RFX6 transcription factor is believed to play a central role in directing cell development of insulin-producing pancreatic islet. RFX6 homozygous mutations cause syndromic neonatal diabetes with hypoplastic pancreas. However, RFX6 heterozygous mutations cause maturity-onset diabetes of the young (MODY) with normal pancreas development. Here, we show that RFX6 may control islet cell development and insulin production in different manners. The rfx6 knockout zebrafish generated by CRISPR/Cas9 exhibited an overt diabetes phenotype. Pancreatic islet failed to form compact structures in the knockout fish. While endocrine pancreatic islet non-β-cells were absent, insulin-producing β-cells were present in the knockout fish. Although insulin mRNA level was normal in the β-cells of the knockout fish, insulin protein level was decreased. High-throughput RNA sequencing (RNAseq) showed that differentially expressed genes were enriched in the translation term in islet β-cells from the knockout fish. Chromatin immunoprecipitation sequencing (ChIPseq) of normally developed islet β-cells from mice demonstrated that rfx6 interacted with translation initiation factors and controlled insulin translation. Our data indicate that Rfx6 may act as a transcription factor regulating the transcription of genes involved in mRNA translation, which may represent a new mechanism and treatment strategy for diseases.
Jing Lu, Cheng Cheng, Zhen-chao Cheng, Qian Wu, Han Shen, Ming-xia Yuan, Bo Zhang, and Jin-Kui Yang
Rong-Ying Li, Xue-Song Li, Li Shao, Zhi-yuan Wu, Wen-Hua Du, Sheng-Xian Li, Shuang-xia Zhao, Ke-min Chen, Ming-Dao Chen, and Huai-Dong Song
Although circulating ghrelin levels correlate inversely with adiposity at baseline, little is known about the effect of percent visceral adipose tissue value (PVATV) on ghrelin expression and secretion in response to fasting. Our study demonstrated that ghrelin increased with 24-h fasting in rats with the lowest PVATV (less than 6%), after 3 days in rats with intermediate PVATV (6–9%) and 5 days in rats with the highest PVATV (greater than 9%). Ghrelin mRNA in the stomach was increased after 3 days in low-PVATV (5.8±0.9%) rats but not in high-PVATV (14±1.6%) rats. Therefore, both ghrelin secretion and mRNA were delayed in response to fasting in rats with increased visceral fat. In rats matched for PVATV, but with different body weights, the fasting induced similar levels of increased ghrelin while in rats with different PVATV ghrelin secretion was different in response to fasting, even when body weights were matched in two groups. These data suggested that the initial PVATV, not lean mass, was related to the pattern of plasma ghrelin in response to fasting in rats.