The immunotoxicity of microplastic pollution in aquatic species is an issue of growing concern. However, the time course and mechanistic crosstalk underlying microplastic-induced hepatic injury remain poorly defined. This study examined the temporal hepatic response of Nile tilapia (Oreochromis niloticus) to 100 nm polystyrene microplastics (PS) over a 21-day exposure period, covering acute (7 days) and sub-chronic (14 and 21 days) phases. Histopathological evaluation showed no obvious liver lesions in exposed fish relative to controls at 7 days post-exposure (dpe). In contrast, progressive tissue damage marked by enhanced inflammatory cell infiltration was apparent at 14 and 21 dpe. PS exposure triggered time-dependent oxidative stress, with reactive oxygen species (ROS) and malondialdehyde (MDA) levels significantly increased and superoxide dismutase (SOD) activity decreased at 14 and 21 dpe. Ultrastructural analysis using transmission electron microscopy (TEM) further revealed distinct mitochondrial swelling and a notable increase in autophagosome numbers within hepatocytes at 7 and 14 dpe. Transcriptomic profiling indicated a biphasic dysregulation affecting both autophagy and inflammatory pathways. Specifically, autophagy-related pathways were significantly upregulated by 7 dpe, which preceded the marked activation of innate immune signaling pathways, such as NOD-like receptors (NLR) and mitogen-activated protein kinase (MAPK) signaling, observed at 14 dpe. After prolonged exposure to 21 dpe, both autophagic and inflammatory pathways were downregulated. qPCR confirmed this time-dependent expression profile for key genes associated with autophagy (sqstm1, map1lc3b, atg4d, atg5, becn1) and immune (il1β, nlrp3, tgfβ, map3k7, tnfa, tnfb, myd88) function. Pharmacological inhibition of autophagy by 3-methyladenine (3-MA) markedly abrogated the activation of NLR and MAPK signaling genes at 14 dpe, confirming a causal regulatory link between autophagy and innate immunity. Collectively, these findings suggest that microplastic exposure triggers a sequential immunotoxic transition in the fish liver. The early induction of autophagy may support subsequent immune activation, which eventually shifts to a broad suppression of immune pathways under sustained stress. This study offers new insight into the dynamic interaction between autophagy and innate immunity during microplastic-induced hepatotoxicity and highlights the potential risk of immunosuppression after long-term microplastic exposure.

Desert Hedgehog (Dhh) mutations cause Leydig cell dysfunction, yet the mechanisms governing Leydig lineage commitment through Dhh-mediated receptor selectivity, transcriptional effector specificity, and steroidogenic coupling remain elusive. In this study, using CRISPR/Cas9-mediated gene knockout and stem Leydig cells (SLCs) transplantation, we identified a critical Dhh/Patched 2 (Ptch2)/Glioma-associated oncogene homolog 1 (Gli1)/steroidogenic factor 1 (Sf1) signaling axis essential for SLC differentiation in Nile tilapia (Oreochromis niloticus). Dhh deficiency resulted in defective adult Leydig cells and androgen insufficiency. Rescue experiments involving 11-ketotestosterone administration and a Dhh agonist treatment, combined with SLCs transplantation, demonstrated that Dhh regulates SLC differentiation, not survival. In vitro knockout of ptch1 and ptch2 in SLCs revealed that Ptch2 likely acts as the functional receptor for Dhh. This was further supported by in vivo genetic rescue experiments, where ptch2 mutation did not impair testicular development, yet completely rescued the testicular defects in dhh mutants—consistent with Ptch2 acting as an inhibitory receptor whose loss alleviates Dhh pathway suppression. Luciferase assays in Gli-knockout SLCs demonstrated that Gli1 acts as the primary transcriptional effector and transactivates sf1 expression. Additionally, functional transplantation assays confirmed that Sf1 is indispensable for SLC differentiation, as Sf1-overexpressing SLCs rescued differentiation, whereas sf1-mutant SLCs failed. Overall, our work delineates the Dhh-Ptch2-Gli1-Sf1 axis and provides fundamental insights into the endocrine regulation of Leydig cell lineage development.

Global aquaculture production continues to rise, but its rate of genetic improvement lags far behind that of livestock, highlighting the need for advanced breeding technologies. Gene editing, particularly CRISPR/Cas-based systems, provides a precise and efficient approach and has been successfully applied to more than 40 farmed fish species. However, its application is still constrained by several bottlenecks: low editing efficiency in many marine fish species, reliance on labor-intensive microinjection, and public concerns that often fail to distinguish between gene editing and transgenesis. Here, we systematically review the current status of gene-editing breeding in farmed fish, summarizing progress in five major trait categories: sex control, growth enhancement, body coloration, disease resistance, and product quality. We also highlight emerging directions in gene editing, including stress reduction, aggression control, and the elimination of fishy odors. Concurrently, we discuss the rapid evolution of editing platforms—ranging from high-fidelity Cas variants and nanoparticle delivery systems to double-strand break-free editors, such as base editors and prime editors—and their potential to overcome existing limitations. Future research should focus on the following aspects: expanding the range of target genes through systematic functional genomics, developing delivery methods that bypass microinjection for marine fish species, establishing transparent regulatory frameworks for gene-edited aquatic products, and clarifying the distinction between gene editing and transgenesis to address public concerns. This review improves public understanding of the current status, challenges, and future directions of gene-editing breeding in aquaculture, thereby facilitating the further advancement of this technology in the field.

In teleosts, homologs of Anti-Müllerian Hormone (Amhy) and its type II receptor (Amhr2/Amhr2y) have been independently recruited as master sex-determination genes in about 50% of known cases. However, it remains unknown whether a conserved transducer pair exists, as the requisite type I receptors and R-Smad effectors remain unidentified amidst their diversity and potential redundancy. In this study, we employed an in vitro reporter assay to screen five type I receptors (Alk2a, Alk2b, Alk3, Alk6a, Alk6b) and three R-Smads (Smad1, Smad5, Smad8), discovering that only Alk3, Alk6a, or Alk6b, in combination with Smad5, significantly activated Amhy/Amhr2 signaling. In Nile tilapia, levels of phosphorylated Smad5 (p-Smad5) were notably elevated in XY gonads compared with XX gonads during the critical sex-determination window (8 to 15 dpf), while total Alk3 and Smad5 expression did not exhibit sexual dimorphism. The inhibition of type I receptors in XY fish resulted in feminization or complete sex reversal. Similarly, CRISPR/Cas9 mutagenesis of alk3 or smad5 led to male-to-female sex reversal in F0 mosaic mutants. Importantly, homozygous mutations in alk3 or smad5 resulted in embryonic lethality at the gastrula stage, whereas mutations in other type I receptors or R-Smads were viable and demonstrated normal sexual development. The conservation of this pathway was further substantiated in Southern catfish, where mutations in alk3a or smad5 also induced sex reversal in XY individuals. Collectively, our findings establish Alk3 and Smad5 as essential and specific transducers of the Amhy/Amhr2-mediated sex-determination pathway, revealing a potentially conserved signaling axis across teleosts.

Neural crest cells give rise to the craniofacial skeleton and multiple pigment cell lineages, yet how duplicated developmental regulators partition their ancestral functions after teleost-specific whole-genome duplication remains unclear. Here, we employed CRISPR/Cas9 to generate alx4a and alx4b single and double mutants in Nile tilapia (Oreochromis niloticus). By integrating phenotype, skeleton, transcriptome, quantitative PCR, and AlphaFold-based structural modeling analyses, we revealed their functional divergence. Loss of alx4a caused a regionally restricted reduction in iridophore-derived reflectance and abnormal cranial morphology, whereas alx4b single mutants showed no obvious phenotype under the conditions examined. By contrast, double mutants exhibited an almost complete loss of iridophore-derived structural coloration and substantially more severe cranial defects, accompanied by reduced calcein labeling in the opercular region, consistent with altered cranial mineralization. Skin transcriptomic and quantitative PCR analyses revealed marked downregulation of pnp4a and tfec, which are associated with iridophore differentiation and coloration, whereas no significant expression differences were detected for the iridophore survival-related genes ltk and mpv17. AlphaFold2-assisted HDOCK protein–DNA modeling yielded more favorable docking metrics for Alx4a than for Alx4b with the pnp4a promoter, supporting a potential Alx4a–pnp4a promoter interaction that requires experimental validation. In contrast, no significant genotype-dependent differences were detected in the measured abundance of melanophores, xanthophores, or erythrophores, and no obvious difference in gross dorsal-fin spine formation was observed under the conditions examined. Together, these findings reveal unequal functional contributions of alx4a and alx4b, with alx4a acting as the dominant paralog in iridophore-associated structural coloration and both paralogs contributing unequally to cranial development, and support pnp4a as a candidate downstream gene associated with Alx4a activity.

The transition from endogenous to exogenous nutrient sources (eeNST) represents a critical developmental phase in oviparous species, imposing significant constraints on early survival. However, the molecular mechanisms regulating this transition, particularly at the gene functional level, remain poorly understood. Glial cell linederived neurotrophic factor receptor alpha 1 (GFR alpha 1) is essential for intestinal neuronal development, yet its role during the eeNST is unknown. In this study, we characterized the Gfr alpha 1 ortholog (gfr alpha 1a) in Nile tilapia (Oreochromis niloticus) and investigated its functional role using CRISPR/Cas9-mediated knockout and RNAsequencing analyses. Gfr alpha 1a expression peaked in the midgut and hindgut at 13 days post-fertilization (dpf), coinciding with the phase during which the eeNST occurs. Notably, no surviving individuals were found among gfr alpha 1a homozygous mutants after 15 dpf. Phenotypic characterization revealed significant intestinal abnormalities, including shortened intestinal length, smaller intestinal outer diameter, and distal intestinal contraction accompanied by a complete absence of digestive residue. The intestinal epithelial cells in homozygous mutants underwent extensive vacuolar degeneration, and scattered apoptotic cells appeared karyopyknosis and karyorrhexis. Differentially expressed genes in the intestines between wild-type fish and gfr alpha 1a homozygous mutants at 13 dpf were enriched in oxidative stress. Furthermore, gfr alpha 1a homozygous mutants exhibited elevated levels of reactive oxygen species and malondialdehyde, indicating profound oxidative damage to the intestine. Our findings identify Gfr alpha 1a as a critical regulator of oxidative homeostasis and intestinal structural integrity during the eeNST in fish, suggesting it a potential target for improving the survival rates of farmed oviparous animals during this critical developmental phase.

The blackchin tilapia (Sarotherodon melanotheron) is an aquaculture species in Southeast Asia, recognized for its adaptability to diverse environmental conditions. Genomic resources for this species remain limited, hindering progress in genetic research and breeding programs. In this study, we generated a high-quality, chromosome-level genome assembly of blackchin tilapia by utilizing Illumina short reads, ONT long reads, Hi-C, and RNA sequencing data. The final assembly spans 1,027.41 Mb (scaffold N50 = 38.87 Mb), with 93.42% of the assembly anchored to 22 chromosomes. Genome completeness, assessed using BUSCO, reached 99.50%. We predicted 27,896 protein-coding genes, of which 90.87% were functionally annotated. Repetitive elements accounted for approximately 42.62% of the genome. This chromosome-scale genome assembly provides a reference for comparative genomic and genetic analyses of blackchin tilapia, supporting investigations into the genetic basis of salinity tolerance and traits relevant to aquaculture breeding.

Hepatic damage in fish induced by microplastic exposure has garnered increasing concern, yet its molecular mechanisms remain insufficiently elucidated. In this study, 30 days after hatching (dah) Nile tilapia were subjected to sub-chronic exposure to polystyrene microplastics (PS; 100 nm) for 14 days. Histopathological examination revealed evident inflammatory cell infiltration in the livers of PS-exposed fish compared to the control fish. Transmission electron microscopy showed elevated mitochondrial rupture and increased autophagosome formation. Immunofluorescence and Western blot analyses showed upregulated Lc3b and downregulated P62 protein levels, suggesting enhanced hepatic autophagy. Transcriptomic profiling of liver tissues and subsequent KEGG enrichment analysis highlighted significant upregulation of genes involved in the MAPK, NOD-like receptor, Toll-like receptor, and autophagy signaling pathways. Metabolomic profiling indicated notable enrichment in glutathione metabolism, ferroptosis, cysteine and methionine metabolism, and the NOD-like receptor pathway. Integrated transcriptomic and metabolomic KEGG analysis consistently identified ferroptosis as a centrally enriched pathway. Further gene expression and metabolite analyses demonstrated marked upregulation of immune-related genes, autophagy-related genes, and ferroptosis-pathway genes. Concurrently, ferroptosis-related metabolites including glutathione and cysteine were significantly decreased. Meanwhile, levels of lipid metabolites such as 2-oleoylglycerol were also reduced, whereas lipid peroxidation products represented by 4-hydroxynonenal were significantly increased. Additional validation confirmed increased expression of inflammatory factors (il-1β, tgf-β, nlrp3) and altered iron homeostasis in the PS-exposed fish liver. These findings indicate that sub-chronic PS exposure promotes hepatic ferroptosis via immune-mediated activation of autophagy, ultimately leading to liver injury in Nile tilapia. Our study provides novel insights into the mechanisms underlying microplastic-induced tissue damage in aquatic organisms.

Chinese longsnout catfish (Leiocassis longirostris), endemic to the Yangtze River in China, faces germplasm depletion due to poor larval survival and growth during seedling cultivation, exacerbated by limited understanding of weaning at the molecular level. Here, the results of growth performance and digestive enzyme activity showed that live prey, such as Limnodilus spp. and Artemia nauplii was the most suitable food for first feeding. Notably, larvae fed Limnodilus spp. for more than five days could undergo sex reversal, opening up scientific avenues for the cultivation of YY supermale and all-male progeny production. For weaning, a combined feeding of live prey and microbound diet for five days was found to be more conducive. RNA-seq analysis of gastrointestinal tract (GIT) during weaning (pre-weaning, mid-weaning and post-weaning) identified 3728 differentially expressed genes enriched in protein digestion and absorption, cholesterol metabolism, starch and sucrose metabolism, and NF-kappa B signaling pathways. Furthermore, the expression patterns of appetite-regulating genes varied during weaning, with the appetite-suppressing gene cck prominently expressed during the mid-weaning and appetite-stimulating genes npy and agrp significantly upregulated during the post-weaning. 16S rRNA sequencing revealed the establishment of a stable core microbial community in the GIT during weaning, with increasing richness and diversity as the weaning progressed, dominated by Proteobacteria, Bacteroidota, and Firmicutes. In conclusion, this study contributed to improving early survival and growth performance of L. longirostris and provided valuable insights into the effects of weaning on body metabolism and intestinal microbial community in farmed carnivorous fish.

piRNAs are a kind of germline specific small RNAs with important roles in transposon silencing and regulation of gene expression. Henmt1 (HEN methyltransferase 1) encodes a 2'-O-methyltransferase that methylated the 2'-OH of the 3'-terminal nucleotide of piRNAs in vertebrates. Mutation of Henmt1 in mouse induces piRNA instability and ultimately leads to male sterility and female subfertility. However, the function of henmt1 in fish remains to be studied. In the present study, henmt1 was found to be highly expressed in the gonads of Nile tilapia, and the expression level in female was higher than that in male. By CRISPR/Cas9, henmt1 homozygous mutant line was established in tilapia. Interestingly, henmt1(-/-) XY fish, showing normal spermatogenesis, were fertile. Gonadal histology and serum estrogen level of henmt1(-/-) female fish showed no difference compared with WT fish. However, mortality was observed in the offspring of henmt1(-/-) XX tilapia at the embryonic stage regardless of mating with henmt1(-/-) XY fish or WT XY tilapia. Significant differences in gene expression profile including key genes involved in embryogenesis and estrogen synthesis were found in eggs between henmt1(-/-) XX and WT fish. Taking together, henmt1 was dispensable for male spermatogenesis, but it played an important role in female fertility.

Somatostatin (SST), named for its ability to inhibit pituitary growth hormone (GH) secretion, is involved in multiple physiological processes though somatostatin receptors (SSTRs). Both in vitro and in vivo studies have demonstrated that SSTR2 mediates GH inhibition by SST. However, whether a deficiency of SSTR2 promotes the somatic growth of fish is unclear. In this study, both sstr2a and sstr2b were predominantly expressed in the pars distalis of the pituitary gland, with sstr2a showing higher expression levels than sstr2b. Mutation of sstr2a was performed in tilapia using the CRISPR/Cas9 system. The sstr2a−/− mutants exhibited a significant increase in body weight at 60, 120, and 180 days post fertilization (dpf) when reared in mixed populations with wild type (WT) fish, being 43 ​% heavier than WT fish at 180 dpf. The sstr2a−/− mutants also demonstrated better growth than WT fish under the separate-tank culture condition, with higher body weight, length, height, and width, weight gain rate, and specific growth rate, as well as lower food intake and feed coefficient, but no difference in condition factor. Furthermore, among female and male sstr2a−/− mutants and WT controls, the growth of male sstr2a−/− mutants was the highest, followed by female sstr2a−/− mutants, then WT males and WT females. No differences were observed between sstr2a−/− mutants and WT fish in the mean area and number of muscle fibers per visual field under the microscope. However, there were fewer lipid droplets in the liver in sstr2a−/− mutants than in WT fish. The deficiency of SSTR2a also led to elevated circulating GH and IGF-1 levels and up-regulated expression of GH/IGF axis genes. Overall, the first established sstr2a−/− mutant line in fish not only holds significant potential to develop into a fast-growth strain of tilapia, but also provides an excellent model for understanding the regulation of growth and metabolism in teleosts.

Female fish reproduction is governed by a tightly controlled endocrine network that ensures healthy gamete formation and species continuation. The hypothalamic-pituitary-gonadal (HPG) axis, with its core hormones (GnRH, FSH, LH, and steroid hormones), serves as the central engine for oogenesis and ovulation. However, this engine is modulated by various “non-classical” endocrine factors, including kisspeptin, dopamine, gonadotropin-inhibitory hormone (GnIH), cortisol, and thyroid hormones (THs). While the individual roles of these components are well-documented, the integration of non-classical signals with the HPG axis in coordinating oocyte growth and maturation remains poorly defined. This review proposes a conceptual framework that positions the HPG axis as the core regulator and non-classical hormones as modulators that fine-tune its output. By synthesizing current molecular and physiological evidence, we highlight how the interaction between classical and non-classical pathways accounts for species-specific variations in reproductive control. Understanding this integrated network is crucial for advancing reproductive biology, precision breeding, and conservation strategies in aquaculture.

Transportation is an unavoidable stressor in aquaculture, often leading to immunosuppression and increased mortality in fish. Schizothorax nukiangensis, an endemic species inhabiting the middle and upper reaches of the Nujiang River in Tibet, is particularly vulnerable to transport stress in both artificial breeding and conservation programs. S. nukiangensis were subjected to simulated transportation for 2, 4, 8, and 12 h, then water quality parameters, histopathological alterations of gills and liver, plasma biochemical indicators, and transcriptomic responses were assessed. Transportation resulted in progressive deterioration of water quality, characterized by significant increases in water temperature and ammonia nitrogen, accompanied by a marked decline in pH (P < 0.05). Prolonged transportation (8 h and 12 h) caused severe pathological damage to gills and liver. ROS and cortisol levels continuously increased, while antioxidant enzymes exhibited elevated activity; however, total antioxidant capacity significantly declined at 8 and 12 h. Transcriptomic analyses revealed that the upregulated differentially expressed genes (DEGs) in the liver were predominantly enriched in pathways related to digestion and lipid metabolism, including fat digestion and absorption, steroid biosynthesis, and glycerophospholipid metabolism. DEGs enriched in immune-related pathways in gill tissue, such as the cytosolic DNA-sensing pathway, the C-type lectin receptor signaling pathway, and the IL-17 signaling pathway, were predominantly downregulated. Protein-protein interaction (PPI) network analysis identified key genes including Fasn, Acaca, Aldh16a1, Nsdhl, Srebf1, Dgat2, Acox3, Cpt1a, Ins, Pck1, Casp3, Casp8, Fos, Fadd, Stat1, and Ikk. Collectively, these findings indicate that transport stress activates the AMPK signaling pathway in the liver, facilitating energy reallocation through lipid metabolism, while concurrently suppressing gill immune function via downregulation of the TNF and NF-kappa B signaling pathways. This study provides novel insights into the physiological and molecular mechanisms underlying transport-induced stress and offers a scientific basis for improving transportation strategies for endemic fish species on the Qinghai-Tibet Plateau.

This study was conducted to determine the effects of knocking out the myostatin gene ( mstnb1 ), which restricts muscle development in rainbow trout ( Oncorhynchus mykiss ), using CRISPR/Cas9 technology on growth performance and feed efficiency. Within the scope of this research, which aims to increase sectoral productivity in aquaculture, two different gRNAs targeting the first exon of the mstnb1 gene were designed. Sanger sequencing analyses confirmed the successful creation of mutations in the F0 generation, involving a 5 bp deletion with gRNA1 and a 1 bp insertion and 6 bp deletion with gRNA2. During a 10-month follow-up period between May 2024 and March 2025, the growth parameters of mutant individuals were compared with a wild-type (WT) control group. At the end of the experiment, mutant fish reached an average weight of 825.0 ± 12.3 g, while the WT group remained at 464.1 ± 9.2 g. These results demonstrate that CRISPR/Cas9-mediated mstnb1 disruption successfully induces the "double muscularity" phenotype and has high biotechnological potential in rainbow trout farming, potentially shortening production time and reducing unit costs.

Proopiomelanocortin (POMC) is a neuroendocrine precursor critical for regulating energy homeostasis and feeding behavior across vertebrates. Although POMC deficiency causes hyperphagia and increased body weight in model organisms including mice and zebrafish, there have been no reports of pomc knockout in commercially farmed fishes to date. This study presents a systematic investigation of pomc knockout in one of the most widely farmed fish, Nile tilapia (Oreochromis niloticus), revealing its dual role in enhancing growth performance through appetite stimulation and endocrine regulation. Compared to wild type fish, pomc−/− fish exhibited 33 % higher feed intake, 65 % greater body weight, and 20 % improved feed conversion ratio (FCR) under full feeding conditions at 150 days post fertilization. Remarkably, even when fed to match wild-type food intake, pomc−/− mutants showed 18 % greater body weight and 15 % improved FCR. Transcriptomic profiling and ELISA demonstrated that POMC deficiency elevated the IGF1 signaling pathway, in line with reduced hepatic lipid storage and accelerated myocyte proliferation in pomc−/− fish found by histological analyses. These results revealed that disruption of pomc prevented obesity and promoted growth. Meanwhile, pomc−/− tilapia exhibited significantly higher levels of crude ash and crude protein, along with reduced crude fat levels in muscle. The increased levels of essential amino acids and flavor amino acids suggest that pomc−/− tilapia may possess superior nutritional value and umami taste. The pomc−/− fish showed reduced polyunsaturated fatty acids (PUFAs), but exhibited unchanged levels of key PUFAs with significant health benefits including EPA and DHA. In summary, pomc disruption represents a promising genetic approach for enhancing growth performance and feed efficiency in Nile tilapia, underscoring its potential as a valuable target in selective breeding programs for aquaculture improvement.

The Kit signaling pathway governs vertebrate pigmentation. However, the mechanisms governing cell fate coordination by duplicated ligand-receptor pairs in teleosts remain elusive. In the present study, we elucidated this network in Nile tilapia (Oreochromis niloticus) by generating single and double mutants of kitlga, kitlgb, kita, and kitb via CRISPR/Cas9-mediated gene editing. Kitlga was identified as the dominant ligand. While kitlgb−/− and kitb−/− single mutants showed no detectable pigment defects, and kita−/− mutants exhibited only partial melanophore reduction, kitlga deficiency caused a severe loss of melanophores. kita−/−; kitb−/− double mutants recapitulated this severe kitlga phenotype, confirming that Kitlga signals through both receptors. Beyond melanophore loss, kitlga−/− mutants developed a “red tilapia”-like appearance with metallic luster. This phenotype arose from chromatophore population remodeling; the suppression of melanophores triggered the compensatory proliferation of erythrophores (quantified by elevated erythrophore numbers and carotenoid levels) and structural reorganization of iridophores. Transmission electron microscopy demonstrated that these mutants developed three layers of guanine crystal platelets, in contrast to the single layer found in wild-type fish. Mechanistically, double-color fluorescence in situ hybridization analysis revealed that, while both receptor genes were co-expressed in melanophores, transcripts in kita were significantly more abundant than those in kitb. Consistent with this, our data suggest that Kitlga acts as a molecular dual switch; it preferentially engages abundant Kita to drive differentiation via mitogen-activated protein kinase (MAPK) while recruiting Kitb to support survival via phosphatidylinositol 3-kinase-protein kinase B (PI3K-Akt). Both pathways converged on mitfa, which was validated by the rescue of defects via mitfa mRNA injection. Collectively, these findings identify Kitlga as an important regulator that orchestrates pigment cell plasticity and structural coloration, thus providing a genetic basis for cichlid color diversity.

Abstract The effects of clustered regularly interspaced short palindromic repeats (CRISPR)/Cas9‐mediated disruption of the myostatin gene (mstnb1) on the growth performance of rainbow trout (Oncorhynchus mykiss) were evaluated. Two specific guide RNAs (gRNAs) targeting the first exon of the target gene were co‐injected into fertilized eggs. While the survival rate of the injected embryos at the swim‐up stage was 23.5%, Sanger sequencing of F0 individuals confirmed the successful generation of mutations. During a 10‐month growing period, quantifiable phenotypic data revealed a significant enhancement in macroscopic somatic growth. The mstnb1‐F0 mosaic fish exhibited an approximate 56% increase in body weight compared to the wild‐type (WT) control group. Specifically, the mutant group reached an average weight of 825.0 ± 12.3 g, significantly outperforming the WT group, which reached 464.1 ± 9.2 g. Our results demonstrate that disruption of the mstnb1 gene using CRISPR/Cas9 technology induces a striking somatic weight gain rather than merely altering microscopic muscle fiber characteristics, demonstrating high biotechnological potential for shortening production time and reducing unit costs in sustainable rainbow trout aquaculture.

The Hedgehog (Hh) signaling pathway is a key regulator of adipogenesis and lipid metabolism. However, the specific role of its receptor, Patched2 (Ptch2), in these processes remains unclear. Here, using a CRISPR/Cas9-mediated ptch2 homozygous mutation model in Nile tilapia (Oreochromis niloticus), we found that Ptch2 deficiency induced visceral and perirenal lipomatosis characterized by small, multinucleated adipocytes. Comparative adipose transcriptomics revealed pronounced adipogenic reprogramming, with marked upregulation of genes governing de novo lipogenesis (e.g., acaca, fasn), fatty acid desaturation (e.g., scd, fadsd6), and triglyceride synthesis (e.g., dgat2, lpl). Biochemically, mutants exhibited elevated blood glucose and liver transaminases (alanine aminotransferase, aspartate aminotransferase) activity, and reduced alkaline phosphatase activity, indicating systemic metabolic dysregulation and hepatic stress. Our findings demonstrate that loss of Ptch2 triggers lipoma formation and adipogenic transcriptome reprogramming, highlighting its essential role in maintaining adipose tissue homeostasis.