Search

Fgfr1 is a fibroblast growth factor receptor involved in regulating cell growth, proliferation, differentiation and migration. Here, we report the isolation and characterization of duplicated fgfr1 genes in blunt snout bream ( Megalobrama amblycephala ). Blunt snout bream fgfr1a and - 1b cDNAs were found to share a relatively high sequence identity of 82%. During embryogenesis, both fgfr1a and - 1b mRNAs were highly detected at zygotes but gradually decreased and then constantly expressed after 16 hpf, besides a strong expression for the fgfr1b mRNA at 12 hpf. Whole-mount in situ hybridization demonstrated that fgfr1a mRNA was transcribed at the eyes, mid-hindbrain boundary (MHB), brain, posterior somites and tailbud at 16 hpf, while the fgfr1b mRNA was only detected at the eyes and posterior somites at the same period. At 28 hpf embryos, both fgfr1a and - 1b mRNAs were expressed in the eyes, brain, pharyngeal arches and tailbud, and in the eyes, brain, pharyngeal arches and notochord at 55 hpf. In adult fish, fgfr1a mRNA was strongly expressed in the gill, gonad, brain and midgut, but examined relatively low in the skin and kidney. In contrast, the fgfr1b mRNA was highly detected in the brain and liver and quite low in the skin, gill and kidney. During starvation, both fgfr1a and - 1b mRNAs were significantly up-regulated in the intestine and liver, but down-regulated in the brain. Moreover, duplicated fgfr1 mRNAs were differentially inhibited in tissues with exogenous recombinant hGH. Our results suggest that two fgfr1 genes play important roles in regulating growth and development in blunt snout bream. [ABSTRACT FROM AUTHOR]

Connective tissue growth factor (CTGF) is a peptide involved in tissue growth and development, and can be regulated by hypoxia stress. This study aimed to isolate and characterize duplicate Ctgf genes in blunt snout bream Megalobrama amblycephala , and determine their expression patterns and response to hypoxia. The blunt snout bream Ctgfa and Ctgfb were found to be highly divergent, sharing a relatively low sequence identity of 57%. During embryogenesis, Ctgfa mRNA expression levels were low, gradually decreased from zygotes to 12 h post-fertilization (hpf), markedly increased from 16 hpf, and then stabilized from 32 to 40 hpf. Ctgfb expression levels were constant but low from zygotes to 20 hpf, then gradually increased from 24 to 40 hpf. Ctgfa mRNA was expressed in the adaxial cells of the somites, floor plate, and tailbud at 24 hpf, and in the notochord and ethmoid plate at 36 hpf, whereas Ctgfb mRNA was weakly expressed in the adaxial cells and floor plate at 24 hpf, and in the notochord at 36 hpf. In adult fish, Ctgfa mRNA was strongly expressed in the kidney, brain, intestine, muscles, and skin, while Ctgfb mRNA was detected in all examined tissues. During hypoxic treatment, the mRNA levels of both Ctgfa and - b were significantly upregulated in the gill and liver, whereas Ctgfa mRNAs in the brain and kidney and Ctgfb mRNAs in the kidney significantly decreased. These results provide new insights into the functional conservation and divergence of Ctgf genes and reveal their responses to hypoxia. [ABSTRACT FROM AUTHOR]

In this study, we found that blunt snout bream ( Megalobrama amblycephala ) had a relatively high critical oxygen tension at which it lost its equilibrium (LOE crit ), confirming that it is a hypoxia sensitive fish. Blunt snout bream has the ability to remodel its gill structure in response to oxygen levels. When blunt snout bream were exposed to 4- or 7-days of hypoxia, the average protruding lamella heights and mean lamellar area of gills were significantly ( P < 0.01) larger than those of normoxic controls. These changes resulted in reduced average interlamellar cell mass (ILCM) height and volume under hypoxia. After 1 week of normoxic recovery, gill lamellae were reversibly embedded with ILCM cells. Irrespective of dissolved oxygen concentration, the average protruding lamella height of fish gills at 25 °C was significantly ( P < 0.01) larger than that of fish cultured at 10 °C, suggesting that blunt snout bream also have the ability to modify gill structure in response to water temperature. In response to hypoxia, blood erythrocyte count and haemoglobin (Hb) concentration increased significantly ( P < 0.01) under hypoxia. Furthermore, the plasma chloride concentration ([Cl − ]) was significantly ( P < 0.01) reduced. Our results are the first to show that blunt snout bream, as a hypoxia sensitive fish, have the capacity to alter respiratory surface area in response to hypoxia and temperature. [ABSTRACT FROM AUTHOR]