The shorter zinc finger protein ZNF230 gene message is transcribed in fertile male testes and may be related to human spermatogenesis

Altered Gene Expression in the Testis of Infertile Patients with Nonobstructive Azoospermia

Background

The molecular mechanism of nonobstructive azoospermia (NOA) remains unclear. The aim of this study was to identify gene expression changes in NOA patients and to explore potential biomarkers and therapeutic targets.

Methods

The gene expression profiles of GSE45885 and GSE145467 were collected from the Gene Expression Omnibus (GEO) database, and the differences between NOA and normal spermatogenesis were analyzed. Enrichment analysis was performed to explore biological functions for common differentially expressed genes (DEGs) in GSE45885 and GSE145467. Coexpression analysis of DEGs in GSE45885 was performed, and two modules with the highest correlation with NOA were screened. Key genes were then screened from the intersection genes of the two modules and common DEGs and PPI network. The expression of key genes was validated by quantitative real-time polymerase chain reaction (qRT-PCR) experiments. Finally, through miRTarBase, miRDB, and RAID, the miRNAs were predicted to regulate key genes, respectively.

Results

A total of 345 common DEGs were identified and they were mainly related to spermatogenesis, insulin signaling pathway. Coexpression analysis of DEGs in GSE45885 yielded eight modules; MEblack and MEturquoise had the highest correlation with NOA. Six genes in MEturquoise and RNF141 in MEblack were identified as key genes. qRT-PCR experiments validated the differential expression of key genes between NOA and control. Furthermore, RNF141 was regulated by the largest number of miRNAs.

Conclusion

Our findings suggest that the significant change expression of key genes may be potential markers and therapeutic targets of NOA and may have some impact on the development of NOA.

Comparative Analysis of Testicular Histology and lncRNA-mRNA Expression Patterns Between Landes Geese (Anser anser) and Sichuan White Geese (Anser cygnoides)

Landes geese and Sichuan White geese are two important genetic materials for commercial goose breeding. However, the differences in the male reproductive capacity between these two breeds and the potential molecular mechanisms and associated key genes have not been reported to date. The present study compared the testicular histology and mRNA-long non-coding RNA (lncRNA) expression patterns to reveal the differences in male reproductive performance between Sichuan White geese and Landes geese, as well as to explore the underlying molecular mechanisms. Histological results showed that the testicular organ index, semen volume, and long diameter of seminiferous tubules of Landes geese were significantly larger than those of Sichuan White geese. Analyses of mRNA-lncRNA expression profile showed that compared with Sichuan White geese, a total of 462 differentially expressed mRNAs (DEGs) (173 up-regulated and 289 down-regulated) and 329 differentially expressed lncRNAs (DE lncRNAs) (280 up-regulated, 49 down-regulated) were identified in Landes geese. Among these DEGs, there were 10 spermatogenesis-related and highly expressed (FPKM > 10) DEGs. Except for SEPP1, all of these DEGs were significantly up-regulated in the testes of Landes geese. Functional enrichment analysis indicated that the pathway related to metabolism progress and phosphoinositol signal is vitally responsible for differences in male reproductive performance between Landes geese and Sichuan White geese. These results show that compared with Sichuan White geese, the spermatogenesis in the testis of Landes geese was more active, which may be mainly related to the inositol phosphate signal. These data contribute to a better understanding of the mechanisms underlying different male reproductive performances between Landes geese and Sichuan White geese. This knowledge might eventually provide a theoretical basis for improving male reproductive performance in geese.

The zinc finger domain of RING finger protein 141 reveals a unique RING fold

Human RING finger protein 141 (RFP141) is a germ cell-specific transcription factor during spermatogenesis. We synthesized a compact construct encoding the C-terminal zinc finger of RFP141 (RFP141C peptide). Herein we determined the solution structure of the RFP141C peptide by nuclear magnetic resonance (NMR). Moreover, NMR data and the chemical modification of cysteine residues demonstrated that the RFP141C peptide binds to two zinc atoms in a cross-brace arrangement. The Simple Modular Architecture Research Tool database predicted the structure of RFP141C as a RING finger. However, the actual structure of the RFP141C peptide adopts an atypical compact C₃ HC₄ -type RING fold. The position and range of the helical active site of the RFP141C structure were elucidated at the atomic level. Therefore, structural analysis may allow RFP141C to be used for designing an artificial RING finger possessing specific ubiquitin-conjugating enzyme (E2)-binding capabilities.

Targeted disruption of the mouse testis-enriched gene Znf230 does not affect spermatogenesis or fertility

The mouse testis-enriched Znf230 gene, which encodes a type of RING finger protein, is present primarily in the nuclei of spermatogonia, the acrosome and the tail of spermatozoa. To investigate the role of Znf230 in spermatogenesis, we generated Znf230-deficient mice by disrupting Znf230 exon-5 and exon-6 using homologous recombination. The homozygous Znf230-knockout (KO) mice did not exhibit Znf230 mRNA expression and Znf230 protein production. Znf230 KO mice exhibited no obvious impairment in body growth or fertility. Male Znf230 KO mice had integral reproductive systems and mature sperm that were regular in number and shape. The developmental stages of male germ cells of Znf230 KO mice were also normal. We further examined variations in the transcriptomes of testicular tissue between Znf230 KO and wild-type mice through microarray analysis. The results showed that the mRNA level of one unclassified transcript 4921513I08Rik was increased and that the mRNA levels of three other transcripts, i.e., 4930448A20Rik, 4931431B13Rik and potassium channel tetramerisation domain containing 14(Kctd14), were reduced more than two-fold in Znf230 KO mice compared with wild-type mice. Using our current examination techniques, these findings suggested that Znf230 deficiency in mice may not affect growth, fertility or spermatogenesis.

KRAB-Zinc Finger Proteins: A Repressor Family Displaying Multiple Biological Functions

Zinc finger proteins containing the Kruppel associated box (KRAB-ZFPs) constitute the largest individual family of transcriptional repressors encoded by the genomes of higher organisms. KRAB domain, positioned at the NH2 terminus of the KRAB-ZFPs, interacts with a scaffold protein, KAP-1, which is able to recruit various transcriptional factors causing repression of genes to which KRAB ZFPs bind. The relevance of such repression is reflected in the large number of the KRAB zinc finger protein genes in the human genome. However, in spite of their numerical abundance little is currently known about the gene targets and the physiological functions of KRAB- ZFPs. However, emerging evidence links the transcriptional repression mediated by the KRAB-ZFPs to cell proliferation, differentiation, apoptosis and cancer. Moreover, the fact that KRAB containing proteins are vertebrate-specific suggests that they have evolved recently, and that their key roles lie in some aspects of vertebrate development. In this review, we will briefly discuss some regulatory functions of the KRAB-ZFPs in different physiological and pathological states, thus contributing to better understand their biological roles.

Germinal Cell Aplasia in Kif18a Mutant Male Mice Due to Impaired Chromosome Congression and Dysregulated BubR1 and CENP-E

Chromosomal instability during cell division frequently causes cell death or malignant transformation. Orderly chromosome congression at the metaphase plate, a paramount process to vertebrate mitosis and meiosis, is controlled by a number of molecular regulators, including kinesins. Kinesin-8 (Kif18A) functions to control mitotic chromosome alignment at the mid-zone by negative regulation of kinetochore oscillation. Here the authors report that disrupting Kif18a function results in complete sterility in male but not in female mice. Histological examination reveals that Kif18a(-/-) testes exhibit severe developmental impairment of seminiferous tubules. Testis atrophy in Kif18a(-/-) mice is caused by perturbation of microtubule dynamics and spindle pole integrity, leading to chromosome congression defects during mitosis and meiosis. Depletion of KIF18A via RNAi causes mitotic arrest accompanied by unaligned chromosomes and increased microtubule nucleating centers in both GC-1 and HeLa cells. Prolonged depletion of KIF18A causes apoptosis due to perturbed microtubule dynamics. Further studies reveal that KIF18A silencing results in degradation of CENP-E and BubR1, which is accompanied by premature sister chromatid separation. KIF18A physically interacts with BubR1 and CENP-E, and this interaction is modulated during mitosis. Combined, the studies indicate that KIF18A is essential for normal chromosome congression during cell division and that the absence of KIF18A function causes severe defects in microtubule dynamics, spindle integrity, and checkpoint activation, leading to germinal cell aplasia in mice.

Molecular cloning and expression analysis of a zebrafish novel zinc finger protein gene rnf141

ZNF230 is a novel zinc finger gene cloned by our laboratory. In order to understand the potential functions of this gene in vertebrate development, we cloned the zebrafish orthologue of human ZNF230, named rnf141. The cDNA fragment of rnf141 was obtained by rapid amplification of cDNA ends (RACE). The open reading frame (ORF) encodes a polypeptide of 222 amino acids which shares 75.65% identity with the human ZNF230. RT-PCR analysis in zebrafish embryo and adult tissues revealed that rnf141 transcripts are maternally derived and that rnf141 mRNA has a broad distribution. Zygotic rnf141 message is strongly localized in the central nervous system, as shown by whole-mount in situ hybridization. Knockdown and over expression of rnf141 can induce abnormal phenotypes, including abnormal development of brain, as well as yolk sac and axis extendsion. Marker gene analysis showed that rnf141 may play a role in normal dorsoventral patterning of zebrafish embryos, suggesting that rnf141 may have a broad function during early development of vertebrates.

DAZL binds to 3'UTR of Tex19.1 mRNAs and regulates Tex19.1 expression

Spermatogenesis is a complex process subject to strict controls at both levels of transcription and translation. It has been proposed that DAZL protein binds to RNA in the cytoplasm of germ cells and controls spermatogenesis. In male mice, loss of Dazl results in numerous defects throughout the mitotic and meiotic process of germ cell development. Tex19.1 also plays an important role during spermatogenesis and Tex19.1(-/-) knockout males exhibit impaired spermatogenesis. Mouse DAZL protein can bind to 3'UTR of mTex19.1 mRNAs and may repress mTex19.1 expression at the translational level. These have been confirmed by both electrophoretic mobility shift assay and translation assay in Zebrafish embryo detecting the luciferase activity. Taken together these data suggest that mDazl may regulate mTex19.1 expression through binding to 3'UTR of mTex19.1 mRNAs in germ cells.

Expression and localization of the spermatogenesis-related gene, Znf230, in mouse testis and spermatozoa during postnatal development

Znf230, the mouse homologue of the human spermatogenesis-related gene, ZNF230, has been cloned by rapid amplification of cDNA ends (RACE). This gene is expressed predominantly in testis, but its expression in different testicular cells and spermatogenic stages has not been previously analyzed in detail. In the present study, the cellular localization of the Znf230 protein in mouse testis and epididymal spermatozoa was determined by RT-PCR, immunoblotting, immunohistochemistry and immunofluorescence. It is primarily expressed in the nuclei of spermatogonia and subsequently in the acrosome system and the entire tail of developing spermatids and spermatozoa. The results indicate that Znf230 may play an important role in mouse spermatogenesis, including spermatogenic cell proliferation and sperm maturation, as well as motility and fertilization.

Spermatogenesis-related ring finger gene ZNF230 promoter: identification and functional analysis

The ZNF230 gene is a recently cloned gene which is transcribed only in fertile male testes and may be related to human spermatogenesis. To characterize the multiple stage-specific transcription elements necessary for ZNF230 expression, we cloned ZNF230 promoter and constructed chimeric luciferase reporter Plasmids. Overexpression and site-directed mutation test were used to characterize the cis-element. The results showed ZNF230 gene promoter to be GC rich and not contain a TATA box. Deletion analysis of the 5'-flanking region of ZNF230 in HEK293 cells indicated that the sequence encompassing from nt -131 to +152 has a basal transcriptional activity. Site-directed mutation test and mithramycin A treatment demonstrated that the ZNF230 promoter contained a functional Sp1 site. Overexpression of the Sox5 protein activated the promoter activity. A 312-bp fragment surrounding the transcription start site exhibits a characteristic CpG island which overlaps with the promoter region. We also provided evidence that both the human and mouse znf230 promoter consist of Sp1 binding site and GC-rich sequences, suggesting Sp1 is required for the transcription of human and mouse ZNF230 genes. In conclusion, these findings suggest that ZNF230 is tightly controlled at transcriptional level and a common mechanism controls the basal transcription of ZNF230 gene.

Transcriptome analysis of differentiating spermatogonia stimulated with kit ligand

Kit ligand (KL) is a survival factor and a mitogenic stimulus for differentiating spermatogonia. However, it is not known whether KL also plays a role in the differentiative events that lead to meiotic entry of these cells. We performed a wide genome analysis of difference in gene expression induced by treatment with KL of spermatogonia from 7-day-old mice, using gene chips spanning the whole mouse genome. The analysis revealed that the pattern of RNA expression induced by KL is compatible with the qualitative changes of the cell cycle that occur during the subsequent cell divisions in type A and B spermatogonia, i.e. the progressive lengthening of the S phase and the shortening of the G2/M transition. Moreover, KL up-regulates in differentiating spermatogonia the expression of early meiotic genes (for instance: Lhx8, Nek1, Rnf141, Xrcc3, Tpo1, Tbca, Xrcc2, Mesp1, Phf7, Rtel1), whereas it down-regulates typical spermatogonial markers (for instance: Pole, Ptgs2, Zfpm2, Egr2, Egr3, Gsk3b, Hnrpa1, Fst, Ptch2). Since KL modifies the expression of several genes known to be up-regulated or down-regulated in spermatogonia during the transition from the mitotic to the meiotic cell cycle, these results are consistent with a role of the KL/kit interaction in the induction of their meiotic differentiation.