Ovarian failure related to eukaryotic initiation factor 2B mutations

Oocyte-specific deletion of eukaryotic translation initiation factor 5 causes apoptosis of mouse oocytes within the early-growing follicles by mitochondrial fission defect-reactive oxygen species-DNA damage

BACKGROUND

Mutations in several translation initiation factors are closely associated with premature ovarian insufficiency (POI), but the underlying pathogenesis remains largely unknown.

METHODS AND RESULTS

We generated eukaryotic translation initiation factor 5 (Eif5) conditional knockout mice aiming to investigate the function of eIF5 during oocyte growth and follicle development. Here, we demonstrated that Eif5 deletion in mouse primordial and growing oocytes both resulted in the apoptosis of oocytes within the early-growing follicles. Further studies revealed that Eif5 deletion in oocytes downregulated the levels of mitochondrial fission-related proteins (p-DRP1, FIS1, MFF and MTFR) and upregulated the levels of the integrated stress response-related proteins (AARS1, SHMT2 and SLC7A1) and genes (Atf4, Ddit3 and Fgf21). Consistent with this, Eif5 deletion in oocytes resulted in mitochondrial dysfunction characterized by elongated form, aggregated distribution beneath the oocyte membrane, decreased adenosine triphosphate content and mtDNA copy numbers, and excessive accumulation of reactive oxygen species (ROS) and mitochondrial superoxide. Meanwhile, Eif5 deletion in oocytes led to a significant increase in the levels of DNA damage response proteins (γH2AX, p-CHK2 and p-p53) and proapoptotic proteins (PUMA and BAX), as well as a significant decrease in the levels of anti-apoptotic protein BCL-xL.

CONCLUSION

These findings indicate that Eif5 deletion in mouse oocytes results in the apoptosis of oocytes within the early-growing follicles via mitochondrial fission defects, excessive ROS accumulation and DNA damage. This study provides new insights into pathogenesis, genetic diagnosis and potential therapeutic targets for POI.

KEY POINTS

Eif5 deletion in oocytes leads to arrest in oocyte growth and follicle development. Eif5 deletion in oocytes impairs the translation of mitochondrial fission-related proteins, followed by mitochondrial dysfunction. Depletion of Eif5 causes oocyte apoptosis via ROS accumulation and DNA damage response pathway.

Mammalian integrated stress responses in stressed organelles and their functions

The integrated stress response (ISR) triggered in response to various cellular stress enables mammalian cells to effectively cope with diverse stressful conditions while maintaining their normal functions. Four kinases (PERK, PKR, GCN2, and HRI) of ISR regulate ISR signaling and intracellular protein translation via mediating the phosphorylation of eukaryotic translation initiation factor 2 α (eIF2α) at Ser51. Early ISR creates an opportunity for cells to repair themselves and restore homeostasis. This effect, however, is reversed in the late stages of ISR. Currently, some studies have shown the non-negligible impact of ISR on diseases such as ischemic diseases, cognitive impairment, metabolic syndrome, cancer, vanishing white matter, etc. Hence, artificial regulation of ISR and its signaling with ISR modulators becomes a promising therapeutic strategy for relieving disease symptoms and improving clinical outcomes. Here, we provide an overview of the essential mechanisms of ISR and describe the ISR-related pathways in organelles including mitochondria, endoplasmic reticulum, Golgi apparatus, and lysosomes. Meanwhile, the regulatory effects of ISR modulators and their potential application in various diseases are also enumerated.

Pearls & Oy-sters: AARS2 Leukodystrophy-Tremor and Tribulations

A 35-year-old woman with a progressive, bilateral upper limb tremor, personality change, behavioral disturbance, and primary ovarian insufficiency was found to have AARS2-related leukodystrophy. She had congenital nystagmus which evolved to head titubation by age 8 years and then developed an upper limb tremor in her mid-teens. These symptoms stabilized during her 20s, but soon after this presentation at age 35 years, neurologic and behavioral disturbances progressed rapidly over a 12-month period requiring transition to an assisted living facility with care support (4 visits/day) and assistance for all activities of daily living. MRI of the brain demonstrated confluent white matter changes predominantly involving the frontal lobes consistent with a leukodystrophy. All other investigations were unremarkable. Nongenetic causes of a leukodystrophy including sexually transmitted diseases and recreational drug use were excluded. Family history was negative for similar symptoms. Gene panel testing identified compound heterozygous pathogenic AARS2 mutations. This case highlights the importance of MRI brain imaging in progressive tremor syndromes, the utility of gene panels in simultaneous testing of multiple disorders with overlapping phenotypes, and the need for awareness of comorbid endocrinological disorders in many of the genetic leukodystrophies, whose identification may aid in clinical diagnosis.

Screening of premature ovarian insufficiency associated genes in Hungarian patients with next generation sequencing

BACKGROUND

Premature ovarian insuffiency (POI) is one of the main cause behind infertility. The genetic analysis of POI should be part of the clinical diagnostics, as several genes have been implicated in the genetic background of it. The aim of our study was to analyse the genetic background of POI in a Hungarian cohort.

METHODS

The age of onset was between 15 and 39 years. All patients had the 46,XX karyotype and they were prescreened for the most frequent POI associated FMR1 premutation. To identify genetic alterations next-generation sequencing (NGS) of 31 genes which were previously associated to POI were carried out in 48 unrelated patients from Hungary.

RESULTS

Monogenic defect was identified in 16.7% (8 of 48) and a potential genetic risk factor was found in 29.2% (14 of 48) and susceptible oligogenic effect was described in 12.5% (6 of 48) of women with POI using the customized targeted panel sequencing. The genetic analysis identified 8 heterozygous damaging and 4 potentially damaging variants in POI-associated genes. Further 10 potential genetic risk factors were detected in seven genes, from which EIF2B and GALT were the most frequent. These variants were related to 15 genes: AIRE, ATM, DACH2, DAZL, EIF2B2, EIF2B4, FMR1, GALT, GDF9, HS6ST2, LHCGR, NOBOX, POLG, USP9X and XPNPEP2. In six cases, two or three coexisting damaging mutations and risk variants were identified.

CONCLUSIONS

POI is characterized by heterogenous phenotypic features with complex genetic background that contains increasing number of genes. Deleterious variants, which were detected in our cohort, related to gonadal development (oogenesis and folliculogenesis), meiosis and DNA repair, hormonal signaling, immune function, and metabolism which were previously associated with the POI phenotype. This is the first genetic epidemiology study targeting POI associated genes in Hungary. The frequency of variants in different POI associated genes were similar to the literature, except EIF2B and GALT. Both of these genes potential risk factor were detected which could influence the phenotype, although it is unlikely that they can be responsible for the development of the disease by themselves. Advances of sequencing technologies make it possible to aid diagnostics of POI Since individual patients show high phenotypic variance because of the complex network controlling human folliculogenesis. Comprehensive NGS screening by widening the scope to genes which were previously linked to infertility may facilitate more accurate, quicker and cheaper genetic diagnoses for POI. The investigation of patient's genotype could support clinical decision-making process and pave the way for future clinical trials and therapies.

General approach to treatment of genetic leukoencephalopathies in children and adults

Despite the enormous advancements seen in recent years, curative therapies for patients with genetic leukoencephalopathies are available for only a relatively small number of disorders. Therefore, symptomatic treatment and preventive management of the multiple clinical manifestations of patients with genetic leukoencephalopathies are critical in their care. The goals of the symptomatic treatment are to improve patients' quality of life, increase their survival, and reduce the impact on medical resources and related expenses. The coordinated work of a multidisciplinary team, including all specialists involved in the care of these patients, is the gold standard approach to manage and treat their complex and evolving clinical picture. Along with a multidisciplinary team, the relationship and close collaboration with the patient and their caregivers are essential. Their insight into the disease manifestations and management of the different issues should be integrated with the assessments of the multidisciplinary team to prevent clinical complications and preserve the quality of life of patients and their caregivers. Genetic leukoencephalopathies are very heterogeneous in terms of age of onset, clinical features, and disease course. However, many clinical features and problems are shared by most forms. Consequently, common therapeutic strategies apply to the majority of these diseases. This chapter presents the symptomatic approach for shared core clinical features presented by patients with genetic leukoencephalopathies divided by systems and, for each system, the specificities of some genetic leukoencephalopathies.

Amino-acyl tRNA synthetases associated with leukodystrophy

Amino-acyl tRNA synthetases (ARSs) are enzymes that catalyze the amino-acylation reaction of a specific amino acid and its cognate tRNA and are divided into type 1 (cytosolic) and type 2 (mitochondrial). In this chapter leukodystrophies caused by tRNA synthetase deficiencies are reviewed.

Vanishing white matter

"Vanishing white matter" (VWM) is a leukodystrophy caused by autosomal recessive pathogenic variants in the genes encoding the subunits of eukaryotic initiation factor 2B (eIF2B). Disease onset and disease course are extremely variable. Onset varies from the antenatal period until senescence. The age of onset is predictive of disease severity. VWM is characterized by chronic neurologic deterioration and, additionally, episodes of rapid and major neurologic decline, provoked by stresses such as febrile infections and minor head trauma. The disease is dominated by degeneration of the white matter of the central nervous system due to dysfunction of oligodendrocytes and in particular astrocytes. Organs other than the brain are rarely affected, with the exception of the ovaries. The reason for the selective vulnerability of the white matter of the central nervous system and, less consistently, the ovaries is poorly understood. eIF2B is a central regulatory factor in the integrated stress response (ISR). Genetic variants decrease eIF2B activity and thereby cause constitutive activation of the ISR downstream of eIF2B. Strikingly, the ISR is specifically activated in astrocytes. Modulation of eIF2B activity and ISR activation in VWM mouse models impacts disease severity, revealing eIF2B-regulated pathways as potential druggable targets.

Adult-Onset White Matter Vanishing Disease With Ovarian Failure in a Salvadoran Patient

White matter vanishing disease is a type of leukodystrophy common in children with hypomyelination linked with ataxia, all of whom have an autosomal recessive inheritance. There are few reports of late-onset cases associated with ovarian failure. In Mesoamerican populations, this disease is mostly reported in children but rarely in adults. We present a case of a 35-year-old Salvadoran female patient with a history of menometrorrhagia, infertility, slowly progressive gait decline, paraparesis, spasticity, cerebellar ataxia, cognitive impairment with predominant executive dysfunction, learning difficulties, and emotional lability. A T2-weighted brain MRI and fluid-attenuated inversion recovery (FLAIR) images showed bilateral symmetrical areas of hyperintensities in the white matter with multiple foci of cystic degeneration within the hyperintense area. Two pathogenic variants were identified in the EIF2B5 gene. This case is of interest to increase awareness of late-onset leukodystrophies, widen the phenotypic spectrum of the disease, and constitute a valuable report for the international community, since it is a less frequently reported disease.

Juxtacortical White Matter Hypointensity on T2*Gradient Echo Image in Vanishing White Matter Disease: A Case Report

BACKGROUND Vanishing white matter disease (VWMD) - also known as childhood ataxia with central nervous system hypomyelination - is one of the most commonly inherited white matter diseases in children. Notably, a course of chronic progressive disease with episodes of rapid and major stress-induced neurological deterioration, such as fever and minor head trauma, is a typical clinical feature of VWMD. The combination of clinical features with specific magnetic resonance imaging findings, including diffuse and extensive white matter lesions with rarefaction or cystic destruction, could recommend a genetic diagnosis. However, VWMD is phenotypically diverse and can affect individuals of all ages. CASE REPORT A 29-year-old female patient presented with recent aggravation in gait disturbance. She had progressive movement disorder, with symptoms ranging from hand tremors to upper- and lower-extremity weakness, for 5 years. Whole-exome sequencing was performed to confirm the diagnosis of VWMD, and it revealed a mutation in homozygous eIF2B2 gene. The temporal evolution of VWMD observed in the patient for 17 years (from the age of 12 to 29 years) indicated an increased extent of T2 white matter hyperintensity in the cerebrum into the cerebellum and an increased amount of dark signal intensities in the globus pallidus and dentate nucleus. Moreover, a T2*-weighted imaging (WI) scan revealed diffuse, linear, and symmetrical hypointensity along the juxtacortical white matter on the magnification view. CONCLUSIONS This is the case report about rare and unusual finding of diffuse linear juxtacortical white matter hypointensity on T2*-WI scan as a potential radiographic marker for adult-onset VWMD.

Identification of a Novel Heterozygous Mutation in the EIF2B4 Gene Associated With Vanishing White Matter Disease

Vanishing white matter disease (VWM) is one of the most common childhood inherited leukoencephalopathies with autosomal recessive inheritance. Mutations in five genes, EIF2B1-5, have been identified as the major cause of VWM. In this study, a targeted gene capture sequencing panel comprising 160 known pathogenic genes associated with leukoencephalopathies was performed in a large Han Chinese family affected by adult-onset VWM, and a novel heterozygous missense mutation (c.1337G > A [p. R446H]) in EIF2B4 (NM_001034116.2) was detected. Further functional studies in HEK 293 cells showed dramatically reduced EIF2Bδ protein levels in the mutated group compared with the wild-type group. This study revealed that a heterozygous missense mutation (c.1337G > A [p. R446H]) in EIF2B4 was potentially associated with the adult-onset mild phenotype of VWM. In contrast to previous reports, autosomal dominant inheritance was also observed in adult-onset VWM.

Association Between Late-Onset Leukoencephalopathy With Vanishing White Matter and Compound Heterozygous EIF2B5 Gene Mutations: A Case Report and Review of the Literature

Leukoencephalopathy with vanishing white matter (LVWM) is an autosomal recessive disease. Ovarioleukodystrophy is defined as LVWM in females showing signs or symptoms of gradual ovarian failure. We present a 38-year-old female with ovarioleukodystrophy who showed status epilepticus, gait instability, slurred speech, abdominal tendon hyperreflexia, and ovarian failure. Abnormal EEG, characteristic magnetic resonance, and unreported EIF2B5 compound heterozygous mutations [c.1016G>A (p.R339Q) and c.1157G>A (p.G386D)] were found. Furthermore, the present report summarizes 20 female patients with adult-onset ovarioleukodystrophy and EIF2B5 gene mutations. In conclusion, a new genetic locus for LVWM was discovered. Compared with previous cases, mutations at different EIF2B5 sites might have different clinical manifestations and obvious clinical heterogeneity.

Causal and Candidate Gene Variants in a Large Cohort of Women With Primary Ovarian Insufficiency

CONTEXT

A genetic etiology likely accounts for the majority of unexplained primary ovarian insufficiency (POI).

OBJECTIVE

We hypothesized that heterozygous rare variants and variants in enhanced categories are associated with POI.

DESIGN

The study was an observational study.

SETTING

Subjects were recruited at academic institutions.

PATIENTS

Subjects from Boston (n = 98), the National Institutes of Health and Washington University (n = 98), Pittsburgh (n = 20), Italy (n = 43), and France (n = 32) were diagnosed with POI (amenorrhea with an elevated follicle-stimulating hormone level). Controls were recruited for health in old age or were from the 1000 Genomes Project (total n = 233).

INTERVENTION

We performed whole exome sequencing (WES), and data were analyzed using a rare variant scoring method and a Bayes factor-based framework for identifying genes harboring pathogenic variants. We performed functional studies on identified genes that were not previously implicated in POI in a D. melanogaster model.

MAIN OUTCOME

Genes with rare pathogenic variants and gene sets with increased burden of deleterious variants were identified.

RESULTS

Candidate heterozygous variants were identified in known genes and genes with functional evidence. Gene sets with increased burden of deleterious alleles included the categories transcription and translation, DNA damage and repair, meiosis and cell division. Variants were found in novel genes from the enhanced categories. Functional evidence supported 7 new risk genes for POI (USP36, VCP, WDR33, PIWIL3, NPM2, LLGL1, and BOD1L1).

CONCLUSIONS

Candidate causative variants were identified through WES in women with POI. Aggregating clinical data and genetic risk with a categorical approach may expand the genetic architecture of heterozygous rare gene variants causing risk for POI.

An eleven-year history of Vanishing White Matter Disease in an adult patient with no cognitive decline and EIF2B5 mutations. A case report

Vanishing White Matter Disease (VWMD) is a rare autosomal recessive leukoencephalopathy . The classical presentation is characterized by a severe cerebellar ataxia, spasticity, neurological deterioration with a chronic progressive course and episodes of acute neurological deterioration after stress conditions.We report a 52-year-old man with VWMD and atypical features who manifested two major events of transient aphasia eleven years apart with complete recovery in 48 hours. No cognitive decline was present. Brain MRI revealed typical aspects of VWMD including diffuse leukoencephalopathy with relative sparing of U-fibers. We identified the presence of c.592G>A (p.Glu198Lys) and c.1360 C>T (p.Pro454Ser) mutations in EIF2B5.

Adult-onset vanishing white matter in a patient with EIF2B3 variants misdiagnosed as multiple sclerosis

BACKGROUND

Vanishing white matter (VWM) is an autosomal recessive disorder characterized by childhood ataxia with central hypomyelination. Adult-onset VWM should be considered as a differential diagnosis for suspected cases of multiple sclerosis (MS).

METHODS

Targeted region sequencing (TRS) and Sanger sequencing validation were performed to identify and validate the likely pathogenic mutations in a family with VWM.

RESULTS

The main clinical manifestations of the proband included decreased vision and sleepiness accompanied by atrophy of the corpus callosum, affected inner rim of the corpus callosum, decreased apparent diffusion coefficient value or persistent hyperintensity-diffusion-weighted imaging, atrophied optic nerve, and no recordable visual evoked potentials. Due to the slow development and atypical VWM image features, MS was initially suspected. After prednisone was administered, the patient's condition did not improve significantly, and other diseases were considered. The TRS and Sanger sequencing identified compound heterozygous mutations of EIF2B3 in the proband; c.965C > G /p.Ala322Gly in exon 8 and c.130G > A/p.Glu44Lys in exon 2 were missense mutations inherited from the mother and father, respectively. The proband's oldest brother had the same compound heterozygous mutations but showed no symptoms.

CONCLUSION

This is the first report of adult-onset VWM in a Chinese family. Initially, MS was suspected, and genetic testing confirmed the diagnosis of VWM. This study may further broaden the clinical spectrum of EIF2B3, thus providing a foundation for further research on the pathogenesis and genetic therapy for VWM.

A (dis)integrated stress response: Genetic diseases of eIF2α regulators

The integrated stress response (ISR) is a conserved mechanism by which eukaryotic cells remodel gene expression to adapt to intrinsic and extrinsic stressors rapidly and reversibly. The ISR is initiated when stress-activated protein kinases phosphorylate the major translation initiation factor eukaryotic translation initiation factor 2ɑ (eIF2ɑ), which globally suppresses translation initiation activity and permits the selective translation of stress-induced genes including important transcription factors such as activating transcription factor 4 (ATF4). Translationally repressed messenger RNAs (mRNAs) and noncoding RNAs assemble into cytoplasmic RNA-protein granules and polyadenylated RNAs are concomitantly stabilized. Thus, regulated changes in mRNA translation, stability, and localization to RNA-protein granules contribute to the reprogramming of gene expression that defines the ISR. We discuss fundamental mechanisms of RNA regulation during the ISR and provide an overview of a growing class of genetic disorders associated with mutant alleles of key translation factors in the ISR pathway. This article is categorized under: RNA Interactions with Proteins and Other Molecules > Protein-RNA Interactions: Functional Implications RNA in Disease and Development > RNA in Disease Translation > Translation Regulation RNA in Disease and Development > RNA in Development.

Identification of novel candidate genes for age at first calving in Nellore cows using a SNP chip specifically developed for Bos taurus indicus cattle

The age at first calving has a great economic impact on the beef cattle system and calving at 24 months is an objective of selection for a more efficient herd. However, an age at first calving around 36 months has been observed for Nellore cattle in Brazil. Thus, a genome-wide association study (GWAS) was carried out with 8376 records of age at first calving and 3239 animals genotyped with the GGP-Indicus 35K, which has been developed specifically for Bos taurus indicus. The weighted single-step genomic best linear unbiased prediction method was used, with adjacent SNPs (single nucleotide polymorphisms) in genomic windows of 1.0 Mb. After quality control, 3239 (2161 males and 1078 females) animals genotyped for 30,519 SNPs were used in GWAS analysis. The average and standard deviation of age at first calving were 1041.7 and 140.6 days, respectively. The heritability estimate was 0.10 ± 0.02. The GWAS analysis found seven genomic regions in BTA1, 2, 5, 12, 18, 21, and 24, which explained a total of 11.24% of the additive genetic variance of age at first calving. In these regions were found 62 protein coding genes, and the genes HSD17B2, SERPINA14, SERPINA1, SERPINA5, STAT1, NFATC1, ATP9B, CTDP1, THPO, ECE2, PSMD2, EIF4G1, EIF2B2, DVL3, POLR2H, TMTC2, and GPC6 are possible candidates for age at first birth due their function. Moreover, two molecular functions ("serine-type endopeptidase inhibitor activity" and "negative regulation of endopeptidase activity") were significant, which depend on several serpin genes. The use of a SNP chip developed especially for Bos taurus indicus allowed to find genomic regions for age at first calving, which are close to QTLs previously reported for other reproduction-related traits. Future studies can reveal the causal variants and their effects on reproductive precocity of Nellore cows.

Saccharomyces cerevisiae ER membrane protein complex subunit 4 (EMC4) plays a crucial role in eIF2B-mediated translation regulation and survival under stress conditions

Background

Eukaryotic initiation factor 2B (eIF2B) initiates and regulates translation initiation in eukaryotes. eIF2B gene mutations cause leukoencephalopathy called vanishing white matter disease (VWM) in humans and slow growth (Slg⁻) and general control derepression (Gcd⁻) phenotypes in Saccharomyces cerevisiae.

Results

To suppress eIF2B mutations, S. cerevisiae genomic DNA library was constructed in high-copy vector (YEp24) and transformed into eIF2B mutant S. cerevisiae strains. The library was screened for wild-type genes rescuing S. cerevisiae (Slg⁻) and (Gcd⁻) phenotypes. A genomic clone, Suppressor-I (Sup-I), rescued S. cerevisiae Slg⁻ and Gcd⁻ phenotypes (gcd7-201 gcn2∆). The YEp24/Sup-I construct contained truncated TAN1, full length EMC4, full length YGL230C, and truncated SAP4 genes. Full length EMC4 (chaperone protein) gene was sub-cloned into pEG (KG) yeast expression vector and overexpressed in gcd7-201 gcn2∆ strain which suppressed the Slg⁻ and Gcd⁻ phenotype. A GST-Emc4 fusion protein of 47 kDa was detected by western blotting using α-GST antibodies. Suppression was specific to gcd7-201 gcn2∆ mutation in eIF2Bβ and Gcd1-502 gcn2∆ in eIF2Bγ subunit. Emc4p overexpression also protected the wild type and mutant (gcd7-201 gcn2∆, GCD7 gcn2∆, and GCD7 GCN2∆) strains from H₂O₂, ethanol, and caffeine stress.

Conclusions

Our results suggest that Emc4p is involved in eIF2B-mediated translational regulation under stress and could provide an amenable tool to understand the eIF2B-mediated defects.

Identification of potential causal variants for premature ovarian failure by whole exome sequencing

BACKGROUND

Premature ovarian failure (POF) is a highly heterogeneous disorder that occurs in 1% of women of reproductive age. Very few causative genes and variants contributing to POF have been detected, and the disease remains incompletely understood. In this study, we used whole exome sequencing (WES) to identify potential causal variants leading to POF.

METHODS

WES was conducted to identify variants in 34 Korean patients with POF, alongside 10 normal controls. Detected variants were filtered using a range of characterized bioinformatics analyses, and the machine learning tools, CADD and VEST, were used to predict pathogenic variants that could cause disease. VarSome was used for a comprehensive interpretation of the variants. Potential causal variants finally screened by these analyses were confirmed using Sanger sequencing.

RESULTS

We identified nine potential causative variants in genes previously associated with POF in 8 of 34 (24%) Korean patients by WES variant analysis. These potentially pathogenic variants included mutations in the MCM8, MCM9, and HFM1 genes, which are involved in homologous recombination, DNA repair, and meiosis, and are established as causing POF. Using a combination of CADD and VEST, 72 coding variants were also identified in 72 genes, including ADAMTSL1 and FER1L6, which have plausible functional links to POF.

CONCLUSIONS

WES is a useful tool to detect genetic variants that cause POF. Accumulation and systematic management of data from a number of WES studies in specialized groups of patients with POF (family data, severe case populations) are needed to better comprehend the genetic landscape underlying POF.

Whole-exome sequencing in patients with premature ovarian insufficiency: early detection and early intervention

Background

The loss of ovarian function in women, referred to as premature ovarian insufficiency (POI), is associated with a series of concomitant diseases. POI is genetically heterogeneous, and in most cases, the etiology is unknown.

Methods

Whole-exome sequencing (WES) was performed on DNA samples obtained from patients with POI, and Sanger sequencing was used to validate the detected potentially pathogenic variants. An in silico analysis was carried out to predict the pathogenicity of the variants.

Results

We recruited 24 patients with POI and identified variants in POI-related genes in 14 patients, including bi-allelic mutations in DNAH6, HFM1, EIF2B2, BNC, and LRPPRC and heterozygous variants in BNC1, EIF2B4, FOXL2, MCM9, FANCA, ATM, EIF2B3, and GHR. No variants in the above genes were detected in the WES data obtained from 29 women in a control group without POI. Determining a clear genetic etiology could significantly increase patient compliance with appropriate intervention strategies.

Conclusions

Our study confirmed that POI is a genetically heterogeneous condition and that whole-exome sequencing is a powerful tool for determining its genetic etiology. The results of this study will aid researchers and clinicians in genetic counseling and suggests the potential of WES for the detection of POI and thus early interventions for patients with POI.

Premature ovarian insufficiency in adolescence: a chance for early diagnosis?

Premature ovarian insufficiency (POI) is typically diagnosed when amenorrhea is combined with high gonadotrophins and hypoestrogenemia in a woman under 40 years of age, although, more rarely, POI can develop in adolescence and present with delayed puberty or amenorrhea, depending on the timing of follicular depletion or insult to the ovary. In a proportion of girls, the diagnosis may be made at an early stage of POI, presenting with abnormal uterine bleeding, when some follicular function is still retained. The natural history of POI in this group of patients is not clear; however, they could represent a subgroup with a unique opportunity for early intervention and thus the provision of fertility preservation options. While the etiology of POI in a large number of girls remains unknown, a growing number will be identified as carriers of genetic mutations, offering clinicians a yet greater opportunity to provide genetic counseling to other female family members. The aim of this review is to provide information regarding the etiology, diagnosis, and treatment of POI in adolescents while detailing the new options for fertility preservation when POI is diagnosed at an early stage.

The disappearance of white matter in an adult-onset disease: a case report

BACKGROUND

Vanishing white matter disease (VWMD) is one of the most prevalent hereditary white matter diseases in childhood, but it is increasingly recognised in adulthood with high phenotypic variation and severity.

CASE PRESENTATION

We report a case of an adult female presenting with emotional lability and cognitive impairment, in addition to progressive dystonia, ataxia, postural instability and recurrent falls. Magnetic resonance imaging (MRI) of the brain and genetic testing confirmed the diagnosis of VWMD.

CONCLUSIONS

VWMD has a broad clinical presentation in adulthood, and the age at onset of symptoms is one of its most important prognostic factors. It is crucial to recognize the pathognomonic MRI patterns and consider VWMD as a differential diagnosis when assessing patients presenting with psychiatric, cognitive and non-specific neurological symptoms.

Diversity of RNA-Binding Proteins Modulating Post-Transcriptional Regulation of Protein Expression in the Maturing Mammalian Oocyte

The oocyte faces a particular challenge in terms of gene regulation. When oocytes resume meiosis at the end of the growth phase and prior to ovulation, the condensed chromatin state prevents the transcription of genes as they are required. Transcription is effectively silenced from the late germinal vesicle (GV) stage until embryonic genome activation (EGA) following fertilisation. Therefore, during its growth, the oocyte must produce the mRNA transcripts needed to fulfil its protein requirements during the active period of meiotic completion, fertilisation, and the maternal-to zygote-transition (MZT). After meiotic resumption, gene expression control can be said to be transferred from the nucleus to the cytoplasm, from transcriptional regulation to translational regulation. Maternal RNA-binding proteins (RBPs) are the mediators of translational regulation and their role in oocyte maturation and early embryo development is vital. Understanding these mechanisms will provide invaluable insight into the oocyte's requirements for developmental competence, with important implications for the diagnosis and treatment of certain types of infertility. Here, we give an overview of post-transcriptional regulation in the oocyte, emphasising the current knowledge of mammalian RBP mechanisms, and develop the roles of these mechanisms in the timely activation and elimination of maternal transcripts.

Astroglia in Leukodystrophies

Leukodystrophies are genetically determined disorders affecting the white matter of the central nervous system. The combination of MRI pattern recognition and next-generation sequencing for the definition of novel disease entities has recently demonstrated that many leukodystrophies are due to the primary involvement and/or mutations in genes selectively expressed by cell types other than the oligodendrocytes, the myelin-forming cells in the brain. This has led to a new definition of leukodystrophies as genetic white matter disorders resulting from the involvement of any white matter structural component. As a result, the research has shifted its main focus from oligodendrocytes to other types of neuroglia. Astrocytes are the housekeeping cells of the nervous system, responsible for maintaining homeostasis and normal brain physiology and to orchestrate repair upon injury. Several lines of evidence show that astrocytic interactions with the other white matter cellular constituents play a primary pathophysiologic role in many leukodystrophies. These are thus now classified as astrocytopathies. This chapter addresses how the crosstalk between astrocytes, other glial cells, axons and non-neural cells are essential for the integrity and maintenance of the white matter in health. It also addresses the current knowledge of the cellular pathomechanisms of astrocytic leukodystrophies, and specifically Alexander disease, vanishing white matter, megalencephalic leukoencephalopathy with subcortical cysts and Aicardi-Goutière Syndrome.

Adult-onset vanishing white matter disease with the EIF2B2 gene mutation presenting as menometrorrhagia

Background

Vanishing white matter disease (VWMD) is one of the most prevalent inherited leukoencephalopathies, which generally presents in childhood as a progressive disorder while less beginning in adulthood. The present report describes the clinical, neuroimaging, and genetic findings of a female patient with adult-onset VWMD. In addition, to provide a clearer delineation of the clinical and genetic characteristics of female adult-onset VWMD patients, 32 genetically confirmed female adult-onset EIF2B-mutated cases are summarized.

Case presentation

The patient described here suffered from long-term menometrorrhagia prior to manifesting progressive neurological impairments that included tremors, bilateral pyramidal tract injury, cerebellar ataxia, and dementia. To the best of our knowledge, this is the first female patient with adult-onset VWMD suffering from long-term menometrorrhagia attributed to the c.254 T > A and c.496A > G mutations in the EIF2B2 gene; the c.496A > G mutation has not been reported in previous studies. The patient also exhibited metabolic dysfunction. The present findings widen the spectrum of phenotypic heterogeneity observed in VWMD patients.

Conclusions

The present report summarizes 33 female patients with adult-onset VWMD to provide an overview of the clinical and genetic characteristics of this disorder and ovarioleukodystrophy. The mean age of clinical onset in female patients with adult-onset VWMD was 36.8 years and the neurological symptoms primarily included motor and cognitive dysfunction such as paraparesis, cerebellar ataxia, and executive deficits. In addition, ovarian failure occurred in all of these female patients and usually preceded the neurological symptoms. Furthermore, several patients also suffered from metabolic dysfunction. All 33 patients had mutations on EIF2B1–5, and of these, the c.338 G > A mutation in the EIF2B5 gene (p.Arg113His) was the most common. These findings suggest that clinicians should be aware of adult-onset forms of VWMD as well as its typical magnetic resonance imaging (MRI) and clinical characteristics although this pathology is usually recognized as a pediatric disorder. No curative treatment is presently available, and thus early recognition is important to prevent triggering events and to allow for genetic counseling.

Electronic supplementary material

The online version of this article (10.1186/s12883-019-1429-9) contains supplementary material, which is available to authorized users.

Vanishing white matter disease imaged over 3 years

Childhood ataxia and central nervous system hypomyelination (CACH), also known as ‘vanishing white matter disease’ (VWM), is a leukoencephalopathy with autosomal recessive inheritance. It is characterised by normal psychomotor development initially, with an onset of neurological deterioration that follows a chronic and progressive course. Stress conditions such as febrile infections, minor head trauma or even acute fright provoke major episodes of neurological deterioration. We present a case of a 2-year-old child who presented with spasticity and cerebellar ataxia. After magnetic resonance imaging (MRI) of the brain, CACH/VWM was diagnosed on the basis of the typical clinical and MRI findings. As there is no known cure for CACH/VWM, our patient was followed up over 3 years with MRIs of the brain to assess the progressive involvement of the cerebral white matter. In those patients with suggestive or inconclusive MRI findings for CACH/VWM, particularly in the presymptomatic stage and adult onset variants, involvement of the inner rim of the corpus callosum should prompt the inclusion of CACH/VWM in the differential diagnosis. Biochemical markers such as the asialotransferrin:transferrin ratio in the cerebrospinal fluid can also potentially be used as a screening tool in this subset of patients prior to gene mutation analysis.

Mutations in the mitochondrial ribosomal protein MRPS22 lead to primary ovarian insufficiency

Primary ovarian insufficiency (POI) is characterized by amenorrhea and loss or dysfunction of ovarian follicles prior to the age of 40. POI has been associated with autosomal recessive mutations in genes involving hormonal signaling and folliculogenesis, however, the genetic etiology of POI most often remains unknown. Here we report MRPS22 homozygous missense variants c.404G>A (p.R135Q) and c.605G>A (p.R202H) identified in four females from two independent consanguineous families as a novel genetic cause of POI in adolescents. Both missense mutations identified in MRPS22 are rare, occurred in highly evolutionarily conserved residues, and are predicted to be deleterious to protein function. In contrast to prior reports of mutations in MRPS22 associated with severe mitochondrial disease, the POI phenotype is far less severe. Consistent with this genotype-phenotype correlation, mitochondrial defects in oxidative phosphorylation or rRNA levels were not detected in fibroblasts derived from the POI patients, suggesting a non-bioenergetic or tissue-specific mitochondrial defect. Furthermore, we demonstrate in a Drosophila model that mRpS22 deficiency specifically in somatic cells of the ovary had no effect on fertility, whereas flies with mRpS22 deficiency specifically in germ cells were infertile and agametic, demonstrating a cell autonomous requirement for mRpS22 in germ cell development. These findings collectively identify that MRPS22, a component of the small mitochondrial ribosome subunit, is critical for ovarian development and may therefore provide insight into the pathophysiology and treatment of ovarian dysfunction.

Vanishing white matter: a leukodystrophy due to astrocytic dysfunction

VWM is one of the most prevalent leukodystrophies with unique clinical, pathological and molecular features. It mostly affects children, but may develop at all ages, from birth to senescence. It is dominated by cerebellar ataxia and susceptible to stresses that act as factors provoking disease onset or episodes of rapid neurological deterioration possibly leading to death. VWM is caused by mutations in any of the genes encoding the five subunits of the eukaryotic translation initiation factor 2B (eIF2B). Although eIF2B is ubiquitously expressed, VWM primarily manifests as a leukodystrophy with increasing white matter rarefaction and cystic degeneration, meager astrogliosis with no glial scarring and dysmorphic immature astrocytes and increased numbers of oligodendrocyte progenitor cells that are restrained from maturing into myelin-forming cells. Recent findings point to a central role for astrocytes in driving the brain pathology, with secondary effects on both oligodendroglia and axons. In this, VWM belongs to the growing group of astrocytopathies, in which loss of essential astrocytic functions and gain of detrimental functions drive degeneration of the white matter. Additional disease mechanisms include activation of the unfolded protein response with constitutive predisposition to cellular stress, failure of astrocyte-microglia crosstalk and possibly secondary effects on the oxidative phosphorylation. VWM involves a translation initiation factor. The group of leukodystrophies due to defects in mRNA translation is also growing, suggesting that this may be a common disease mechanism. The combination of all these features makes VWM an intriguing natural model to understand the biology and pathology of the white matter.

Expanding the phenotype of IBA57 mutations: related leukodystrophy can remain asymptomatic

Biallelic mutations in IBA57 cause a mitochondrial disorder with a broad phenotypic spectrum that ranges from severe intellectual disability to adolescent-onset spastic paraplegia. Only 21 IBA57 mutations have been reported, therefore the phenotypic spectrum of IBA57-related mitochondrial disease has not yet been fully elucidated. In this study, we performed whole-exome sequencing on a Sepharadi Jewish and Japanese family with leukodystrophy. We identified four novel biallelic variants in IBA57 in the two families: one frameshift insertion and three missense variants. The three missense variants were predicted to be disease-causing by multiple in silico tools. The 29-year-old Sepharadi Jewish male had infantile-onset optic atrophy with clinically asymptomatic leukodystrophy involving periventricular white matter. The 19-year-old younger brother, with the same compound heterozygous IBA57 variants, had a similar clinical course until 7 years of age. However, he then developed a rapidly progressive spastic paraparesis following a febrile illness. A 7-year-old Japanese girl had developmental regression, spastic quadriplegia, and abnormal periventricular white matter signal on brain magnetic resonance imaging performed at 8 months of age. She had febrile convulsions at the age of 18 months and later developed epilepsy. In summary, we have identified four novel IBA57 mutations in two unrelated families. Consequently, we describe a patient with infantile-onset optic atrophy and asymptomatic white matter involvement, thus broadening the phenotypic spectrum of biallelic IBA57 mutations.

Identification of variants in pleiotropic genes causing "isolated" premature ovarian insufficiency: implications for medical practice

Next-generation sequencing (NGS) is increasingly being used in a clinical setting for the molecular diagnosis of patients with heterogeneous disorders, such as premature ovarian insufficiency (POI). We performed NGS of ~1000 candidate genes in four unrelated patients with POI. We discovered the genetic cause of "isolated" POI in two cases, both of which had causative variants in surprising genes. In the first case, a homozygous nonsense variant in NBN was causative. Recessive function-altering NBN variants typically cause Nijmegen breakage syndrome characterized by microcephaly, cancer predisposition, and immunodeficiency, none of which are evident in the patient. At a cellular level, we found evidence of chromosomal instability. In the second case, compound heterozygous variants in EIF2B2 were causative. Recessive EIF2B2 function-altering variants usually cause leukoencephalopathy with episodic decline. Subsequent MRI revealed subclinical neurological abnormalities. These cases demonstrate that variants in NBN and EIF2B2, which usually cause severe syndromes, can cause apparently isolated POI, and that (1) NGS can precede clinical diagnosis and guide patient management, (2) NGS can redefine the phenotypic spectrum of syndromes, and (3) NGS may make unanticipated diagnoses that must be sensitively communicated to patients. Although there is rigorous debate about the handling of secondary/incidental findings using NGS, there is little discussion of the management of causative pleiotropic gene variants that have broader implications than that for which genetic studies were sought.

Regulation of translation initiation factor eIF2B at the hub of the integrated stress response

Phosphorylation of the translation initiation factor eIF2 is one of the most widely used and well-studied mechanisms cells use to respond to diverse cellular stresses. Known as the integrated stress response (ISR), the control pathway uses modulation of protein synthesis to reprogram gene expression and restore homeostasis. Here the current knowledge of the molecular mechanisms of eIF2 activation and its control by phosphorylation at a single-conserved phosphorylation site, serine 51 are discussed with a major focus on the regulatory roles of eIF2B and eIF5 where a current molecular view of ISR control of eIF2B activity is presented. How genetic disorders affect eIF2 or eIF2B is discussed, as are syndromes where excess signaling through the ISR is a component. Finally, studies into the action of recently identified compounds that modulate the ISR in experimental systems are discussed; these suggest that eIF2B is a potential therapeutic target for a wide range of conditions. This article is categorized under: Translation > Translation Regulation.

EIF2B2 mutations in vanishing white matter disease hypersuppress translation and delay recovery during the integrated stress response

Mutations in eIF2B genes cause vanishing white matter disease (VWMD), a fatal leukodystrophy that can manifest following physical trauma or illness, conditions that activate the integrated stress response (ISR). EIF2B is the guanine exchange factor for eIF2, facilitating ternary complex formation and translation initiation. During the ISR, eIF2α is phosphorylated and inhibits eIF2B, causing global translation suppression and stress-induced gene translation, allowing stress adaptation and recovery. We demonstrate that VWMD patient cells hypersuppress translation during the ISR caused by acute ER stress, delaying stress-induced gene expression and interrupting a negative feedback loop that allows translational recovery by GADD34-mediated dephosphorylation of phospho-eIF2α. Thus, cells from VWMD patients undergo a prolonged state of translational hyperrepression and fail to recover from stress. We demonstrate that small molecules targeting eIF2B or the eIF2α kinase PERK rescue translation defects in patient cells. Therefore, defects in the ISR could contribute to white matter loss in VWMD.

Ocimum basilicum miRNOME revisited: A cross kingdom approach

O. basilicum is medicinally important herb having inevitable role in human health. However, the mechanism of action is largely unknown. Present study aims to understand the mechanism of regulation of key human target genes that could plausibly modulated by O. basilicum miRNAs in cross kingdom manner using computational and system biology approach. O. basilicum miRNA sequences were retrieved and their corresponding human target genes were identified using psRNA target and interaction analysis of hub nodes. Six O. basilicum derived miRNAs were found to modulate 26 human target genes which were associated `with PI3K-AKTand MAPK signaling pathways with PTPN11, EIF2S2, NOS1, IRS1 and USO1 as top 5 Hub nodes. O. basilicum miRNAs not only regulate key human target genes having a significance in various diseases but also paves the path for future studies that might explore potential of miRNA mediated cross-kingdom regulation, prevention and treatment of various human diseases including cancer.

Adulthood leukodystrophies

The leukodystrophies are a group of inherited white matter disorders with a heterogeneous genetic background, considerable phenotypic variability and disease onset at all ages. This Review focuses on leukodystrophies with major prevalence or primary onset in adulthood. We summarize 20 leukodystrophies with adult presentations, providing information on the underlying genetic mutations and on biochemical assays that aid diagnosis, where available. Definitions, clinical characteristics, age of onset, MRI findings and treatment options are all described, providing a comprehensive overview of the current knowledge of the various adulthood leukodystrophies. We highlight the distinction between adult-onset leukodystrophies and other inherited disorders with white matter involvement, and we propose a diagnostic pathway for timely recognition of adulthood leukodystrophies in a routine clinical setting. In addition, we provide detailed clinical information on selected adult-onset leukodystrophies, including X-linked adrenoleukodystrophy, metachromatic leukodystrophy, cerebrotendinous xanthomatosis, hereditary diffuse leukoencephalopathy with axonal spheroids, autosomal dominant adult-onset demyelinating leukodystrophy, adult polyglucosan body disease, and leukoencephalopathy with vanishing white matter. Ultimately, this Review aims to provide helpful suggestions to identify treatable adulthood leukodystrophies at an early stage in the disease course.

Primary Ovarian Insufficiency and Azoospermia in Carriers of a Homozygous PSMC3IP Stop Gain Mutation

CONTEXT

The etiology of primary ovarian insufficiency (POI) remains unknown in most cases.

OBJECTIVE

We sought to identify the genes causing POI.

DESIGN

The study was a familial genetic study.

SETTING

The study was performed at two academic institutions.

PATIENTS

We identified a consanguineous Yemeni family in which four daughters had POI. A brother had azoospermia.

INTERVENTION

DNA was subjected to whole genome sequencing. Shared regions of homozygosity were identified using Truploidy and prioritized using the Variant Annotation, Analysis, and Search Tool with control data from 387 healthy subjects. Imaging and quantification of protein localization and mitochondrial function were examined in cell lines.

MAIN OUTCOME

Homozygous recessive gene variants shared by the four sisters.

RESULTS

The sisters shared a homozygous stop gain mutation in exon 6 of PSMC3IP (c.489 C>G, p.Tyr163Ter) and a missense variant in exon 1 of CLPP (c.100C>T, p.Pro34Ser). The affected brother also carried the homozygous PSMC3IP mutation. Functional studies demonstrated mitochondrial fragmentation in cells infected with the CLPP mutation. However, no abnormality was found in mitochondrial targeting or respiration.

CONCLUSIONS

The PSMC3IP mutation provides additional evidence that mutations in meiotic homologous recombination and DNA repair genes result in distinct female and male reproductive phenotypes, including delayed puberty and primary amenorrhea caused by POI (XX gonadal dysgenesis) in females but isolated azoospermia with normal pubertal development in males. The findings also suggest that the N-terminal missense mutation in CLPP does not cause substantial mitochondrial dysfunction or contribute to ovarian insufficiency in an oligogenic manner.

New Insights in Vanishing White Matter Disease: Isolated Bilateral Optic Neuropathy in Adult Onset Disease

BACKGROUND

Vanishing white matter disease (VWMD) is a rare disease affecting cerebral white matter. The adult form is even rarer and manifests with motor symptoms, behavioral problems, and dementia. There is no treatment and progression is inevitable. We describe a case with atypical manifestations and an unusual course.

METHODS

Description of a 42-year-old man with VWMD complaining of progressive visual loss in the right eye.

RESULTS

The patient's visual acuity was 20/60, right eye, and 20/25, left eye, with pale optic nerves bilaterally. MRI showed atrophy of the corpus callosum, diffuse rarefaction of cerebral white matter including the anterior and posterior visual pathways.

CONCLUSION

Our patient had no further symptoms besides loss of visual acuity, which is rare in patients with VWMD of the same age and genetic mutation.

Leukodystrophies: a proposed classification system based on pathological changes and pathogenetic mechanisms

Leukodystrophies are genetically determined disorders characterized by the selective involvement of the central nervous system white matter. Onset may be at any age, from prenatal life to senescence. Many leukodystrophies are degenerative in nature, but some only impair white matter function. The clinical course is mostly progressive, but may also be static or even improving with time. Progressive leukodystrophies are often fatal, and no curative treatment is known. The last decade has witnessed a tremendous increase in the number of defined leukodystrophies also owing to a diagnostic approach combining magnetic resonance imaging pattern recognition and next generation sequencing. Knowledge on white matter physiology and pathology has also dramatically built up. This led to the recognition that only few leukodystrophies are due to mutations in myelin- or oligodendrocyte-specific genes, and many are rather caused by defects in other white matter structural components, including astrocytes, microglia, axons and blood vessels. We here propose a novel classification of leukodystrophies that takes into account the primary involvement of any white matter component. Categories in this classification are the myelin disorders due to a primary defect in oligodendrocytes or myelin (hypomyelinating and demyelinating leukodystrophies, leukodystrophies with myelin vacuolization); astrocytopathies; leuko-axonopathies; microgliopathies; and leuko-vasculopathies. Following this classification, we illustrate the neuropathology and disease mechanisms of some leukodystrophies taken as example for each category. Some leukodystrophies fall into more than one category. Given the complex molecular and cellular interplay underlying white matter pathology, recognition of the cellular pathology behind a disease becomes crucial in addressing possible treatment strategies.

Role of Saccharomyces cerevisiae TAN1 (tRNA acetyltransferase) in eukaryotic initiation factor 2B (eIF2B)-mediated translation control and stress response

Eukaryotic initiation factor 2B (eIF2B) controls the first step of translation by catalyzing guanine nucleotide exchange on eukaryotic initiation factor 2 (eIF2). Mutations in the genes encoding eIF2B subunits inhibit the nucleotide exchange and eventually slow down the process of translation, causing vanishing white matter disease. We constructed a Saccharomyces cerevisiae genomic DNA library in YEp24 vector and screened it for the identification of extragenic suppressors of eIF2B mutations, corresponding to human eIF2B mutations. We found a suppressor-II (Sup-II) genomic clone, as suppressor of eIF2Bβ (gcd7-201) mutation. Identification of Sup-II reveals the presence of truncated SEC15, full-length TAN1 (tRNA acetyltransferase), full-length EMC4, full-length YGL230C (putative protein) and truncated SAP4 genes. Full-length TAN1 (tRNA acetyltransferase) gene, subcloned into pEG(KG) vector and overexpressed in gcd7-201 gcn2∆ strain, suppresses the slow-growth (Slg^-) and general control derepression (Gcd^-) phenotype of gcd7-201 gcn2∆ mutation, but YGL230C did not show any effect. A GST-Tan1p fusion protein of 60 kDa was detected by western blotting using α-GST antibodies. Interestingly, Tan1p overexpression also suppresses the temperature-sensitive (Ts^-), Slg^- and Gcd^- phenotype of eIF2Bγ (gcd1-502) mutant. Role of Tan1p protein in eIF2B-mediated translation regulation was also studied. Results revealed that Tan1p overexpression confers resistance to GCD7 GCN2, gcd7-201 gcn2∆, GCD7 gcn2∆ growth defect under ethanol, H₂O₂ and caffeine stress. No resistance to DMSO-, NaCl- and DTT-mediated growth defect upon GCD7 gcn2∆, GCD7 GCN2, gcd7-201 gcn2∆ was observed by overexpression of TAN1. Hence, we proposed that Tan1p is involved directly or indirectly in regulating eIF2B-mediated translation.

Premature Ovarian Insufficiency: New Perspectives on Genetic Cause and Phenotypic Spectrum

Premature ovarian insufficiency (POI) is one form of female infertility, defined by loss of ovarian activity before the age of 40 and characterized by amenorrhea (primary or secondary) with raised gonadotropins and low estradiol. POI affects up to one in 100 females, including one in 1000 before the age of 30. Substantial evidence suggests a genetic basis for POI; however, the majority of cases remain unexplained, indicating that genes likely to be associated with this condition are yet to be discovered. This review discusses the current knowledge of the genetic basis of POI. We highlight genes typically known to cause syndromic POI that can be responsible for isolated POI. The role of mouse models in understanding POI pathogenesis is discussed, and a thorough list of candidate POI genes is provided. Identifying a genetic basis for POI has multiple advantages, such as enabling the identification of presymptomatic family members who can be offered counseling and cryopreservation of eggs before depletion, enabling personalized treatment based on the cause of an individual's condition, and providing better understanding of disease mechanisms that ultimately aid the development of improved treatments.

Paradoxical Sensitivity to an Integrated Stress Response Blocking Mutation in Vanishing White Matter Cells

The eukaryotic translation initiation factor eIF2B promotes mRNA translation as a guanine nucleotide exchange factor (GEF) for translation initiation factor 2 (eIF2). Endoplasmic reticulum (ER) stress-mediated activation of the kinase PERK and the resultant phosphorylation of eIF2’s alpha subunit (eIF2α) attenuates eIF2B GEF activity thereby inducing an integrated stress response (ISR) that defends against protein misfolding in the ER. Mutations in all five subunits of human eIF2B cause an inherited leukoencephalopathy with vanishing white matter (VWM), but the role of the ISR in its pathogenesis remains unclear. Using CRISPR-Cas9 genome editing we introduced the most severe known VWM mutation, EIF2B4^A391D, into CHO cells. Compared to isogenic wildtype cells, GEF activity of cells with the VWM mutation was impaired and the mutant cells experienced modest enhancement of the ISR. However, despite their enhanced ISR, imposed by the intrinsic defect in eIF2B, disrupting the inhibitory effect of phosphorylated eIF2α on GEF by a contravening EIF2S1/eIF2α^S51A mutation that functions upstream of eIF2B, selectively enfeebled both EIF2B4^A391D and the related severe VWM EIF2B4^R483W cells. The basis for paradoxical dependence of cells with the VWM mutations on an intact eIF2α genotype remains unclear, as both translation rates and survival from stressors that normally activate the ISR were not reproducibly affected by the VWM mutations. Nonetheless, our findings support an additional layer of complexity in the development of VWM, beyond a hyperactive ISR.

Ovarioleukodystrophy due to EIF2B5 mutations

Ovarioleukodystrophy-the co-occurrence of leukodystrophy and premature ovarian failure-is a rare presentation now recognised to be part of the clinical spectrum of vanishing white matter disease. We describe a woman with epilepsy and neuroimaging changes consistent with leukoencephalopathy who presented with non-convulsive status epilepticus after starting hormone replacement therapy in the context of premature ovarian failure. Genetic testing confirmed her to be a compound heterozygote for EIF2B5 mutations; the gene encodes a subunit of eukaryotic translation initiation factor 2B. Mutations in EIF2B1-5 result in vanishing white matter disease. We highlight the importance of ovarian failure as a diagnostic pointer to eukaryotic translation initiation factor 2B (eIF2B)-related ovarioleukodystrophy and present a brief literature review of ovarioleukodystrophy.

Transcriptome Display During Testicular Differentiation of Channel Catfish (Ictalurus punctatus) as Revealed by RNA-Seq Analysis

Channel catfish (Ictalurus punctatus) has been recognized as a dominant freshwater aquaculture species in the United States. It is also a suitable model for studying the mechanisms of sex determination and differentiation because of its sexual plasticity and exhibition of both genetic and environmental sex determination. The testicular differentiation in male channel catfish normally starts between 90 and 102 days postfertilization (dpf), while the ovarian differentiation starts early from 19 dpf. As such, efforts to better understand the postponed testicular development at the molecular level are needed. Toward that end, we conducted transcriptomic comparison of gene expression of male and female gonads at 90, 100, and 110 dpf using high-throughput RNA-Seq. Transcriptomic profiles of male gonads on 90 and 100 dpf exhibited high similarities except for a small number of significantly up-regulated genes that were involved in development of germ cell-supporting somatic cells, while drastic changes were observed during 100-110 dpf, with a group of highly up-regulated genes that were involved in germ cells development, including nanog and pou5f1 Transcriptomic comparison between testes and ovaries identified male-preferential genes, such as gsdf, cxcl12, as well as other cytokines mediated the development of the gonad into a testis. Co-expression analysis revealed highly correlated genes and potential pathways underlying germ cell differentiation and spermatogonia stem cell development. The candidate genes and pathways identified in this study set the foundation for further studies on sex determination and differentiation in catfish as well as other teleosts.

Molecular insights into the aetiology of female reproductive ageing

As age at pubertal onset declines and age at first pregnancy increases, the mechanisms that regulate female reproductive lifespan become increasingly relevant to population health. The timing of menarche and menopause can have profound effects not only on fertility but also on the risk of diseases such as type 2 diabetes mellitus, cardiovascular disease and breast cancer. Genetic studies have identified dozens of highly penetrant rare mutations associated with reproductive disorders, and also ∼175 common genetic variants associated with the timing of puberty or menopause. These findings, alongside other functional studies, have highlighted a diverse range of mechanisms involved in reproductive ageing, implicating core biological processes such as cell cycle regulation and energy homeostasis. The aim of this article is to review the contribution of such genetic findings to our understanding of the molecular regulation of reproductive timing, as well as the biological basis of the epidemiological links between reproductive ageing and disease risk.

Large-scale genomic analyses link reproductive aging to hypothalamic signaling, breast cancer susceptibility and BRCA1-mediated DNA repair

Menopause timing has a substantial impact on infertility and risk of disease, including breast cancer, but the underlying mechanisms are poorly understood. We report a dual strategy in ∼70,000 women to identify common and low-frequency protein-coding variation associated with age at natural menopause (ANM). We identified 44 regions with common variants, including two regions harboring additional rare missense alleles of large effect. We found enrichment of signals in or near genes involved in delayed puberty, highlighting the first molecular links between the onset and end of reproductive lifespan. Pathway analyses identified major association with DNA damage response (DDR) genes, including the first common coding variant in BRCA1 associated with any complex trait. Mendelian randomization analyses supported a causal effect of later ANM on breast cancer risk (∼6% increase in risk per year; P = 3 × 10(-14)), likely mediated by prolonged sex hormone exposure rather than DDR mechanisms.

Joint MiRNA/mRNA expression profiling reveals changes consistent with development of dysfunctional corpus luteum after weight gain

Obese women exhibit decreased fertility, high miscarriage rates and dysfunctional corpus luteum (CL), but molecular mechanisms are poorly defined. We hypothesized that weight gain induces alterations in CL gene expression. RNA sequencing was used to identify changes in the CL transcriptome in the vervet monkey (Chlorocebus aethiops) during weight gain. 10 months of high-fat, high-fructose diet (HFHF) resulted in a 20% weight gain for HFHF animals vs. 2% for controls (p = 0.03) and a 66% increase in percent fat mass for HFHF group. Ovulation was confirmed at baseline and after intervention in all animals. CL were collected on luteal day 7-9 based on follicular phase estradiol peak. 432 mRNAs and 9 miRNAs were differentially expressed in response to HFHF diet. Specifically, miR-28, miR-26, and let-7b previously shown to inhibit sex steroid production in human granulosa cells, were up-regulated. Using integrated miRNA and gene expression analysis, we demonstrated changes in 52 coordinately regulated mRNA targets corresponding to opposite changes in miRNA. Specifically, 2 targets of miR-28 and 10 targets of miR-26 were down-regulated, including genes linked to follicular development, steroidogenesis, granulosa cell proliferation and survival. To the best of our knowledge, this is the first report of dietary-induced responses of the ovulating ovary to developing adiposity. The observed HFHF diet-induced changes were consistent with development of a dysfunctional CL and provide new mechanistic insights for decreased sex steroid production characteristic of obese women. MiRNAs may represent novel biomarkers of obesity-related subfertility and potential new avenues for therapeutic intervention.

Genetics of primary ovarian insufficiency: new developments and opportunities

BACKGROUND

Primary ovarian insufficiency (POI) is characterized by marked heterogeneity, but with a significant genetic contribution. Identifying exact causative genes has been challenging, with many discoveries not replicated. It is timely to take stock of the field, outlining the progress made, framing the controversies and anticipating future directions in elucidating the genetics of POI.

METHODS

A search for original articles published up to May 2015 was performed using PubMed and Google Scholar, identifying studies on the genetic etiology of POI. Studies were included if chromosomal analysis, candidate gene screening and a genome-wide study were conducted. Articles identified were restricted to English language full-text papers.

RESULTS

Chromosomal abnormalities have long been recognized as a frequent cause of POI, with a currently estimated prevalence of 10-13%. Using the traditional karyotype methodology, monosomy X, mosaicism, X chromosome deletions and rearrangements, X-autosome translocations, and isochromosomes have been detected. Based on candidate gene studies, single gene perturbations unequivocally having a deleterious effect in at least one population include Bone morphogenetic protein 15 (BMP15), Progesterone receptor membrane component 1 (PGRMC1), and Fragile X mental retardation 1 (FMR1) premutation on the X chromosome; Growth differentiation factor 9 (GDF9), Folliculogenesis specific bHLH transcription factor (FIGLA), Newborn ovary homeobox gene (NOBOX), Nuclear receptor subfamily 5, group A, member 1 (NR5A1) and Nanos homolog 3 (NANOS3) seem likely as well, but mostly being found in no more than 1-2% of a single population studied. Whole genome approaches have utilized genome-wide association studies (GWAS) to reveal loci not predicted on the basis of a candidate gene, but it remains difficult to locate causative genes and susceptible loci were not always replicated. Cytogenomic methods (array CGH) have identified other regions of interest but studies have not shown consistent results, the resolution of arrays has varied and replication is uncommon. Whole-exome sequencing in non-syndromic POI kindreds has only recently begun, revealing mutations in the Stromal antigen 3 (STAG3), Synaptonemal complex central element 1 (SYCE1), minichromosome maintenance complex component 8 and 9 (MCM8, MCM9) and ATP-dependent DNA helicase homolog (HFM1) genes. Given the slow progress in candidate-gene analysis and relatively small sample sizes available for GWAS, family-based whole exome and whole genome sequencing appear to be the most promising approaches for detecting potential genes responsible for POI.

CONCLUSION

Taken together, the cytogenetic, cytogenomic (array CGH) and exome sequencing approaches have revealed a genetic causation in ∼20-25% of POI cases. Uncovering the remainder of the causative genes will be facilitated not only by whole genome approaches involving larger cohorts in multiple populations but also incorporating environmental exposures and exploring signaling pathways in intragenic and intergenic regions that point to perturbations in regulatory genes and networks.

Efficient detection of frequent eIF2B mutations for the rapid molecular diagnosis of CACH/VWM syndrome

OBJECTIVES

The aim of this study was to develop a reliable, rapid and cost-effective molecular diagnostic assay allowing widespread routine investigation of eIF2B-related disorders (CACH/VWM syndrome). This heterogeneous disease is caused by autosomal recessive mutations in the genes encoding the five subunits of the translation-initiation factor eIF2B. Such a diagnostic method would be particularly adapted to the apparently acute presentation of the disease.

DESIGN AND METHODS

We developed a multiplex PCR amplification method for 7 genomic regions of the eIF2B genes in a single run. This method targeted the 8 most frequent mutations representing 61.4% of all mutations identified to date in our laboratory. These mutations affected eIF2B2 exon 5, eIF2B3 exon 2, eIF2B4 exons 8 and 11 and eIF2B5 exons 5, 7 and 8. PCR products were then pooled and subjected to a primer-extension assay validated using previously genotyped samples.

RESULTS

The results were compared to screening and/or direct sequencing methods: 100% agreement between methods confirmed equivalent sensitivity and specificity. The new assay was highly superior in terms of cost, time to results and robustness despite sample heterogeneity.

CONCLUSIONS

This genotyping strategy allows the detection of all eIF2B mutations targeted. A second multiplex primer-extension assay is in development to detect the 11 next-most frequent mutations, thus raising the global detection rate to 76.8%. Our approach is widely applicable as it involves standard techniques and equipment. Moreover, it can easily be further adapted to the clinical and genetic heterogeneity of eIF2B-related disorders by including or excluding mutations.