The parent-of-origin effect of 10q22 in pre-eclamptic females coincides with two regions clustered for genes with down-regulated expression in androgenetic placentas

Preeclampsia and STOX1 (storkhead-box protein 1): Molecular evaluation of STOX1 in preeclampsia

Preeclampsia (PE) is clinically defined as a part of pregnancy characterized by hypertension and multiple organ failure. PE is broadly categorized into two types: "placental" and "maternal". Placental PE is associated with fetal growth restriction and adverse maternal and neonatal outcomes. STOX1 (Storkhead box 1), a transcription factor, discovered through a complete transcript analysis of the PE susceptibility locus of 70,000 bp on chromosome 10q22.1. So far, studies investigating the relationship between STOX1 and PE have focused on STOX1 overexpression, STOX1 isoform imbalance, and STOX1 variations that could have clinical consequence. Initially, the Y153H variation of STOX was associated with the placental form of PE. Additionally, studies focusing on the maternal and fetal interface have shown that NODAL and STOX1 variations play a role together in the unsuccessful remodeling of the spiral arteries. Research specifically addressing the overexpression of STOX1 has shown that its disruption of cellular hemoastasis, leading to impaired hypoxia response, disruption of the cellular antioxidant system, and nitroso/redox imbalance. Furthermore, functional studies have been conducted showing that the imbalance between STOX1 isoforms contributes to the pathogenesis of placental PE. Research indicates that STOX1B competes with STOX1A and that the overexpression of STOX1B reverses cellular changes that STOX1A induces to the pathogenesis of PE. In this review, we aimed at elucidating the relationship between STOX1 and PE as well as function of STOX1. In conclusion, based on a comprehensive literature review, numerous studies support the role of STOX1 in the pathogenesis of PE.

CircSTAM inhibits migration and invasion of trophoblast cells by regulating miR-148a-5p/PTEN axis

BACKGROUND

The mechanisms underlying the pathogenesis of preeclampsia (PE) remains unclear. Exploring the molecular players in PE progression can provide insights into targeted therapy.

METHODS

The expression levels of circSTAM in placental chorionic tissues of PE patients and normal pregnant women were compared by RT-qPCR. CircSTAM was knocked down by small interfering RNA to investigate its role in migration, invasion and epithelial-mesenchymal transformation (EMT) of trophoblast HTR-8/SVneo cells. The downstream target of circSTAM was predicted using online bioinformatics resources, and their molecular interaction was examined by luciferase reporter assay.

RESULTS

CircSTAM was upregulated in PE placenta tissues in comparison to normal placental tissues. CircSTAM knockdown significantly enhanced cellular invasion, migration, as well as EMT. Mir-148a-5p was identified as a target of circSTAM to regulate cell migration and invasion. Mir-148a-5p negatively regulated PTEN expression in trophoblast HTR-8 /SVneo cells.

CONCLUSION

In summary, circSTAM upregulation in PE trophoblasts promoted the invasion, migration and EMT. CircSTAM may modulate trophoblast phenotype by impinging on mir-148a-5p/PTEN axis. These data provided novel insights into the pathogenesis of PE.

STOX1 promotor region -922 T > C polymorphism is associated with Early-Onset preeclampsia

Preeclampsia (PE), affecting 5-8% of pregnancies, is a common pregnancy disease that has harmful effects on mother and foetus. It has been found that the STOX1 (Storkhead Box 1), which is a transcription factor, carries variants associated with PE. Previous studies showed that, there was a strong relationship between PE and STOX1 variants. Therefore, we hypothesised that variants in the promoter region of the gene may be related to the onset of PE. The aim of this study is to investigate the contribution of STOX1 gene promoter region variants to PE. The blood samples taken from 118 PE patients and 96 healthy pregnant women were analysed by Sanger sequencing method. Sequence analysis results showed that, there is a-922 T > C polymorphism (rs884181) in the promoter region of the STOX1 gene. This polymorphism was found to be statistically significant in individuals with early onset PE (p = 0.02) and in PE (p = 0.014) compared to the control group.IMPACT STATEMENTWhat is already known on this subject? As a result of whole-exon studies on the STOX1 gene, polymorphisms were found to disrupt the structure/expression/function of the gene and strengthen its relationship with PE and HELLP syndrome. A previous study by our team found an association between Y153H, the most common polymorphism of STOX1, and early onset PE.What do the results of this study add? In our study, it was aimed to investigate the effect of genetic modifications in STOX1 gene promoter region on PE through the maternal genotype. Because any change in the promoter region affects the expression level of the gene. Also, for the first time, sequence analysis of the promoter region of STOX1 is investigated in PE. The variations in STOX1 appear to be important in PE especially in Early Onset PE.What are the implications of these findings for clinical practice and/or further research? Although PE is a disease that occurs with pregnancy and shows its effects most during this period, women and children with a history of PE are more prone to various disorders, especially cardiovascular diseases in the following years. Therefore, understanding the pathogenesis of the disease is important for both prevention and treatment process. Variations on STOX1 appear to be important in terms of disease risk.

Maternal-fetal genetic interactions, imprinting, and risk of placental abruption

RESULTS

Abruption cases were more likely to experience preeclampsia, have shorter gestational age, and deliver infants with lower birthweight compared with controls. Models with MFGI effects provided improved fit than models with only maternal and fetal genotype main effects for SNP rs12530904 (p-value = 1.2e-04) in calcium/calmodulin-dependent protein kinase [CaM kinase] II beta (CAMK2B), and, SNP rs73136795 (p-value = 1.9e-04) in peroxisome proliferator-activated receptor-gamma (PPARG), both MB genes. We identified 320 SNPs in 45 maternally-imprinted genes (including potassium voltage-gated channel subfamily Q member 1 [KCNQ1], neurotrimin [NTM], and, ATPase phospholipid transporting 10 A [ATP10A]) associated with abruption. Top hits included rs2012323 (p-value = 1.6E-16) and rs12221520 (p-value1.3e-13) in KCNQ1, rs8036892 (p-value = 9.3E-17) and rs188497582 in ATP10A, rs12589854 (p-value = 2.9E-11) and rs80203467 (p-value = 4.6e-11) in maternally expressed 8, small nucleolar RNA host (MEG8), and rs138281088 in solute carrier family 22 member 2 (SLC22A2) (p-value = 6.8e-9).

CONCLUSIONS

We identified novel PA-related maternal-fetal MB gene interactions and imprinting effects that highlight the role of the fetus in PA risk development. Findings can inform mechanistic investigations to understand the pathogenesis of PA.

Long non-coding RNA RPAIN regulates the invasion and apoptosis of trophoblast cell lines via complement protein C1q

Long non-coding RNAs (lncRNAs) are key regulatory molecules that are involved in a variety of biological processes and human diseases. Their impact on early onset preeclampsia remains unclear. In this study, we tested the expression of RPAIN (transcript variant 12 of RPA interacting protein, a non-coding RNA, NR_027683.1) in placenta tissues derived from 25 pregnant women with PE and 15 healthy pregnant women using quantitative real-time PCR. The effect of RPAIN on trophoblast proliferation, invasion, and apoptosis and the underlying mechanisms were examined in trophoblast cell lines (HTR-8/SVneo). The results showed that RPAIN expression levels were significantly increased in early onset preeclamptic placentas compared to normal controls. The proliferation and invasive abilities of the trophoblast cells were significantly inhibited, and the apoptosis abilities of the trophoblast cells were significantly promoted when RPAIN was overexpressed. In addition, the overexpression of RPAIN inhibited the expression of complement protein C1q. Furthermore, C1q overexpression rescued the decreased cell invasion and enhanced cell apoptosis in RPAIN-overexpressing trophoblast cells. Our results suggest that increased RPAIN levels may contribute to the development of preeclampsia through regulating trophoblast invasion and apoptosis via C1q. Therefore, we proposed RPAIN as a novel lncRNA molecule, which might contribute to the development of PE (preeclampsia) and might compose a potential diagnostic and therapeutic target for this disease.

YAP Is Decreased in Preeclampsia and Regulates Invasion and Apoptosis of HTR-8/SVneo

Preeclampsia (PE) is a gestational disorder with hypertension and proteinuria leading to maternal and fetal morbidity and mortality. Yes-associated protein (YAP), a transcription coactivator of Hippo pathway, was identified as an oncoprotein participated in tumorigenesis. However, the effect of YAP on trophoblast has not been investigated. In our study, YAP expression levels in first-trimester, full-term, and PE placentas were detected using quantitative real-time polymerase chain reaction (PCR), Western blot assays, and immunohistochemistry. Yes-associated protein expression was also detected in BeWo and HTR-8/SVneo. Overexpression plasmid and YAP small interfering RNA were introduced into trophoblast cells. Furthermore, we utilized a Transwell invasion assay, flow cytometry, and Cell Counting Kit-8 analysis to examine the role of YAP in the invasion, apoptosis, and proliferation of HTR-8/SVneo trophoblast cells. The result showed that both YAP messenger RNA (mRNA) and protein expression levels were less in preeclamptic placentas. Yes-associated protein mRNA and protein expression levels were more highly expressed in BeWo. Yes-associated protein enhanced cell invasion, reduced the cellular apoptotic response, and had no effect on proliferation. In addition, the overexpression of YAP activated the expression of caudal-related homeobox transcription factor 2 (CDX2), whereas reduced expression of YAP inhibited the expression of CDX2. Our results demonstrate that decreased YAP levels may contribute to the development of PE by regulating trophoblast invasion and apoptosis involving regulation of CDX2. Collectively, we proposed decreased YAP may contribute to trophoblast dysfunction, which suggests it might represent a prognostic biomarker and therapeutic target for PE.

Genetic Approaches in Preeclampsia

Preeclampsia (PE) is a serious hypertensive disorder that affects up to 8% of all pregnancies annually. An established risk factor for PE is family history, clearly demonstrating an underlying genetic component to the disorder. To date, numerous genetic studies, using both the candidate gene and genome-wide approach, have been undertaken to tease out the genetic basis of PE and understand its origins. Such studies have identified some promising candidate genes such as STOX1 and ACVR2A. Nevertheless, researchers face ongoing challenges of replicating these genetic associations in different populations and performing the functional validation of identified genetic variants to determine their causality in the disorder. This chapter will review the genetic approaches used in the study of PE, discuss their limitations and possible confounders, and describe current strategies.

Survival and growth of C57BL/6J mice lacking the BK channel, Kcnma1: lower adult body weight occurs together with higher body fat

Big conductance potassium (BK) channels contribute to K⁺ flow and electrical behavior in many cell types. Mice made null for the gene (Kcnma1) producing the BK channel (BK^KO) exhibit numerous deficits in physiological functions. Breeding mice lacking a single allele of Kcnma1 (C57BL/6J background) had litter sizes of approximately eight pups. For the period of maternal care (P0–P21), pup deaths peaked at P1 with a second less severe interval of death peaking near P13. Early deaths were twice as likely during a 20‐month period of building construction compared with the quiescent period after cessation of construction. Births during construction were not consistent with Mendelian predictions indicating the likelihood of a specific disadvantage induced by this environmental stressor. Later BK^KO pup deaths (~P13) also were more numerous than Mendelian expectations. After weaning, weight gain was slower for BK^KO mice compared with wild‐type littermates: 5 g less for male BK^KO mice and 4 g less for female BK^KO mice. Body composition determined by quantitative magnetic resonance indicated a higher fat proportion for wild‐type female mice compared with males, as well as a higher hydration ratio. Both male and female BK^KO mice showed higher fat proportions than wild‐type, with female BK^KO mice exhibiting greater variation. Together, these results indicate that BK^KO mice suffered disadvantages that lead to prenatal and perinatal death. A metabolic difference likely related to glucose handling led to the smaller body size and distinct composition for BK^KO mice, suggesting a diversion of energy supplies from growth to fat storage.

Epigenetic modifications at DMRs of placental genes are subjected to variations in normal gestation, pathological conditions and folate supplementation

Invasive placentation and cancer development shares many similar molecular and epigenetic pathways. Paternally expressed, growth promoting genes (SNRPN, PEG10 and MEST) which are known to play crucial role in tumorogenesis, are not well studied during placentation. This study reports for the first time of the impact of gestational-age, pathological conditions and folic acid supplementation on dynamic nature of DNA and histone methylation present at their differentially methylated regions (DMRs). Here, we reported the association between low DNA methylation/H3K27me3 and higher expression of SNRPN, PEG10 and MEST in highly proliferating normal early gestational placenta. Molar and preeclamptic placental villi, exhibited aberrant changes in methylation levels at DMRs of these genes, leading to higher and lower expression of these genes, respectively, in reference to their respective control groups. Moreover, folate supplementation could induce gene specific changes in mRNA expression in placental cell lines. Further, MEST and SNRPN DMRs were observed to show the potential to act as novel fetal DNA markers in maternal plasma. Thus, variation in methylation levels at these DMRs regulate normal placentation and placental disorders. Additionally, the methylation at these DMRs might also be susceptible to folic acid supplementation and has the potential to be utilized in clinical diagnosis.

Noncoding RNA-regulated gain-of-function of STOX2 in Finnish pre-eclamptic families

The familial forms of early onset pre-eclampsia and related syndromes (HELLP) present with hypertension and proteinuria in the mother and growth restriction of the fetus. Genetically, these clinically similar entities are caused by different founder-dependent, placentally-expressed paralogous genes. All susceptibility genes (STOX1, lincHELLP, INO80B) identified so far are master control genes that regulate an essential trophoblast differentiation pathway, but act at different entry points. Many genes remain to be identified. Here we demonstrate that a long non-coding RNA (lncRNA) within intron 3 of the STOX2 gene on 4q35.1 acts as a permissive cis-acting regulator of alternative splicing of STOX2. When this lncRNA is mutated or absent, an alternative exon (3B) of STOX2 is included. This introduces a stop codon resulting in the deletion of a highly conserved domain of 64 amino acids in the C-terminal of the STOX2 protein. A mutation present within a regulatory region within intron 1 of STOX2 has the same effect after blocking with CRISPR technology: transcripts with exon 3B are upregulated. This proces appears related to transcriptional control by a chromatin-splicing adaptor complex as described for FGFR2. For STOX2, CHD5, coding for a chromodomain helicase DNA binding protein, qualifies as the chromatin modifier in this process.

Genomic imprinting in the human placenta

With the launch of the National Institute of Child Health and Human Development/National Institutes of Health Human Placenta Project, the anticipation is that this often-overlooked organ will be the subject of much intense research. Compared with somatic tissues, the cells of the placenta have a unique epigenetic profile that dictates its transcription patterns, which when disturbed may be associated with adverse pregnancy outcomes. One major class of genes that is dependent on strict epigenetic regulation in the placenta is subject to genomic imprinting, the parent-of-origin-dependent monoallelic gene expression. This review discusses the differences in allelic expression and epigenetic profiles of imprinted genes that are identified between different species, which reflect the continuous evolutionary adaption of this form of epigenetic regulation. These observations divulge that placenta-specific imprinted gene that is reliant on repressive histone signatures in mice are unlikely to be imprinted in humans, whereas intense methylation profiling in humans has uncovered numerous maternally methylated regions that are restricted to the placenta that are not conserved in mice. Imprinting has been proposed to be a mechanism that regulates parental resource allocation and ultimately can influence fetal growth, with the placenta being the key in this process. Furthermore, I discuss the developmental dynamics of both classic and transient placenta-specific imprinting and examine the evidence for an involvement of these genes in intrauterine growth restriction and placenta-associated complications. Finally, I focus on examples of genes that are regulated aberrantly in complicated pregnancies, emphasizing their application as pregnancy-related disease biomarkers to aid the diagnosis of at-risk pregnancies early in gestation.

Balance within the Neurexin Trans-Synaptic Connexus Stabilizes Behavioral Control

Autism spectrum disorder (ASD) is characterized by a broad spectrum of behavioral deficits of unknown etiology. ASD associated mutations implicate numerous neurological pathways including a common association with the neurexin trans-synaptic connexus (NTSC) which regulates neuronal cell-adhesion, neuronal circuitry, and neurotransmission. Comparable DNA lesions affecting the NTSC, however, associate with a diversity of behavioral deficits within and without the autism spectrum including a very strong association with Tourette syndrome. The NTSC is comprised of numerous post-synaptic ligands competing for trans-synaptic connection with one of the many different neurexin receptors yet no apparent association exists between specific NTSC molecules/complexes and specific behavioral deficits. Together these findings indicate a fundamental role for NTSC-balance in stabilizing pre-behavioral control. Further molecular and clinical characterization and stratification of ASD and TS on the basis of NTSC status will help elucidate the molecular basis of behavior – and define how the NTSC functions in combination with other molecular determinates to strengthen behavioral control and specify behavioral deficits.

Associations of personal and family preeclampsia history with the risk of early-, intermediate- and late-onset preeclampsia

Preeclampsia encompasses multiple conditions of varying severity. We examined the recurrence and familial aggregation of preeclampsia by timing of onset, which is a marker for severity. We ascertained personal and family histories of preeclampsia for women who delivered live singletons in Denmark in 1978-2008 (almost 1.4 million pregnancies). Using log-linear binomial regression, we estimated risk ratios for the associations between personal and family histories of preeclampsia and the risk of early-onset (before 34 weeks of gestation, which is typically the most severe), intermediate-onset (at 34-36 weeks of gestation), and late-onset (after 36 weeks of gestation) preeclampsia. Previous early-, intermediate-, or late-onset preeclampsia increased the risk of recurrent preeclampsia with the same timing of onset 25.2 times (95% confidence interval (CI): 21.8, 29.1), 19.7 times (95% CI: 17.0, 22.8), and 10.3 times (95% CI: 9.85, 10.9), respectively, compared with having no such history. Preeclampsia in a woman's family was associated with a 24%-163% increase in preeclampsia risk, with the strongest associations for early- and intermediate-onset preeclampsia in female relatives. Preeclampsia in the man's family did not affect a woman's risk of early-onset preeclampsia and was only weakly associated with her risks of intermediate- and late-onset preeclampsia. Early-onset preeclampsia appears to have the largest genetic component, whereas environmental factors likely contribute most to late-onset preeclampsia. The role of paternal genes in the etiology of preeclampsia appears to be limited.

(Epi)genetics of pregnancy-associated diseases

This review describes the current knowledge regarding genetics and epigenetics of pregnancy-associated diseases with placental origin. We discuss the effect on genetic linkage analyses when the fetal genotype determines the maternal phenotype. Secondly, the genes identified by genome-wide linkage studies to be associated with pre-eclampsia (ACVR2A, STOX1) and the HELLP-syndrome (LINC-HELLP) are discussed regarding their potential functions in the etiology of disease. Furthermore, susceptibility genes identified by candidate gene approaches (e.g., CORIN) are described. Next, we focus on the additional challenges that come when epigenetics also play a role in disease inheritance. We discuss the maternal transmission of the chromosome 10q22 pre-eclampsia linkage region containing the STOX1 gene and provide further evidence for the role of epigenetics in pre-eclampsia based on the cdkn1c mouse model of pre-eclampsia. Finally, we provide recommendations to unravel the genetics of pregnancy-associated diseases, specifically regarding clear definitions of patient groups and sufficient patient numbers, and the potential usefulness of (epi)genetic data in early non-invasive biomarker development.

Maternal Nodal inversely affects NODAL and STOX1 expression in the fetal placenta

Nodal, a secreted signaling protein from the transforming growth factor beta (TGF-β)-super family plays a vital role during early embryonic development. Recently, it was found that maternal decidua-specific Nodal knockout mice show intrauterine growth restriction (IUGR) and preterm birth. The chromosomal location of NODAL is in the same linkage area as the placental (fetal) pre-eclampsia (PE) susceptibility gene STOX1, which is associated with the familial form of early-onset, IUGR-complicated PE. As the STOX1 linkage was originally identified in women being born from a pre-eclamptic pregnancy as well as suffering from PE themselves, the linkage could in part be caused by NODAL, which is why the potential maternal–fetal interaction between STOX1 and NODAL was investigated. In the PE families with the STOX1 susceptibility allele carried by the children born from pre-eclamptic pregnancies, it was found that the pre-eclamptic mothers themselves all carried the NODAL H165R SNP, which causes a 50% reduced activity. Surprisingly, in decidua-specific Nodal knockout mice the fetal placenta showed up-regulation of STOX1 and NODAL expression. Conditioned media of human first trimester decidua and a human endometrial stromal cell line (T-HESC) treated with siRNAs against NODAL or carrying the H165R SNP were also able to induce NODAL and STOX1 expression when added to SGHPL-5 first trimester extravillous trophoblast cells. Finally, a human TGF-β/BMP signaling pathway PCR-array on decidua and the T-HESC cell line with Nodal knockdown revealed upregulation of Activin-A, which was confirmed in conditioned media by ELISA. We show that maternal decidua Nodal knockdown gives upregulation of NODAL and STOX1 mRNA expression in fetal extravillous trophoblast cells, potentially via upregulation of Activin-A in the maternal decidua. As both Activin-A and Nodal have been implicated in PE, being increased in serum of pre-eclamptic women and upregulated in pre-eclamptic placentas respectively, this interaction at the maternal–fetal interface might play a substantial role in the development of PE.

Neocortical development as an evolutionary platform for intragenomic conflict

Embryonic development in mammals has evolved a platform for genomic conflict between mothers and embryos and, by extension, between maternal and paternal genomes. The evolutionary interests of the mother and embryo may be maximized through the promotion of sex-chromosome genes and imprinted alleles, resulting in the rapid evolution of postzygotic phenotypes preferential to either the maternal or paternal genome. In eutherian mammals, extraordinary in utero maternal investment in the brain, and neocortex especially, suggests that convergent evolution of an expanded mammalian neocortex along divergent lineages may be explained, in part, by parent-of-origin-linked gene expression arising from parent-offspring conflict. The influence of this conflict on neocortical development and evolution, however, has not been investigated at the genomic level. In this hypothesis and theory article, we provide preliminary evidence for positive selection in humans in the regions of two platforms of intragenomic conflict—chromosomes 15q11-q13 and X—and explore the potential relevance of cis-regulated imprinted domains to neocortical expansion in mammalian evolution. We present the hypothesis that maternal- and paternal-specific pressures on the developing neocortex compete intragenomically to influence neocortical expansion in mammalian evolution.

Non-coding RNA and DNA as epigenetic biomarkers for pre-eclampsia

The human genome contains a hidden and large layer of biologic information that is not accessible by proteomic or metabolic methods. Insight into the nature, size, function and importance of this information is increasing rapidly. This additional layer of information includes non-coding RNA and DNA and can be retrieved and analyzed using nucleic acids that circulate in the maternal plasma during pregnancy, originate from the developing placenta and provide information on fetal well being. This review explains why, when and how fetal information as carried on and provided by the placental DNA and RNA molecules circulating in the plasma of pregnant women can be explored to understand and to analyze the primary placental processes, that underlie pre-eclampsia and related disorders.

Parent-offspring conflict and the persistence of pregnancy-induced hypertension in modern humans

Preeclampsia is a major cause of perinatal mortality and disease affecting 5–10% of all pregnancies worldwide, but its etiology remains poorly understood despite considerable research effort. Parent-offspring conflict theory suggests that such hypertensive disorders of pregnancy may have evolved through the ability of fetal genes to increase maternal blood pressure as this enhances general nutrient supply. However, such mechanisms for inducing hypertension in pregnancy would need to incur sufficient offspring health benefits to compensate for the obvious risks for maternal and fetal health towards the end of pregnancy in order to explain why these disorders have not been removed by natural selection in our hunter-gatherer ancestors. We analyzed >750,000 live births in the Danish National Patient Registry and all registered medical diagnoses for up to 30 years after birth. We show that offspring exposed to pregnancy-induced hypertension (PIH) in trimester 1 had significantly reduced overall later-life disease risks, but increased risks when PIH exposure started or developed as preeclampsia in later trimesters. Similar patterns were found for first-year mortality. These results suggest that early PIH leading to improved postpartum survival and health represents a balanced compromise between the reproductive interests of parents and offspring, whereas later onset of PIH may reflect an unbalanced parent-offspring conflict at the detriment of maternal and offspring health.

Chorionic villous vascularization related to phenotype and genotype in first trimester miscarriages in a recurrent pregnancy loss cohort

STUDY QUESTION

Is there an association between chorionic villous vascularization, ultrasound findings and corresponding chromosome results in early miscarriage specimens from a cohort of recurrent pregnancy loss patients?

SUMMARY ANSWER

We did not find a significant difference in vascularization scores of chorionic villi between embryonic, yolk sac or empty sac miscarriages, or between euploid and noneuploid miscarriages.

WHAT IS KNOWN ALREADY

At least half of first trimester miscarriages are due to embryopathogenesis associated with chromosome errors and/or major congenital anomalies, resulting in an empty sac, a yolk sac or an embryonic miscarriage. Absent and decreased chorionic villous vascularization is usually present in these pregnancies.

STUDY DESIGN, SIZE, DURATION

For this retrospective study, 60 hematoxylin and eosin slides of miscarriage tissue of less than 10 weeks gestational age were collected from an academic institution. All patients were seen in consultation between July 2004 and October 2009.

PARTICIPANTS, SETTING, METHODS

Chorionic villous vascularization was determined using a previously published classification. The results were validated and compared with the ultrasound findings and corresponding chromosome results.

MAIN RESULTS AND THE ROLE OF CHANCE

There were 53 embryonic miscarriages, 5 yolk sac miscarriages and 2 empty sac miscarriages. Chromosome results were obtained in 59 of the 60 miscarriages; 37.3% were euploid and 62.7% were noneuploid. Validation of the vascularization score between observers was reasonable to good (Kappa 0.47-0.76), and 59% of the cases were classified as avascular. The vascularization score did not differ between euploid or noneuploid miscarriages, or between embryonic, yolk sac or empty sac miscarriages. Avascular villi were seen more frequently in miscarriages trisomic for chromosome 16, when compared with miscarriages with other trisomies (6 out of 7 versus 8 out of 22, P = 0.04).

LIMITATIONS, REASONS FOR CAUTION

Unfortunately, the number of samples in the study was limited.

WIDER IMPLICATIONS OF THE FINDINGS

Avascular villi may indicate abnormal early placentation as a part of embryopathogenesis. Further study is warranted to determine whether a genetic cause can be found to explain these results.

Pathogenetic model for Tourette syndrome delineates overlap with related neurodevelopmental disorders including Autism

Tourette syndrome (TS) is a highly heritable neuropsychiatric disorder characterised by motor and vocal tics. Despite decades of research, the aetiology of TS has remained elusive. Recent successes in gene discovery backed by rapidly advancing genomic technologies have given us new insights into the genetic basis of the disorder, but the growing collection of rare and disparate findings have added confusion and complexity to the attempts to translate these findings into neurobiological mechanisms resulting in symptom genesis. In this review, we explore a previously unrecognised genetic link between TS and a competing series of trans-synaptic complexes (neurexins (NRXNs), neuroligins (NLGNs), leucine-rich repeat transmembrane proteins (LRRTMs), leucine rich repeat neuronals (LRRNs) and cerebellin precursor 2 (CBLN2)) that links it with autism spectrum disorder through neurodevelopmental pathways. The emergent neuropathogenetic model integrates all five genes so far found to be uniquely disrupted in TS into a single pathogenetic chain of events described in context with clinical and research implications.

Allele-biased expression in differentiating human neurons: implications for neuropsychiatric disorders

Stochastic processes and imprinting, along with genetic factors, lead to monoallelic or allele-biased gene expression. Stochastic monoallelic expression fine-tunes information processing in immune cells and the olfactory system, and imprinting plays an important role in development. Recent studies suggest that both stochastic events and imprinting may be more widespread than previously considered. We are interested in allele-biased gene expression occurring in the brain because parent-of-origin effects suggestive of imprinting appear to play a role in the transmission of schizophrenia (SZ) and autism spectrum disorders (ASD) in some families. In addition, allele-biased expression could help explain monozygotic (MZ) twin discordance and reduced penetrance. The ability to study allele-biased expression in human neurons has been transformed with the advent of induced pluripotent stem cell (iPSC) technology and next generation sequencing. Using transcriptome sequencing (RNA-Seq) we identified 801 genes in differentiating neurons that were expressed in an allele-biased manner. These included a number of putative SZ and ASD candidates, such as A2BP1 (RBFOX1), ERBB4, NLGN4X, NRG1, NRG3, NRXN1, and NLGN1. Overall, there was a modest enrichment for SZ and ASD candidate genes among those that showed evidence for allele-biased expression (chi-square, p = 0.02). In addition to helping explain MZ twin discordance and reduced penetrance, the capacity to group many candidate genes affecting a variety of molecular and cellular pathways under a common regulatory process – allele-biased expression – could have therapeutic implications.

Detection of parent-of-origin specific expression quantitative trait loci by cis-association analysis of gene expression in trios

Parent-of-origin (PofO) effects, such as imprinting are a phenomenon in which homologous chromosomes exhibit differential gene expression and epigenetic modifications according to their parental origin. Such non-Mendelian inheritance patterns are generally ignored by conventional association studies, as these tests consider the maternal and paternal alleles as equivalent. To identify regulatory regions that show PofO effects on gene expression (imprinted expression Quantitative Trait Loci, ieQTLs), here we have developed a novel method in which we associate SNP genotypes of defined parental origin with gene expression levels. We applied this method to study 59 HapMap phase II parent-offspring trios. By analyzing mother/father/child trios, rules of Mendelian inheritance allowed the parental origin to be defined for ∼95% of SNPs in each child. We used 680,475 informative SNPs and corresponding expression data for 92,167 probe sets from Affymetrix GeneChip Human Exon 1.0 ST arrays and performed four independent cis-association analyses with the expression level of RefSeq genes within 1 Mb using PLINK. Independent analyses of maternal and paternal genotypes identified two significant cis-ieQTLs (p<10⁻⁷) at which expression of genes SFT2D2 and SRRT associated exclusively with maternally inherited SNPs rs3753292 and rs6945374, respectively. 28 additional suggestive cis-associations with only maternal or paternal SNPs were found at a lower stringency threshold of p<10⁻⁶, including associations with two known imprinted genes PEG10 and TRAPPC9, demonstrating the efficacy of our method. Furthermore, comparison of our method that utilizes independent analyses of maternal and paternal genotypes with the Likelihood Ratio Test (LRT) showed it to be more effective for detecting imprinting effects than the LRT. Our method represents a novel approach that can identify imprinted regulatory elements that control gene expression, suggesting novel PofO effects in the human genome.

Parent-of-origin effects of FAS and PDLIM1 in attention-deficit/hyperactivity disorder

BACKGROUND

Previous studies have suggested that there may be a parent-of-origin effect for attention-deficit/hyperactivity disorder(ADHD) candidate genes. The objective of the present study was to investigate parent-of-origin effects using a genome-wide association analysis of the International Multicentre ADHD Genetics (IMAGE) study sample.

METHODS

Family-based association analysis for ADHD using 846 ADHD probands and their parents was performed using the PLINK program, and parent-of-origin effects were studied using a Z score for the difference in paternal versus maternal odds ratios.

RESULTS

We identified 44 single nucleotide polymorphisms (SNPs) showing parent-of-origin effects at a significance level of p < 0.001. The most significant SNP, rs7614907, is at position 3q13.33 in the CDGAP gene (p = 0.000064 for parent-of-origin effect). Furthermore, 2 genes (FAS and PDLIM1) showed moderate parent-of-origin effects (p = 0.00086 for rs9658691 and p = 0.00077 for rs11188249) and strong maternal transmission (p = 0.000059 for rs9658691 and p = 0.0000068 for rs11188249). In addition, ZNF775 showed a moderate parent-of-origin effect (p = 0.00036 for rs7790549) and strong paternal transmission (p = 0.000041 for rs7790549).

LIMITATIONS

We only had 1 sample available for analysis.

CONCLUSION

These results suggest several genes or regions with moderate parent-of-origin effects, and these findings will serve as a resource for replication in other populations to elucidate the potential role of these genetic variants in ADHD.

Alpha T-catenin (CTNNA3): a gene in the hand is worth two in the nest

Alpha-T-Catenin (CTNNA3) is a key protein of the adherens junctional complex in epithelial cells playing a crucial role in cellular adherence. What makes this gene particularly interesting is that it is located within a common fragile site, is epigenetically regulated, is transcribed through multiple promoters, and generates a variety of alternate transcripts. Finally, CTNNA3 has a nested gene (LRTMM3) embedded within its genomic context transcribed in the opposite direction. Apart from the complexity of its regulation, alterations in both CTNNA3 and LRTMM3 are implicated in human disease.

The etiology of preeclampsia: the role of the father

Preeclampsia is often considered as simply a maternal disease with variable degrees of fetal involvement. More and more the unique immunogenetic maternal-paternal relationship is appreciated, and also the specific 'genetic conflict' that is characteristic of haemochorial placentation. From that perspective, pre-eclampsia can be seen as a disease of an individual couple with primarily maternal and fetal manifestations. The maternal and fetal genomes perform different roles during development. Heritable paternal, rather than maternal, imprinting of the genome is necessary for normal trophoblast development. Large population studies have estimated that 35% of the variance in susceptibility to preeclampsia is attributable to maternal genetic effects; 20% to fetal genetic effects (with similar contributions of both parents), 13% to the couple effect, less than 1% to the shared sibling environment and 32% to unmeasured factors. Not one of these large population studies focussed on the paternal contribution to preeclampsia, which is demonstrated by (1) the effect of the length of the sexual relationship; (2) the concept of primipaternity versus primigravidity; and (3) the existence of the so-called 'dangerous' father, as demonstrated in various large population studies. It is currently unknown how the father exerts this effect. Possible mechanisms include seminal cytokine levels and their effect on maternal immune deviation, specific paternal HLA characteristics and specific paternal single nucleotide polymorphisms (SNPs), in particular in the paternally expressed genes affecting placentation. Several large cohort studies, including the large international SCOPE consortium, have identified paternal SNPs with strong associations with preeclampsia.

The genetics of pre-eclampsia and other hypertensive disorders of pregnancy

Hypertension is the most frequent medical complication occurring during pregnancy. In this chapter, we aim to address the genetic contribution to these disorders, with specific focus on pre-eclampsia. The pathogenic mechanisms underlying pre-eclampsia remain to be elucidated; however, immune maladaptation, inadequate placental development and trophoblast invasion, placental ischaemia, oxidative stress and thrombosis are all thought to represent key factors in the development of disease. Furthermore, all of these components have genetic factors that may be involved in the pathogenic changes occurring. The familial nature of pre-eclampsia has been known for many years and, as such, extensive genetic research has been carried out in this area using strategies that include candidate gene studies and linkage analysis. Interactions between fetal and maternal genotypes, the effect of environmental factors, and epistasis will also be considered.

STOX1: Key player in trophoblast dysfunction underlying early onset preeclampsia with growth retardation

Currently, only two preeclampsia susceptibility genes (ACVR2A, STOX1) have been identified within confirmed regions with significant genome-wide linkage, although many genetic screens in multiple populations have been performed. In this paper, we focus on the STOX1 gene. The epigenetic status of this gene is discussed explaining the maternal transmission of the STOX1 susceptibility allele observed in preeclamptic families. The known upstream regulation and downstream effector genes of the transcription factor STOX1 are described. Finally, we propose a model in which we combine the cell type-specific and allele-specific effects of STOX1. This includes intrinsic effects (differential CpG island methylation) and extrinsic effects (regulation of effector genes).

STOX2 but not STOX1 is differentially expressed in decidua from pre-eclamptic women: data from the Second Nord-Trondelag Health Study

Variation in the Storkhead box-1 (STOX1) gene has previously been associated with pre-eclampsia. In this study, we assess candidate single nucleotide polymorphisms (SNPs) in STOX1 in an independent population cohort of pre-eclamptic (n = 1.139) and non-pre-eclamptic (n = 2.269) women (the HUNT2 study). We also compare gene expression levels of STOX1 and its paralogue, Storkhead box-2 (STOX2) in decidual tissue from pregnancies complicated by pre-eclampsia and/or fetal growth restriction (FGR) (n = 40) to expression levels in decidual tissue from uncomplicated pregnancies (n = 59). We cannot confirm association of the candidate SNPs to pre-eclampsia (P > 0.05). For STOX1, no differential gene expression was observed in any of the case groups, whereas STOX2 showed significantly lower expression in deciduas from pregnancies complicated by both pre-eclampsia and FGR as compared with controls (P = 0.01). We further report a strong correlation between transcriptional alterations reported previously in choriocarcinoma cells over expressing STOX1A and alterations observed in decidual tissue of pre-eclamptic women with FGR.

Imprinted genes show unique patterns of sequence conservation

BACKGROUND

Genomic imprinting is an evolutionary conserved mechanism of epigenetic gene regulation in placental mammals that results in silencing of one of the parental alleles. In order to decipher interactions between allele-specific DNA methylation of imprinted genes and evolutionary conservation, we performed a genome-wide comparative investigation of genomic sequences and highly conserved elements of imprinted genes in human and mouse.

RESULTS

Evolutionarily conserved elements in imprinted regions differ from those associated with autosomal genes in various ways. Whereas for maternally expressed genes strong divergence of protein-encoding sequences is most prominent, paternally expressed genes exhibit substantial conservation of coding and noncoding sequences. Conserved elements in imprinted regions are marked by enrichment of CpG dinucleotides and low (TpG+CpA)/(2·CpG) ratios indicate reduced CpG deamination. Interestingly, paternally and maternally expressed genes can be distinguished by differences in G+C and CpG contents that might be associated with unusual epigenetic features. Especially noncoding conserved elements of paternally expressed genes are exceptionally G+C and CpG rich. In addition, we confirmed a frequent occurrence of intronic CpG islands and observed a decelerated degeneration of ancient LINE-1 repeats. We also found a moderate enrichment of YY1 and CTCF binding sites in imprinted regions and identified several short sequence motifs in highly conserved elements that might act as additional regulatory elements.

CONCLUSIONS

We discovered several novel conserved DNA features that might be related to allele-specific DNA methylation. Our results hint at reduced CpG deamination rates in imprinted regions, which affects mostly noncoding conserved elements of paternally expressed genes. Pronounced differences between maternally and paternally expressed genes imply specific modes of evolution as a result of differences in epigenetic features and a special response to selective pressure. In addition, our data support the potential role of intronic CpG islands as epigenetic key regulatory elements and suggest that evolutionary conserved LINE-1 elements fulfill regulatory functions in imprinted regions.

The origins and evolution of genetic disease risk in modern humans

Patterns and risks of human disease have evolved. In this article, I review evidence regarding the importance of recent adaptive evolution, positive selection, and genomic conflicts in shaping the genetic and phenotypic architectures of polygenic human diseases. Strong recent selection in human populations can create and maintain genetically based disease risk primarily through three processes: increased scope for dysregulation from recent human adaptations, divergent optima generated by intraspecific genomic conflicts, and transient or stable deleterious by-products of positive selection caused by antagonistic pleiotropy, ultimately due to trade-offs at the levels of molecular genetics, development, and physiology. Human disease due to these processes appears to be concentrated in three sets of phenotypes: cognition and emotion, reproductive traits, and life-history traits related to long life-span. Diverse, convergent lines of evidence suggest that a small set of tissues whose pleiotropic patterns of gene function and expression are under especially strong selection-brain, placenta, testis, prostate, breast, and ovary-has mediated a considerable proportion of disease risk in modern humans.

Epigenetics and the placenta

BACKGROUND

The placenta is of utmost importance for intrauterine fetal development and growth. Deregulation of placentation can lead to adverse outcomes for both mother and fetus, e.g. gestational trophoblastic disease (GTD), pre-eclampsia and fetal growth retardation. A significant factor in placental development and function is epigenetic regulation.

METHODS

This review summarizes the current knowledge in the field of epigenetics in relation to placental development and function. Relevant studies were identified by searching PubMed, Medline and reference sections of all relevant studies and reviews.

RESULTS

Epigenetic regulation of the placenta evolves during preimplantation development and further gestation. Epigenetic marks, like DNA methylation, histone modifications and non-coding RNAs, affect gene expression patterns. These expression patterns, including the important parent-of-origin-dependent gene expression resulting from genomic imprinting, play a pivotal role in proper fetal and placental development. Disturbed placental epigenetics has been demonstrated in cases of intrauterine growth retardation and small for gestational age, and also appears to be involved in the pathogenesis of pre-eclampsia and GTD. Several environmental effects have been investigated so far, e.g. ethanol, oxygen tension as well as the effect of several aspects of assisted reproduction technologies on placental epigenetics.

CONCLUSIONS

Studies in both animals and humans have made it increasingly clear that proper epigenetic regulation of both imprinted and non-imprinted genes is important in placental development. Its disturbance, which can be caused by various environmental factors, can lead to abnormal placental development and function with possible consequences for maternal morbidity, fetal development and disease susceptibility in later life.

Geno-transcriptomic dissection of proteinuria in the uninephrectomized rat uncovers a molecular complexity with sexual dimorphism

Investigation of proteinuria, whose pathophysiology remains incompletely understood, is confounded by differences in the phenotype between males and females. We initiated a sex-specific geno-transcriptomic dissection of proteinuria in uninephrectomized male and female Sabra rats that spontaneously develop focal and segmental glomerulosclerosis, testing the hypothesis that different mechanisms might underlie the pathophysiology of proteinuria between the sexes. In the genomic arm, we scanned the genome of 136 male and 111 female uninephrectomized F2 populations derived from crosses between SBH/y and SBN/y. In males, we identified proteinuria-related quantitative trait loci (QTLs) on RNO2 and 20 and protective QTLs on RNO6 and 9. In females, we detected proteinuria-related QTLs on RNO11, 13, and 20. The only QTL overlap between the sexes was on RNO20. Using consomic strains, we confirmed the functional significance of this QTL in both sexes. In the transcriptomic arm, we searched on a genomewide scale for genes that were differentially expressed in kidneys of SBH/y and SBN/y with and without uninephrectomy. These studies identified within each sex differentially expressed genes of relevance to proteinuria. Integrating genomics with transcriptomics, we identified differentially expressed genes that mapped within the boundaries of the proteinuria-related QTLs, singling out 24 transcripts in males and 30 in females, only 4 of which (Tubb5, Ubd, Psmb8, and C2) were common to both sexes. Data mining revealed that these transcripts are involved in multiple molecular mechanisms, including immunity, inflammation, apoptosis, matrix deposition, and protease activity, with no single molecular pathway predominating in either sex. These results suggest that the pathophysiology of proteinuria is highly complex and that some of the underlying mechanisms are shared between the sexes, while others are sex specific and may account for the difference in the proteinuric phenotype between males and females.

Identification of copy number variants in miscarriages from couples with idiopathic recurrent pregnancy loss

BACKGROUND

Recurrent pregnancy loss (RPL), defined as two or more miscarriages, affects 3-5% of couples trying to establish a family. Despite extensive evaluation, no factor is identified in ∼40% of cases. In this study, we investigated the possibility that submicroscopic chromosomal changes, not detectable by conventional cytogenetic analysis, exist in miscarriages with normal karyotypes (46,XY or 46,XX) from couples with idiopathic RPL.

METHODS

Array comparative genomic hybridization (array-CGH) was used to assess for DNA copy number variants (CNVs) in 26 miscarriages with normal karyotypes. Parental array-CGH analysis was performed to determine if miscarriage CNVs were de novo or inherited.

RESULTS

There were 11 unique (previously not described) CNVs, all inherited, identified in 13 miscarriages from 8 couples. The maternal origin of two CNVs was of interest as they involved the imprinted genes TIMP2 and CTNNA3, which are only normally expressed from the maternal copy in the placenta. Two additional cohorts, consisting of 282 women with recurrent miscarriage (RM) and 61 fertile women, were screened for these two CNVs using a Quantitative Multiplex Fluorescent PCR of Short Fragments assay. One woman with RM, but none of the fertile women, carried the CTNNA3-associated CNV.

CONCLUSIONS

This preliminary study shows that array-CGH is useful for detecting CNVs in cases of RPL. Further investigations of CNVs, particularly those involving genes that are imprinted in placenta, in women with RPL could be worthwhile.

The importance of imprinting in the human placenta

As a field of study, genomic imprinting has grown rapidly in the last 20 years, with a growing figure of around 100 imprinted genes known in the mouse and approximately 50 in the human. The imprinted expression of genes may be transient and highly tissue-specific, and there are potentially hundreds of other, as yet undiscovered, imprinted transcripts. The placenta is notable amongst mammalian organs for its high and prolific expression of imprinted genes. This review discusses the development of the human placenta and focuses on the function of imprinting in this organ. Imprinting is potentially a mechanism to balance parental resource allocation and it plays an important role in growth. The placenta, as the interface between mother and fetus, is central to prenatal growth control. The expression of genes subject to parental allelic expression bias has, over the years, been shown to be essential for the normal development and physiology of the placenta. In this review we also discuss the significance of genes that lack conservation of imprinting between mice and humans, genes whose imprinted expression is often placental-specific. Finally, we illustrate the importance of imprinting in the postnatal human in terms of several human imprinting disorders, with consideration of the brain as a key organ for imprinted gene expression after birth.

The STOX1 genotype associated with pre-eclampsia leads to a reduction of trophoblast invasion by alpha-T-catenin upregulation

By using complementary in vitro and ex vivo approaches, we show that the risk allele (Y153H) of the pre-eclampsia susceptibility gene STOX1 negatively regulates trophoblast invasion by upregulation of the cell-cell adhesion protein alpha-T-catenin (CTNNA3). This is effectuated at the crucial epithelial-mesenchymal transition of proliferative into invasive extravillous trophoblast. This STOX1-CTNNA3 interaction is direct and includes Akt-mediated phosphorylated control of nucleo-cytoplasmic shuttling and ubiquitin-mediated degradation as shared with the FOX multigene family. This, to our knowledge, is the first time a genotype associated with pre-eclampsia has been shown to directly limit first trimester extravillous trophoblast invasion, the earliest hallmark of pre-eclampsia.

The ERAP2 gene is associated with preeclampsia in Australian and Norwegian populations

Preeclampsia is a heritable pregnancy disorder that presents new onset hypertension and proteinuria. We have previously reported genetic linkage to preeclampsia on chromosomes 2q, 5q and 13q in an Australian/New Zealand (Aust/NZ) familial cohort. This current study centered on identifying the susceptibility gene(s) at the 5q locus. We first prioritized candidate genes using a bioinformatic tool designed for this purpose. We then selected a panel of known SNPs within ten prioritized genes and genotyped them in an extended set of the Aust/NZ families and in a very large, independent Norwegian case/control cohort (1,139 cases, 2,269 controls). In the Aust/NZ cohort we identified evidence of a genetic association for the endoplasmic reticulum aminopeptidase 1 (ERAP1) gene (rs3734016, P (uncorr) = 0.009) and for the endoplasmic reticulum aminopeptidase 2 (ERAP2) gene (rs2549782, P (uncorr) = 0.004). In the Norwegian cohort we identified evidence of a genetic association for ERAP1 (rs34750, P (uncorr) = 0.011) and for ERAP2 (rs17408150, P (uncorr) = 0.009). The ERAP2 SNPs in both cohorts remained statistically significant (rs2549782, P (corr) = 0.018; rs17408150, P (corr) = 0.039) after corrections at an experiment-wide level. The ERAP1 and ERAP2 genes encode enzymes that are reported to play a role in blood pressure regulation and essential hypertension in addition to innate immune and inflammatory responses. Perturbations within vascular, immunological and inflammatory pathways constitute important physiological mechanisms in preeclampsia pathogenesis. We herein report a novel preeclampsia risk locus, ERAP2, in a region of known genetic linkage to this pregnancy-specific disorder.

Alpha-T-catenin (CTNNA3) gene was identified as a risk variant for toluene diisocyanate-induced asthma by genome-wide association analysis

BACKGROUND

Toluene diisocyanate (TDI) is the most important cause of occupational asthma, but the genetic mechanism of TDI-induced asthma is still unknown.

OBJECTIVE

The objective of the study was to identify susceptibility alleles associated with the TDI-induced asthma phenotype.

METHODS

We conducted a genome-wide association study in 84 patients with TDI-induced asthma and 263 unexposed healthy normal controls using Affymetrix 500K SNPchip. We also investigated the relationships between genetic polymorphisms and transcript levels in Epstein-Barr virus-transformed lymphoblastoid cell lines from patients with TDI-induced asthma enrolled in this study.

RESULTS

Genetic polymorphisms of CTNNA3 (catenin alpha 3, alpha-T catenin) were significantly associated with the TDI-induced asthma phenotype (5.84 x 10(-6) for rs10762058, 1.41 x 10(-5) for rs7088181, 2.03 x 10(-5) for rs4378283). Carriers with the minor haplotype, HT2 [GG], of two genetic polymorphisms (rs10762058 and rs7088181) showed significantly lower PC(20) methacholine level (P=0.041) and lower mRNA expression of CTNNA3 than non-carriers (P=0.040). A genetic polymorphism in the 3' downstream region of CTNNA3 (rs1786929), as identified by DNA direct sequencing, was significantly associated with the TDI-induced asthma phenotype (P=0.015 in recessive analysis model) and the prevalence of serum-specific IgG to cytokeratin 19 (P=0.031).

CONCLUSION

These findings suggested that multiple genetic polymorphisms of CTNNA3 may be determinants of susceptibility to TDI-induced asthma.

Genomic imprinting in the development and evolution of psychotic spectrum conditions

I review and evaluate genetic and genomic evidence salient to the hypothesis that the development and evolution of psychotic spectrum conditions have been mediated in part by alterations of imprinted genes expressed in the brain. Evidence from the genetics and genomics of schizophrenia, bipolar disorder, major depression, Prader-Willi syndrome, Klinefelter syndrome, and other neurogenetic conditions support the hypothesis that the etiologies of psychotic spectrum conditions commonly involve genetic and epigenetic imbalances in the effects of imprinted genes, with a bias towards increased relative effects from imprinted genes with maternal expression or other genes favouring maternal interests. By contrast, autistic spectrum conditions, including Kanner autism, Asperger syndrome, Rett syndrome, Turner syndrome, Angelman syndrome, and Beckwith-Wiedemann syndrome, commonly engender increased relative effects from paternally expressed imprinted genes, or reduced effects from genes favouring maternal interests. Imprinted-gene effects on the etiologies of autistic and psychotic spectrum conditions parallel the diametric effects of imprinted genes in placental and foetal development, in that psychotic spectrum conditions tend to be associated with undergrowth and relatively-slow brain development, whereas some autistic spectrum conditions involve brain and body overgrowth, especially in foetal development and early childhood. An important role for imprinted genes in the etiologies of psychotic and autistic spectrum conditions is consistent with neurodevelopmental models of these disorders, and with predictions from the conflict theory of genomic imprinting.

Psychosis and autism as diametrical disorders of the social brain

Autistic-spectrum conditions and psychotic-spectrum conditions (mainly schizophrenia, bipolar disorder, and major depression) represent two major suites of disorders of human cognition, affect, and behavior that involve altered development and function of the social brain. We describe evidence that a large set of phenotypic traits exhibit diametrically opposite phenotypes in autistic-spectrum versus psychotic-spectrum conditions, with a focus on schizophrenia. This suite of traits is inter-correlated, in that autism involves a general pattern of constrained overgrowth, whereas schizophrenia involves undergrowth. These disorders also exhibit diametric patterns for traits related to social brain development, including aspects of gaze, agency, social cognition, local versus global processing, language, and behavior. Social cognition is thus underdeveloped in autistic-spectrum conditions and hyper-developed on the psychotic spectrum.;>We propose and evaluate a novel hypothesis that may help to explain these diametric phenotypes: that the development of these two sets of conditions is mediated in part by alterations of genomic imprinting. Evidence regarding the genetic, physiological, neurological, and psychological underpinnings of psychotic-spectrum conditions supports the hypothesis that the etiologies of these conditions involve biases towards increased relative effects from imprinted genes with maternal expression, which engender a general pattern of undergrowth. By contrast, autistic-spectrum conditions appear to involve increased relative bias towards effects of paternally expressed genes, which mediate overgrowth. This hypothesis provides a simple yet comprehensive theory, grounded in evolutionary biology and genetics, for understanding the causes and phenotypes of autistic-spectrum and psychotic-spectrum conditions.

Genes and the preeclampsia syndrome

Preeclampsia is specific to pregnancy and is still a leading cause of maternal and perinatal mortality and morbidity, affecting about 3% of women, but the underlying pathogenetic mechanisms still remain unclear. Immune maladaptation, placental ischemia and increased oxidative stress represent the main components discussed to be of etiologic importance, and they all may have genetic implications. Since the familial nature of preeclampsia is known for many years, extensive research on the genetic contribution to the pathogenesis of this severe pregnancy disorder has been performed. In this review, we will overview the linkage and candidate gene studies carried out so far as well as summarize important historical notes on the genetic hypotheses generated in preeclampsia research. Moreover, the influence of maternal and fetal genes and their interaction as well as the role of genomic imprinting in preeclampsia will be discussed.

STOX1 gene in pre-eclampsia and intrauterine growth restriction

The STOX1 gene, identified as a candidate gene for pre-eclampsia in Dutch women, is placentally expressed and subject to imprinting with preferential transmission of the maternal allele. In our study, STOX1-Y153H frequencies were similar in 157 women with pre-eclampsia (65%) and in 157 controls (64%) from the general Dutch population. In an isolated Dutch population, a distortion could not be demonstrated in the transmission of STOX1-Y153H variation from heterozygous mothers to offspring in 50 and 56 families with pregnancies complicated by pre-eclampsia or intrauterine growth restriction, respectively. Our findings do not confirm previous suggestions that STOX1 plays a major role in Dutch women with pre-eclampsia.

Epigenetics in reproductive medicine

Imprinted genes comprise a small subset of the genome whose epigenetic reprogramming in the germ line is necessary for subsequent normal embryonic development. This reprogramming and resetting of the imprints, through an erasure/acquisition/maintenance cycle, is a subtle and tightly orchestrated phenomenon, involving specific genomic regions and methylation enzymes. Dysregulation of imprinted genes has indeed been shown to lead to several human disorders as well as to affect placental and fetal growth. There have been numerous and conflicting studies assessing the possible association of imprinting disorders with assisted reproductive techniques. This work analyzes all relevant and available reports with regard to the association between assisted reproductive techniques and imprinting disorders. It also discusses whether this possibly increased risk of imprinting disorders may be linked to specific steps of these reproductive techniques or already present in the gametes of infertile patients. A better understanding of epigenetic reprogramming in the germ line is absolutely necessary both to assess the safety of these methods and of the use of impaired spermatogenesis gametes for assisted reproduction.