Dnmt3aa but Not Dnmt3ab Is Required for Maintenance of Gametogenesis in Nile Tilapia (Oreochromis niloticus).

Dnmt3a, a de novo methyltransferase, is essential for mammalian germ line DNA methylation. Only one Dnmt3a is identified in mammals, and homozygous mutants of Dnmt3a are lethal, while two Dnmt3a paralogs, dnmt3aa and dnmt3ab, are identified in teleosts due to the third round of genome duplication, and homozygous mutants of dnmt3aa and dnmt3ab are viable in zebrafish. The expression patterns and roles of dnmt3aa and dnmt3ab in gonadal development remain poorly understood in teleosts. In this study, we elucidated the precise expression patterns of dnmt3aa and dnmt3ab in tilapia gonads. Dnmt3aa was highly expressed in oogonia, phase I and II oocytes and granulosa cells in ovaries and spermatogonia and spermatocytes in testes, while dnmt3ab was mainly expressed in ovarian granulosa cells and testicular spermatocytes. The mutation of dnmt3aa and dnmt3ab was achieved by CRISPR/Cas9 in tilapia. Lower gonadosomatic index (GSI), increased apoptosis of oocytes and spermatocytes and significantly reduced sperm quality were observed in dnmt3aa-/- mutants, while normal gonadal development was observed in dnmt3ab-/- mutants. Consistently, the expression of apoptotic genes was significantly increased in dnmt3aa-/- mutants. In addition, the 5-methylcytosine (5-mC) level in dnmt3aa-/- gonads was decreased significantly, compared with that of dnmt3ab-/- and wild type (WT) gonads. Taken together, our results suggest that dnmt3aa, not dnmt3ab, plays important roles in maintaining gametogenesis in teleosts.

Prediction and analysis of natural gas consumption in chongqing with a grey prediction model group in the context of COVID-19.

In this paper, a grey prediction model group is employed to quantitatively study the impact of COVID-19 on natural gas consumption in Chongqing, China. First, a grey prediction model group suitable for the prediction of Chongqing's natural gas consumption is introduced, which consists of GM(1,1), TWGM(1,1), and the newly-developed ODGM(1,1). Then, the model group is constructed to predict Chongqing's natural gas consumption in 2020. Finally, compare the predicted results of the model group with the actual consumption and quantitatively analyze the impact of the epidemic on natural gas in Chongqing. It is found that the impact of the epidemic on the consumption of natural gas in the first quarter of the year is very small, but relatively bigger in the second and third quarters. The study is of positive significance to maintain the supply and demand balance of natural gas consumption in Chongqing in the background of COVID-19; and it enriches and develops the theoretical system of grey prediction models.

Genome-wide identification, evolution of histone lysine demethylases (KDM) genes and their expression during gonadal development in Nile tilapia.

Histone lysine demethylases (KDM) are responsible for histone demethylation and are involved in gene expression regulation. Previous studies have shown that histone lysine demethylation plays an important role in gonadal development of vertebrates. The KDM family consists of eight subfamilies, i.e., kdm1, kdm2, kdm3, kdm4, kdm5, kdm6, kdm7 and JmjC-only subfamily. In this study, 13 to 63 KDM genes in 23 representative species were identified based on the available version of genome assembly. Phylogenetic relationships, domain architecture, and synteny of these genes were comprehensively analyzed and the results suggested KDM genes probably originated from the early diverging metazoan and significantly expanded in vertebrates with multiple whole genome duplication, especially in the third-round whole genome duplication (3R-WGD) and polyploidization of teleosts. The subfamilies of kdm2, kdm3, kdm4, kdm5, kdm6 and kdm7 were duplicated with 1R-2R events, and duplicates of kdm2a, kdm4a, kdm5b and kdm6b were resulted from 3R-WGD. Based on transcriptome data, the KDM genes were found to be dominantly expressed in the ovary and testis. More than 80% of KDM genes displayed sexual dimorphic expression, with 15 genes dominantly expressed in ovaries, and 12 genes dominantly expressed in testes. Importantly, from transcriptome data, qRT-PCR and fluorescence in situ hybridization during sex reversal, genes with higher expression in ovary than testis, such as kdm1b and two JmjC-only subfamily members hspbap1 and riox1, were downregulated, while other genes, such as kdm3c, kdm5bb, kdm6ba, kdm6bb and kdm7b, with higher expression in testis than ovary, were upregulated in ovotestis, indicating these genes play critical roles in the gonadal development and sex reversal. This study provided new insights into the evolution of the KDM genes and a fundamental clue for understanding their important roles in sex differentiation and gonadal development in teleosts.