Molecular cloning and characterization of a mouse spermatogenesis-related ring finger gene znf230

Replication analysis confirms the association of several variants with acute myeloid leukemia in Chinese population

PURPOSE

Two genome-wide association studies (GWASs) have identified several new acute leukemia susceptibility loci in populations of European descent. However, the roles of these loci in the development of acute leukemia in other populations are largely unknown.

METHODS

We genotyped 16 single-nucleotide polymorphisms selected from published GWASs in an independent case-control study with a total of 545 acute myeloid leukemia (AML) cases and 1034 cancer-free controls in a Chinese population. Multivariate logistic regression was used to analyze the associations between these variants and AML risk.

RESULTS

We found that with the similar effect to GWASs, risk alleles of rs2191566, rs9290663, rs11155133, rs2239633, rs10821936, and rs2242041 significantly increased the risk of AML in at least one genetic model [odds ratios (ORs) range from 1.26 to 4.34, P values range from <0.001 to 0.043]. However, the variant T allele of rs10873876 decreased the AML risk, which was in the opposite effect direction (OR 0.62, P < 0.001 in additive model). Besides, we found significant multiplicative interaction between rs9290663 and age (≤45 years old and >45 years old; P = 0.009).

CONCLUSION

Our results indicated that genetic variants associated with acute leukemia risk in European populations may also play important roles in AML development in Chinese population.

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.

A new mutant transcript generated in Znf230 exon 2 knockout mice reveals a potential exon structure in the targeting vector sequence

Testis gene Znf230 may play a role in mammalian spermatogenesis according to previous reports. Deleting 5' important exons to block the formation of protein was a routine way in gene-knockout experiments. To investigate the physiological function of Znf230 gene, the mutant mice with disrupted exon 2 of Znf230 were generated in this study. Results showed that, mutant Znf230 mice were fertile and showed normal body, genitourinary organs, testes weights, and spermatid number but the litter size of the offspring reduced with unclear reasons. Hematoxylin and eosin staining showed that the testicular tissue of mutant mice was intact. Reverse transcriptase polymerase chain reaction analysis showed that two novel mutant transcripts appeared in the mutant mice: the short one including exon-1 and exon-3 to -6, the long one unexpectedly containing a partial sequence from the pPNT vector acting as a new exon 2. Bioinformatic analysis of the long transcript revealed that it might code a 24-kDa N-terminal mutant protein with the same 182 amino acids as that of the wild-type Znf230 in the C-terminus, indicating that the potential functional region of C3HC4-type RING finger was intact in mutant protein. Western blot and immunohistochemistry analyses also implied that this N-terminal mutation of Znf230 might not disrupt the possible role that wild-type Znf230 played in spermatogenesis. In summary, a potential exon structure in the targeting vector sequence involved in the expression of targeting Znf230 gene and disturbed the strategy of this gene-targeting experiment.

Surfing the wave, cycle, life history, and genes/proteins expressed by testicular germ cells. Part 4: intercellular bridges, mitochondria, nuclear envelope, apoptosis, ubiquitination, membrane/voltage-gated channels, methylation/acetylation, and transcription factors

As germ cells divide and differentiate from spermatogonia to spermatozoa, they share a number of structural and functional features that are common to all generations of germ cells and these features are discussed herein. Germ cells are linked to one another by large intercellular bridges which serve to move molecules and even large organelles from the cytoplasm of one cell to another. Mitochondria take on different shapes and features and topographical arrangements to accommodate their specific needs during spermatogenesis. The nuclear envelope and pore complex also undergo extensive modifications concomitant with the development of germ cell generations. Apoptosis is an event that is normally triggered by germ cells and involves many proteins. It occurs to limit the germ cell pool and acts as a quality control mechanism. The ubiquitin pathway comprises enzymes that ubiquitinate as well as deubiquitinate target proteins and this pathway is present and functional in germ cells. Germ cells express many proteins involved in water balance and pH control as well as voltage-gated ion channel movement. In the nucleus, proteins undergo epigenetic modifications which include methylation, acetylation, and phosphorylation, with each of these modifications signaling changes in chromatin structure. Germ cells contain specialized transcription complexes that coordinate the differentiation program of spermatogenesis, and there are many male germ cell-specific differences in the components of this machinery. All of the above features of germ cells will be discussed along with the specific proteins/genes and abnormalities to fertility related to each topic.

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.

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.

Expression of Pkd2l2 in testis is implicated in spermatogenesis

Pkd2l2 is a novel member of the polycystic kidney disease (PKD) gene family in mammals. Prominently expressed in testis, this gene is still poorly understood. In this study, reverse transcription polymerase chain reaction (RT-PCR) results showed a time-dependent expression pattern of Pkd2l2 in postnatal mouse testis. Immunohistochemical analysis revealed that Pkd2l2 encoded a protein, polycystin-L2, which was predominantly detectable in the plasma membrane of spermatocytes and round spermatids, as well as in the head and tail of elongating spermatids within seminiferous tubules in mouse testis tissue sections of postnatal day 14 and adult mice. A green fluorescent fusion protein of Pkd2l2 resided in the plasma membrane of HEK 293 and MDCK cells, suggesting that it functions as a plasma membrane protein. Overexpression of Pkd2l2 increased the intracellular calcium concentration of MDCK cells, as detected by flow cytometry. Collectively, these data indicated that Pkd2l2 may be involved in the mid-late stage of spermatogenesis through modulation of the intracellular calcium concentration.

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.

RNF151, a testis-specific RING finger protein, interacts with dysbindin

RING finger proteins play important roles in spermatogenesis. Here, we report that a novel RING finger protein RNF151, with a C3HC4-type RING finger domain, a putative nuclear localization signal (NLS), and a TRAF-type zinc finger domain, was exclusively expressed in the mouse testis and developmentally regulated during spermatogenesis. While RNF151 mRNA was present in round spermatids, its protein was expressed in elongating spermatids of the stage VIII-IX seminiferous tubules. The NLS together with the RING domain were necessary and sufficient for the nuclear localization of RNF151-EGFP in transfected cells. Yeast two-hybrid screening identified the physical interaction of mouse RNF151 and dysbindin, which was confirmed by the co-immunoprecipitation of the proteins and by their co-localization in intact cells. As dysbindin has lately been shown to be involved in membrane biogenesis and fusion, a key process for acrosome formation, we propose that RNF151 may play a role in acrosome formation.