Genome-wide methylation changes are associated with muscle fiber density and drip loss in male three-yellow chickens.

In eukaryotes, DNA methylation is an important epigenetic modification involved in gene expression regulation. Meat quality traits are complicated traits that are controlled by many genes. Changes in the methylation levels of certain genes controlling meat quality traits will inevitably affect their expression levels, thereby affecting meat quality. The objectives of this study were to investigate the differences in the DNA methylation level in pectoral muscle tissues using fluorescent-labeled methylation sensitive amplified polymorphism and their relationships with meat quality traits in three-yellow chickens. The results showed that the differences in the DNA methylation level had a highly significant effect on muscle fiber density and drip loss (P<0.01). However, no significant correlations were found between the DNA methylation levels and the other investigated traits (P>0.05).

Prevalence and inconformity of refractive errors and ocular biometry of 3573 medical university freshman students for 4 consecutive years.

AIM: To evaluate the prevalence of refractive errors and ocular biometry in 3573 freshman students at Tianjin Medical University for 4 consecutive years. METHODS: In this university-based, cross-sectional study, comprising 3573 students, visual acuity (VA), slit-lamp examination, non-cycloplegic auto-refraction, and ocular biometry were recorded. RESULTS: The prevalence of myopia increased annually, from 2017 to 2020 were 93.5%, 94.5%, 95.9%, and 96.2%, respectively (P=0.03), and the prevalence of high myopia was 25.7%, 26.9%, 28.6%, and 28.6%, respectively. Males tended to have a higher percentage of total astigmatism than females, with astigmatism ≥0.75 and ≥1.0 D criteria. The percentage of with-the-rule astigmatism, against-the-rule astigmatism, and oblique astigmatism was 90.3%, 5.8%, and 3.9%, respectively, with astigmatism ≥1.00 D criteria. The mean spherical equivalent, axial length (AL), central corneal thickness (CCT), anterior chamber depth (ACD), lens thickness (LT), corneal radius (CR), and lens position (LP) were 4.37±2.52 D, 25.28±1.24 mm, 539.49±34.98 µm, 3.31±0.34 mm, 3.47±0.21 mm, 7.8±0.28 mm, and 5.04±0.32 mm, respectively. With diopter increase in myopia, the AL became longer, CR became steeper, ACD became deeper, LT became thinner, and LP became more posterior (all P<0.01). Females had a shorter AL, thinner CCT, smaller CR, shallower ACD, thicker lens, and more anterior LP than males (P<0.01). The 64% of high myopia had AL≥26 mm, meanwhile, 5.8% mild myopia and 21.1% moderate myopia had AL≥26 mm. With AL≥26 mm, mild and moderate myopia compared to high myopia, AL was shorter (26.51±0.46 vs 26.87±0.70 mm), CR was larger (8.10±0.3 vs 7.85±0.23 mm) and LT was thinner (3.39±0.19 vs 3.45±0.19 mm, P<0.001). CONCLUSION: The prevalence of myopia and high myopia is significantly high in freshman students. The majority of astigmatism is with-the-rule. Inconformity of refractive errors and ocular biometry existed in some students. Attention should be paid to the ocular biometry of myopia.

Patterns of variation of the major histocompatibility complex class IIB loci in Chinese goose (Anser Cygnoides).

In order to understand the variations of genomic organization of the major histocompatibility complex (MHC) and provide data for the studies on disease resistance of avian species, the MHC class II polymorphism in Chinese Z-goose was investigated for the first time in the present study. Eight alleles, which probably came from different loci, were found in six different geese with only one obvious band in the restriction fragment length polymorphism data. The numbers of nonsynonymous substitutions (dN) in peptide binding region of exon 2 were higher than that of synonymous substitutions (dS), and no stop codons or frameshift mutations were found in this region, indicating that balance selection was in operation, and the sequences are not likely to be pseudogenes. In addition, we successfully obtained five different long MHC class II fragments (about 1,162 bp) in six geese and found that the length of intron 1 was longer than that in chicken and some other birds, but intron 2 seemed to be intermediate in length. The phylogenetic tree appeared to branch in an order consistent with accepted evolutionary pathway.

Low-density lipoprotein receptor-related protein 1 regulates muscle fiber development in cooperation with related genes to affect meat quality.

Low-density lipoprotein receptor-related protein 1 (LRP1) is an important signal protein that is widely involved in physiological processes, such as lipid metabolism, cell movement, and disease processes. However, the relationship between LRP1 and meat quality remains unknown in chickens. The present study aimed to investigate the correlation between LRP1 and meat quality that builds on our preliminary research, as well as to reveal the underlying molecular mechanism of LRP1 on meat-quality traits. The results showed that LRP1 was significantly correlated with shear force (P < 0.05). Several key genes involved in muscle growth and development, including IGF-1, IGFBP-5, IGF-1R, IGF-2, and MyoD, were down-regulated significantly (P < 0.05 or P < 0.01), and MSTN was up-regulated significantly (P < 0.01) in the presence of LRP1 interference. Cell proliferation- or apoptosis-related genes, including PMP22, CDKN2C, and p53, increased significantly (P < 0.05 or P < 0.01), whereas Bcl-x decreased significantly (P < 0.05) in the RNAi group. We conclude that LRP1 regulates muscle fiber development in cooperation with related genes that affect myoblast proliferation and apoptosis, thereby impacting shear force in chickens. This study will provide a valuable resource for biological investigations of muscle growth and meat-quality-related genes in chickens. The results could be useful in identifying candidate genes that could be used for selective breeding to improve meat quality.

Lithium chloride's inhibition of 3T3-L1 cell differentiation by regulating the Wnt/ß-catenin pathway and enhancing villin 2 expression.

The aim of this study is to reveal the relation among villin 2, Wnt/ß-catenin, and adipogenesis by adding appropriate lithium chloride (LiCl). The study comprises three parts: the selection of LiCl concentration, the effect of LiCl on adipocyte differentiation during and after differentiation induction. By comprehensively analyzing the results of the experiments, we proved that LiCl can inhibit adipocyte differentiation and enhance villin 2 and ß-catenin expressions not only during differentiation induction but also after it. Moreover, villin 2 has a significant impact on ß-catenin. We suggest that villin 2 may participate in Wnt/ß-catenin signaling.

A comparative profile of the microRNA transcriptome in immature and mature porcine testes using Solexa deep sequencing.

MicroRNAs (miRNAs) are small noncoding regulatory RNAs that play key roles in many diverse biological processes such as spermatogenesis. However, no study has been performed on the miRNA transcriptome of developing porcine testes. Here, we employed Solexa deep sequencing technology to extend the repertoire of porcine testis miRNAs and extensively compare the expression patterns of sexually immature and mature porcine testes. Solexa sequencing of two small RNA libraries derived from immature (30 days) and mature (180 days) pig testis samples yielded over 25 million high-quality reads. Overall, the two developmental stages had significantly different small RNA compositions. A custom data analysis pipeline identified 398 known and/or homologous conserved porcine miRNAs, 15 novel pig-specific miRNAs and 56 novel candidate miRNAs. We further observed multiple mature miRNA variants and identified a new bidirectional transcribed miRNA locus, ssc-mir-181a. A total of 122 miRNAs were differentially expressed in the immature and mature testes, and 10 were validated using quantitative RT-PCR. Furthermore, GO and KEGG pathway analyses of the predicted miRNA targets further illustrate the likely roles for these differentially expressed miRNAs in spermatogenesis. This study is the first comparative profile of the miRNA transcriptome in immature and mature porcine testes using a deep sequencing approach, and it provides a useful resource for future studies on the role of miRNAs in spermatogenesis and male infertility treatment.