature mortality of animals (11 months), accompanied by significant histopathological disorders.
It has been found that both hetero- and homozygous knockout of Ctnna1 results in an increase in the activity of Pi3K / Akt signaling (increasing the content of phosphorylated AKT according to serine 473), MAPK cascade violation and inhibition of the cAMP / PKA signaling cascade (decrease in the content of phosphorylated PKA).
This study has established that knockout of Ctnna1 gene causes a violation of the molecular mechanisms regulating the metabolism of lipids in the heart.
On the basis of the results of the study, a hypothesis according to which the genes of the adherine complex (Cdh2, Ctnna1 and Ctnnb1) have critical significance for normal development and functioning of the heart is proposed. The inhibition (or excitation) of the expression of the Cdh2, Ctnna1, and Ctnnb1 genes causes lethality and molecular genetic patterns of myocardial changes in the experimental mice due to the violation of the adhesive and regulatory function of their products (N-cadherin, α-E-catenin and β-catenin, respectively). Ctnna1 and Ctnnb1 gene mutations in humans may also be associated with impaired cardiac development and function.
