Publications by authors named "Saffet Ozturk"

35 Publications

Telomere associated gene expression as well as TERT protein level and telomerase activity are altered in the ovarian follicles of aged mice.

Sci Rep 2021 Jul 30;11(1):15569. Epub 2021 Jul 30.

Department of Histology and Embryology, Akdeniz University School of Medicine, Campus, 07070, Antalya, Turkey.

Telomeres cap the ends of eukaryotic chromosomes to maintain genomic stability and integrity during an organism's lifespan. The length of telomeres inevitably shortens due to DNA replication, genotoxic agents, and biological aging. A limited number of cell types, e.g., stem cells, germline cells, and early embryos can elongate shortened telomeres via the enzymatic action of telomerase, which is composed of telomerase reverse transcriptase (TERT) and telomerase RNA component (Terc). Additionally, telomere-associated proteins including telomeric repeat binding factor 1 (TRF1) and 2 (TRF2), as well as protection of telomeres 1a (POT1a), bind to telomeres to maintain their structural integrity and length. During ovarian aging in mammals, telomeres progressively shorten, accompanied by fertility loss; however, the molecular mechanism underlying this attrition during follicle development remains unclear. In this study, the primary, secondary, preantral, and antral follicles were obtained either from 6-week-old adult (n = 19) or 52-week-old aged (n = 12) mice. We revealed that the Tert, Terc, Trf1, Trf2, and Pot1a gene expression (P < 0.001) and TERT protein (P < 0.01) levels significantly decreased in certain ovarian follicles of the aged group when compared to those of the adult group. Also, telomerase activity exhibited remarkable changes in the follicles of both groups. Consequently, altered telomere-associated gene expression and reduced TERT protein levels in the follicles of aged mice may be a determinant of telomere shortening during ovarian aging, and infertility appearing in the later decades of reproductive lifespan. Further investigations are required to determine the molecular mechanisms underlying these alterations in the follicles during ovarian aging.
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http://dx.doi.org/10.1038/s41598-021-95239-5DOI Listing
July 2021

Primary Extraosseous Ewing's Sarcoma of the Lung: Radiologic and Pathologic correlation.

Cureus 2021 May 4;13(5):e14830. Epub 2021 May 4.

Pathology, Osmangazi University Faculty of Medicine, Eskisehir, TUR.

Ewing's sarcoma (ES) is a rare and highly aggressive tumor belonging to a family of neoplasms of neuroectodermal origin, which primarily affects the bones or soft tissues. ES originating from lung parenchyma without chest wall involvement is extremely rare with less than 40 cases reported in the English literature. A 41-year-old man admitted to the thoracic surgery department presenting with intermittent non-productive cough, dyspnea, left-sided chest pain for two months for further evaluation and treatment with a preliminary diagnosis of pulmonary mass. Contrast-enhanced thorax CT and MRI revealed a large heterogeneous soft-tissue mass in the left lower lobe with no distant metastases or occult primary tumor. Following the percutaneous transthoracic biopsy, histopathological and immunohistochemical results were consistent with primary pulmonary ES. Though rare, primary pulmonary ES should be considered in the differential diagnosis of young patients presenting with a large heterogeneous soft tissue mass in the lung. This case report highlights the diagnosis, radiologic and pathologic findings, and management of primary pulmonary ES.
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http://dx.doi.org/10.7759/cureus.14830DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8191847PMC
May 2021

Clinical and radiological characteristics of COVID‑19 patients without comorbidities : A single-center study.

Wien Klin Wochenschr 2021 Jun 3. Epub 2021 Jun 3.

Department of Infectious Disease and Clinical Microbiology, Sungurlu State Hospital, 19300, Çorum, Turkey.

Objective: To evaluate the clinical characteristics and detailed imaging features in coronavirus disease 2019 (COVID-19) patients without comorbidities.

Material And Methods: This retrospective study included laboratory-confirmed and symptomatic COVID-19 patients without comorbid diseases who were admitted to our second level hospital between March 2020 and September 2020. We assessed the clinical, biochemical and imaging diagnostic parameters on admission. The patients were classified as non-severe and progress to severe group and then the initial parameters were compared.

Results: We enrolled 135 adult COVID-19 patients, 12 progressed to severe disease during hospitalization. Compared to the non-severe group, patients who progressed to severe were older (p < 0.001) and were more likely to manifest coughing (p = 0.011) and have higher lactate dehydrogenase (LDH) levels (p = 0.011). On chest computed tomography (CT) images, multilobar (p = 0.016), peripherally (p = 0.001) distributed mixed ground glass opacities and consolidation (p < 0.001), crazy paving (p = 0.007) and higher total CT severity score (p < 0.001) were significantly associated with severe disease.

Conclusion: Knowledge of the clinical and radiological parameters associated with disease severity might be useful to guide clinical decision-making for COVID-19 patients without comorbidities.
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http://dx.doi.org/10.1007/s00508-021-01880-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC8173504PMC
June 2021

The spatiotemporal expression of TERT and telomere repeat binding proteins in the postnatal mouse testes.

Andrologia 2021 Apr 5;53(3):e13976. Epub 2021 Feb 5.

Department of Histology and Embryology, Akdeniz University School of Medicine, Antalya, Turkey.

Telomeres consist of repetitive DNA sequences and telomere-associated proteins. Telomeres located at the ends of eukaryotic chromosomes undergo shortening due to DNA replication, genotoxic factors and reactive oxygen species. The short telomeres are elongated by the enzyme telomerase expressed in the germ line, embryonic and stem cells. Telomerase is in the structure of ribonucleoprotein composed of telomerase reverse transcriptase (TERT), telomerase RNA component (Terc) and other components. Among telomere-associated proteins, telomeric repeat binding factor 1 (TRF1) and 2 (TRF2) exclusively bind to the double-stranded telomeric DNA to regulate its length. However, protection of telomeres 1 (POT1) interacts with the single-stranded telomeric DNA to protect from DNA damage response. Herein, we characterised the spatial and temporal expression of the TERT, TRF1, TRF2 and POT1 proteins in the postnatal mouse testes at the ages of 6, 8, 16, 20, 29, 32 and 88 days by using immunohistochemistry. Significant differences in the spatiotemporal expression patterns and levels of these proteins were determined in the postnatal testes (p < .05). These findings indicate that TERT and telomere repeat binding proteins seem to be required for maintaining the length and structural integrity of telomeres in the spermatogenic cells from newborn to adult terms.
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http://dx.doi.org/10.1111/and.13976DOI Listing
April 2021

Selection of competent oocytes by morphological criteria for assisted reproductive technologies.

Authors:
Saffet Ozturk

Mol Reprod Dev 2020 10 9;87(10):1021-1036. Epub 2020 Sep 9.

Department of Histology and Embryology, Akdeniz University School of Medicine, Antalya, Turkey.

Invasive and noninvasive methods are commonly used to select developmentally competent oocytes that can improve the take-home baby rates in assisted reproductive technology (ART) centers. One of the noninvasive methods conventionally utilized to determine competent oocytes is the morphological analysis of cumulus complex, first polar body, zona pellucida, perivitelline space, meiotic spindle, and ooplasm. Successful fertilization, early embryo development, uterine implantation, and healthy pregnancy depend on the quality of oocytes, and morphological evaluation is one of the options used to predict quality levels. In this review, the morphological criteria being utilized in certain ART centers are comprehensively evaluated with special references to their predictive values and potential contributions to selecting high-quality oocytes.
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http://dx.doi.org/10.1002/mrd.23420DOI Listing
October 2020

Decreased expression of TERT and telomeric proteins as human ovaries age may cause telomere shortening.

J Assist Reprod Genet 2021 Feb 27;38(2):429-441. Epub 2020 Aug 27.

Department of Histology and Embryology, Akdeniz University School of Medicine, Campus, 07070, Antalya, Turkey.

Objective: Telomeres are repetitive sequences localized at the ends of eukaryotic chromosomes comprising noncoding DNA and telomere-binding proteins. TRF1 and TRF2 both bind to the double-stranded telomeric DNA to regulate its length throughout the lifespan of eukaryotic cells. POT1 interacts with single-stranded telomeric DNA and contributes to protecting genomic integrity. Previous studies have shown that telomeres gradually shorten as ovaries age, coinciding with fertility loss. However, the molecular background of telomere shortening with ovarian aging is not fully understood.

Methods: The present study aimed to determine the spatial and temporal expression levels of the TERT, TRF1, TRF2, and POT1 proteins in different groups of human ovaries: fetal (n = 11), early postnatal (n = 10), premenopausal (n = 12), and postmenopausal (n = 14). Also, the relative telomere signal intensity of each group was measured using the Q-FISH method.

Results: We found that the telomere signal intensities decreased evenly and significantly from fetal to postmenopausal groups (P < 0.05). The TERT, TRF1, TRF2, and POT1 proteins were localized in the cytoplasmic and nuclear regions of the oocytes, granulosa and stromal cells. Furthermore, the expression levels of these proteins reduced significantly from fetal to postmenopausal groups (P < 0.05).

Conclusion: These findings suggest that decreased TERT and telomere-binding protein expression may underlie the telomere shortening of ovaries with age, which may be associated with female fertility loss. Further investigations are required to elicit the molecular mechanisms regulating the gradual decrease in the expression of TERT and telomere-binding proteins in human oocytes and granulosa cells during ovarian aging.
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http://dx.doi.org/10.1007/s10815-020-01932-1DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC7884544PMC
February 2021

The loss of global DNA methylation due to decreased DNMT expression in the postnatal mouse ovaries may associate with infertility emerging during ovarian aging.

Histochem Cell Biol 2020 Sep 8;154(3):301-314. Epub 2020 Jun 8.

Department of Histology and Embryology, Akdeniz University School of Medicine, 07070, Antalya, Turkey.

Ovarian aging is one of the main causes of female infertility, and its molecular background is still largely unknown. As DNA methylation regulates many oogenesis/folliculogenesis-related genes, the expression levels and cellular localizations of DNA methyltransferases (DNMTs) playing key roles in this process is important in the ovaries from early to aged terms. In the present study, we aimed to evaluate the spatial and temporal expression of the Dnmt1, Dnmt3a, Dnmt3b, and Dnmt3l genes as well as global DNA methylation levels in the mouse ovaries during aging. For this purpose, the following groups were created: young (1- and 2-week old; n = 3 from each week), prepubertal (3- and 4-week-old; n = 3 from each week), pubertal (5- and 6-week-old; n = 3 from each week), postpubertal (16- and 18-week-old; n = 3 from each week), and aged (52-, 60- and 72-week-old; n = 3 from each week). We found here that Dnmt1, Dnmt3a, and Dnmt3l genes' expression at mRNA and protein levels as well as global DNA methylation profiles were gradually and significantly decreased in the postnatal ovaries from young to aged groups (P < 0.05). In contrast, there was a remarkable increase of Dnmt3b expression in the pubertal, postpubertal and aged groups (P < 0.05). Our findings suggest that the significantly altered DNMT expression and global DNA methylation levels during ovarian aging may contribute to female infertility development at the later terms of lifespan. Also, new researches are required to determine the molecular biological mechanism(s) that how altered DNMT expression and decreased DNA methylation lead to ovarian aging.
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http://dx.doi.org/10.1007/s00418-020-01890-wDOI Listing
September 2020

The altered expression of telomerase components and telomere-linked proteins may associate with ovarian aging in mouse.

Exp Gerontol 2020 09 25;138:110975. Epub 2020 May 25.

Department of Histology and Embryology, Akdeniz University School of Medicine, Antalya, Turkey. Electronic address:

Telomeres are repetitive DNA sequences localized at the ends of eukaryotic chromosomes, and shorten during ovarian aging. The molecular background of telomere shortening during ovarian aging is not fully understood. As the telomerase components (TERT and Terc) and telomere-associated proteins (TRF1, TRF2, and POT1a) play key roles in the elongation and maintenance of telomeres, we aimed to determine their spatial and temporal expression and cellular localization in the mouse ovaries at the different ages of postnatal life. For this purpose, five groups were generated based on the ovarian histological changes in the postnatal mouse ovaries as follows: young (1- and 2-week-old; n = 3 from each week), prepubertal (3- and 4-week-old; n = 3 from each week), pubertal (5- and 6-week-old; n = 3 from each week), postpubertal (16- and 18-week-old; n = 3 from each week) and aged (52-, 60- and 72-week-old, n = 3 from each week). We found significant changes for the Tert, Terc, Trf1, Trf2, and Pot1a genes expression in the postnatal ovary groups from young to aged (P < 0.05) as well as in the follicles from primordial to antral stages and their oocytes and granulosa cells. Also, we have detected gradually decreasing telomere length from young to aged groups (P < 0.001). In conclusion, the altered Tert, Terc, Trf2, and Pot1a genes expression compatible with telomere shortening may be associated with ovarian aging.
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http://dx.doi.org/10.1016/j.exger.2020.110975DOI Listing
September 2020

The translational functions of embryonic poly(A)-binding protein during gametogenesis and early embryo development.

Authors:
Saffet Ozturk

Mol Reprod Dev 2019 11 13;86(11):1548-1560. Epub 2019 Aug 13.

Department of Histology and Embryology, Akdeniz University School of Medicine, Antalya, Turkey.

Embryonic poly(A)-binding protein (EPAB) is an RNA-binding protein that binds to the poly(A) tails and AU-rich element at the 3' ends of messenger RNA (mRNAs). The main functions of EPAB are to protect stored mRNAs from undergoing deadenylation and subsequent degradation and to be involved in their translational regulation during spermatogenesis, oogenesis, and early embryogenesis. Following the first characterization of Epab in the Xenopus oocytes and early embryos, spatial and temporal expression and potential roles of the Epab gene have been determined in the vertebrate germ cells and early embryos. In this review, we have comprehensively evaluated all studies in this field and discussed the particular functions of EPAB in the spermatogenic cells, oocytes, early embryos, and somatic cells in vertebrates.
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http://dx.doi.org/10.1002/mrd.23253DOI Listing
November 2019

Decreased expression of DNA methyltransferases in the testes of patients with non-obstructive azoospermia leads to changes in global DNA methylation levels.

Reprod Fertil Dev 2019 Apr 29. Epub 2019 Apr 29.

DNA methylation plays key roles in epigenetic regulation during mammalian spermatogenesis. DNA methyltransferases (DNMTs) function in de novo and maintenance methylation processes by adding a methyl group to the fifth carbon atom of the cytosine residues within cytosine-phosphate-guanine (CpG) and non-CpG dinucleotide sites. Azoospermia is one of the main causes of male infertility, and is classified as obstructive (OA) or non-obstructive (NOA) azoospermia based on histopathological characteristics. The molecular background of NOA is still largely unknown. DNA methylation performed by DNMTs is implicated in the transcriptional regulation of spermatogenesis-related genes. The aim of the present study was to evaluate the cellular localisation and expression levels of the DNMT1, DNMT3A and DNMT3B proteins, as well as global DNA methylation profiles in testicular biopsy samples obtained from men with various types of NOA, including hypospermatogenesis (hyposperm), round spermatid (RS) arrest, spermatocyte (SC) arrest and Sertoli cell-only (SCO) syndrome. In the testicular biopsy samples, DNMT1 expression and global DNA methylation levels decreased gradually from the hyposperm to SCO groups (P<0.05). DNMT3A expression was significantly decreased in the RS arrest, SC arrest and SCO groups compared with the hyposperm group (P<0.05). DNMT3B expression was significantly lower in the RS arrest and SCO groups than in the hyposperm group (P<0.05). Although both DNMT1 and DNMT3A were localised in the cytoplasm and nucleus of the spermatogenic cells, staining for DNMT3B was more intensive in the nucleus of spermatogenic cells. In conclusion, the findings suggest that significant changes in DNMT expression and global DNA methylation levels in spermatogenic cells may contribute to development of male infertility in the NOA groups. Further studies are needed to determine the molecular biological effects of the altered DNMT expression and DNA methylation levels on development of male infertility.
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http://dx.doi.org/10.1071/RD18246DOI Listing
April 2019

Embryonic poly(A)-binding protein is differently expressed and interacts with the messenger RNAs in the mouse oocytes and early embryos.

J Cell Biochem 2019 03 9;120(3):4694-4709. Epub 2018 Oct 9.

Department of Histology and Embryology, Akdeniz University School of Medicine, Antalya, Turkey.

The embryonic poly(A)-binding protein (EPAB) functions in the translational regulation of the maternal messenger RNAs (mRNAs) required during oocyte maturation, fertilization, and early embryo development. Since there is no antibody specific to mammalian EPAB protein, all studies related to the Epab gene could be performed at the mRNA levels except for the investigations in the Xenopus. In this study, we have produced an EPAB-specific antibody. When we examined its expressional distribution in the mouse gonadal and somatic tissues, the EPAB protein was found to be expressed only in the mouse ovary and testis tissues, but it is undetectable level in the somatic tissues including stomach, liver, heart, small intestine, and kidney. Additionally, the spatial and temporal expression patterns of the EPAB and poly(A)-binding protein cytoplasmic 1 (PABPC1) proteins were analyzed in the mouse germinal vesicle (GV) and metaphase II (MII) oocytes, one-cell, and two-cell embryos. While EPAB expression gradually decreased from GV oocytes to two-cell embryos, the PABPC1 protein level progressively increased from GV oocytes to one-cell embryos and remarkably declined in the two-cell embryos ( P < 0.05). We have also described herein that the EPAB protein interacted with Epab, Pabpc1, Ccnb1, Gdf9, and Bmp15 mRNAs dependent upon the developmental stages of the mouse oocytes and early embryos. As a result, we have first produced an EPAB-specific antibody and characterized its expression patterns and interacting mRNAs in the mouse oocytes and early embryos. The findings suggest that EPAB in cooperation with PABPC1 implicate in the translational control of maternal mRNAs during oogenesis and early embryo development.
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http://dx.doi.org/10.1002/jcb.27759DOI Listing
March 2019

Telomere length and telomerase activity during folliculogenesis in mammals.

J Reprod Dev 2018 Dec 28;64(6):477-484. Epub 2018 Sep 28.

Department of Histology and Embryology, Akdeniz University School of Medicine, Antalya 07070, Turkey.

Telomeres are repetitive non-coding DNA sequences located at the ends of chromosomes in eukaryotic cells. Their most important function is to protect chromosome ends from being recognized as DNA damage. They are also implicated in meiosis and synapse formation. The length of telomeres inevitably shortens at the end of each round of DNA replication and, also, as a consequence of the exposure to oxidative stress and/or genotoxic agents. The enzyme telomerase contributes to telomere lengthening. It has been reported that telomerase is exclusively expressed in germ cells, granulosa cells, early embryos, stem cells, and various types of cancerous cells. Granulosa cells undergo many mitotic divisions and either granulosa cells or oocytes are exposed to a variety of genotoxic agents throughout folliculogenesis; thus, telomerase plays an important role in the maintenance of telomere length. In this review article, we have comprehensively evaluated the studies focusing on the regulation of telomerase expression and activity, as well as telomere length, during folliculogenesis from primordial to antral follicles, in several mammalian species including mice, bovines, and humans. Also, the possible relationships between female infertility caused by follicular development defects and alterations in the telomeres and/or telomerase activity are discussed.
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http://dx.doi.org/10.1262/jrd.2018-076DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6305847PMC
December 2018

Peripheral apelin mediates stress-induced alterations in gastrointestinal motor functions depending on the nutritional status.

Clin Exp Pharmacol Physiol 2019 01 16;46(1):29-39. Epub 2018 Oct 16.

Department of Histology and Embryology, Faculty of Medicine, Akdeniz University, Antalya, Turkey.

Exposure to stress induces gastrointestinal (GI) dysmotility. In rodents, acute restraint stress (ARS) inhibits gastric emptying (GE) and intestinal transit (IT) via central and peripheral corticotropin-releasing factor (CRF)-mediated pathways. Peripherally administered apelin-13 was shown to inhibit GI motor functions; moreover, stress-induced upregulation of gastric apelin content was demonstrated in rats suggesting that peripheral apelin may mediate stress-induced alterations in GI motility. We investigated the role of endogenous peripheral apelin in stress-induced GI dysfunction. GE, IT and gastro-duodenal fasting motility were measured in non-stressed (NS), CRF-injected and ARS-loaded rats. CRF and apelin receptor antagonists astressin or F13A was administered before ARS or peripheral CRF injection. Apelin and APJ receptor expressions were determined using immunohistochemistry and quantified by qRT-PCR. Double immunofluorescence was performed for enteric neuronal apelin. GE and IT were delayed by CRF and ARS. ARS-induced changes were attenuated by F13A, whereas astressin was ineffective. CRF-induced alterations in GE and IT were restored completely by astressin, while they were diminished by F13A. Antral phase III-like contractions were disturbed following ARS which were preserved by preadministration of astressin, but not F13A. CRF impaired gastric and duodenal fasting contractions, while these changes were not altered by F13A. ARS increased apelin expression in stomach and duodenum. Apelin immunoreactivity was detected in mucosa, smooth muscles and myenteric plexi, whereas dense APJ receptor expression was observed within tunica muscularis. APJ receptor was downregulated in rats fasted overnight. These results suggest that enteric apelin acts as an inhibitor stress mediator in the postprandial state.
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http://dx.doi.org/10.1111/1440-1681.13032DOI Listing
January 2019

Potential roles of the poly(A)-binding proteins in translational regulation during spermatogenesis.

J Reprod Dev 2018 Aug 18;64(4):289-296. Epub 2018 May 18.

Department of Histology and Embryology, Akdeniz University, School of Medicine, Antalya, Turkey.

Spermatogenesis is briefly defined as the production of mature spermatozoa from spermatogonial stem cells at the end of a strictly regulated process. It is well known that, to a large extent, transcriptional activity ceases at mid-spermiogenesis. Several mRNAs transcribed during early stages of spermatogenesis are stored as ribonucleoproteins (RNPs). During the later stages, translational control of these mRNAs is mainly carried out in a time dependent-manner by poly(A)-binding proteins (PABPs) in cooperation with other RNA-binding proteins and translation-related factors. Conserved PABPs specifically bind to poly(A) tails at the 3' ends of mRNAs to regulate their translational activity in spermatogenic cells. Studies in this field have revealed that PABPs, particularly poly(A)-binding protein cytoplasmic 1 (Pabpc1), Pabpc2, and the embryonic poly(A)-binding protein (Epab), play roles in the translational regulation of mRNAs required at later stages of spermatogenesis. In this review article, we evaluated the spatial and temporal expression patterns and potential functions of these PABPs in spermatogenic cells during spermatogenesis. The probable relationship between alterations in PABP expression and the development of male infertility is also reviewed.
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http://dx.doi.org/10.1262/jrd.2018-026DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC6105736PMC
August 2018

Superovulation alters DNA methyltransferase protein expression in mouse oocytes and early embryos.

J Assist Reprod Genet 2018 Mar 22;35(3):503-513. Epub 2017 Nov 22.

Department of Histology and Embryology, School of Medicine, Akdeniz University, Campus, 07070, Antalya, Turkey.

Purpose: DNA methylation is an epigenetic mechanism that plays critical roles during mammalian oocyte and preimplantation embryo development. It is achieved by adding a methyl group to the fifth carbon atom of cytosine residues within cytosine-phosphate-guanine (CpG) and non-CpG dinucleotide sites using DNA methyltransferase (DNMT) enzymes for de novo and maintenance methylation processes. DNMT1, DNMT3A, and DNMT3B play important roles in establishing methylation of developmentally related genes in oocytes and early embryos. The purpose of this study is to identify the effect of superovulation on the expression and subcellular localizations of these three DNMT enzymes in the mouse oocytes and early embryos.

Methods: Three groups composed of control, normal dose [5 IU pregnant mare serum gonadotropin (PMSG) and 5 IU human chorionic gonadotropin (hCG)], and high dose [7.5 IU PMSG and 7.5 IU hCG] were created from 4-5-week-old female BALB/c mice. The relative expression and subcellular localizations of the DNMT proteins in the control and experiment groups have been characterized by using immunofluorescence staining subsequently analyzed in detailed.

Results: DNMT1, DNMT3A, and DNMT3B protein expression in the germinal vesicle and metaphase II oocytes and in one-cell and two-cell embryos differed significantly when some of the normal- and high-dose groups were compared with the control counterparts.

Conclusion: This study has demonstrated for the first time that superovulation alters expression levels of the DNMT proteins, a finding that indicates that certain developmental defects in superovulated oocytes and early embryos may result from impaired DNA methylation processes.
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http://dx.doi.org/10.1007/s10815-017-1087-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC5904060PMC
March 2018

DNMT1, DNMT3A and DNMT3B proteins are differently expressed in mouse oocytes and early embryos.

J Mol Histol 2017 Dec 13;48(5-6):417-426. Epub 2017 Oct 13.

Department of Histology and Embryology, Akdeniz University School of Medicine, Campus, 07070, Antalya, Turkey.

DNA methylation is one of the epigenetic mechanisms and plays important roles during oogenesis and early embryo development in mammals. DNA methylation is basically known as adding a methyl group to the fifth carbon atom of cytosine residues within cytosine-phosphate-guanine (CpG) and non-CpG dinucleotide sites. This mechanism is composed of two main processes: de novo methylation and maintenance methylation, both of which are catalyzed by specific DNA methyltransferase (DNMT) enzymes. To date, six different DNMTs have been characterized in mammals defined as DNMT1, DNMT2, DNMT3A, DNMT3B, DNMT3C, and DNMT3L. While DNMT1 primarily functions in maintenance methylation, both DNMT3A and DNMT3B are essentially responsible for de novo methylation. As is known, either maintenance or de novo methylation processes appears during oocyte and early embryo development terms. The aim of the present study is to investigate spatial and temporal expression levels and subcellular localizations of the DNMT1, DNMT3A, and DNMT3B proteins in the mouse germinal vesicle (GV) and metaphase II (MII) oocytes, and early embryos from 1-cell to blastocyst stages. We found that there are remarkable differences in the expressional levels and subcellular localizations of the DNMT1, DNMT3A and DNMT3B proteins in the GV and MII oocytes, and 1-cell, 2-cell, 4-cell, 8-cell, morula, and blastocyst stage embryos. The fluctuations in the expression of DNMT proteins in the analyzed oocytes and early embryos are largely compatible with DNA methylation changes and genomic imprintestablishment appearing during oogenesis and early embryo development. To understand precisemolecular biological meaning of differently expressing DNMTs in the early developmental periods, further studies are required.
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http://dx.doi.org/10.1007/s10735-017-9739-yDOI Listing
December 2017

DNA Methyltransferases in Mammalian Oocytes.

Results Probl Cell Differ 2017;63:211-222

Department of Histology and Embryology, School of Medicine, Akdeniz University, Campus, 07070, Antalya, Turkey.

Epigenetic mechanisms play important roles in properly occurring mammalian oogenesis. One of these mechanisms is DNA methylation adding a methyl group to the fifth carbon atom of the cytosine residues using S-adenosyl-L-methionine as a methyl donor. DNA methylation generally takes place at cytosine-phosphate-guanine (CpG) dinucleotide sites and rarely occurs at cytosine-phosphate-thymine (CpT), cytosine-phosphate-adenine (CpA), or cytosine-phosphate-cytosine sites, known as non-CpG sites. Basically, two different DNA methylation processes are identified: de novo methylation and maintenance methylation. While the de novo methylation functions in methylation of unmethylated DNA strands, maintenance methylation is capable of methylating hemi-methylated DNA strands following DNA replication. Both DNA methylation processes are catalyzed by special DNA methyltransferase (DNMT) enzymes. To date, five different DNMTs have been identified: DNMT1, DNMT3A, DNMT3B, DNMT3L, and DNMT2. In this chapter, we focus particularly on temporal and spatial expression of DNMTs in mammalian oocytes and granulosa cells.
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http://dx.doi.org/10.1007/978-3-319-60855-6_10DOI Listing
June 2019

Poly(A)-binding proteins are required for translational regulation in vertebrate oocytes and early embryos.

Reprod Fertil Dev 2017 Sep;29(10):1890-1901

Department of Histology and Embryology, Akdeniz University, School of Medicine, Campus, 07070, Antalya, Turkey.

Poly(A)-binding proteins (PABPs) function in the timely regulation of gene expression during oocyte maturation, fertilisation and early embryo development in vertebrates. To this end, PABPs bind to poly(A) tails or specific sequences of maternally stored mRNAs to protect them from degradation and to promote their translational activities. To date, two structurally different PABP groups have been identified: (1) cytoplasmic PABPs, including poly(A)-binding protein, cytoplasmic 1 (PABPC1), embryonic poly(A)-binding protein (EPAB), induced PABP and poly(A)-binding protein, cytoplasmic 3; and (2) nuclear PABPs, namely embryonic poly(A)-binding protein 2 and nuclear poly(A)-binding protein 1. Many studies have been undertaken to characterise the spatial and temporal expression patterns and subcellular localisations of PABPC1 and EPAB in vertebrate oocytes and early embryos. In the present review, we comprehensively evaluate and discuss the expression patterns and particular functions of the EPAB and PABPC1 genes, especially in mouse and human oocytes and early embryos.
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http://dx.doi.org/10.1071/RD16283DOI Listing
September 2017

DNA methyltransferases exhibit dynamic expression during spermatogenesis.

Reprod Biomed Online 2016 Dec 12;33(6):690-702. Epub 2016 Sep 12.

Department of Histology and Embryology, Akdeniz University, School of Medicine, Campus 07070, Antalya, Turkey. Electronic address:

DNA methylation is one of the epigenetic marks and plays critically important functions during spermatogenesis in mammals. DNA methylation is catalysed by DNA methyltransferase (DNMT) enzymes, which are responsible for the addition of a methyl group to the fifth carbon atom of the cytosine residues within cytosine-phosphate-guanine (CpG) and non-CpG dinucleotide sites. Structurally and functionally five different DNMT enzymes have been identified in mammals, including DNMT1, DNMT2, DNMT3A, DNMT3B and DNMT3L. These enzymes mainly play roles in two DNA methylation processes: maintenance and de novo. While DNMT1 is primarily responsible for maintenance methylation via transferring methyl groups to the hemi-methylated DNA strands following DNA replication, both DNMT3A and DNMT3B are capable of methylating unmodified cytosine residues, known as de novo methylation. However, DNMT3L indirectly participates in de novo methylation, and DNMT2 carries out methylation of the cytosine 38 in the anticodon loop of aspartic acid transfer RNA. To date, many studies have been performed to determine spatial and temporal expression levels and functional features of the DNMT in the male germ cells. This review article comprehensively discusses dynamic expression of the DNMT during spermatogenesis and their relationship with male infertility development in the light of existing investigations.
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http://dx.doi.org/10.1016/j.rbmo.2016.08.022DOI Listing
December 2016

The poly(A)-binding protein genes, EPAB, PABPC1, and PABPC3 are differentially expressed in infertile men with non-obstructive azoospermia.

J Assist Reprod Genet 2016 Mar 3;33(3):335-348. Epub 2016 Feb 3.

Department of Histology and Embryology, Akdeniz University, School of Medicine, Campus, 07070, Antalya, Turkey.

Purpose: Azoospermia is one of the major causes of male infertility and is basically classified into obstructive (OA) and non-obstructive azoospermia (NOA). The molecular background of NOA still largely remains elusive. It has been shown that the poly(A)-binding proteins (PABPs) essentially play critical roles in stabilization and translational control of the mRNAs during spermatogenesis.

Methods: In the present study, we aim to evaluate expression levels of the PABP genes, EPAB, PABPC1, and PABPC3, in the testicular biopsy samples and in the isolated spermatocyte (SC) and round spermatid (RS) fractions obtained from men with various types of NOA including hypospermatogenesis (hyposperm), RS arrest, SC arrest, and Sertoli cell-only syndrome (SCO).

Results: In the testicular biopsy samples, both PABPC1 and PABPC3 mRNA expressions were gradually decreased from hyposperm to SCO groups (P < 0.05), whereas there was no remarkable difference for the EPAB expression among groups. The expression levels of cytoplasmically localized PABPC1 and PABPC3 proteins dramatically reduced from hyposperm to SCO groups (P < 0.05). In the isolated SC and RS fractions, the EPAB, PABPC1, and PABPC3 mRNA expressions were gradually decreased from hyposperm to SC arrest groups (P < 0.05). Similarly, both PABPC1 and PABPC3 proteins were expressed at higher levels in the SC and RS fractions from hyposperm group when compared to the SC and RS fractions from either RS arrest or SC arrest group (P < 0.05).

Conclusion: Our findings suggest that observed significant alterations in the PABPs expression may have an implication for development of different NOA forms.
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http://dx.doi.org/10.1007/s10815-016-0654-zDOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4785164PMC
March 2016

CD90 and CD105 expression in the mouse ovary and testis at different stages of postnatal development.

Reprod Biol 2015 Dec 27;15(4):195-204. Epub 2015 Oct 27.

Department of Histology and Embryology, Faculty of Medicine, Akdeniz University, 07070, Campus, Antalya, Turkey. Electronic address:

CD90 (i.e., THY1) and CD105 (i.e., endoglin) are glycoproteins known as mesenchymal stem cell markers that are expressed in various cell types including male and female gonadal cells. We aimed to determine ovarian and testicular expression of CD90 and CD105 in various cell types during postnatal development in mice. The present study was carried out on male (C57BL/6) and female (Balb/C) mice during critical stages of gonadal development. Immunohistochemical localization of CD90 and CD105 was determined in the ovaries obtained at postnatal days (PND) -1, -7, -21 and -60 and in the testes obtained at PND6, -8, -16, -20, -29, -32 and -88. The relative expression of CD90 and CD105 was evaluated by ImageJ software and data were analyzed by analysis of variance. The relative expression of CD90 and CD105 varied during postnatal development and increased significantly in the adult ovary (PND60) and testis (PND88) compared to the early postnatal gonads. In the ovaries, the expression of CD90 was significantly higher in somatic cells in comparison to germ cell compartments. In the testis, CD90 expression was greater in germ cells and Sertoli cells compared to other cell types. Expression of CD105 was higher in germ cells than somatic cells of both the ovary and testis. In addition to different expression of CD90 and CD105 during various developmental stages, also their altered expression in particular cell types suggests specific roles of these glycoproteins in physiological processes of mouse gonads.
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http://dx.doi.org/10.1016/j.repbio.2015.10.004DOI Listing
December 2015

Dynamic expression of DNA methyltransferases (DNMTs) in oocytes and early embryos.

Biochimie 2015 Sep 2;116:103-13. Epub 2015 Jul 2.

Department of Histology and Embryology, Akdeniz University, School of Medicine, Antalya, Turkey. Electronic address:

Epigenetic mechanisms play critical roles in oogenesis and early embryo development in mammals. One of these epigenetic mechanisms, DNA methylation is accomplished through the activities of DNA methyltransferases (DNMTs), which are responsible for adding a methyl group to the fifth carbon atom of the cytosine residues within cytosine-phosphate-guanine (CpG) and non-CpG dinuclotide sites. Five DNMT enzymes have been identified in mammals including DNMT1, DNMT2, DNMT3A, DNMT3B, and DNMT3L. They function in two different methylation processes: maintenance and de novo. For maintenance methylation, DNMT1 preferentially transfers methyl groups to the hemi-methylated DNA strands following DNA replication. However, for de novo methylation activities both DNMT3A and DNMT3B function in the methylation of the unmodified cytosine residues. Although DNMT3L indirectly contributes to de novo methylation process, DNMT2 enables the methylation of the cytosine 38 in the anticodon loop of aspartic acid transfer RNA and does not methylate DNA. In this review article, we have evaluated and discussed the existing published studies to characterize the spatial and temporal expression patterns of the DNMTs in mouse, bovine and human oocytes and early embryos. We have also reviewed the effects of in vitro culture conditions (serum abundance and glucose concentration), aging, superovulation, vitrification, and somatic cell nuclear transfer technology on the dynamics of DNMTs.
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http://dx.doi.org/10.1016/j.biochi.2015.06.019DOI Listing
September 2015

The p38 MAPK signalling pathway is required for glucose metabolism, lineage specification and embryo survival during mouse preimplantation development.

Mech Dev 2015 Nov 27;138 Pt 3:375-98. Epub 2015 May 27.

Department of Histology and Embryology, Akdeniz University, School of Medicine, Campus, 07070, Antalya, Turkey. Electronic address:

Preimplantation embryo development is an important and unique period and is strictly controlled. This period includes a series of critical events that are regulated by multiple signal-transduction pathways, all of which are crucial in the establishment of a viable pregnancy. The p38 mitogen-activated protein kinase (MAPK) signalling pathway is one of these pathways, and inhibition of its activity during preimplantation development has a deleterious effect. The molecular mechanisms underlying the deleterious effects of p38 MAPK suppression in early embryo development remain unknown. To investigate of the effect of p38 MAPK inhibition on late preimplantation stages in detail, we cultured 2-cell stage embryos in the presence of SB203580 for 48 h and analysed the 8-cell, morula, and blastocyst stages. We determined that prolonged inhibition of the p38 MAPK altered the expression levels of Glut1 and Glut4, decreased glucose uptake during the 8-cell to blastocyst transition, changed the expression levels of transcripts which will be important to lineage commitment, including Oct4/Pou5f1, Nanog, Sox2, and Gata6, and increased cell death in 8-16 cell stage embryos onwards. Strikingly, while the expression levels of Nanog, Gata6 and Oct4/Pou5f1 mRNAs were significantly decreased, Sox2 mRNA was increased in SB203580-treated blastocysts. Taken together, our results provide important insight into the biological processes controlled by the p38 MAPK pathway and its critical role during preimplantation development.
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http://dx.doi.org/10.1016/j.mod.2015.05.002DOI Listing
November 2015

Telomerase activity and telomere length in male germ cells.

Authors:
Saffet Ozturk

Biol Reprod 2015 Feb 7;92(2):53. Epub 2015 Jan 7.

Department of Histology and Embryology, Akdeniz University, School of Medicine, Campus, Antalya, Turkey

Telomeres are located at the outermost ends of all eukaryotic chromosomes and provide for the maintenance of genomic stability and integrity during the life span of organisms. The length of telomeres shortens due to each round of DNA replication, genotoxic insults, and/or reactive oxygen species. To counteract this shortening, certain types of cells, including stem cells, male/female germline cells, granulosa cells, early embryos, and most cancerous cells, express an enzyme known as telomerase, which has the potential of restoring the shortened telomeres. Presence of telomerase activity in the male germ cells ensures maintenance of telomere length at maximum levels during spermatogenesis despite telomere attrition due to DNA replication or other genotoxic factors. In this review, telomerase activity and telomere length in mammalian male germ cells during spermatogenesis are evaluated in detail based on the studies in this field. Also, the relationship between telomerase activity/telomere length and development of male infertility is comprehensively discussed.
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http://dx.doi.org/10.1095/biolreprod.114.124008DOI Listing
February 2015

Epab and Pabpc1 are differentially expressed in the postnatal mouse ovaries.

J Assist Reprod Genet 2015 Jan 5;32(1):137-46. Epub 2014 Nov 5.

Department of Histology and Embryology, School of Medicine, Akdeniz University, Campus, 07070, Antalya, Turkey.

Purpose: Embryonic poly(A)-binding protein (EPAB) and poly(A)-binding protein, cytoplasmic 1 (PABPC1) bind poly(A) tails of mRNAs and mediate their translational regulation in germ cells and early preimplantation embryos. Although expression patterns and possible functions of the Epab and Pabpc1 genes have been examined in vertebrate germ cells and early embryos, their expression levels and cellular localizations in the postnatal mouse ovaries remained elusive.

Methods: In the present study, we first aimed to characterize expression levels of the Epab and Pabpc1 genes in the prepubertal (1-, 2-, and 3-week old), pubertal (4-, 5-, and 6-week old), postpubertal (16-week and 18-week old), and aged (52-, 60-, and 72-week old) mouse ovaries by using quantitative real-time polymerase chain reaction (qRT-PCR).

Results: Epab mRNA was predominantly expressed in the prepubertal ovaries when compared to later developmental periods. However, Pabpc1 transcript was highly generated in the prepubertal and pubertal mouse ovaries except for 1-week old ovary than those of other developmental terms. In the prepubertal mouse ovaries, RNA in situ hybridization localized both Epab and Pabpc1 transcripts in the cytoplasm of oocytes and granulosa cells of all follicular stages. Consistently, Epab and Pabpc1 gene expression were detected in the cumulus cells and MII oocytes obtained from cumulus oocyte complexes (COCs). Ovarian follicle counting in the postnatal ovaries revealed that total number of follicles was higher in the prepubertal ovaries in comparison with later stages of development.

Conclusion: As a result, Epab and Pabpc1 expression exhibit differences at postnatal ovary development stages and both genes are transcribed in the granulosa cells and oocytes. These findings suggest that EPAB may predominantly play roles in translational regulation of the mRNAs during early oogenesis and folliculogenesis, but PABPC1 most likely perform these roles in the later terms of ovarian development along with EPAB protein.
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http://dx.doi.org/10.1007/s10815-014-0362-5DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4294878PMC
January 2015

Superovulation alters embryonic poly(A)-binding protein (Epab) and poly(A)-binding protein, cytoplasmic 1 (Pabpc1) gene expression in mouse oocytes and early embryos.

Reprod Fertil Dev 2016 Mar;28(3):375-83

Department of Histology and Embryology, Akdeniz University, School of Medicine, Campus, 07070, Antalya, Turkey.

Embryonic poly(A)-binding protein (EPAB) and poly(A)-binding protein, cytoplasmic 1 (PABPC1) play critical roles in translational regulation of stored maternal mRNAs required for proper oocyte maturation and early embryo development in mammals. Superovulation is a commonly used technique to obtain a great number of oocytes in the same developmental stages in assisted reproductive technology (ART) and in clinical or experimental animal studies. Previous studies have convincingly indicated that superovulation alone can cause impaired oocyte maturation, delayed embryo development, decreased implantation rate and increased postimplantation loss. Although how superovulation results in these disturbances has not been clearly addressed yet, putative changes in genes related to oocyte and early embryo development seem to be potential risk factors. Thus, the aim of the present study was to determine the effect of superovulation on Epab and Pabpc1 gene expression. To this end, low- (5IU) and high-dose (10IU) pregnant mare's serum gonadotropin (PMSG) and human chorionic gonadotrophin (hCG) were administered to female mice to induce superovulation, with naturally cycling female mice serving as controls. Epab and Pabpc1 gene expression in germinal vesicle (GV) stage oocytes, MII oocytes and 1- and 2-cell embryos collected from each group were quantified using quantitative reverse transcription-polymerase chain reaction. Superovulation with low or high doses of gonadotropins significantly altered Epab and Pabpc1 mRNA levels in GV oocytes, MII oocytes and 1- and 2-cell embryos compared with their respective controls (P<0.05). These changes most likely lead to variations in expression of EPAB- and PABPC1-regulated genes, which may adversely influence the quality of oocytes and early embryos retrieved using superovulation.
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http://dx.doi.org/10.1071/RD14106DOI Listing
March 2016

Epab is dispensable for mouse spermatogenesis and male fertility.

Mol Reprod Dev 2014 May 4;81(5):390. Epub 2014 Apr 4.

Department of Obstetrics, Gynecology and Reproductive Sciences, Yale University, School of Medicine, New Haven, Connecticut.

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http://dx.doi.org/10.1002/mrd.22319DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4079073PMC
May 2014

Telomere length and telomerase activity during oocyte maturation and early embryo development in mammalian species.

Mol Hum Reprod 2014 Jan 8;20(1):15-30. Epub 2013 Aug 8.

Department of Histology and Embryology, School of Medicine, Akdeniz University Campus, 07070 Antalya, Turkey.

Telomeres are located at the ends of all eukaryotic chromosomes and protect them from deleterious events such as inappropriate DNA repair, illegitimate recombination or improper segregation of the chromosomes during mitotic or meiotic divisions. However, telomeres gradually shorten primarily due to successive rounds of genomic DNA replication and also as the result of the adverse effects of oxidative stress, genotoxic agents, diseases related to ageing and environmental factors on the nuclear materials of dividing or non-dividing cells. Germline cells, proliferative granulosa cells, early embryos, stem cells, highly proliferative somatic cells and many cancer cells contain the enzyme telomerase so that they are capable of elongating the shortened telomeres. Although numerous studies have revealed the length of telomeres and telomerase activity in oocytes, granulosa cells and early embryos, only a few studies have analyzed and compared the work performed on distinct mammalian species. In this comprehensive review article, we compare and discuss telomere length and telomerase activity in oocytes, granulosa cells and early embryos in different mammalian species including mice, bovines and humans.
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http://dx.doi.org/10.1093/molehr/gat055DOI Listing
January 2014

Activation of vagus nerve by semapimod alters substance P levels and decreases breast cancer metastasis.

Regul Pept 2012 Nov 11;179(1-3):101-8. Epub 2012 Sep 11.

Department of Pharmacology, Akdeniz University, School of Medicine, Antalya 07070, Turkey.

Chronic inflammation is involved in initiation as well as in progression of cancer. Semapimod, a tetravalent guanylhydrazon and formerly known as CNI-1493, inhibits the release of inflammatory cytokines from activated macrophages and this effect is partly mediated by the vagus nerve. Our previous findings demonstrated that inactivation of vagus nerve activity as well sensory neurons enhanced visceral metastasis of 4THM breast carcinoma. Hence semapimod by activating vagus nerve may inhibit breast cancer metastasis. Here, effects of semapimod on breast cancer metastasis, the role of vagal sensory neurons on this effect and changes in mediators of the neuroimmune connection, such as substance P (SP) as well as neprilysin-like activity, were examined. Vagotomy was performed on half of the control animals that were treated with semapimod following orthotopic injection of 4THM breast carcinoma cells. Semapimod decreased lung and liver metastases in control but not in vagotomized animals with an associated increased SP levels in sensory nerve endings. Semapimod also increased neprilysin-like activity in lung tissue of control animals but not in tumor-bearing animals. This is the first report demonstrating that semapimod enhances vagal sensory nerve activity and may have anti-tumoral effects under in-vivo conditions. Further studies, however, are required to elucidate the conditions and the mechanisms involved in anti-tumoral effects of semapimod.
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http://dx.doi.org/10.1016/j.regpep.2012.08.001DOI Listing
November 2012

Epab and Pabpc1 are differentially expressed during male germ cell development.

Reprod Sci 2012 Sep 18;19(9):911-22. Epub 2012 Jul 18.

Department of Obstetrics, Gynecology and Reproductive Sciences, Yale University School of Medicine, New Haven, CT 06520-8063, USA.

Modification of poly(A) tail length constitutes the main posttranscriptional mechanism by which gene expression is regulated during spermatogenesis. Embryonic poly(A)-binding protein (EPAB) and somatic cytoplasmic poly(A)-binding protein (PABPC1) are the 2 key proteins implicated in this pathway. In this study we characterized the temporal and spatial expression of Epab and Pabpc1 in immature (D6-D32) and mature (D88) mouse testis and in isolated spermatogenic cells. Both Epab and Pabpc1 expression increased during early postnatal life and reached their peak at D32 testis. This was due to an increase in both spermatogonia (SG) and spermatocytes. In the mature testis, the highest levels of Epab were detected in SG, followed by round spermatids (RSs), while the most prominent Pabpc1 expression was detected in spermatocytes and RSs. Our findings suggest that PABPC1 may play a role in translational regulation of gene expression by cytoplasmic polyadenylation, which occurs in spermatocytes, while both EPAB and PABPC1 may help stabilize stored polyadenylated messenger RNAs in RSs.
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http://dx.doi.org/10.1177/1933719112446086DOI Listing
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4046314PMC
September 2012
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