Alpha-fetoprotein, the major fetal serum protein, is not essential for embryonic development but is required for female fertility

A framework for identifying fertility gene targets for mammalian pest control

Fertility-targeted gene drives have been proposed as an ethical genetic approach for managing wild populations of vertebrate pests for public health and conservation benefit. This manuscript introduces a framework to identify and evaluate target gene suitability based on biological gene function, gene expression and results from mouse knockout models. This framework identified 16 genes essential for male fertility and 12 genes important for female fertility that may be feasible targets for mammalian gene drives and other non-drive genetic pest control technology. Further, a comparative genomics analysis demonstrates the conservation of the identified genes across several globally significant invasive mammals. In addition to providing important considerations for identifying candidate genes, our framework and the genes identified in this study may have utility in developing additional pest control tools such as wildlife contraceptives.

A framework for identifying fertility gene targets for mammalian pest control

Fertility-targeted gene drives have been proposed as an ethical genetic approach for managing wild populations of vertebrate pests for public health and conservation benefit.This manuscript introduces a framework to identify and evaluate target gene suitability based on biological gene function, gene expression, and results from mouse knockout models.This framework identified 16 genes essential for male fertility and 12 genes important for female fertility that may be feasible targets for mammalian gene drives and other non-drive genetic pest control technology. Further, a comparative genomics analysis demonstrates the conservation of the identified genes across several globally significant invasive mammals.In addition to providing important considerations for identifying candidate genes, our framework and the genes identified in this study may have utility in developing additional pest control tools such as wildlife contraceptives.

High serum alpha-fetoprotein levels in primary infertile men

BACKGROUND

Alfa-fetoprotein (AFP) is a serum glycoprotein highly produced during fetal development. While AFP synthesis drops dramatically after birth, AFP production only persists or returns under specific pathological condition.

OBJECTIVE

We sought to investigate the rate of and the potential meaning of high AFP serum levels in men seeking first medical attention for couple's primary infertility.

MATERIALS AND METHODS

Socio-demographic and clinical data from 1803 non-Finnish, White-European primary infertile men were retrospectively analysed. AFP was routinely measured in each patient (high AFP was defined as >7 ng/ml). Men with history of liver diseases, testicular cancer, or other known causes of increased AFP levels were excluded from the final analysis. Semen analyses were based on the 2010 World Health Organization reference criteria. Descriptive statistics and logistic regression models tested the association between serum AFP and clinical variables. Possible nonlinear relationships were graphically explored with locally estimated scatterplot smoothing method.

RESULTS

Overall, high serum AFP level was found in 29 (1.7%) patients. Normal versus high AFP levels patients were comparable in terms of body mass index (BMI), Charlson Comorbidity Index, waist circumference, smoking habits, history of cryptorchidism, testicular volume, and serum hormones (i.e., follicle-stimulating hormone, luteinizing hormone, and total testosterone). Conversely, men with higher AFP levels were older (p = 0.02), had lower sperm concentration (p = 0.003), and were more frequently oligozoospermic and azoospermic (all p ≤ 0.03). At multivariate analysis, high AFP levels were independently associated with oligozoospermia (OR 3.79; p = 0.033) and azoospermia (OR 3.29; p = 0.006). Likewise, if AFP levels increase, patients were found to be older, with higher BMI and to have more comorbidities (all p < 0.05).

DISCUSSION

Unexplained high AFP levels account for almost 2% of cases in primary infertile patients without a previous history of associated disorders. Higher serum AFP levels are linked with aberrant sperm counts, older age, obesity, and a greater amount of comorbid conditions.

CONCLUSION

Despite the need for additional validation, these data suggest that serum AFP measurement might have a multifaceted role over the diagnostic work-up of males presenting for couple's infertility.

A Novel Cell-Based Model for a Rare Disease: The Tks4-KO Human Embryonic Stem Cell Line as a Frank-Ter Haar Syndrome Model System

Tyrosine kinase substrate with four SH3 domains (Tks4) scaffold protein plays roles in cell migration and podosome formation and regulates systemic mechanisms such as adult bone homeostasis and adipogenesis. Mutations in the Tks4 gene (SH3PXD2b) cause a rare developmental disorder called Frank-Ter Haar syndrome (FTHS), which leads to heart abnormalities, bone tissue defects, and reduced adiposity. We aimed to produce a human stem cell-based in vitro FTHS model system to study the effects of the loss of the Tks4 protein in different cell lineages and the accompanying effects on the cell signalome. To this end, we used CRISPR/Cas9 (clustered, regularly interspaced, short palindromic repeats (CRISPR)/CRISPR associated (Cas9)) to knock out the SH3PXD2b gene in the HUES9 human embryonic stem cell line (hESC), and we obtained stable homo- and heterozygous knock out clones for use in studying the potential regulatory roles of Tks4 protein in embryonic stem cell biology. Based on pluripotency marker measurements and spontaneous differentiation capacity assays, we concluded that the newly generated Tks4-KO HUES9 cells retained their embryonic stem cell characteristics. We propose that the Tks4-KO HUES9 cells could serve as a tool for further cell differentiation studies to investigate the involvement of Tks4 in the complex disorder FTHS. Moreover, we successfully differentiated all of the clones into mesenchymal stem cells (MSCs). The derived MSC cultures showed mesenchymal morphology and expressed MSC markers, although the expression levels of mesodermal and osteogenic marker genes were reduced, and several EMT (epithelial mesenchymal transition)-related features were altered in the Tks4-KO MSCs. Our results suggest that the loss of Tks4 leads to FTHS by altering cell lineage differentiation and cell maturation processes, rather than by regulating embryonic stem cell potential.

Insights into in vivo follicle formation: a review of in vitro systems

In vitro systems capable of reconstituting the process of mouse oogenesis are now being established to help develop further understanding of the mechanisms underlying oocyte/follicle development and differentiation. These systems could also help increase the production of useful livestock or genetically modified animals, and aid in identifying the causes of infertility in humans. Recently, we revealed, using an in vitro system for recapitulating oogenesis, that the activation of the estrogen signaling pathway induces abnormal follicle formation, that blocking estrogen-induced expression of anti-Müllerian hormone is crucial for normal follicle formation, and that the production of α-fetoprotein in fetal liver tissue is involved in normal in vivo follicle formation. In mouse fetuses, follicle formation is not carried out by factors within the ovaries but is instead orchestrated by distal endocrine factors. This review outlines findings from genetics, endocrinology, and in vitro studies regarding the factors that can affect the formation of primordial follicles in mammals.

Targeted whole exome sequencing and Drosophila modelling to unveil the molecular basis of primary ovarian insufficiency

STUDY QUESTION

Can a targeted whole exome sequencing (WES) on a cohort of women showing a primary ovarian insufficiency (POI) phenotype at a young age, combined with a study of copy number variations, identify variants in candidate genes confirming their deleterious effect on ovarian function?

SUMMARY ANSWER

This integrated approach has proved effective in identifying novel candidate genes unveiling mechanisms involved in POI pathogenesis.

WHAT IS KNOWN ALREADY

POI, a condition occurring in 1% of women under 40 years of age, affects women’s fertility leading to a premature loss of ovarian reserve. The genetic causes of POI are highly heterogeneous and several determinants contributing to its prominent oligogenic inheritance pattern still need to be elucidated.

STUDY DESIGN, SIZE, DURATION

WES screening for pathogenic variants of 41 Italian women with non-syndromic primary and early secondary amenorrhoea occurring before age 25 was replicated on another 60 POI patients, including 35 French and 25 American women, to reveal statistically significant shared variants.

PARTICIPANTS/MATERIALS, SETTING, METHODS

The Italian POI patients’ DNA were processed by targeted WES including 542 RefSeq genes expressed or functioning during distinct reproductive or ovarian processes (e.g. DNA repair, meiosis, oocyte maturation, folliculogenesis and menopause). Extremely rare variants were filtered and selected by means of a Fisher Exact test using several publicly available datasets. A case-control Burden test was applied to highlight the most significant genes using two ad-hoc control female cohorts. To support the obtained data, the identified genes were screened on a novel cohort of 60 Caucasian POI patients and the same case-control analysis was carried out. Comparative analysis of the human identified genes was performed on mouse and Drosophila melanogaster by analysing the orthologous genes in their ovarian phenotype, and two of the selected genes were fruit fly modelled to explore their role in fertility.

MAIN RESULTS AND THE ROLE OF CHANCE

The filtering steps applied to search for extremely rare pathogenic variants in the Italian cohort revealed 64 validated single-nucleotide variants/Indels in 59 genes in 30 out of 41 screened women. Burden test analysis highlighted 13 ovarian genes as being the most enriched and significant. To validate these findings, filtering steps and Burden analysis on the second cohort of Caucasian patients yielded 11 significantly enriched genes. Among them, AFP, DMRT3, MOV10, FYN and MYC were significant in both patient cohorts and hence were considered strong candidates for POI. Mouse and Drosophila comparative analysis evaluated a conserved role through the evolution of several candidates, and functional studies using a Drosophila model, when applicable, supported the conserved role of the MOV10 armitage and DMRT3 dmrt93B orthologues in female fertility.

LARGE SCALE DATA

The datasets for the Italian cohort generated during the current study are publicly available at ClinVar database (http://www.ncbi.nlm.nih.gov/clinvar/): accession numbers SCV001364312 to SCV001364375.

LIMITATIONS, REASONS FOR CAUTION

This is a targeted WES analysis hunting variants in candidate genes previously identified by different genomic approaches. For most of the investigated sporadic cases, we could not track the parental inheritance, due to unavailability of the parents’ DNA samples; in addition, we might have overlooked additional rare variants in novel candidate POI genes extracted from the exome data. On the contrary, we might have considered some inherited variants whose clinical significance is uncertain and might not be causative for the patients’ phenotype. Additionally, as regards the Drosophila model, it will be extremely important in the future to have more mutants or RNAi strains available for each candidate gene in order to validate their role in POI pathogenesis.

WIDER IMPLICATIONS OF THE FINDINGS

The genomic, statistical, comparative and functional approaches integrated in our study convincingly support the extremely heterogeneous oligogenic nature of POI, and confirm the maintenance across the evolution of some key genes safeguarding fertility and successful reproduction. Two principal classes of genes were identified: (i) genes primarily involved in meiosis, namely in synaptonemal complex formation, asymmetric division and oocyte maturation and (ii) genes safeguarding cell maintenance (piRNA and DNA repair pathways).

STUDY FUNDING/COMPETING INTEREST(S)

This work was supported by Italian Ministry of Health grants ‘Ricerca Corrente’ (08C621_2016 and 08C924_2019) provided to IRCCS Istituto Auxologico Italiano, and by ‘Piano Sostegno alla Ricerca’ (PSR2020_FINELLI_LINEA_B) provided by the University of Milan; M.P.B. was supported by Telethon-Italy (grant number GG14181). There are no conflicts of interest.

Blocking estrogen-induced AMH expression is crucial for normal follicle formation

In mammals, primordial follicles assembled in fetuses or during infancy constitute the oocyte resources for life. Exposure to 17beta-estradiol and phytogenic or endocrine-disrupting chemicals during pregnancy and/or the perinatal period leads to the failure of normal follicle formation. However, the mechanisms underlying estrogen-mediated abnormal follicle formation and physiological follicle formation in the presence of endogenous natural estrogen are not well understood. Here, we reveal that estrogen receptor 1, activated by estrogen, binds to the 5' region of the anti-Mullerian hormone (Amh) gene and upregulates its transcription before follicle formation in cultured mouse fetal ovaries. Ectopic expression of AMH protein was observed in pregranulosa cells of these explants. Furthermore, the addition of AMH to the culture medium inhibited normal follicle formation. Conversely, alpha-fetoprotein (AFP) produced in the fetal liver reportedly blocks estrogen action, although its role in follicle formation is unclear. We further demonstrated that the addition of AFP to the medium inhibited ectopic AMH expression via estrogen, leading to successful follicle formation in vitro Collectively, our in vitro experiments suggest that upon estrogen exposure, the integrity of follicle assembly in vivo is ensured by AFP.

Pregnancy outcomes of women with elevated second-trimester maternal serum alpha-fetoprotein

OBJECTIVE

The aim of this study was to investigate the overall distribution of pregnancy outcomes in women with elevated second-trimester maternal serum alpha-fetoprotein (MS-AFP), and to determine the risk of adverse pregnancy outcomes (APOs) by MS-AFP level.

MATERIALS AND METHODS

We retrospectively analyzed the clinical data of 429 women with elevated MS-AFP (≥2.5 multiple of the median (MOM)) and 1555 women with normal MS-AFP (0.5-2.49MOM) from a total of 46,741 prenatally screened singleton pregnant women. The overall distribution of APOs of the two groups, the risk of APOs by MS-AFP level, and the predictive value of elevated MS-AFP to APOs were analyzed.

RESULTS

The incidence rate of APOs in elevated MS-AFP group was significantly higher than that in normal MS-AFP group (42.89 vs. 8.23%). In elevated MS-AFP group, the top three APOs, in term of incidence rate, were structural fetal abnormalities (7.93%), spontaneous abortion (7.46%) and preterm birth (7.23%); regarding to the risk, the top three APOs were stillbirth, spontaneous abortion and early-onset preeclampsia (odds ratio 35.98, 20.81 and 8.58 respectively). For structural fetal abnormalities, MS-AFP had predictive values for fetal open neural tube defects (ONTDs), gastroschisis and multiple malformations.

CONCLUSION

Elevated MS-AFP is associated with increased risks of APOs. ONTDs complicate merely a small proportion of pregnancies with elevated MS-AFP, and the rest of them have high risks of obstetric complications. MS-AFP can help to identify these women at high risk of APOs in earlier second-trimester.

AFP promotes HCC progression by suppressing the HuR-mediated Fas/FADD apoptotic pathway

Hepatocellular carcinoma (HCC) is a major leading cause of cancer-related death worldwide. Alpha fetoprotein (AFP) is reactivated in a majority of hepatocellular carcinoma (HCC) and associated with poor patient outcomes. Although increasing evidence has shown that AFP can regulate HCC cell growth, the precise functions of AFP in hepatocarcinogenesis and the associated underlying mechanism remain incompletely understood. In this study, we demostrated that depleting AFP significantly suppressed diethylnitrosamine (DEN)-induced liver tumor progression in an AFP gene-deficient mouse model. Similarly, knocking down AFP expression inhibited human HCC cell proliferation and tumor growth by inducing apoptosis. AFP expression level was inversely associated with the apoptotic rate in mouse and human HCC specimens. Investigation of potential cross-talk between AFP and apoptotic signaling revealed that AFP exerted its growth-promoting effect by suppressing the Fas/FADD-mediated extrinsic apoptotic pathway. Mechanistically, AFP bound to the RNA-binding protein HuR, increasing the accumulation of HuR in the cytoplasm and subsequent inhibition of Fas mRNA translation. In addition, we found that inhibiting AFP enhanced the cytotoxicity of therapeutics to AFP-positive HCC cells by activating HuR-mediated Fas/FADD apoptotic signaling. Conclusion: Our study defined the pro-oncogenic role of AFP in HCC progression and uncovered a novel antiapoptotic mechanism connecting AFP to HuR-mediated Fas translation. Our findings suggest that AFP is involved in the pathogenesis and chemosensitivity of HCC and that blockade of AFP may be a promising strategy to treat advanced HCC.

A rat model of placental inflammation explains the unexplained elevated maternal serum alpha-fetoprotein associated with adverse pregnancy outcomes

AIM

It has been reported in numerous studies that elevated maternal serum alpha-fetoprotein (MS-AFP) is associated with adverse pregnancy outcomes (APO), such as pre-eclampsia, stillbirth, preterm birth and fetal growth restriction. However, the mechanism linking elevated MS-AFP and APO is obscure. In this study, we tried to explore the mechanism by using pregnant rats.

METHODS

Lipopolysaccharide (LPS) was used to induce placental inflammation in pregnant rats. Maternal serum and placental inflammatory cytokines and placental morphology were used to assess the level of placental inflammation. The incidences of APO and the levels of MS-AFP were evaluated. The expressions of alpha-fetoprotein (AFP) in the related organs and fetal serum AFP levels were detected.

RESULTS

Compared to saline-treated pregnant rats, LPS led to elevated maternal serum and placental inflammatory cytokines and a higher rate of placental inflammation. Lipopolysaccharide resulted in the features of APO and at the same time elevated MS-AFP. Maternal serum alpha-fetoprotein levels were significantly correlated to the evaluation parameters of APO. Lipopolysaccharide did not increase the expressions of AFP in fetal liver, maternal liver and placenta, but reduced the fetal serum AFP levels.

CONCLUSION

The phenomenon that elevated MS-AFP is associated with APO, which has been reported in human pregnancies, is observed in our rat model. Placental inflammation can be the potential cause linking the two manifestations together. Although the source of elevated MS-AFP is not identified, fetal blood circulation is suspected. Our study may provide an animal model for the future studies on this subject.

Proteomic Analysis of Charcoal-Stripped Fetal Bovine Serum Reveals Changes in the Insulin-like Growth Factor Signaling Pathway

Charcoal-stripped fetal bovine serum (CS-FBS) is commonly used to study androgen responsiveness and androgen metabolism in cultured prostate cancer (CaP) cells. Switching CaP cells from FBS to CS-FBS may reduce the activity of androgen receptor (AR), inhibit cell proliferation, or modulate intracellular androgen metabolism. The removal of proteins by charcoal stripping may cause changes in biological functions and has not yet been investigated. Here we profiled proteins in FBS and CS-FBS using an ion-current-based quantitative platform consisting of reproducible surfactant-aided precipitation/on-pellet digestion, long-column nanoliquid chromatography separation, and ion-current-based analysis. A total of 143 proteins were identified in FBS, among which 14 proteins including insulin-like growth factor 2 (IGF-2) and IGF binding protein (IGFBP)-2 and -6 were reduced in CS-FBS. IGF-1 receptor (IGF1R) and insulin receptor were sensitized to IGFs in CS-FBS. IGF-1 and IGF-2 stimulation fully compensated for the loss of AR activity to maintain cell growth in CS-FBS. Endogenous production of IGF and IGFBPs was verified in CaP cells and clinical CaP specimens. This study provided the most comprehensive protein profiles of FBS and CS-FBS and offered an opportunity to identify new protein regulators and signaling pathways that regulate AR activity, androgen metabolism, and proliferation of CaP cells.

Signatures of positive selection in African Butana and Kenana dairy zebu cattle

Butana and Kenana are two types of zebu cattle found in Sudan. They are unique amongst African indigenous zebu cattle because of their high milk production. Aiming to understand their genome structure, we genotyped 25 individuals from each breed using the Illumina BovineHD Genotyping BeadChip. Genetic structure analysis shows that both breeds have an admixed genome composed of an even proportion of indicine (0.75 ± 0.03 in Butana, 0.76 ± 0.006 in Kenana) and taurine (0.23 ± 0.009 in Butana, 0.24 ± 0.006 in Kenana) ancestries. We also observe a proportion of 0.02 to 0.12 of European taurine ancestry in ten individuals of Butana that were sampled from cattle herds in Tamboul area suggesting local crossbreeding with exotic breeds. Signatures of selection analyses (iHS and Rsb) reveal 87 and 61 candidate positive selection regions in Butana and Kenana, respectively. These regions span genes and quantitative trait loci (QTL) associated with biological pathways that are important for adaptation to marginal environments (e.g., immunity, reproduction and heat tolerance). Trypanotolerance QTL are intersecting candidate regions in Kenana cattle indicating selection pressure acting on them, which might be associated with an unexplored level of trypanotolerance in this cattle breed. Several dairy traits QTL are overlapping the identified candidate regions in these two zebu cattle breeds. Our findings underline the potential to improve dairy production in the semi-arid pastoral areas of Africa through breeding improvement strategy of indigenous local breeds.

Alpha-Fetoprotein: From a Diagnostic Biomarker to a Key Role in Female Fertility

Alpha-fetoprotein (AFP) is a well-known diagnostic biomarker used in medicine to detect fetal developmental anomalies such as neural tube defects or Down's syndrome, or to follow up the development of tumors such as hepatocellular carcinomas. However, and despite the fact that the protein was discovered almost half a century ago, little was known about its physiological function. The study of Afp knock-out mice uncovered a surprising function of AFP: it is essential for female fertility and for expression of normal female behaviors, and this action is mediated through its estrogen binding capacity. AFP sequestrates estrogens and by so doing protects the female developing brain from deleterious (defeminizing/masculinizing) effects of these hormones.

Physiology of Alpha-Fetoprotein as a Biomarker for Perinatal Distress: Relevance to Adverse Pregnancy Outcome

The many physiologic roles of human alpha-fetoprotein (HAFP) and its correlation with perinatal distress/pregnancy outcome are rarely addressed together in the biomedical literature, even though HAFP has long been used as a biomarker for fetal birth defects. Although the well being of the fetus can be monitored by the measurement of gestational age–dependent HAFP in biologic fluid levels (serum, amniotic fluid, urine, and vaginal fluids) throughout pregnancy, the majority of clinical reports reflect largely second trimester and (less likely) first trimester testing due to regulatory clinical restrictions. However, reports of third-trimester and pregnancy term measurement of HAFP levels performed in clinical research and/or investigational settings have gradually increased over the years and have expanded our base knowledge of AFP-associated pregnancy disorders during these stages. The different structural forms of HAFP (isoforms, epitopes, molecular variants, etc.) detected in the various biologic fluid compartments have been limited by antibody recognition of specific epitopic sites developed by the kit manufacturers based on antibody specificity, sensitivity, and precision. Concomitantly, the advances in elucidating the various biologic actions of AFP are opening new vistas toward understanding the physiologic roles of AFP during pregnancy. The present review surveys HAFP as a biomarker for fetal distress during the perinatal period in view of its structural and functional properties. An attempt is then made to relate the AFP fluid levels to adverse pregnancy complications and outcomes. Hence, the present review was divided into two major sections: (I) AFP structure and function considerations and (II) the relationship of AFP levels to the distressed fetus during the third trimester and at term.

Vascular and Immunobiology of the Circulatory Sphingosine 1-Phosphate Gradient

Vertebrates are endowed with a closed circulatory system, the evolution of which required novel structural and regulatory changes. Furthermore, immune cell trafficking paradigms adapted to the barriers imposed by the closed circulatory system. How did such changes occur mechanistically? We propose that spatial compartmentalization of the lipid mediator sphingosine 1-phosphate (S1P) may be one such mechanism. In vertebrates, S1P is spatially compartmentalized in the blood and lymphatic circulation, thus comprising a sharp S1P gradient across the endothelial barrier. Circulatory S1P has critical roles in maturation and homeostasis of the vascular system as well as in immune cell trafficking. Physiological functions of S1P are tightly linked to shear stress, the key biophysical stimulus from blood flow. Thus, circulatory S1P confinement could be a primordial strategy of vertebrates in the development of a closed circulatory system. This review discusses the cellular and molecular basis of the S1P gradients and aims to interpret its physiological significance as a key feature of the closed circulatory system.

Alpha-foetoprotein (AFP): A multi-purpose marker in hepatocellular carcinoma

Alpha-foetoprotein (AFP), one of the first protein tumour markers discovered, is widely used today in clinical practice. Its application for the screening and diagnosis of hepatocellular carcinoma (HCC), the most frequent form of primary liver tumour, is a matter of extensive debate. In addition to the studies focused on the role of the AFP in the diagnosis of HCC, in recent years AFP has been used to guide the therapeutic choice in HCC and monitor the treatment. Here, we summarize the latest studies that show the interest of AFP quantification in determining the suitability of liver transplantation or to follow-up on patients receiving the targeted treatment sorafenib. We also highlight the recent studies showing the active role of AFP in tumour progression, and the new modes of regulation of this tumour marker. Among these is the regulation of AFP through tumour proteostasis and the Unfolded Protein Response (UPR). We discuss the implications of this new knowledge in the therapeutic context, in terms of interpreting serum levels of AFP, and the new perspectives offered by AFP for the study of tumour proteostasis.

Circulating predictive and diagnostic biomarkers for hepatitis B virus-associated hepatocellular carcinoma

Chronic hepatitis B virus (HBV) infected patients have an almost 100-fold increased risk to develop hepatocellular carcinoma (HCC). HCC is the fifth most common and third most deadly cancer worldwide. Up to 50% of newly diagnosed HCC cases are attributed to HBV infection. Early detection improves survival and can be achieved through regular screening. Six-monthly abdominal ultrasound, either alone or in combination with alpha-fetoprotein serum levels, has been widely endorsed for this purpose. Both techniques however yield limited diagnostic accuracy, which is not improved when they are combined. Alternative circulating or histological markers to predict or diagnose HCC are therefore urgently needed. Recent advances in systems biology technologies have enabled the identification of several new putative circulating biomarkers. Although results from studies assessing combinations of these biomarkers are promising, evidence for their clinical utility remains low. In addition, most of the studies conducted so far show limitations in design. Attention must be paid for instance to different ethnicities and different etiologies when studying biomarkers for hepatocellular carcinoma. This review provides an overview on the current understandings and recent progress in the field of diagnostic and predictive circulating biomarkers for hepatocellular carcinoma in chronically infected HBV patients and discusses the future prospects.

Genome-wide association and identification of candidate genes for age at puberty in swine

Background

Reproductive efficiency has a great impact on the economic success of pork production. Gilts comprise a significant portion of breeding females and gilts that reach puberty earlier tend to stay in the herd longer and be more productive. About 10 to 30 % of gilts never farrow a litter and the most common reasons for removal are anestrus and failure to conceive. Puberty in pigs is usually defined as the female’s first estrus in the presence of boar stimulation. Genetic markers associated with age at puberty will allow for selection on age at puberty and traits correlated with sow lifetime productivity.

Results

Gilts (n = 759) with estrus detection measurements ranging from 140–240 days were genotyped using the Illumina PorcineSNP60 BeadChip and SNP were tested for significant effects with a Bayesian approach using GenSel software. Of the available 8111 five-marker windows, 27 were found to be statistically significant with a comparison-wise error of P < 0.01. Ten QTL were highly significant at P < 0.005 level. Two QTL, one on SSC12 at 15 Mb and the other on SSC7 at 75 Mb, explained 16.87 % of the total genetic variance. The most compelling candidate genes in these two regions included the growth hormone gene (GH1) on SSC12 and PRKD1 on SSC7. Several loci confirmed associations previously identified for age at puberty in the pig and loci for age at menarche in humans.

Conclusions

Several of the loci identified in this study have a physiological role for the onset of puberty and a genetic basis for sexual maturation in humans. Understanding the genes involved in regulation of the onset of puberty would allow for the improvement of reproductive efficiency in swine. Because age at puberty is a predictive factor for sow longevity and lifetime productivity, but not routinely measured or selected for in commercial herds, it would be beneficial to be able to use genomic or marker-assisted selection to improve these traits.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-016-0352-y) contains supplementary material, which is available to authorized users.

2D DIGE proteomic analysis highlights delayed postnatal repression of α-fetoprotein expression in homocystinuria model mice

Cystathionine β-synthase-deficient (Cbs (-/-)) mice, an animal model for homocystinuria, exhibit hepatic steatosis and juvenile semilethality via as yet unknown mechanisms. The plasma protein profile of Cbs (-/-) mice was investigated by proteomic analysis using two-dimensional difference gel electrophoresis and matrix-assisted laser desorption/ionization-time of flight/mass spectrometry. We found hyperaccumulation of α-fetoprotein (AFP) and downregulation of most other plasma proteins. AFP was highly expressed in fetal liver, but its expression declined dramatically via transcriptional repression after birth in both wild-type and Cbs (-/-) mice. However, the repression was delayed in Cbs (-/-) mice, causing high postnatal AFP levels, which may relate to transcriptional repression of most plasma proteins originating from liver and the observed hepatic dysfunction.

Absence of Female-Typical Pheromone-Induced Hypothalamic Neural Responses and Kisspeptin Neuronal Activity in α-Fetoprotein Knockout Female Mice

Pheromones induce sexually dimorphic neuroendocrine responses, such as LH secretion. However, the neuronal network by which pheromones are converted into signals that will initiate and modulate endocrine changes remains unclear. We asked whether 2 sexually dimorphic populations in the anteroventral periventricular and periventricular nuclei that express kisspeptin and tyrosine hydroxylase (TH) are potential candidates that will transduce the olfactory signal to the neuroendocrine system. Furthermore, we assessed whether this transduction is sensitive to perinatal actions of estradiol by using female mice deficient in α-fetoprotein (AfpKO), which lack the protective actions of Afp against maternal estradiol. Wild-type (WT) and AfpKO male and female mice were exposed to same- versus opposite-sex odors and the expression of Fos (the protein product of the immediate early gene c-Fos) was analyzed along the olfactory projection pathways as well as whether kisspeptin, TH, and GnRH neurons are responsive to opposite-sex odors. Male odors induced a female-typical Fos expression in target forebrain sites of olfactory inputs involved in reproduction in WT, but not in AfpKO females, whereas female odors induced a male-typical Fos expression in males of both genotypes. In WT females, opposite-sex odors induced Fos in kisspeptin and TH neurons, whereas in AfpKO females and WT males, only a lower, but still significant, Fos expression was observed in TH but not in kisspeptin neurons. Finally, opposite-sex odors did not induce any significant Fos expression in GnRH neurons of both sexes or genotypes. Our results strongly suggest a role for fetal estrogen in the sexual differentiation of neural responses to sex-related olfactory cues.

Placental extracts induce the expression of antioxidant enzyme genes and suppress melanogenesis in B16 melanoma cells

One of the activities of placental extracts (PEs) is skin-whitening effect, but the physiological and genetic mechanism for this effect has not yet been clarified. Here, we focus on PE as a regulator of antioxidant enzyme genes. Porcine PE was prepared, and its activity was investigated in B16 melanoma cells. PE treatment decreased the melanin content of UV-irradiated B16 cells in a dose-dependent manner. PE directly reduced the enzyme activity of tyrosinase in a cell-free assay. In addition, PE treatment increased the gene expression of cytosolic superoxide dismutase (SOD-1), extracellular SOD (SOD-3) and catalase but did not affect the expression of tyrosinase. Moreover, PE protected the B16 cells from H2O2-induced cell death. Taken together, our data suggest that PEs could play a role not only as a suppressor of melanin synthesis but also as a regulator of antioxidant genes and might protect the skin against oxidative stress.

Albuminoid genes: evolving at the interface of dispensability and selection

The albuminoid gene family comprises vitamin D-binding protein (GC), alpha-fetoprotein (AFP), afamin (AFM), and albumin (ALB). Albumin is the most abundant human serum protein, and, as the other family members, acts as a transporter of endogenous and exogenous substances including thyroxine, fatty acids, and drugs. Instead, the major cargo of GC is 25-hydroxyvitamin D. We performed an evolutionary study of albuminoid genes and we show that ALB evolved adaptively in mammals. Most positively selected sites are located within albumin-binding sites for fatty acids and thyroxine, as well as at the contact surface with neonatal Fc receptor. Positive selection was also detected for residues forming the prostaglandin-binding pocket. Adaptation to hibernation/torpor might explain the signatures of episodic positive selection we detected for few mammalian lineages. Application of a population genetics-phylogenetics approach showed that purifying selection represented a major force acting on albuminoid genes in both humans and chimpanzees, with the strongest constraint observed for human GC. Population genetic analysis revealed that GC was also the target of locally exerted selective pressure, which drove the frequency increase of different haplotypes in distinct human populations. A search for known variants that modulate GC and 25-hydroxyvitamin D concentrations revealed linkage disequilibrium with positively selected variants, although European and Asian major GC haplotypes carry alleles with reported opposite effect on GC concentration. Data herein indicate that albumin, an extremely abundant housekeeping protein, was the target of pervasive and episodic selection in mammals, whereas GC represented a selection target during the recent evolution of human populations.

Alpha-fetoprotein, identified as a novel marker for the antioxidant effect of placental extract, exhibits synergistic antioxidant activity in the presence of estradiol

Placenta, as a reservoir of nutrients, has been widely used in medical and cosmetic materials. Here, we focused on the antioxidant properties of placental extract and attempted to isolate and identify the main antioxidant factors. Porcine placental extracts were prepared through homogenization or acid hydrolysis, and their antioxidant activity was investigated in the human keratinocyte HaCaT cell line. Treatment with homogenized placental extract (H-PE) increased the cell viability of H2O2-treated HaCaT cells more than two-fold. H-PE treatment suppressed H2O2-induced apoptotic and necrotic cell death and decreased intracellular ROS levels in H2O2-treated HaCaT cells. The antioxidant factors in H-PE were found to be thermo-unstable and were thus expected to include proteins. The candidate antioxidant proteins were fractionated with cation-exchange, anion-exchange, and size-exclusion chromatography, and the antioxidant properties of the chromatographic fractions were investigated. We obtained specific antioxidant fractions that suppressed ROS generation and ROS-induced DNA strand breaks. From silver staining and MALDI-TOF analyses, alpha-fetoprotein (AFP) precursor was identified as a main marker for the antioxidant effect of H-PE. Purified AFP or ectopically expressed AFP exhibited synergistic antioxidant activity in the presence of estradiol. Taken together, our data suggest that AFP, a serum glycoprotein produced at high levels during fetal development, is a novel marker protein for the antioxidant effect of the placenta that exhibits synergistic antioxidant activity in the presence of estradiol.

Alpha-fetoprotein, a fascinating protein and biomarker in neurology

Alpha-fetoprotein (AFP) is present in fetal serum in concentrations up to 5,000,000 μg/l. After birth, AFP gene expression is turned down with a subsequent fall of the serum concentrations of this albumin-like protein to 'adult values' of circa 0.5-15 μg/l from the age of 2 years onwards. Irrespective of its assumed important functions, individuals with AFP deficiency appear fully healthy. The other way around, the presence of AFP in the circulation after the first years of life doesn't seem to harm, since individuals with 'hereditary persistence of AFP' are also without clinical abnormalities. During pregnancy, AFP (in maternal serum) has long been recognized as a marker for congenital anomalies of the fetus. Equally well known is AFP as biomarker for hepatocellular carcinoma and some other malignancies. There are at least four neurodegenerative disorders, all inherited as autosomal recessive traits and characterized by the presence of cerebellar ataxia, abnormal ocular movements, and neuropathy, for which an elevated concentration of serum AFP is an important diagnostic biomarker. The availability of a reliable biomarker is not only important during screening or diagnostic processes, but is also relevant for objective follow-up during (future) therapeutic interventions.

A comparative analysis of synonymous codon usage bias pattern in human albumin superfamily

Synonymous codon usage bias is an inevitable phenomenon in organismic taxa across the three domains of life. Though the frequency of codon usage is not equal across species and within genome in the same species, the phenomenon is non random and is tissue-specific. Several factors such as GC content, nucleotide distribution, protein hydropathy, protein secondary structure, and translational selection are reported to contribute to codon usage preference. The synonymous codon usage patterns can be helpful in revealing the expression pattern of genes as well as the evolutionary relationship between the sequences. In this study, synonymous codon usage bias patterns were determined for the evolutionarily close proteins of albumin superfamily, namely, albumin, α-fetoprotein, afamin, and vitamin D-binding protein. Our study demonstrated that the genes of the four albumin superfamily members have low GC content and high values of effective number of codons (ENC) suggesting high expressivity of these genes and less bias in codon usage preferences. This study also provided evidence that the albumin superfamily members are not subjected to mutational selection pressure.

Alpha-fetoprotein: a renaissance. Tumour Biol. 2013;34:2075-2091. [PMID: 23765762 DOI: 10.1007/s13277-013-0904-y]

Alpha-fetoprotein (AFP) is a major mammalian embryo-specific and tumor-associated protein that is also present in small quantities in adults at normal conditions. Discovery of the phenomenon of AFP biosynthesis in carcinogenesis by G. Abelev and Yu. Tatarinov 50 years ago, in 1963, provoked intensive studies of this protein. AFPs of some mammalian species were isolated, purified and physico-chemically and immunochemically characterized. Despite the significant success in study of AFP, its three-dimensional structure, mechanisms of receptor binding along with a structure of the receptor itself and, what is the most important, its biological role in embryo- and carcinogenesis remain still obscure. Due to difficulties linked with methodological limitations, research of AFP was to some extent extinguished by the 1990 s. However, over the last decade a growing number of investigations of AFP and its usage as a tumor-specific biomarker have been observed. This was caused by the use of new technologies, primarily, computer-based and genetic engineering approaches in studying of this very important oncodevelopmental protein. Our review summarizes efforts of different scientific groups throughout the world in studying AFP for 50 years with emphasis on detailed description of recent achievements in this field.

Characterization of alpha-fetoprotein levels in three dolphin species: development of sensitive immunoassays for analysis of the pregnancy-associated variations

A single radial immunodiffusion (SRID) assay and a chemiluminescent immunoassay (CLIA) were initially developed for alpha-fetoprotein (AFP) of the striped dolphin. Utilizing these developed assays, we investigated pregnancy-associated changes in the levels of AFP in the sera of fetuses and pregnant females of three dolphin species; samples were either collected from captive individuals or obtained as fishery by-products. The concentrations of AFP in the fetal serum ranged from 419.0 to 2026.3 μg/ml in the striped dolphin, 12.6 to 1218.7 μg/ml (for an AFP equivalent; eqAFP) in the common bottlenose dolphin and 770.6 to 3129.1 μg eqAFP/ml in the Risso's dolphin. AFP levels decreased with increased fetal size in fetuses over 20 cm in length. The concentrations of AFP in sera of pregnant females ranged from 7.18 to 8068.7 ng/ml in the striped dolphin, 6.6 to 1241.1 ng eqAFP/ml in the common bottlenose dolphin and 3.4 to 2868.7 ng eqAFP/ml in the Risso's dolphin. The levels in most pregnant females were equal to or lower than those found in males and nonpregnant individuals, although a few pregnant females exhibited extremely high levels (in the range of hundreds to thousands of nanograms per milliliter). Such high levels of AFP were not observed during pseudopregnancy. To our knowledge, this is the first report on basal profiles for serum AFP levels in small odontocetes. The profiles indicated that AFP may play a significant role during embryonic development, although maternal levels do not appear to be a diagnostic biomarker for monitoring pregnancy.

Liver transplantation should be offered to patients with small solitary hepatocellular carcinoma and a positive serum alpha fetoprotein rather than resection

BACKGROUND

As debate continues as to what surgical modality should be offered to patients with hepatocellular carcinoma, the authors submit that serum α-fetoprotein (AFP) is an important variable to consider.

METHODS

Using the Surveillance, Epidemiology and End Results database, patients with solitary tumors within the Milan criteria were further stratified into 2 groups, those who underwent orthotopic liver transplantation (OLT) and those who underwent segmentectomy, lobectomy, or extended lobectomy (resection). Patients were further grouped according to serum AFP status (negative or positive). Relative survival was retrospectively evaluated for 3 years using the log-rank test.

RESULTS

In the AFP-negative group, resection (n = 165) offered equivalent survival compared with OLT (n = 116); 3-year survival was 73.8% and 81.6%, respectively (P = .245). In the AFP-positive group, 3-year survival for resection (n = 200) was 59%, while survival was 75.3% for OLT (n = 181), which showed a clear survival advantage (P = .001).

CONCLUSIONS

The results of this study demonstrate that patients with solitary hepatocellular carcinoma lesions within the Milan criteria and AFP-positive status should not undergo resection but rather be offered OLT.

Organizational and activational effects of sex steroids on kisspeptin neuron development

Kisspeptin, encoded by the Kiss1 gene, is a neuropeptide required for puberty and adult reproductive function. Understanding the regulation and development of the kisspeptin system provides valuable knowledge about the physiology of puberty and adult fertility, and may provide insights into human pubertal or reproductive disorders. Recent studies, particularly in rodent models, have assessed how kisspeptin neurons develop and how hormonal and non-hormonal factors regulate this developmental process. Exposure to sex steroids (testosterone and estradiol) during critical periods of development can induce organizational (permanent) effects on kisspeptin neuron development, with respect to both sexually dimorphic and non-sexually dimorphic aspects of kisspeptin biology. In addition, sex steroids can also impart activational (temporary) effects on kisspeptin neurons and Kiss1 gene expression at various times during neonatal and peripubertal development, as they do in adulthood. Here, we discuss the current knowledge--and in some cases, lack thereof--of the influence of hormones and other factors on kisspeptin neuronal development.

Organogenesis of the ovary: a comparative review on vertebrate ovary formation

The general perspective of ovary organogenesis is that the ovary is the default organ which develops in the absence of testis-promoting factors. Testis formation, on the other hand, is a male-specific event promoted by active components that override the default ovarian process. However, when comparing the sex determination mechanism among different vertebrate species, it is apparent that this default view of ovary formation can only be applied to mammals. In species such as reptiles and birds, ovary formation is an active process stimulated by estrogen. Remnants of this estrogen-dominant pathway are still present in marsupials, a close relative of eutherian mammals, like humans and mice. Although initial formation of the mammalian ovary has become strictly regulated by genetic components and is therefore independent of estrogen, the feminizing effect of estrogen regains its command in adult ovaries. When estrogen production, or its signaling, is inhibited, transdifferentiation of ovarian tissues to testis structures occur in adult females. Taken together, these observations prompt us to reconsider the process of ovary organogenesis as the default organ and question if testis development is actually the default pathway.

Cystathionine β-synthase deficiency causes infertility by impairing decidualization and gene expression networks in uterus implantation sites

Hyperhomocysteinemia has been reported in human reproduction as a risk factor for early pregnancy loss, preeclampsia, and congenital birth defects like spina bifida. Female infertility was also observed in cystathionine beta synthase-deficient mice ( Cbs-KO) as an animal model for severe hyperhomocysteinemia. The aim for the present research was to elucidate the time-point of pregnancy loss and to pinpoint gene and cellular changes involved in the underlying pathological mechanism. By mating 90-day-old wild-type and Cbs-KO female mice with their homologous male partners, we found that pregnancy loss in Cbs-KO occurred between the 8th and 12th gestation day during placenta formation. DNA microarrays were carried out on uterus from implantation and interimplantation samples obtained on day 8. The results allowed us to select genes potentially involved in embryo death; these were individually confirmed by RT-qPCR, and their expressions were also followed throughout pregnancy. We found that changes in expression of Calb1, Ttr, Expi, Inmt, Spink3, Rpgrip1, Krt15, Mt-4, Gzmc, Gzmb, Tdo2, and Afp were important for pregnancy success, since a different regulation in Cbs-KO mice was found. Also, differences in relationships among selected genes were observed, indicating a dysregulation of these genes in Cbs-KO females. In conclusion, our data provide more information on the gene expression cascade and its timely regulated process required for a successful pregnancy. In addition, we unveil new potential avenues to explore further investigations in pregnancy loss.

Female mice deficient in alpha-fetoprotein show female-typical neural responses to conspecific-derived pheromones

The neural mechanisms controlling sexual behavior are sexually differentiated by the perinatal actions of sex steroid hormones. We recently observed using female mice deficient in alpha-fetoprotein (AFP-KO) and which lack the protective actions of AFP against maternal estradiol, that exposure to prenatal estradiol completely defeminized the potential to show lordosis behavior in adulthood. Furthermore, AFP-KO females failed to show any male-directed mate preferences following treatment with estradiol and progesterone, indicating a reduced sexual motivation to seek out the male. In the present study, we asked whether neural responses to male- and female-derived odors are also affected in AFP-KO female mice. Therefore, we compared patterns of Fos, the protein product of the immediate early gene, c-fos, commonly used as a marker of neuronal activation, between wild-type (WT) and AFP-KO female mice following exposure to male or estrous female urine. We also tested WT males to confirm the previously observed sex differences in neural responses to male urinary odors. Interestingly, AFP-KO females showed normal, female-like Fos responses, i.e. exposure to urinary odors from male but not estrous female mice induced equivalent levels of Fos protein in the accessory olfactory pathways (e.g. the medial part of the preoptic nucleus, the bed nucleus of the stria terminalis, the amygdala, and the lateral part of the ventromedial hypothalamic nucleus) as well as in the main olfactory pathways (e.g. the piriform cortex and the anterior cortical amygdaloid nucleus), as WT females. By contrast, WT males did not show any significant induction of Fos protein in these brain areas upon exposure to either male or estrous female urinary odors. These results thus suggest that prenatal estradiol is not involved in the sexual differentiation of neural Fos responses to male-derived odors.

Alpha-fetoprotein-thymidine kinase-luciferase knockin mice: a novel model for dual modality longitudinal imaging of tumorigenesis in liver

BACKGROUND & AIMS

Hepatocellular carcinoma (HCC) is frequently a lethal disease and one of the few malignancies that is still increasing in incidence around the world. Better animal models are highly desired to investigate the molecular basis of HCC and to develop novel therapeutic strategies. Alpha-fetoprotein (Afp) gene is expressed in fetal liver, silenced soon after birth, and highly re-expressed in hepatocellular carcinomas (HCC). We aimed to take advantage of the dramatic re-expression of the Afp gene in HCC to develop a hepatocarcinogenesis reporter (HCR) mouse model for dual-modality, longitudinal in vivo imaging of liver tumor development, and progression.

METHODS

Knock in mice were established by placing a thymidinekinase (tk)-luciferase (luc) reporter gene cassette under the transcriptional control of the endogenous Afp promoter. DEN, a liver carcinogen, was used to induce liver tumors, which was monitored by both luc-based bioluminescent (BL) and tk-based positron emission tomography (PET) imaging.

RESULTS

The expression profile of luc was identical to that of the endogenous Afp gene during development. As early as 2 months after the exposure to DEN, BLI revealed multifocal signals in the liver, long before the appearance of histologically apparent neoplastic lesions. By 6 months, BL and PET dual imaging showed strong signals in malignant HCC. By serendipity, a strong BL signal was also detected in adult testes, a previously unknown site of Afp expression.

CONCLUSIONS

The HCR model enables longitudinal monitoring of liver tumor development and progression, providing a powerful tool in developing chemoprevention and therapeutic strategies for HCC.

Diverse roles for sex hormone-binding globulin in reproduction

Sex hormone-binding globulin (SHBG) transports androgens and estrogens in blood and regulates their access to target tissues. Hepatic production of SHBG fluctuates throughout the life cycle and is influenced primarily by metabolic and hormonal factors. Genetic differences also contribute to interindividual variations in plasma SHBG levels. In addition to controlling the plasma distribution, metabolic clearance, and bioavailability of sex steroids, SHBG accumulates in the extravascular compartments of some tissues and in the cytoplasm of specific epithelial cells, where it exerts novel effects on androgen and estrogen action. In mammals, the gene-encoding SHBG is expressed primarily in the liver but also at low levels in other tissues, including the testis. In subprimate species, Shbg expression in Sertoli cells is under the control of follicle-stimulating hormone and produces the androgen-binding protein that influences androgen actions in the seminiferous tubules and epididymis. In humans, the SHBG gene is not expressed in Sertoli cells, but its expression in germ cells produces an SHBG isoform that accumulates in the acrosome. In fish, Shbg is produced by the liver but has a unique function in the gill as a portal for natural steroids and xenobiotics, including synthetic steroids. However, salmon have retained a second, poorly conserved Shbg gene that is expressed only in ovary, muscle, and gill and that likely exerts specialized functions in these tissues. The present review compares the production and functions of SHBG in different species and its diverse effects on reproduction.

Zhx2 and Zbtb20: novel regulators of postnatal alpha-fetoprotein repression and their potential role in gene reactivation during liver cancer

The mouse alpha-fetoprotein (AFP) gene is abundantly expressed in the fetal liver, normally silent in the adult liver but is frequently reactivated in hepatocellular carcinoma. The basis for AFP expression in the fetal liver has been studied extensively. However, the basis for AFP reactivation during hepatocarcinogenesis is not well understood. Two novel factors that control postnatal AFP repression, Zhx2 and Zbtb20, were recently identified. Here, we review the transcription factors that regulate AFP in the fetal liver, as well as Zhx2 and Zbtb20, and raise the possibility that the loss of these postnatal repressors may be involved in AFP reactivation in liver cancer.

Potential contribution of prenatal estrogens to the sexual differentiation of mate preferences in mice

The neural mechanisms controlling sexual behavior are sexually differentiated by perinatal actions of gonadal hormones. We recently observed using female mice deficient in alpha-fetoprotein (AFP-KO) and which lack the protective actions of AFP against maternal estrogens, that exposure to prenatal estrogens completely defeminized their potential to show lordosis behavior in adulthood. Therefore, we determined here whether mate preferences were also affected in female AFP-KO mice. We observed a robust preference for an estrous female over an intact male in female AFP-KO mice, which were ovariectomized in adulthood and subsequently treated with estradiol and progesterone, whereas similarly treated WT females preferred the intact male over the estrous female. Gonadally intact WT males preferred the estrous female over the male, but only when visual cues were blocked by placing stimulus animals behind opaque partitions. Furthermore, when given the choice between an intact male and a castrated male, WT females preferred the intact male, whereas AFP-KO females showed no preference. Finally when given the choice between an estrous female and an ovariectomized female, WT males preferred the estrous female whereas AFP-KO females preferred the ovariectomized female or showed no preference depending on whether they could see the stimulus animals or not. Taken together, when AFP-KO females are tested under estrous conditions, they do not show any male-directed preferences, indicating a reduced sexual motivation to seek out the male in these females. However, they do not completely resemble males in their mate preferences suggesting that the male-typical pattern of mate preferences is not solely organized by prenatal estrogens.

Male-like sexual behavior of female mouse lacking fucose mutarotase

Background

Mutarotases are recently characterized family of enzymes that are involved in the anomeric conversions of monosaccharides. The mammalian fucose mutarotase (FucM) was reported in cultured cells to facilitate fucose utilization and incorporation into protein by glycosylation. However, the role of this enzyme in animal has not been elucidated.

Results

We generated a mutant mouse specifically lacking the fucose mutarotase (FucM) gene. The FucM knockout mice displayed an abnormal sexual receptivity with a drastic reduction in lordosis score, although the animals were fertile due to a rare and forced intromission by a typical male. We examined the anteroventral periventricular nucleus (AVPv) of the preoptic region in brain and found that the mutant females showed a reduction in tyrosine hydoxylase positive neurons compared to that of a normal female. Furthermore, the mutant females exhibited a masculine behavior, such as mounting to a normal female partner as well as showing a preference to female urine. We found a reduction of fucosylated serum alpha-fetoprotein (AFP) in a mutant embryo relative to that of a wild-type embryo.

Conclusions

The observation that FucM^-/- female mouse exhibits a phenotypic similarity to a wild-type male in terms of its sexual behavior appears to be due to the neurodevelopmental changes in preoptic area of mutant brain resembling a wild-type male. Since the previous studies indicate that AFP plays a role in titrating estradiol that are required to consolidate sexual preference of female mice, we speculate that the reduced level of AFP in FucM^-/- mouse, presumably resulting from the reduced fucosylation, is responsible for the male-like sexual behavior observed in the FucM knock-out mouse.

The alpha-fetoprotein knock-out mouse model suggests that parental behavior is sexually differentiated under the influence of prenatal estradiol

In rodent species, sexual differentiation of the brain for many reproductive processes depends largely on estradiol. This was recently confirmed again by using the alpha-fetoprotein knockout (AFP-KO) mouse model, which lacks the protective actions of alpha-fetoprotein against maternal estradiol and as a result represents a good model to determine the contribution of prenatal estradiol to the sexual differentiation of the brain and behavior. Female AFP-KO mice were defeminized and masculinized with regard to their neuroendocrine responses as well as sexual behavior. Since parental behavior is also strongly sexually differentiated in mice, we used the AFP-KO mouse model here to ask whether parental responses are differentiated prenatally under the influence of estradiol. It was found that AFP-KO females showed longer latencies to retrieve pups to the nest and also exhibited lower levels of crouching over the pups in the nest in comparison to WT females. In fact, they resembled males (WT and AFP-KO). Other measures of maternal behavior, for example the incidence of infanticide, tended to be higher in AFP-KO females than in WT females but this increase failed to reach statistical significance. The deficits observed in parental behavior of AFP-KO females could not be explained by any changes in olfactory function, novelty recognition or anxiety. Thus our results suggest that prenatal estradiol defeminizes the parental brain in mice.

Alpha-fetoprotein related gene (ARG): a new member of the albumin gene family that is no longer functional in primates

The serum albumin gene family is comprised of albumin, alpha-fetoprotein, alpha-albumin (afamin), and the more distantly related Vitamin D binding protein. These genes arose from a common ancestor through a series of duplication events, are expressed primarily in the liver and tightly linked in all species where this has been investigated. Here, we describe a fifth member of the albumin gene family that we have named Alpha-fetoprotein Related Gene (ARG) since it exhibits greatest similarity to this family member. ARG is activated in the liver perinatally, but is expressed at very low levels. The ARG gene is present and intact in the mouse, rat, dog and horse genomes. In contrast, the ARG gene in human, chimpanzee, rhesus monkey, and marmoset contains a number of mutations common to all four species, indicating that this gene has been an inactive pseudogene in primates for at least 40 million years. Low expression and aberrant splicing of the ARG gene in the mouse liver suggests that ARG may have less functional significance than other members of the serum albumin gene family even in species where it is still intact.

Cytoplasmic alpha-fetoprotein functions as a co-repressor in RA-RAR signaling to promote the growth of human hepatoma Bel 7402 cells. Cancer Lett. 2009;285:190-199. [PMID: 19501957 DOI: 10.1016/j.canlet.2009.05.014]

The role of AFP in the retinoic acid-RAR signaling pathway was investigated in human hepatoma Bel 7402 cells. The results showed that AFP and RAR-beta were co-localized and interacted in cytoplasm. AFP may inhibit translocation of RAR-beta into the nucleus via competitive binding to RAR-beta with ATRA, which was reversed by AFP-siRNA transfection. Our data suggest that the ATRA resistance of Bel 7402 cells is at least in part attributable to their high level of cytoplasmic AFP. Thus, by counteracting the effect of AFP, it may be possible to increase the sensitivity of tumor cells to ATRA.

Study on correlation of signal molecule genes and their receptor-associated genes with rat liver regeneration

To investigate the effect of signal molecules and their receptor-associated genes on rat liver regeneration (LR) at the transcriptional level, the associated genes were originally obtained by retrieving the databases and related scientific publications; their expression profiles in rat LR were then checked using the Rat Genome 230 2.0 microarray. The LR-associated genes were identified by comparing gene expression difference between partial hepatectomy groups and operation-control groups. A total of 454 genes were proved to be LR related. The genes associated with the seven kinds of signal molecules (steroid hormones, fatty acid derivatives, protein and polypeptide hormones, amino acids and their derivatives, choline, cytokines, and gas signal molecules) were detected to be enriched in a cluster characterized by upregulated expression in LR. The number of genes related to the seven kinds of signal molecules was, in sequence, 63, 27, 100, 102, 16, 166, and 18. The 1027 frequencies of upregulation and 823 frequencies of downregulation in total as well as 42 types of different expression patterns suggest the complex and diverse gene expression changes in LR. It is presumed that signal molecules played an important role in metabolism, inflammation, cell proliferation, growth and differentiation, etc., during rat LR.

Alpha-fetoprotein (AFP)-derived peptides as epitopes for hepatoma immunotherapy: a commentary

The various immunological roles of human alpha-fetoprotein (HAFP), and its correlation with hepatomas, that is, hepatocellular carcinomas (HCCs), are not often addressed together in biomedical reports considering that HAFP is an established biomarker for hepatomas. Studies reporting measurement of HAFP serum levels in hepatoma patients in basic/clinical research settings has greatly increased over the years. Recent reports have now expanded our base knowledge in the mounting of an immune response against AFP, a self antigen, during hepatoma tumorigenesis. Advances in the detection and identification of AFP-derived peptide epitopes are opening new vistas of knowledge regarding the immunological role of AFP-peptides as T cell stimulating antigens in the course of hepatoma growth and progression. The present commentary addresses HAFP-derived peptides as immunologic responders in HCC and their use in the study and generation of AFP-peptide sensitized T cells directed against hepatoma cells. Attempts were further made to relate the AFP-derived peptide epitopes to T cell activities during the course of hepatoma immunotherapies and to profile the traits and properties of the peptides themselves. Hence, the present commentary was divided into two sections; (1) the characterization, properties, and traits of AFP peptide epitopes, and (2) the use of AFP-derived peptides in the therapeutic induction of T cells primed against hepatoma cells using both in vivo and in vitro models.

Zinc finger protein ZBTB20 is a key repressor of alpha-fetoprotein gene transcription in liver

The alpha-fetoprotein (AFP) gene is highly activated in fetal liver but is dramatically repressed shortly after birth. The mechanisms that underlie AFP transcriptional repression in postpartum liver are not well understood. AFP enhancer, repressor region, and promoter are implicated to be involved in AFP postnatal repression, but the major transcriptional repressor remains undefined. We previously identified a zinc finger protein gene ZBTB20. To determine its physiological functions in vivo, we have generated hepatocyte-specific ZBTB20 knockout mice by the Cre/loxP approach and demonstrated here that ZBTB20 ablation in liver led to dramatic derepression of the AFP gene in entire liver throughout adult life, although the hepatocytes were normally under nonproliferating status. Furthermore, we found that ZBTB20 was a transcriptional repressor capable of specifically inhibiting AFP promoter-driven transcriptional activity. Liver chromatin immunoprecipitation and mobility shift assays showed that ZBTB20 bound to AFP promoter directly. ZBTB20 was developmentally activated in liver after birth and inversely correlated with its AFP gene expression, suggesting that activated ZBTB20 expression in liver mediated AFP gene repression. Our data point to ZBTB20 as a key regulator governing AFP gene transcription and postulate a new model for the postnatal gene repression of AFP in liver.

Alpha-fetoprotein, stem cells and cancer: how study of the production of alpha-fetoprotein during chemical hepatocarcinogenesis led to reaffirmation of the stem cell theory of cancer

Identification of the cells in the liver that produce alpha-fetoprotein during development, in response to liver injury and during the early stages of chemical hepatocarcinogenesis led to the conclusion that maturation arrest of liver-determined tissue stem cells was the cellular process that gives rise to hepatocellular carcinomas. When the cellular changes in these processes were compared to that of the formation of teratocarcinomas, the hypothesis arose that all cancers arise from maturation arrest of tissue-determined stem cells. This was essentially a reinterpretation of the embryonal rest theory of cancer whereby tissue stem cells take the role of embryonal rests. A corollary of the stem cell theory of the origin of cancer is that cancers contain the same functional cell populations as normal tissues: stem cells, transit-amplifying cells and mature cells. Cancer stem cells retain the essential feature of normal stem cells: the ability to self-renew. Growth of cancers is due to continued proliferation of cancer transit-amplifying cells that do not differentiate to mature cells (maturation arrest). On the other hand, cancer stem cells generally divide very rarely and contribute little to tumor growth. However, the presence of cancer stem cells in tumors is believed to be responsible for the properties of immortalization, transplantability and resistance to therapy characteristic of cancers. Current therapies for cancer (chemotherapy, radiotherapy, antiangiogenesis and differentiation therapy) are directed against the cancer transit-amplifying cells. When these therapies are discontinued, the cancer reforms from the cancer stem cells. Therapy directed toward interruption of the cell signaling pathways that maintain cancer stem cells could lead to new modalities to the prevention of regrowth of the cancer.

Fetal alcohol syndrome (FAS) in C57BL/6 mice detected through proteomics screening of the amniotic fluid

BACKGROUND

Fetal Alcohol Syndrome (FAS), a severe consequence of the Fetal Alcohol Spectrum Disorders, is associated with craniofacial defects, mental retardation, and stunted growth. Previous studies in C57BL/6J and C57BL/6N mice provide evidence that alcohol-induced pathogenesis follows early changes in gene expression within specific molecular pathways in the embryonic headfold. Whereas the former (B6J) pregnancies carry a high-risk for dysmorphogenesis following maternal exposure to 2.9 g/kg alcohol (two injections spaced 4.0 h apart on gestation day 8), the latter (B6N) pregnancies carry a low-risk for malformations. The present study used this murine model to screen amniotic fluid for biomarkers that could potentially discriminate between FAS-positive and FAS-negative pregnancies.

METHODS

B6J and B6N litters were treated with alcohol (exposed) or saline (control) on day 8 of gestation. Amniotic fluid aspirated on day 17 (n = 6 replicate litters per group) was subjected to trypsin digestion for analysis by matrix-assisted laser desorption-time of flight mass spectrometry with the aid of denoising algorithms, statistical testing, and classification methods.

RESULTS

We identified several peaks in the proteomics screen that were reduced consistently and specifically in exposed B6J litters. Preliminary characterization by liquid chromatography tandem mass spectrometry and multidimensional protein identification mapped the reduced peaks to alpha fetoprotein (AFP). The predictive strength of AFP deficiency as a biomarker for FAS-positive litters was confirmed by area under the receiver operating characteristic curve.

CONCLUSIONS

: These findings in genetically susceptible mice support clinical observations in maternal serum that implicate a decrease in AFP levels following prenatal alcohol damage.

Absence of gonadotropin-releasing hormone 1 and Kiss1 activation in alpha-fetoprotein knockout mice: prenatal estrogens defeminize the potential to show preovulatory luteinizing hormone surges

Sex differences in gonadal function are driven by either cyclical (females) or tonic (males) hypothalamic GnRH1 release and, subsequently, gonadotrophin (LH and FSH) secretion from the pituitary. This sex difference seems to depend on the perinatal actions of gonadal hormones on the hypothalamus. We used alpha-fetoprotein (AFP) knockout mice (Afp(-/-)) to study the mechanisms by which estrogens affect the sexual differentiation of the GnRH1 system. Afp(-/-) mice lack the protective actions of AFP against estrogens circulating during embryonic development, leading to infertility probably due to a hypothalamic dysfunction. Therefore, we first determined whether Afp(-/-) females are capable of showing a steroid-induced preovulatory LH surge by FOS/GnRH1 immunohistochemistry and RIA of plasma LH levels. Because the KISS1/GPR54 system is a key upstream regulator of the GnRH1 system as well as being sexually dimorphic, we also analyzed whether Kisspeptin-10 neurons were activated in Afp(-/-) mice after treatment with estradiol and progesterone. We found that the GnRH1 and Kisspeptin-10 neuronal systems are defeminized in Afp(-/-) females because they did not show either steroid-induced LH surges or significant FOS/GnRH1 double labeling. Furthermore, Kisspeptin-10 immunoreactivity and neural activation, measured by the number of double-labeled FOS/Kisspeptin-10 cells, were lower in Afp(-/-) females, suggesting a down-regulation of GnRH1 function. Thus, the sex difference in the ability to show preovulatory LH surges depends on the prenatal actions of estrogens in the male hypothalamus and, thus, is lost in Afp(-/-) females because they lack AFP to protect them against the defeminizing effects of estrogens during prenatal development.