HMGA2 expression distinguishes between different types of postpubertal testicular germ cell tumour

Multi-breed genomic predictions and functional variants for fertility of tropical bulls

Worldwide, most beef breeding herds are naturally mated. As such, the ability to identify and select fertile bulls is critically important for both productivity and genetic improvement. Here, we collected ten fertility-related phenotypes for 6,063 bulls from six tropically adapted breeds. Phenotypes were comprised of four bull conformation traits and six traits directly related to the quality of the bull's semen. We also generated high-density DNA genotypes for all the animals. In total, 680,758 single nucleotide polymorphism (SNP) genotypes were analyzed. The genomic correlation of the same trait observed in different breeds was positive for scrotal circumference and sheath score on most breed comparisons, but close to zero for the percentage of normal sperm, suggesting a divergent genetic background for this trait. We confirmed the importance of a breed being present in the reference population to the generation of accurate genomic estimated breeding values (GEBV) in an across-breed validation scenario. Average GEBV accuracies varied from 0.19 to 0.44 when the breed was not included in the reference population. The range improved to 0.28 to 0.59 when the breed was in the reference population. Variants associated with the gene HDAC4, six genes from the spermatogenesis-associated (SPATA) family of proteins, and 29 transcription factors were identified as candidate genes. Collectively these results enable very early in-life selection for bull fertility traits, supporting genetic improvement strategies currently taking place within tropical beef production systems. This study also improves our understanding of the molecular basis of male fertility in mammals.

X chromosome variants are associated with male fertility traits in two bovine populations

BACKGROUND

Twenty-five phenotypes were measured as indicators of bull fertility (1099 Brahman and 1719 Tropical Composite bulls). Measurements included sperm morphology, scrotal circumference, and sperm chromatin phenotypes such as DNA fragmentation and protamine deficiency. We estimated the heritability of these phenotypes and carried out genome-wide association studies (GWAS) within breed, using the bovine high-density chip, to detect quantitative trait loci (QTL).

RESULTS

Our analyses suggested that both sperm DNA fragmentation and sperm protamine deficiency are heritable (h2 from 0.10 to 0.22). To confirm these first estimates of heritability, further studies on sperm chromatin traits, with larger datasets are necessary. Our GWAS identified 12 QTL for bull fertility traits, based on at least five polymorphisms (P < 10-8) for each QTL. Five QTL were identified in Brahman and another seven in Tropical Composite bulls. Most of the significant polymorphisms detected in both breeds and nine of the 12 QTL were on chromosome X. The QTL were breed-specific, but for some traits, a closer inspection of the GWAS results revealed suggestive single nucleotide polymorphism (SNP) associations (P < 10-7) in both breeds. For example, the QTL for inhibin level in Braham could be relevant to Tropical Composites too (many polymorphisms reached P < 10-7 in the same region). The QTL for sperm midpiece morphological abnormalities on chromosome X (QTL peak at 4.92 Mb, P < 10-17) is an example of a breed-specific QTL, supported by 143 significant SNPs (P < 10-8) in Brahman, but absent in Tropical Composites. Our GWAS results add evidence to the mammalian specialization of the X chromosome, which during evolution has accumulated genes linked to spermatogenesis. Some of the polymorphisms on chromosome X were associated to more than one genetically correlated trait (correlations ranged from 0.33 to 0.51). Correlations and shared polymorphism associations support the hypothesis that these phenotypes share the same underlying cause, i.e. defective spermatogenesis.

CONCLUSIONS

Genetic improvement for bull fertility is possible through genomic selection, which is likely more accurate if the QTL on chromosome X are considered in the predictions. Polymorphisms associated with male fertility accumulate on this chromosome in cattle, as in humans and mice, suggesting its specialization.

Downregulation of miR-196-5p Induced by Hypoxia Drives Tumorigenesis and Metastasis in Hepatocellular Carcinoma

In hepatocellular carcinoma (HCC), the hypoxic tumor microenvironment can drive enhance tumor malignancy and recurrence. The microRNA (miRNA) miR-196-5p has been shown to modulate the progression of several cancer types, but its roles in HCC remain uncertain. In the present report we observed significant miR-196-5p downregulation in HCC tissues and cells, and we found that the expression of this miRNA significantly impaired the proliferation and metastatic potential of HCC in vitro and in vivo. We identified high-mobility group AT-hook 2 (HMGA2) as a miR-196-5p target gene that was associated with the ability of miR-196-5p to modulate the progression of HCC. Expression of miR-196-5p and HMGA2 were correlated with the clinical characteristics and poor outcomes in patients with HCC. Finally, we found that hypoxic conditions were linked with reduced miR-196-5p expression in the context of HCC. Together these results highlight the role for miR-196-5p as an inhibitor of the proliferation and metastasis of HCC via the targeting of HMGA2, with this novel hypoxia/miR-196-5p/HMGA2 pathway serving as a potential target for future therapeutic intervention.

BRCA1 regulates HMGA2 levels in the Swan71 trophoblast cell line

During early placental development, tumor suppressors and oncogenes work synergistically to regulate cell proliferation and differentiation in a restrained manner compared with the uncontrollable growth in cancer. One example of this partnership is the regulation of the oncofetal protein HMGA2 by BRCA1. BRCA1 forms a repressor complex with ZNF350 and CtIP to bind to the promoter of HMGA2, preventing transcription. Chromatin immunoprecipitation determined BRCA1 forms this repressor complex in human trophoblast cells, suggesting a role in the placenta. Furthermore, miR-182 has been shown to target BRCA1 mRNA in ovarian cancer cells, blocking the formation of the BRCA1 repressor complex and allowing increased transcription of HMGA2. miR-182 was one of the first miRNAs described as elevated in the serum and placentas of preeclamptic women. Therefore, we hypothesized that BRCA1 is essential for normal trophoblast cell development. We used CRISPR-Cas9 genome editing and miR-182 overexpression to decrease BRCA1 protein in the Swan71 cell line. HMGA2 was significantly increased in the BRCA1 KO and miR-182 overexpressing cells compared to controls. We also determined that BRCA1 repressor complex binding to HMGA2 was significantly reduced in BRCA1 KO and miR-182 overexpressing cells compared with controls, leading us to conclude that increased HMGA2 was because of decreased binding of the BRCA1 repressor complex. Finally, we found that the caspase activity was significantly higher in BRCA1 KO and miR-182 overexpressing cells suggesting an increased amount of apoptosis. These data suggest that BRCA1 is an important regulator of the oncofetal protein HMGA2 and promotes cell survival in human placental cells.

Nanoscale Assembly of High-Mobility Group AT-Hook 2 Protein with DNA Replication Fork

High mobility group AT-hook 2 (HMGA2) protein is composed of three AT-hook domains. HMGA2 expresses at high levels in both embryonic stem cells and cancer cells, where it interacts with and stabilizes replication forks (RFs), resulting in elevated cell proliferation rates. In this study, we demonstrated that HMGA2 knockdown reduces cell proliferation. To understand the features required for interaction between HMGA2 and RFs, we studied the solution structure of HMGA2, free and in complex with RFs, using an integrated host of biophysical techniques. Circular dichroism and NMR experiments confirmed the disordered state of unbound HMGA2. Dynamic light scattering and sedimentation velocity experiments demonstrated that HMGA2 and RF are monodisperse in solution, and form an equimolar complex. Small-angle x-ray scattering studies revealed that HMGA2 binds in a side-by-side orientation to RF where 3 AT-hooks act as a clamp to wrap around a distorted RF. Thus, our data provide insights into how HMGA2 interacts with stalled RFs and the function of the process.