MTM1 gene is essential for SOD2 activity and normal mitochondrial function. MTM1 deletion results in decreased SOD2 activity, impaired mitochondrial function and growth defect on nonfermentable carbon source. A yeast genomic library was transformed into mtm1 deletion mutant to screen for suppressor genes of MTM1. The damage caused by MTM1 deletion is irreversible and even overexpression of MTM1 can not rescue the growth defect of mtm1 deletion mutant. Another screening strategy was adopted: a plasmid overexpressing MTM1 was transformed into wild type before the MTM1 gene on chromosome was deleted. The resulting strain, designated YES2MTM1, was transformed with a yeast genomic library. Transformants lost the plasmid overexpressing MTM1 after 5-FOA treatment. Yeast strains able to grow on nonfermentable carbon source with MTM1 deletion and overexpression of some DNA fragments were picked up and candidate suppressor genes were identified. Overexpression of five genes were identified to be able to rescue the growth defect on nonfermentable carbon source. The study will provide reference for MTM1 gene function and screening for suppressor of genes whose deletion result in irreversible damage.

Objective:To analyze and compare the differentially expressed genes (DEGs) of Yes-associated protein (YAP)-positive and negative hepatocytes and further understand the preliminary functional characteristics of YAP-positive hepatocytes in an early mouse model of nonalcoholic steatohepatitis (NASH) with transcriptome sequence (RNA-Seq).Methods:C57BL/6 mice were fed with methionine-choline deficiency (MCD) diet for 2 weeks to establish an early NASH model, and the control group was fed with normal diet. Liver tissue was stained with hematoxylin-eosin (HE) and Sirius red, and the pathological score was recorded. The expression of YAP and P-YAP were determined by immunohistochemistry (IHC) in liver tissues. Primary hepatocytes with viability greater than 90% were isolated and purified by collagenase perfusion combined with Percoll density gradient centrifugation. YAP-positive and negative hepatocytes were assessed by YAP antibody, flow cytometry and RNA-Seq analyses. Sequencing results were screened by GO, KEGG and interaction network analysis methods. RT-PCR was used to verify the expression levels of YAP and some DEGs in liver tissue model group. Two samples mean was compared by independent samples t-test. Results:Compared with the control group, the HE-stained liver tissue of MCD-induced mice at 2 weeks showed steatosis (pathological score 1.07±0.21), accompanied by lobular inflammation (pathological score 1.13±0.32) and ballooned hepatocyte (pathological score 0.80) ±0.20). Sirius red staining showed non-significant liver fibrosis (pathological score 0.40±0.40). IHC showed partial YAP-positive hepatocytes expression in an early stage of NASH. RNA-Seq analysis showed that clean reads of YAP-positive and negative hepatocytes were 49 310 604 and 5 4820 036, respectively. Compared with YAP-negative hepatocytes, YAP-positive hepatocytes had differential expression of 5 565 genes, including 1 662 up-regulated genes and 3 903 down-regulated genes. GO analysis of up-regulated genes showed that the metabolic processes related to mitochondrial functions, such as purine nucleoside triphosphate and nucleoside triphosphate were significantly enriched in biological processes (BP), while down-regulated gene analysis showed that olfactory-related receptor were significantly enriched in BP. KEGG analysis showed that DEGs were enriched in 292 pathways, and oxidative phosphorylation (OXPHOS) pathway was significantly enriched in signaling pathway. RT-PCR validated that inflammatory factors (interleukin-1β, interleukin-6), YAP and its target genes (Cyr61, Ankrd1), and Cox5b and Sdhc genes were significantly up-regulated in the OXPHOS pathway, which was consistent with the sequencing results. In addition, eight key genes with interaction network analysis were predicted.Conclusion:Changes in hepatocyte metabolic levels may be associated with increased YAP activity in an early stage of NASH.