Cloning of GJA1 (connexin43) and its expression in canine ovarian follicles throughout the estrous cycle

Fertility restoration in mice with chemotherapy induced ovarian failure using differentiated iPSCs

BACKGROUND

Treatment options for premature ovarian insufficiency (POI) are limited to hormone replacement and donor oocytes. A novel induced pluripotent stem cell (iPSC) transplant paradigm in a mouse model has potential translational applications for management of POI.

METHODS

Mouse ovarian granulosa cell derived-iPSCS were labelled with green fluorescent protein (GFP) reporter and differentiated in vitro into oocytes. Differentiated cells were assayed for estradiol and progesterone secretion by enzyme-linked immunosorbent assays. After Fluorescence-Activated Cell Sorting (FACS) for the cell surface marker anti-Mullerian hormone receptor (AMHR2), enriched populations of differentiated cells were surgically transplanted into ovaries of mice that had POI secondary to gonadotoxic pre-treatment with alkylating agents. A total of 100 mice were used in these studies in five separate experiments with 56 animals receiving orthotopic ovarian injections of either FACS sorted or unsorted differentiated iPSCSs and the remaining animals receiving sham injections of PBS diluent. Following transplantation surgery, mice were stimulated with gonadotropins inducing oocyte development and underwent oocyte retrieval. Nine transplanted mice were cross bred with wild-type mice to assess fertility. Lineage tracing of resultant oocytes, F1 (30 pups), and F2 (42 pups) litters was interrogated by GFP expression and validation by short tandem repeat (STR) lineage tracing.

FINDINGS

[1] iPSCs differentiate into functional oocytes and steroidogenic ovarian cells which [2] express an ovarian (GJA1) and germ cell (ZP1) markers. [3] Endocrine function and fertility were restored in mice pretreated with gonadotoxic alkylating agents via orthotopic transplantation of differentiated iPSCS, thus generating viable, fertile mouse pups.

INTERPRETATION

iPSC-derived ovarian tissue can reverse endocrine and reproductive sequelae of POI.

FUNDING

Center for Infertility and Reproductive Surgery Research Award, Siezen Foundation award (RMA). Reproductive Scientist Development Program, Marriott Foundation, Saltonstall Foundation, Brigham Ovarian Cancer Research Fund (K.E).

Gap junction proteins are key drivers of endocrine function

It has long been known that the main secretory cells of exocrine and endocrine glands are connected by gap junctions, made by a variety of connexin species that ensure their electrical and metabolic coupling. Experiments in culture systems and animal models have since provided increasing evidence that connexin signaling contributes to control the biosynthesis and release of secretory products, as well as to the life and death of secretory cells. More recently, genetic studies have further provided the first lines of evidence that connexins also control the function of human glands, which are central to the pathogenesis of major endocrine diseases. Here, we summarize the recent information gathered on connexin signaling in these systems, since the last reviews on the topic, with particular regard to the pancreatic beta cells which produce insulin, and the renal cells which produce renin. These cells are keys to the development of various forms of diabetes and hypertension, respectively, and combine to account for the exploding, worldwide prevalence of the metabolic syndrome. This article is part of a Special Issue entitled: Gap Junction Proteins edited by Jean Claude Herve.

Gap junction connexins in female reproductive organs: implications for women's reproductive health

BACKGROUND

Connexins comprise a family of ~20 proteins that form intercellular membrane channels (gap junction channels) providing a direct route for metabolites and signalling molecules to pass between cells. This review provides a critical analysis of the evidence for essential roles of individual connexins in female reproductive function, highlighting implications for women's reproductive health.

METHODS

No systematic review has been carried out. Published literature from the past 35 years was surveyed for research related to connexin involvement in development and function of the female reproductive system. Because of the demonstrated utility of genetic manipulation for elucidating connexin functions in various organs, much of the cited information comes from research with genetically modified mice. In some cases, a distinction is drawn between connexin functions clearly related to the formation of gap junction channels and those possibly linked to non-channel roles.

RESULTS AND CONCLUSIONS

Based on work with mice, several connexins are known to be required for female reproductive functions. Loss of connexin43 (CX43) causes an oocyte deficiency, and follicles lacking or expressing less CX43 in granulosa cells exhibit reduced growth, impairing fertility. CX43 is also expressed in human cumulus cells and, in the context of IVF, has been correlated with pregnancy outcome, suggesting that this connexin may be a determinant of oocyte and embryo quality in women. Loss of CX37, which exclusively connects oocytes with granulosa cells in the mouse, caused oocytes to cease growing without acquiring meiotic competence. Blocking of CX26 channels in the uterine epithelium disrupted implantation whereas loss or reduction of CX43 expression in the uterine stroma impaired decidualization and vascularization in mouse and human. Several connexins are important in placentation and, in the human, CX43 is a key regulator of the fusogenic pathway from the cytotrophoblast to the syncytiotrophoblast, ensuring placental growth. CX40, which characterizes the extravillous trophoblast (EVT), supports proliferation of the proximal EVTs while preventing them from differentiating into the invasive pathway. Furthermore, women with recurrent early pregnancy loss as well as those with endometriosis exhibit reduced levels of CX43 in their decidua. The antimalaria drug mefloquine, which blocks gap junction function, is responsible for increased risk of early pregnancy loss and stillbirth, probably due to inhibition of intercellular communication in the decidua or between trophoblast layers followed by an impairment of placental growth. Gap junctions also play a critical role in regulating uterine blood flow, contributing to the adaptive response to pregnancy. Given that reproductive impairment can result from connexin mutations in mice, it is advised that women suffering from somatic disease symptoms associated with connexin gene mutations be additionally tested for impacts on reproductive function. Better knowledge of these essential connexin functions in human female reproductive organs is important for safeguarding women's reproductive health.

Associations between two genetic variants in NKX2-5 and risk of congenital heart disease in Chinese population: a meta-analysis

Background

NKX2-5 is a transcriptional factor, which plays an important role in heart formation and development. Two genetic variants in the coding region of NKX2-5, 63A>G (rs2277923) and 606G>C (rs3729753), have been investigated in the risk of congenital heart disease (CHD), although with inconsistent results. Thus, a meta-analysis was performed to clarify the associations between the two variants and CHD risk in the Chinese population.

Methods and Results

Relevant studies were identified by searching PubMed, ISI Web of Science and CNKI databases and by reviewing the reference lists of retrieved articles. Then, the data from eligible studies were combined in an allelic model. A total of 7 and 4 studies were ultimately included for 63A>G and 606G>C, respectively. The results of overall meta-analyses showed that significant association was detected for 63A>G (OR = 1.26, 95% CI = 1.02–1.56, P_{heterogeneity} = 0.009, I² = 65.1%), but not for 606G>C (OR = 1.22, 95% CI = 0.75–1.96, P_{heterogeneity} = 0.412, I² = 0.0%). Regarding 63A>G variant, positive results were also obtained in the subgroups of atrial septal defect and large-sample-size study. Besides, the sensitivity analysis indicated that significant association was still detected after deletion of the individual studies with positive result and striking heterogeneity.

Conclusion

Our results revealed that the 63A>G variant in NKX2-5, but not the 606G>C, may contribute to CHD risk for Chinese.

Spinal cord injury induced arrest in estrous cycle of rats is ameliorated by S-nitrosoglutathione: novel therapeutic agent to treat amenorrhea

INTRODUCTION

Amenorrhea following spinal cord injury (SCI) has been well documented. There has been little research on the underlying molecular mechanisms and therapeutics.

AIM

The purpose of the present study was to investigate the effect of GSNO in ameliorating SCI-induced amenorrhea through affecting the expression of CX43, NFkB, and ERβ protein.

METHODS

SCI was induced in female SD rats at the T9-T10 level. Estrous stage was determined by vaginal smear. GSNO (50 µg/kg body weight) was gavage fed daily. Animals were sacrificed on day 7 and 14 post SCI. Ovaries were fixed for histological and biochemical studies. Expression levels of ERβ, CX-43, and NFkB were analyzed by Western blot and immunofluorescence.

MAIN OUTCOME MEASURES

GSNO hastens resumption of the estrous cycle following SCI-induced transient arrest.

RESULTS

Resumption of estrous cycle was hastened by GSNO. Atretic and degenerating follicles seen in the ovary of SCI rats on day 14 post-SCI were decreased in GSNO treated animals. The increased CX43 expression observed with SCI ovary was decreased by GSNO. ERβ expression decreased significantly on day 7 and 14 post-SCI and was restored with GSNO treatment. Following SCI, NFkB expression was increased in the ovarian follicles and the expression was reduced with GSNO administration. The number of terminal deoxynucleotidyl transferase-mediated biotinylated uridine triphosphate (UTP) nick end labeling positive follicular and luteal cells was increased after SCI. GSNO-treated animals had significantly fewer apoptotic cells in the ovary.

CONCLUSION

SCI-induced amenorrhea is accompanied by an increase in CX43 expression and a decrease in ERβ expression. SCI animals treated with GSNO resumed the estrous cycle significantly earlier. These results indicate a potential therapeutic value for GSNO in treating amenorrhea among SCI patients.

Connexin-dependent signaling in neuro-hormonal systems

The advent of multicellular organisms was accompanied by the development of short- and long-range chemical signalling systems, including those provided by the nervous and endocrine systems. In turn, the cells of these two systems have developed mechanisms for interacting with both adjacent and distant cells. With evolution, such mechanisms have diversified to become integrated in a complex regulatory network, whereby individual endocrine and neuro-endocrine cells sense the state of activity of their neighbors and, accordingly, regulate their own level of functioning. A consistent feature of this network is the expression of connexin-made channels between the (neuro)hormone-producing cells of all endocrine glands and secretory regions of the central nervous system so far investigated in vertebrates. This review summarizes the distribution of connexins in the mammalian (neuro)endocrine systems, and what we know about the participation of these proteins on hormone secretion, the life of the producing cells, and the action of (neuro)hormones on specific targets. The data gathered since the last reviews on the topic are summarized, with particular emphasis on the roles of Cx36 in the function of the insulin-producing beta cells of the endocrine pancreas, and of Cx40 in that of the renin-producing juxta-glomerular epithelioid cells of the kidney cortex. This article is part of a Special Issue entitled: The Communicating junctions, composition, structure and characteristics.

Connexin 43 gene expression in male and female gonads of porcine offspring following in utero exposure to an anti-androgen, flutamide

The aim of this study was to show the effect of maternal exposure to flutamide on connexin 43 (Cx43) gene expression in testes and ovaries of 2-day-old piglets. Additionally, anogenital distance (AGD) was measured both in male and female offspring. Immunohistochemistry, Western blotting, and RT-PCR were performed to assess the immunoreactivity and the presence of Cx43 protein and it's mRNA, respectively. Following flutamide exposure strong immunostaining for Cx43 was observed between testicular Leydig cells, between granulosa cells of primary follicles, and between interstitial cells surrounding clusters of oocyte nests in the ovarian cortex as in the respective controls. Differences between the flutamide-treated groups and the controls obtained by qualitative immunohistochemistry were confirmed by quantitative image analysis (*P<0.05; **P<0.01). In Western blotting, Cx43 appeared as a band of 43kDa, whereas electrophoresis revealed PCR products of the predicted sizes. Screening for Cx43 expression revealed the presence of a transcript, both in control and in flutamide-treated pigs. The AGD values differed significantly from the control (*P<0.05). Overall, since no obvious changes in gonad morphology were observed and the Cx43 signal was present in all the examined tissues, it seems likely that androgens acting through ARs are not involved in the control of Cx43 gene expression in neonatal pig gonads.

The Role of Gap Junction Proteins in Infertility

Testis and ovary serve an important role of producing male and female gametes. Their normal functioning is very important for the proper formation of sperm and ovum and thus has a critical role in the successful fertility outcome. Synchronized activity of various cells in the gonads is needed to provide favorable niche for the growth and development of the germ cells. Among various ways of cellular communication, intercellular communication is mediated by gap junctions, which provides open but selective exchange of ion and molecules of restricted size between two adjoining cells. The basic unit of gap junction is connexins. Their important role has been speculated in the maintenance of homeostasis, morphogenesis, cell differentiation, and growth control in higher organisms. The expression of gap junction proteins in reproductive tissues has drawn the attention and interest of researcher to investigate their role in the reproductive outcome. The reports about the correlation of gap junction protein expression pattern in infertility patients and in animal models have suggested their implication in fertility. Some of these gap junction proteins seem to have redundant functions, whereas some could be very critical in the normal fertility and could not be dispensable for the successful outcome of the reproduction.

Molecular cloning and evolutionary analysis of the GJA1 (connexin43) gene from bats (Chiroptera)

Gap junction protein connexin43 (Cx43), encoded by the GJA1 gene, is the most abundant connexin in the cardiovascular system and was reported as a crucial factor maintaining cardiac electrical conduction, as well as having a very important function in facilitating the recycling of potassium ions from hair cells in the cochlea back into the cochlear endolymph during auditory transduction processes. In mammals, bats are the only taxon possessing powered flight, placing exceptional demand on many organismal processes. To meet the demands of flying, the hearts of bats show many specialties. Moreover, ultrasonic echolocation allows bat species to orientate and often detect and locate food in darkness. In this study, we cloned the full-length coding region of GJA1 gene from 12 different species of bats and obtained orthologous sequences from other mammals. We used the maximum likelihood method to analyse the evolution of GJA1 gene in mammals and the lineage of bats. Our results showed this gene is much conserved in mammals, as well as in bats' lineage. Compared with other mammals, we found one private amino acid substitution shared by bats, which is located on the inner loop domain, as well as some species-specific amino acid substitutions. The evolution rate analyses showed the signature of purifying selection on not only different classification level lineages but also the different domains and amino acid residue sites of this gene. Also, we suggested that GJA1 gene could be used as a good molecular marker to do the phylogenetic reconstruction.

Expression of connexin 43 in normal canine testes and canine testicular tumors

In human testis, gap junctions containing connexin(Cx)43 are located within the seminiferous epithelium between Sertoli cells and between Sertoli and germ cells. Cx43 is known to play a role in the differentiation and proliferation of these cell types. It can further be associated with human seminoma development. The dog has been proposed as a model for studies of the male reproductive system, because of the frequent occurrence of testicular neoplasms. Thus, we investigated Cx43-mRNA and -protein expression in testes of normal prepubertal dogs, adult dogs, and in canine testicular tumors. Sertoli cells in prepubertal cords express Cx43 mRNA, but do synthesize only less Cx43 protein. Within the seminiferous tubules, Cx43 mRNA was detected in Sertoli cells, spermatogonia, and spermatocytes. Cx43 protein was mainly present in the basal compartment. In canine testicular tumors Cx43 mRNA was detectable in both seminoma and neoplastic Sertoli cells, whereas Cx43 protein was only found in neoplastic Sertoli cells. Our data indicate that Cx43 is regulated differentially in testicular tumors and that alterations of Cx43 expression may be involved in the pathogenesis of canine testicular malignancies. This study represents the first morphological work on the spatiotemporal expression pattern of Cx43 in normal and neoplastic canine testis.