Genome-wide sequence divergence of satellite DNA could underlie meiotic failure in male hybrids of bighead catfish and North African catfish (Clarias, Clariidae).

Hybrid sterility, a hallmark of postzygotic isolation, arises from parental genome divergence disrupting meiosis. While chromosomal incompatibility is often implicated, the underlying mechanisms remain unclear. This study investigated meiotic behavior and genome-wide divergence in bighead catfish (C. macrocephalus), North African catfish (C. gariepinus), and their sterile male hybrids (important in aquaculture). Repetitive DNA analysis using bioinformatics and cytogenetics revealed significant divergence in satellite DNA (satDNA) families between parental species. Notably, one hybrid exhibited successful meiosis and spermatozoa production, suggesting potential variation in sterility expression. Our findings suggest that genome-wide satDNA divergence, rather than chromosome number differences, likely contributes to meiotic failure and male sterility in these catfish hybrids.

Questioning inbreeding: Could outbreeding affect productivity in the North African catfish in Thailand?

The North African catfish (Clarias gariepinus) is a significant species in aquaculture, which is crucial for ensuring food and nutrition security. Their high adaptability to diverse environments has led to an increase in the number of farms that are available for their production. However, long-term closed breeding adversely affects their reproductive performance, leading to a decrease in production efficiency. This is possibly caused by inbreeding depression. To investigate the root cause of this issue, the genetic diversity of captive North African catfish populations was assessed in this study. Microsatellite genotyping and mitochondrial DNA D-loop sequencing were applied to 136 catfish specimens, collected from three populations captured for breeding in Thailand. Interestingly, extremely low inbreeding coefficients were obtained within each population, and distinct genetic diversity was observed among the three populations, indicating that their genetic origins are markedly different. This suggests that outbreeding depression by genetic admixture among currently captured populations of different origins may account for the low productivity of the North African catfish in Thailand. Genetic improvement of the North African catfish populations is required by introducing new populations whose origins are clearly known. This strategy should be systematically integrated into breeding programs to establish an ideal founder stock for selective breeding.

Disclosing the hidden nucleotide sequences: a journey into DNA barcoding of raptor species in public repositories.

BACKGROUND: In nucleotide public repositories, studies discovered data errors which resulted in incorrect species identification of several accipitrid raptors considered for conservation. Mislabeling, particularly in cases of cryptic species complexes and closely related species, which were identified based on morphological characteristics, was discovered. Prioritizing accurate species labeling, morphological taxonomy, and voucher documentation is crucial to rectify spurious data. OBJECTIVE: Our study aimed to identify an effective DNA barcoding tool that accurately reflects the efficiency status of barcodes in raptor species (Accipitridae). METHODS: Barcode sequences, including 889 sequences from the mitochondrial cytochrome c oxidase I (COI) gene and 1052 sequences from cytochrome b (Cytb), from 150 raptor species within the Accipitridae family were analyzed. RESULTS: The highest percentage of intraspecific nearest neighbors from the nearest neighbor test was 88.05% for COI and 95.00% for Cytb, suggesting that the Cytb gene is a more suitable marker for accurately identifying raptor species and can serve as a standard region for DNA barcoding. In both datasets, a positive barcoding gap representing the difference between inter-and intra-specific sequence divergences was observed. For COI and Cytb, the cut-off score sequence divergences for species identification were 4.00% and 3.00%, respectively. CONCLUSION: Greater accuracy was demonstrated for the Cytb gene, making it the preferred primary DNA barcoding marker for raptors.

Overcoming taxonomic challenges in DNA barcoding for improvement of identification and preservation of clariid catfish species.

DNA barcoding without assessing reliability and validity causes taxonomic errors of species identification, which is responsible for disruptions of their conservation and aquaculture industry. Although DNA barcoding facilitates molecular identification and phylogenetic analysis of species, its availability in clariid catfish lineage remains uncertain. In this study, DNA barcoding was developed and validated for clariid catfish. 2,970 barcode sequences from mitochondrial cytochrome c oxidase I (COI) and cytochrome b (Cytb) genes and D-loop sequences were analyzed for 37 clariid catfish species. The highest intraspecific nearest neighbor distances were 85.47%, 98.03%, and 89.10% for COI, Cytb, and D-loop sequences, respectively. This suggests that the Cytb gene is the most appropriate for identifying clariid catfish and can serve as a standard region for DNA barcoding. A positive barcoding gap between interspecific and intraspecific sequence divergence was observed in the Cytb dataset but not in the COI and D-loop datasets. Intraspecific variation was typically less than 4.4%, whereas interspecific variation was generally more than 66.9%. However, a species complex was detected in walking catfish and significant intraspecific sequence divergence was observed in North African catfish. These findings suggest the need to focus on developing a DNA barcoding system for classifying clariid catfish properly and to validate its efficacy for a wider range of clariid catfish. With an enriched database of multiple sequences from a target species and its genus, species identification can be more accurate and biodiversity assessment of the species can be facilitated.

Periostin induces epithelial­to­mesenchymal transition via the integrin α5ß1/TWIST­2 axis in cholangiocarcinoma.

Periostin (PN) (also known as osteoblast­specific factor OSF­2) is a protein that in humans is encoded by the POSTN gene and has been correlated with a reduced survival of cholangiocarcinoma (CCA) patients, with the well­known effect of inducing epithelial­to­mesenchymal transition (EMT). The present study investigated the effect of PN, through integrin (ITG)α5ß1, in EMT­mediated CCA aggressiveness. The alterations in EMT­related gene and protein expression were investigated by real­time PCR, western blot analysis and zymogram. The effects of PN on migration and the level of TWIST­2 were assessed in CCA cells with and without siITGα5 transfection. PN was found to induce CCA cell migration and EMT features, including increments in Twist­related protein 2 (TWIST­2), zinc finger protein SNAI1 (SNAIL­1), α-smooth muscle actin (ASMA), vimentin (VIM) and matrix metallopeptidase 9 (MMP­9), and a reduction in cytokeratin 19 (CK­19) together with cytoplasmic translocation of E-cadherin (CDH­1). Additionally, PN markedly induced MMP­9 activity. TWIST­2 was significantly induced in PN­treated CCA cells; this effect was attenuated in the ITGα5ß1­knockdown cells and corresponded to reduced migration of the cancer cells. These results indicated that PN induced CCA migration through ITGα5ß1/TWIST-2­mediated EMT. Moreover, clinical samples from CCA patients showed that higher levels of TWIST­2 were significantly correlated with shorter survival time. In conclusion, the ITGα5ß1­mediated TWIST­2 signaling pathway regulates PN­induced EMT in CCA progression, and TWIST­2 is a prognostic marker of poor survival in CCA patients.

Periostin activates integrin α5ß1 through a PI3K/AKT­dependent pathway in invasion of cholangiocarcinoma.

Periostin (PN) is mainly produced from stromal fibroblasts in cholangiocarcinoma (CCA) and shows strong impact in cancer promotion. This work aimed to investigate the mechanism that PN uses to drive CCA invasion. It was found that ITGα5ß1 and α6ß4 showed high expression in non-tumorigenic biliary epithelial cells and in almost all CCA cell lines. PN had preferential binding to CCA cells via ITGα5ß1 and blocking this receptor by either neutralizing antibody or siITGα5 could attenuate PN-induced invasion. After PN-ITGα5ß1 binding, intracellular pAKT was upregulated whereas there was no change in pERK. Moreover, PN could not activate AKT in condition of treatment with a PI3K inhibitor. These data provide evidence that PN-activated invasion of CCA cells is through the ITGα5ß1/PI3K/AKT pathway. Strategies aimed to inhibit this pathway may, thus, provide therapeutic benefits.