Preliminary Study On The Phenotypes Of Different Organs After Extensive Knockout Of Rtcb Gene In Adult Mice

RTCB is currently the only known RNA ligase in metamorphosis,and it is a non-broad-spectrum RNA ligase that only specifically connects the 2’,3’-cyclic phosphate and 5’-hydroxyl ends produced by RNA shearing and mainly paticipates in the process of RNA splicing and repair in animals.It has been found that in metazoans,RTCB regulates the unfolded protein response by participating in the splicing of XBP1 during endoplasmic reticulum stress.At present,little is known about the physiological functions of RTCB,and there are only a few reports that it is involved in physiological processes such as the morphology of the mouse nervous system and early embryonic development.Since the knockout of the Rtcb gene resulted in the death of mouse embryos,follow-up studies could not be carried out.There is no report about the role of RTCB in different organs of the whole body.This study used UBC-Cre-ERT2 tool mice to construct Rtcb^f/f;UBC-Cre-ERT2gene conditional knockout mice to explore the functions of Rtcb genes in various types of mouse organs.PCR,frozen section of animal tissues,H&E staining and immunohistochemistry were used to detect the effect of Rtcb genes on fertility and histomorphology of each system after the Rtcb gene was knocked out in adult mice.The main results are as follows:（1）In this experiment,Rtcb^f/fmice were mated with UBC-Cre-ERT2 tool mice which express Cre recombinase specific in time and space throughout the body to obtain adult Rtcb^f/f;UBC-Cre-ERT2 knockout mice,successfully circumventing the embryonic lethality of Rtcb knockout mice,and Rtcb^f/f;UBC-Cre-ERT2 double transgenic mice have reproductive capacity without drug induction.（2）Before and after Tamoxifen induction,Rtcb^f/f;UBC-Cre-ERT2 mice had different levels of Rtcb gene knockout in the heart,liver,spleen,lung,kidney,brain,testis,large intestine,and small intestine.Although in theory,Cre-ERT cannot enter the nucleus to exert recombinase activity without Tamoxifen induction,in fact,Rtcb^f/f;UBC-Cre-ERT2 mice will undergo different degrees of DNA recombination even in the uninduced state.（3）Rtcb gene knockout caused pathological changes in most of the mouse system organs,such as mouse lungs,intestines,and olfactory bulbs.The smooth muscle thickness of the jejunum,cecum and rectum of Rtcb knockout mice was further measured.The results showed that the smooth muscle layer of ACTA-labeled Rtcb knockout mice was significantly thinner.In summary,this study shows that Rtcb has an important effect on the structure and physiological functions of the whole body organs and tissues of mice.Rtcb knockout causes systemic inflammation in mice,severe intestinal cell defects and even structural incompleteness,but its specific molecular regulation mechanism still needs to be studied in depth.