Ndrg3 gene regulates DSB repair during meiosis through modulation the ERK signal pathway in the male germ cells

Relationship between serum NDRG3 and papillary thyroid carcinoma

BACKGROUND

In recent years, papillary thyroid carcinoma is considered to be one of the fastest increaseing cancer. NDRG family member 3 (NDRG3) has been proposed as a molecular marker of tumor, and is expected to be used in clinic.

METHODS

Enzyme-linked immunosorbent assay was used to detect the serum NDRG3 expression in 81 papillary thyroid carcinoma cases, 75 benign thyroid nodules cases and 77 healthy control cases, respectively. Electrochemiluminescence method was applied to measure the levels of triiodothyronine, tetraiodothyronine, thyrotropin, thyroglobulin antibody and thyroid peroxidase antibody. Immunohistochemical staining was used to detect the expression of NDRG3 in papillary thyroid carcinoma, benign thyroid nodules and normal tissues adjacent to cancer.

RESULTS

The expression of serum triiodothyronine, tetraiodothyronine, thyrotropin, thyroglobulin antibody and thyroid peroxidase antibody and NDRG3 were significantly different among benign thyroid nodules, papillary thyroid carcinoma cases and healthy control groups (P <0.001). Only the expression of serum NDRG3 was significantly different between benign thyroid nodules and papillary thyroid carcinoma groups (P <0.001). Immunohistochemistry showed that NDRG3 was expressed in all three groups, the lowest in papillary thyroid carcinoma, the second in benign thyroid nodules, and the highest in normal tissues adjacent to cancer. Logistic regression analysis showed that serum NDRG3 was an independent protective factor for papillary thyroid carcinoma (OR =0.964, 95%CI =0.953 to 0.974, P <0.001). The ROC curve of non-papillary thyroid carcinoma diagnosed by serum NDRG3 showed the optimal cut-off value of 481.38 pg/ml, sensitivity of 72.4%, specificity of 90.1%, and the maximum area under the curve (AUC =0.902, 95%CI =0.863 to 0.940, P <0.001). The ROC curve of benign thyroid nodules diagnosed by serum NDRG3 showed the optimal critical value of 459.28 pg/ml, sensitivity of 81.3%, and specificity of 74.1% (AUC =0.863, 95%CI =0.808 to 0.919, P <0.001). The expression level of serum NDRG3 was significantly correlated with extrathyroid extensionand (P =0.007) and lymphatic metastasis of papillary thyroid carcinoma (P =0.019).

CONCLUSIONS

The decrease of NDRG3 expression can not only differential diagnosis benign thyroid nodules and papillary thyroid carcinoma, but also serve as a molecular marker for the diagnosis of papillary thyroid carcinoma.

A novel posttranslational modification of histone, H3 S-sulfhydration, is down-regulated in asthenozoospermic sperm

Oxidative stress is one of the major causes leading to male infertility including asthenozoospermia. Hydrogen sulfide (H₂S) has been widely recognized to be a potent antioxidant whose role is partially implemented by protein S-sulfhydration. However, protein S-sulfhydration has not been reported in germ cells. Therefore, we investigated whether asthenozoospermia could be associated with sperm protein S-sulfhydration. S-sulfhydrated proteins in human sperm were enriched via biotin-switch assay and analyzed using LC-MS/MS spectrometry. Two hundred forty-four S-sulfhydrated proteins were identified. Importantly, we validated that sperm histones H3.1 and H3.3 were the S-sulfhydrated proteins. Their S-sulfhydrated amino acid residue was Cysteine111. Abundances of S-sulfhydrated H3 (sH3) and S-sulfhydrated H3.3 (sH3.3) were significantly down-regulated in asthenozoospermic sperm, compared with the fertile controls, and were significantly correlated with progressive motility. Retinoic acid (RA) up-regulated level of sH3.3 in primary round spermatids and the C18-4 cells (a mouse spermatogonial stem cell line). Overexpression of the mutant H3.3 (Cysteine111 was replaced with serine) affected expression of 759 genes and raised growth rate of C18-4 cells. For the first time, S-sulfhydration H3 and H3.3 were demonstrated in the present study. Our results highlight that aberrant S-sulfhydration of H3 is a new pathophysiological basis in male infertility.

High expression of NDRG3 in osteoarthritis patients

BACKGROUND

Osteoarthritis (OA), as a common disease, seriously affects the quality of life of the victims, but its pathogenesis remains unclear. It has been confirmed that hypoxia-induced factor (HIF)-mediated hypoxia response plays an important role in the development and progression of OA. As a member of the N-myc downstream regulatory gene families, NDRG3 has been reported to independently regulate the hypoxic response of tumour cells, but the relationship between NDRG3 and OA development has not been reported so far.

METHODS

In this study, seven OA patients were admitted to Guizhou Provincial People's Hospital from January 2017 to December 2018. The OA group included 5 patients clinically diagnosed with hip/knee OA, which required arthroplasty. The normal group included 2 patients with no previous history of OA and rheumatoid arthritis, which required amputation due to trauma or tumour. The articular cartilage samples were collected to detect the expression of HIF-1α, HIF-2α and NDRG3 using immunohistochemical (IHC), haematoxylin and eosin (HE) and toluidine blue (TB) staining.

RESULTS

HE and TB staining indicated that the cartilage surface of the normal group was smooth and intact, with a columnar arrangement of hyaline chondrocytes, while the cartilage surface of the OA group was discontinuous, with cartilage missing and fibrous soft tissue growing into the defect site. HIF-1α staining was positive in both groups. Moreover, HIF-2α and NDRG3 staining was weakly positive in the normal group, but were uniformly and strongly positive in the OA group. The positively stained areas and integral optical density for NDRG3 were significantly greater in OA group than in the normal group (p < 0.05).

CONCLUSIONS

NDRG3 might be closely related to the development and progression of OA. However, the relationship between NDRG3 and OA, which is independent of the HIF pathway, warrants further research.

UHRF1-repressed 5'-hydroxymethylcytosine is essential for the male meiotic prophase I

5’-hydroxymethylcytosine (5hmC), an important 5’-cytosine modification, is altered highly in order in male meiotic prophase. However, the regulatory mechanism of this dynamic change and the function of 5hmC in meiosis remain largely unknown. Using a knockout mouse model, we showed that UHRF1 regulated male meiosis. UHRF1 deficiency led to failure of meiosis and male infertility. Mechanistically, the deficiency of UHRF1 altered significantly the meiotic gene profile of spermatocytes. Uhrf1 knockout induced an increase of the global 5hmC level. The enrichment of hyper-5hmC at transcriptional start sites (TSSs) was highly associated with gene downregulation. In addition, the elevated level of the TET1 enzyme might have contributed to the higher 5hmC level in the Uhrf1 knockout spermatocytes. Finally, we reported Uhrf1, a key gene in male meiosis, repressed hyper-5hmC by downregulating TET1. Furthermore, UHRF1 facilitated RNA polymerase II (RNA-pol2) loading to promote gene transcription. Thus our study demonstrated a potential regulatory mechanism of 5hmC dynamic change and its involvement in epigenetic regulation in male meiosis.

Structural and Biophysical Analyses of Human N-Myc Downstream-Regulated Gene 3 (NDRG3) Protein

The N-Myc downstream-regulated gene (NDRG) family belongs to the α/β-hydrolase fold and is known to exert various physiologic functions in cell proliferation, differentiation, and hypoxia-induced cancer metabolism. In particular, NDRG3 is closely related to proliferation and migration of prostate cancer cells, and recent studies reported its implication in lactate-triggered hypoxia responses or tumorigenesis. However, the underlying mechanism for the functions of NDRG3 remains unclear. Here, we report the crystal structure of human NDRG3 at 2.2 Å resolution, with six molecules in an asymmetric unit. While NDRG3 adopts the α/β-hydrolase fold, complete substitution of the canonical catalytic triad residues to non-reactive residues and steric hindrance around the pseudo-active site seem to disable the α/β-hydrolase activity. While NDRG3 shares a high similarity to NDRG2 in terms of amino acid sequence and structure, NDRG3 exhibited remarkable structural differences in a flexible loop corresponding to helix α6 of NDRG2 that is responsible for tumor suppression. Thus, this flexible loop region seems to play a distinct role in oncogenic progression induced by NDRG3. Collectively, our studies could provide structural and biophysical insights into the molecular characteristics of NDRG3.

Association of UHRF1 gene polymorphisms with oligospermia in Chinese males

BACKGROUND

UHRF1 plays an important role in maintaining DNA methylation patterns during spermatogenesis. This study was performed to evaluate the association between UHRF1 gene variations and infertility in males with oligozoospermia in a Chinese population.

METHODS

In this case-control study of 735 Chinese men, single-nucleotide polymorphism (SNP) genotypes and alleles in the UHRF1 gene were assessed by direct sequencing. The effects of the mutations on UHRF1 transcription were investigated using a dual-luciferase reporter gene assay.

RESULTS

We identified 24 SNPs, including nine SNPs in the promoter region, three in the 5' untranslated region, five in introns, and seven in exons. Interestingly, the genotype frequencies of SNP rs2656927 (P = 0.014) and rs8103849 (P < 0.001) significantly differed between men with oligozoospermia in case group 1 and normozoospermic men. Moreover, four variants (three were novel) were detected only in the patient group, with two in introns and the others in the promoter region. The results of the luciferase assay showed that the -1615C>T-C and -1562A>G-A alleles increased luciferase activity compared with the -1615C>T-T and -1562A>G-G alleles.

CONCLUSIONS

We detected two SNPs in the UHRF1 gene showing a significant difference between the case and control groups. Two screened SNPs affected UHRF1 promoter activity, improving the understanding of the pathophysiology of oligozoospermia.

CDK2 regulates the NRF1/Ehmt1 axis during meiotic prophase I

Palmer et al. identify NRF1 as a novel CDK2 interactor and substrate. This interaction was found to be important for the DNA-binding activity of NRF1. Their findings demonstrate that the loss of CDK2 expression impairs the regulation of NRF1 transcriptional activity, leading to inappropriate transcription during meiotic division.

Meiosis generates four genetically distinct haploid gametes over the course of two reductional cell divisions. Meiotic divisions are characterized by the coordinated deposition and removal of various epigenetic marks. Here we propose that nuclear respiratory factor 1 (NRF1) regulates transcription of euchromatic histone methyltransferase 1 (EHMT1) to ensure normal patterns of H3K9 methylation during meiotic prophase I. We demonstrate that cyclin-dependent kinase (CDK2) can bind to the promoters of a number of genes in male germ cells including that of Ehmt1 through interaction with the NRF1 transcription factor. Our data indicate that CDK2-mediated phosphorylation of NRF1 can occur at two distinct serine residues and negatively regulates NRF1 DNA binding activity in vitro. Furthermore, induced deletion of Cdk2 in spermatocytes results in increased expression of many NRF1 target genes including Ehmt1. We hypothesize that the regulation of NRF1 transcriptional activity by CDK2 may allow the modulation of Ehmt1 expression, therefore controlling the dynamic methylation of H3K9 during meiotic prophase.

NDRG3 facilitates colorectal cancer metastasis through activating Src phosphorylation

Background

NDRG3 is an N-myc downregulated gene (NDRG). The aim of this article was to identify the role of NDRG3 in colorectal cancer (CRC) and to determine the mechanism underlying its function.

Methods

Using immunohistochemical staining, expression and clinicopathological variables of NDRG3 were analyzed in 170 CRC samples. Overexpression of NDRG3 was employed in SW1116 cells, downregulation of NDRG3 was achieved in RKO cells, then migration and invasion assays were performed in vitro, and a mouse model was constructed in vivo.

Results

Increased expression of NDRG3 was observed in primary CRC tissues, and this expression was correlated with distant metastasis. Consistently, ectopic expression of NDRG3 in SW1116 cells enhanced cell migration and invasion, while knockdown of NDRG3 in RKO cells significantly suppressed CRC cell metastasis. The portal vein injection models suggested that NDRG3 overexpression facilitates liver metastasis. These events were associated with the phosphorylation of Src (c-Src) at Tyr 419 site.

Conclusion

Our results showed that NDRG3 facilitates CRC migration and invasion by activating Src phosphorylation, suggesting the role of NDRG3 as a candidate oncogene.

Increased Expression of NDRG3 in Mouse Uterus During Embryo Implantation and in Mouse Endometrial Stromal Cells During In Vitro Decidualization

Decidualization is an indispensable event in the embryo implantation process, but its underlying molecular mechanisms remain elusive. In this study, we showed that in mice, the uterine expression of N-myc downstream-regulated gene 3 (NDRG3), a member of the α/β hydrolase superfamily, was induced by estradiol and progesterone. During the embryo implantation process, uterine Ndrg3 expression was remarkably upregulated, and its expression level at implantation sites (IS) was significantly higher than that at inter-IS. Increased uterine expression of Ndrg3 was associated with artificial decidualization and the activation of delayed implantation. The in vitro decidualization of mouse endometrial stromal cells (ESCs) induced by estradiol and progesterone was also accompanied by increased Ndrg3 expression, and downregulated Ndrg3 expression in ESCs effectively inhibited decidualization. miR-290b-5p was identified as an upstream regulator of Ndrg3, and the uterine expression level of miR-290b-5p was decreased during the implantation process. Furthermore, overexpression of miR-290b-5p in mouse ESCs inhibited their in vitro decidualization. Taken together, these data suggested that Ndrg3 might play an important role in embryo implantation by regulating decidualization potentially via the estrogen/progesterone/miR-290b-5p pathway.