Chemokine signaling links cell-cycle progression and cilia formation for left-right symmetry breaking.

Zebrafish dorsal forerunner cells (DFCs) undergo vigorous proliferation during epiboly and then exit the cell cycle to generate Kupffer's vesicle (KV), a ciliated organ necessary for establishing left-right (L-R) asymmetry. DFC proliferation defects are often accompanied by impaired cilia elongation in KV, but the functional and molecular interaction between cell-cycle progression and cilia formation remains unknown. Here, we show that chemokine receptor Cxcr4a is required for L-R laterality by controlling DFC proliferation and KV ciliogenesis. Functional analysis revealed that Cxcr4a accelerates G1/S transition in DFCs and stabilizes forkhead box j1a (Foxj1a), a master regulator of motile cilia, by stimulating Cyclin D1 expression through extracellular regulated MAP kinase (ERK) 1/2 signaling. Mechanistically, Cyclin D1-cyclin-dependent kinase (CDK) 4/6 drives G1/S transition during DFC proliferation and phosphorylates Foxj1a, thereby disrupting its association with proteasome 26S subunit, non-ATPase 4b (Psmd4b), a 19S regulatory subunit. This prevents the ubiquitin (Ub)-independent proteasomal degradation of Foxj1a. Our study uncovers a role for Cxcr4 signaling in L-R patterning and provides fundamental insights into the molecular linkage between cell-cycle progression and ciliogenesis.

Cloning, expression profiling, and effects of fasting status on neuropeptide Y in Schizothorax davidi.

To better comprehend the mechanism that neuropeptide Y (npy) regulates feeding in Schizothorax davidi, we cloned and identified the full-length cDNA sequence of the npy gene in this species using RACE technology. Subsequently, we explored the npy mRNA distribution in 18 tissues and investigated the expression of npy mRNA at postprandial and fasting stages. We found that the npy full-length cDNA sequence is 803 bp. Moreover, npy mRNAs extensively expressed in all detected tissues, with the highest expression in hypothalamus. In postprandial study, the expression of npy mRNA in the hypothalamus was significantly decreased after eating (p < 0.01). In addition, the expression of the npy gene was significantly increased on the fifth day after fasting (p < 0.05). However, after refeeding, the expression of the npy gene was decreased significantly on days 9, 11, and 14 (p < 0.01). Our research suggest that npy may have an orexigenic role in S. davidi. PRACTICAL APPLICATIONS: S. davidi, a coldwater fish native to China, has high economic value, and it has gained great popularity. To date, there is still no large-scale breeding of S. davidi in China. How to strengthen the production performance of S. davidi is a hot research area. Neuropeptide Y (NPY), a 36-amino-acid single-chain polypeptide, is one of the main appetite regulation factors. However, to date, no studies have reported on the biological function of npy in the feeding of S. davidi. In our study, we revealed that the trend of hypothalamic npy expression during the postprandial and fasting stages. The results suggested that npy might be an appetite-promoting factor in this species. Overall, we provide the theoretical basis for how to strengthen the production performance of S. davidi through appetite regulation.

Aplnra/b Sequentially Regulate Organ Left-Right Patterning via Distinct Mechanisms.

The G protein-coupled receptor APJ/Aplnr has been widely reported to be involved in heart and vascular development and disease, but whether it contributes to organ left-right patterning is largely unknown. Here, we show that in zebrafish, aplnra/b coordinates organ LR patterning in an apela/apln ligand-dependent manner using distinct mechanisms at different stages. During gastrulation and early somitogenesis, aplnra/b loss of function results in heart and liver LR asymmetry defects, accompanied by disturbed KV/cilia morphogenesis and disrupted left-sided Nodal/spaw expression in the LPM. In this process, only aplnra loss of function results in KV/cilia morphogenesis defect. In addition, only apela works as the early endogenous ligand to regulate KV morphogenesis, which then contributes to left-sided Nodal/spaw expression and subsequent organ LR patterning. The aplnra-apela cascade regulates KV morphogenesis by enhancing the expression of foxj1a, but not fgf8 or dnh9, during KV development. At the late somite stage, both aplnra and aplnrb contribute to the expression of lft1 in the trunk midline but do not regulate KV formation, and this role is possibly mediated by both endogenous ligands, apela and apln. In conclusion, our study is the first to identify a role for aplnra/b and their endogenous ligands apela/apln in LR patterning, and it clarifies the distinct roles of aplnra-apela and aplnra/b-apela/apln in orchestrating organ LR patterning.

Three forms of cocaine- and amphetamine-regulated transcript may be involved in food intake regulation in gibel carp (Carassius auratus gibelio).

In fish, as in mammals, several studies have demonstrated that the cocaine- and amphetamine-regulated transcript (CART) plays an important role in feeding. However, thus far, the function of CART in gibel carp (Carassius auratus gibelio) feeding regulation has not been reported. In our study, we first identified three forms of CART peptide precursors from gibel carp brain and named these CART-1, CART-2, and CART-3. The full-length cDNA sequences of CART-1, CART-2, and CART-3 were 616 bp, 705 bp, and 760 bp, respectively, encoding peptides of 118, 120, and 104 amino acid residues. We detected mRNA expression of CART-1, CART-2, and CART-3 in a wide range of peripheral and central tissues, with the highest expression detected in the brain. After a meal, mRNA expression of CART-1, CART-2, and CART-3 was significantly elevated, suggesting that CART-1, CART-2, and CART-3 may act as postprandial satiety signals. Moreover, mRNA expression of all three CART-1, CART-2, and CART-3 was significantly reduced during fasting and significantly elevated with refeeding. Our findings indicate that CART-1, CART-2, and CART-3 might function as a satiety factor in the gibel carp.

Molecular characterization and expression analysis of complement component C3 in southern catfish (Silurus meridionalis) and a whole mount in situ hybridization study on its ontogeny.

The complement system plays an important role in protecting fish against attack by pathogens early in life. Complement component C3 is a central component in the complement system. The present work aimed to clone the full length C3 cDNA sequence of southern catfish (Silurus meridionalis), detect the tissue expression patterns of C3, investigate the ontogeny of C3 in embryo and larva, and assess the expression of C3 in response to pathogen infection. The full length C3 cDNA sequence of 5157 bp with an open reading frame (ORF) of 4938 bp was cloned from southern catfish. The deduced amino acid sequence showed similarity with other teleost fish. The mRNA expression of C3 was detected in liver, spleen, stomach, intestine, and head kidney with RT-PCR and in situ hybridization. Whole mount in situ hybridization results revealed that C3 was first expressed in the yolk syncytial layer at 34 h post fertilization (hpf), followed by the liver at 36 h post hatching (hph). When challenged with Aeromonas hydrophila, the transcripts of C3 showed a significant up-regulation in liver and spleen at 24 h. The results suggested that complement C3 played a key role in defense against invading pathogens in the early development stages of southern catfish. Therefore, these results provide important information to understand the functions of C3 during fish early development in Siluriformes.

Molecular characterization, expression analysis, and ontogeny of complement component C9 in southern catfish (Silurus meridionalis).

The complement system plays an important role in host defense against invading microorganisms. Complement component C9 is the last component that is involved in the formation of the membrane attack complex (MAC) on the surface of target cells. In the present study, the full length C9 cDNA sequence of 1984 bp with an open reading frame (ORF) of 1809 bp was cloned from southern catfish (Silurus meridionalis). The deduced amino acid sequence showed similarity with other teleost fish. The mRNA expression of C9 was detected in the liver, spleen, stomach, intestine, and head kidney, with highest levels detected in the liver. The mRNA of C9 was first detected in the yolk syncytial layer at 34 h post fertilization (hpf) with whole mount in situ hybridization, followed by the liver at 36 h post hatching (hph). The mRNA expression of C9 was upregulated significantly in the liver, spleen, and intestine following the injection with Aeromonas hydrophila, suggesting that C9 played an important role in defense against invading pathogens in southern catfish. Therefore, these results provide important information to understand the functions of C9 during fish early development in fish.

Structural and functional characterization of peptide YY on feeding in Schizothorax davidi.

Several studies have demonstrated that the neuropeptide peptide YY (PYY) plays an important role in feeding in mammals and fish. However, thus far, the feeding regulation function of PYY in Schizothorax davidi has not been well understood. Here, we identified the full-length cDNA sequence of PYY in S. davidi for the first time. S. davidi PYY contains 803 bp nucleotides including a 328 bp 3' untranslated region (UTR), a 181 bp 5' UTR, and a 294 bp open reading frame encoding a peptide of 97 amino acids. S. davidi PYY expression was observed in almost all tissues, with the highest expression detected in the hypothalamus. PYY mRNA expression in the hypothalamus was significantly elevated after a meal (P < 0.01), and significantly decreased after fasting (P < 0.01). PYY expression levels were increased sharply following refeeding after 9 days (P < 0.01), suggesting that it might function as a satiety factor in S. davidi.

Characterization of Spleen Transcriptome of Schizothorax prenanti during Aeromonas hydrophila Infection.

Schizothorax prenanti (S. prenanti) is an indigenous fish species and is popularly cultured in southwestern China. In recent years, intensive farming of S. prenanti and water quality deterioration has increased the susceptibility of this fish to various pathogens, including Aeromonas hydrophila (A. hydrophila), which has caused severe damage to S. prenanti production. However, the understanding of molecular immune response of S. prenanti to A. hydrophila infection is still lacking. In order to better comprehend the S. prenanti time series immune response process against A. hydrophila, we conducted the first transcriptomic comparison in S. prenanti spleen at 4, 24, and 48 h after the infection challenge of A. hydrophila against their control counterparts. In total, 628 million clean reads were obtained from 18 libraries and assembled into 262,745 transcripts. After eliminating sequence redundancy, 69,373 unigenes with an average length of 1476 bp were obtained. Comparative analysis revealed 1890 unigenes with significantly differential expression, including 172, 455, 589 upregulated and 27, 676, 551 unigenes downregulated genes for 4, 24, and 48 h post-infection, respectively. Differentially expressed genes (DEGs) were validated using qPCR for 15 randomly selected genes. Enrichment and pathway analysis of DEGs was carried out to understand the functions of the immune-related genes. Our results revealed that many important functional genes relating to complement and coagulation cascades, chemokine signaling pathway, toll-like receptor signaling pathway, NOD-like receptor signaling pathway and leukocyte transendothelial migration were regulated during the infection of A. hydrophila, and the expression of those genes reflected the transcriptome profiles during the challenging stages.

De novo assembly of Schizothorax waltoni transcriptome to identify immune-related genes and microsatellite markers.

Schizothorax waltoni (S. waltoni) is one kind of the subfamily Schizothoracinae and an indigenous economic tetraploid fish to Tibet in China. It is rated as a vulnerable species in the Red List of China's Vertebrates, owing to overexploitation and biological invasion. S. waltoni plays an important role in ecology and local fishery economy, but little information is known about genetic diversity, local adaptation, immune system and so on. Functional gene identification and molecular marker development are the first and essential step for the following biological function and genetics studies. For this purpose, the transcriptome from pooled tissues of three adult S. waltoni was sequenced and analyzed. Using paired-end reads from the Illumina Hiseq4000 platform, 83 103 transcripts with an N50 length of 2337 bp were assembled, which could be further clustered into 66 975 unigenes with an N50 length of 2087 bp. The majority of the unigenes (58 934, 87.99%) were successfully annotated by 7 public databases, and 15 KEGG pathways of immune-related genes were identified for the following functional research. Furthermore, 19 497 putative simple sequence repeats (SSRs) of 1-6 bp unit length were detected from 14 690 unigenes (21.93%) with an average distribution density of 1 : 3.28 kb. We identified 3590 unigenes (5.36%) containing more than one SSR, providing abundant potential polymorphic markers in functional genes. This is the first reported high-throughput transcriptome analysis of S. waltoni, and it would provide valuable genetic resources for the functional genes involved in multiple biological processes, including the immune system, genetic conservation, and molecular marker-assisted breeding of S. waltoni.

Evidence that ghrelin may be associated with the food intake of gibel carp (Carassius auratus gibelio).

Ghrelin, a non-amidated peptide hormone, is a potent anorectic neuropeptide implicated in feeding regulation in mammals and non-mammalian vertebrates. However, the involvement of ghrelin in the feeding behavior of teleosts has not been well understood. To better understand the role of ghrelin in the regulation of appetite in fish, in this study, we cloned the cDNAs encoding ghrelin and investigated their mRNA distributions in gibel carp tissues. We also assessed the effects of different nutritional status on ghrelin mRNA abundance. Ghrelin mRNAs were ubiquitously expressed in ten tissues (intestine, liver, brain, mesonephron, head kidney, spleen, skin, heart, muscle, gill and pituitary gland), and relatively high expression levels were detected in the gut. Postprandial studies analysis revealed a significant postprandial decrease in ghrelin mRNA expression in the gut (1 and 3 h after the regular feeding time). In addition, ghrelin mRNA expression in the gut significantly increased at day 7 after fasting and declined sharply after refeeding, which suggested that ghrelin might be involved in the regulation of appetite in gibel carp. Overall, our result provides basis for further investigation into the regulation of feeding in gibel carp.

The complete mitochondrion genome of the Barbodes hexagonolepis (Cypriniformes, cyprinidae).

The Barbodes hexagonolepis, as an important commercial species, had the limited resources on biology and genetics. We reported the complete mitogenome of this species, and got a whole length of 16 587 bp (containing two rRNAs, 22 tRNAs, 13 mRNAs and one D-loop region). The two rRNAs located between tRNAphe and tRNAleu and were separated by tRNAval. The 22 tRNAs was ranged from 66 bp (tRNAcys) to 76 bp (tRNAleu and tRNAlys) in length. The 13 mRNAs had four overlap regions, three types of start codons and four types of termination codons. The D-loop region was found between tRNAPro and tRNAPhe. To further explore the phylogenetic relationship of the B. hexagonolepis, we constructed the phylogenetic tree and verified that the B. hexagonolepi was a part of the Barbinae and independent from other genus of the Barbinae. This result provided the valuable evidence on phylogenetic relationship of the B. hexagonolepi at the molecular level and essential resource for further research on this species.