Rapid construction of genome map for large yellow croaker (Larimichthys crocea) by the whole-genome mapping in BioNano Genomics Irys system.

BACKGROUND: Large yellow croaker (Larimichthys crocea) is an important commercial fish in China and East-Asia. The annual product of the species from the aqua-farming industry is about 90 thousand tons. In spite of its economic importance, genetic studies of economic traits and genomic selections of the species are hindered by the lack of genomic resources. Specifically, a whole-genome physical map of large yellow croaker is still missing. The traditional BAC-based fingerprint method is extremely time- and labour-consuming. Here we report the first genome map construction using the high-throughput whole-genome mapping technique by nanochannel arrays in BioNano Genomics Irys system. RESULTS: For an optimal marker density of ~10 per 100 kb, the nicking endonuclease Nt.BspQ1 was chosen for the genome map generation. 645,305 DNA molecules with a total length of ~112 Gb were labelled and detected, covering more than 160X of the large yellow croaker genome. Employing IrysView package and signature patterns in raw DNA molecules, a whole-genome map of large yellow croaker was assembled into 686 maps with a total length of 727 Mb, which was consistent with the estimated genome size. The N50 length of the whole-genome map, including 126 maps, was up to 1.7 Mb. The excellent hybrid alignment with large yellow croaker draft genome validated the consensus genome map assembly and highlighted a promising application of whole-genome mapping on draft genome sequence super-scaffolding. The genome map data of large yellow croaker are accessible on lycgenomics.jmu.edu.cn/pm. CONCLUSION: Using the state-of-the-art whole-genome mapping technique in Irys system, the first whole-genome map for large yellow croaker has been constructed and thus highly facilitates the ongoing genomic and evolutionary studies for the species. To our knowledge, this is the first public report on genome map construction by the whole-genome mapping for aquatic-organisms. Our study demonstrates a promising application of the whole-genome mapping on genome maps construction for other non-model organisms in a fast and reliable manner.

The Influence of Immune Heterogeneity on the Effectiveness of Immune Checkpoint Inhibitors in Multifocal Hepatocellular Carcinomas.

PURPOSE: Immune checkpoint inhibitor therapy is emerging as the promising option for patients with advanced hepatocellular carcinoma. We aimed to investigate the heterogeneity of different tumor nodules of the same patient with multifocal hepatocellular carcinomas in response to immunotherapy and its molecular mechanisms. EXPERIMENTAL DESIGN: We attained 45 surgical tumor samples including 33 small and 12 large nodules from 12 patients with multifocal hepatocellular carcinoma and evaluated genomic and immune heterogeneity among tumors through whole-genome sequencing and RNA sequencing. IHC was performed to validate the expression of immune markers. The responses to anti-programmed cell death protein-1 (PD-1) therapy in patients with multifocal hepatocellular carcinoma were evaluated. RESULTS: The small and large tumors within the same patient presented with similar genomic characteristics, indicating their same genomic origin. We further found the small tumors had higher immune cell infiltration including more CD8+ T cells, M1 macrophages, and monocytes as compared with large tumors. Besides, the expression of interferon signature predictive of response to anti-PD-1 therapy was significantly upregulated in the small tumors. Moreover, the immune pathways were more vigorous along with less active proliferation pathways in the small tumors. In keeping with this, we found that small nodules were more sensitive to anti-PD-1 therapy than large nodules in patients with multifocal hepatocellular carcinoma. CONCLUSIONS: The small tumors in patients with multifocal hepatocellular carcinoma had higher immune cell infiltration and upregulation of immune pathways as compared with the large tumors, which can partially explain the different responses of small and large tumors in the same case to anti-PD-1 therapy.

Preservation of the fecal samples at ambient temperature for microbiota analysis with a cost-effective and reliable stabilizer EffcGut.

With the increasing researches on the role of gut microbiota in human health and disease, appropriate storage method of fecal samples at ambient temperature would conveniently guarantee the precise and reliable microbiota results. Nevertheless, less choice of stabilizer that is cost-efficient and feasible to be used in longer preservation period obstructed the large-scale metagenomics studies. Here, we evaluated the efficacy of a guanidine isothiocyanate-based reagent method EffcGut and compared it with the other already used storage method by means of 16S rRNA gene sequencing technology. We found that guanidine isothiocyanate-based reagent method at ambient temperature was not inferior to OMNIgene·GUT OM-200 and it could retain the similar bacterial community as that of -80 °C within 24 weeks. Furthermore, bacterial diversity and community structure difference were compared among different sample fraction (supernatant, suspension and precipitate) preserved in EffcGut and -80 °C. We found that supernatant under the preservation of EffcGut retained the similar community structure and composition as that of the low temperature preservation method.

Gene map of large yellow croaker (Larimichthys crocea) provides insights into teleost genome evolution and conserved regions associated with growth.

The genetic map of a species is essential for its whole genome assembly and can be applied to the mapping of important traits. In this study, we performed RNA-seq for a family of large yellow croakers (Larimichthys crocea) and constructed a high-density genetic map. In this map, 24 linkage groups comprised 3,448 polymorphic SNP markers. Approximately 72.4% (2,495) of the markers were located in protein-coding regions. Comparison of the croaker genome with those of five model fish species revealed that the croaker genome structure was closer to that of the medaka than to the remaining four genomes. Because the medaka genome preserves the teleost ancestral karyotype, this result indicated that the croaker genome might also maintain the teleost ancestral genome structure. The analysis also revealed different genome rearrangements across teleosts. QTL mapping and association analysis consistently identified growth-related QTL regions and associated genes. Orthologs of the associated genes in other species were demonstrated to regulate development, indicating that these genes might regulate development and growth in croaker. This gene map will enable us to construct the croaker genome for comparative studies and to provide an important resource for selective breeding of croaker.