SLC7 family transporters control the establishment of left-right asymmetry during organogenesis in medaka by activating mTOR signaling

Glucocorticoid Regulates the Synthesis of Porcine Muscle Protein through m6A Modified Amino Acid Transporter SLC7A7

The occurrence of stress is unavoidable in the process of livestock production, and prolonged stress will cause the decrease of livestock productivity. The stress response is mainly regulated by the hypothalamic-pituitary-adrenal axis (HPA axis), which produces a large amount of stress hormones, namely glucocorticoids (GCs), and generates a severe impact on the energy metabolism of the animal body. It is reported that m⁶A modification plays an important role in the regulation of stress response and also participates in the process of muscle growth and development. In this study, we explored the effect of GCs on the protein synthesis procession of porcine skeletal muscle cells (PSCs). We prove that dexamethasone affects the expression of SLC7A7, a main amino acid transporter for protein synthesis by affecting the level of m⁶A modification in PSCs. In addition, we find that SLC7A7 affects the level of PSC protein synthesis by regulating the conduction of the mTOR signaling pathway, which indicates that the reduction of SLC7A7 expression may alleviate the level of protein synthesis under stress conditions.

A global Slc7a7 knockout mouse model demonstrates characteristic phenotypes of human lysinuric protein intolerance

Lysinuric protein intolerance (LPI) is an inborn error of cationic amino acid (arginine, lysine, ornithine) transport caused by biallelic pathogenic variants in SLC7A7, which encodes the light subunit of the y+LAT1 transporter. Treatments for the complications of LPI, including growth failure, renal disease, pulmonary alveolar proteinosis, autoimmune disorders and osteoporosis, are limited. Given the early lethality of the only published global Slc7a7 knockout mouse model, a viable animal model to investigate global SLC7A7 deficiency is needed. Hence, we generated two mouse models with global Slc7a7 deficiency (Slc7a7em1Lbu/em1Lbu; Slc7a7Lbu/Lbu and Slc7a7em1(IMPC)Bay/em1(IMPC)Bay; Slc7a7Bay/Bay) using CRISPR/Cas9 technology by introducing a deletion of exons 3 and 4. Perinatal lethality was observed in Slc7a7Lbu/Lbu and Slc7a7Bay/Bay mice on the C57BL/6 and C57BL/6NJ inbred genetic backgrounds, respectively. We noted improved survival of Slc7a7Lbu/Lbu mice on the 129 Sv/Ev × C57BL/6 F2 background, but postnatal growth failure occurred. Consistent with human LPI, these Slc7a7Lbu/Lbu mice exhibited reduced plasma and increased urinary concentrations of the cationic amino acids. Histopathological assessment revealed loss of brush border and lipid vacuolation in the renal cortex of Slc7a7Lbu/Lbu mice, which combined with aminoaciduria suggests proximal tubular dysfunction. Micro-computed tomography of L4 vertebrae and skeletal radiographs showed delayed skeletal development and suggested decreased mineralization in Slc7a7Lbu/Lbu mice, respectively. In addition to delayed skeletal development and delayed development in the kidneys, the lungs and liver were observed based on histopathological assessment. Overall, our Slc7a7Lbu/Lbu mouse model on the F2 mixed background recapitulates multiple human LPI phenotypes and may be useful for future studies of LPI pathology.

Myelination during fracture healing in vivo in myelin protein zero (p0) transgenic medaka line

During the fracture healing process, osteoblasts and osteoclasts, as well as the nervous system are known to play important roles for signaling in the body. Glia cells contribute to the healing process by myelination, which can increase the speed of signals transmitted between neurons. However, the behavior of myelinating cells at a fracture site remains unclear. We developed a myelin protein zero (mpz)-EGFP transgenic medaka line for tracing myelinating cells. Mpz-enhanced green fluorescence protein (EGFP)-positive (mpz⁺) cells are driven by the 2.9-kb promoter of the medaka mpz gene, which is distributed throughout the nervous system, such as the brain, spinal cord, lateral line, and peripheral nerves. In the caudal fin region, mpz⁺ cells were found localized parallel with the fin ray (bone) in the adult stage. mpz⁺ cells were not distributed with fli-DsRed positive (fli⁺) blood vessels, but with some nerve fibers, and were dyed with the anti-acetylated tubulin antibody. We then fractured one side of the caudal lepidotrichia in a caudal fin of mpz-EGFP medaka and found a unique phenomenon, in that mpz⁺ cells were accumulated at 1 bone away from the fracture site. This mpz⁺ cell accumulation phenomenon started from 4 days after fracture of the proximal bone. Thereafter, mpz⁺ cells became elongated from the proximal bone to the distal bone and finally showed a crosslink connection crossing the fracture site to the distal bone at 28 days after fracture. Finally, the effects of rapamycin, known as a mTOR inhibitor, on myelination was examined. Rapamycin treatment of mpz-EGFP/osterix-DsRed double transgenic medaka inhibited not only the crosslink connection of mpz⁺ cells but also osterix⁺ osteoblast accumulation at the fracture site, accompanied with a fracture healing defect. These findings indicated that mTOR signaling plays important roles in bone formation and neural networking during fracture healing. Taken together, the present results are the first to show the dynamics of myelinating cells in vivo.

Solute carriers in scallop genome: Gene expansion and expression regulation after exposure to toxic dinoflagellate

The solute carriers (SLCs) are membrane proteins that transport many endogenous and exogenous substances such as xenobiotic toxins. Bivalve mollusks, mainly feeding on microalgae, show marked capacity to accumulate paralytic shellfish toxins (PSTs), the most common and hazardous marine biotoxins produced by dinoflagellates. Exploring the SLCs related to PST accumulation in bivalve could benefit our understanding about the mechanisms of PST bioavailability in bivalve and the adaptations of these species. Herein, we provided the first systematic analysis of SLC genes in mollusks, which identified 673 SLCs (PySLCs, 48 subfamilies) in Yesso scallop (Patinopecten yessoensis), 510 (48 subfamilies) in Pacific oyster (Crassostrea gigas), and 350 (47 subfamilies) in gastropod owl limpet (Lottia gigantea). Significant expansion of subfamilies SLC5, SLC6, SLC16, and SLC23 in scallop, and SLC46 subfamily in both scallop and oyster were revealed. Different PySLC members were highly expressed in the developmental stages and adult tissues, and hepatopancreas harboured more specifically expressed PySLCs than other tissues/organs. After feeding the scallops with PST-producing dinoflagellate, 131 PySLCs were regulated and more than half of them were from the expanded subfamilies. The trend of expression fold change in regulated PySLCs was consistent with that of PST changes in hepatopancreas, implying the possible involvement of these PySLCs in PST transport and homeostasis. In addition, the PySLCs from the expanded subfamily were revealed to be under positive selection, which might be related to lineage-specific adaptation to the marine environments with algae derived biotoxins.

GLIS3 is indispensable for TSH/TSHR-dependent thyroid hormone biosynthesis and follicular cell proliferation

Deficiency in Krüppel-like zinc finger transcription factor GLI-similar 3 (GLIS3) in humans is associated with the development of congenital hypothyroidism. However, the functions of GLIS3 in the thyroid gland and the mechanism by which GLIS3 dysfunction causes hypothyroidism are unknown. In the current study, we demonstrate that GLIS3 acts downstream of thyroid-stimulating hormone (TSH) and TSH receptor (TSHR) and is indispensable for TSH/TSHR-mediated proliferation of thyroid follicular cells and biosynthesis of thyroid hormone. Using ChIP-Seq and promoter analysis, we demonstrate that GLIS3 is critical for the transcriptional activation of several genes required for thyroid hormone biosynthesis, including the iodide transporters Nis and Pds, both of which showed enhanced GLIS3 binding at their promoters. The repression of cell proliferation of GLIS3-deficient thyroid follicular cells was due to the inhibition of TSH-mediated activation of the mTOR complex 1/ribosomal protein S6 (mTORC1/RPS6) pathway as well as the reduced expression of several cell division-related genes regulated directly by GLIS3. Consequently, GLIS3 deficiency in a murine model prevented the development of goiter as well as the induction of inflammatory and fibrotic genes during chronic elevation of circulating TSH. Our study identifies GLIS3 as a key regulator of TSH/TSHR-mediated thyroid hormone biosynthesis and proliferation of thyroid follicular cells and uncovers a mechanism by which GLIS3 deficiency causes neonatal hypothyroidism and prevents goiter development.

Complementary transcriptomic and proteomic analyses reveal regulatory mechanisms of milk protein production in dairy cows consuming different forages

Forage plays a critical role in the milk production of dairy cows; however, the mechanisms regulating bovine milk synthesis in dairy cows fed high forage rations with different basal forage types are not well-understood. In the study, rice straw (RS, low-quality) and alfalfa hay (AH, high-quality) diets were fed to lactating cows to explore how forage quality affected the molecular mechanisms regulating milk production using RNA-seq transcriptomic method with iTRAQ proteomic technique. A total of 554 transcripts (423 increased and 131 decreased) and 517 proteins (231 up-regulated and 286 down-regulated) were differentially expressed in the mammary glands of the two groups. The correlation analysis demonstrated seven proteins (six up-regulated and one down-regulated) had consistent mRNA expression. Functional analysis of the differentially expressed transcripts/proteins suggested that enhanced capacity for energy and fatty acid metabolism, increased protein degradation, reduced protein synthesis, decreased amino acid metabolism and depressed cell growth were related to RS consumption. The results indicated cows consuming RS diets may have had depressed milk protein synthesis because these animals had decreased capacity for protein synthesis, enhanced proteolysis, inefficient energy generation and reduced cell growth. Additional work evaluating RS- and AH-based rations may help better isolate molecular adaptations to low nutrient availability during lactation.