A novelIGF2/H19domain triplication in the 11p15.5 imprinting region causing either Beckwith-Wiedemann or Silver-Russell syndrome in a single family

Tandem Triplication 11p15.5-ICR1 (H19/IGF2) Detected by Microarray and Optical Genome Mapping in a Prenatal Beckwith-Wiedemann Case

Optical genome mapping (OGM) appears as a new tool for matching standard cytogenetic methods (karyotype and microarray) into a single assay. The chromosomal region 11p15.5 harbours two differentially methylated regions, the imprinting centre regions 1 and 2 (ICR1, ICR2). Disturbances in both regions alter human growth and are associated with two imprinting disorders, Beckwith-Wiedemann (BWS) and Silver-Russell syndromes. Herein, we present a prenatal case with a triplication in 11p15.5, including the H19/IGF2 imprinted region, detected by microarray and OGM. A 30-year-old pregnant woman of 17 weeks of gestation was referred for prenatal karyotype and microarray study because of increased nuchal translucency, short femur, megabladder, hyperechogenic bowel, and renal ectasia. Microarray, OGM, and MS-MLPA were performed, and a tandem cis-triplication in 11p15.5 and hypermethylation of the ICR1 region, compatible with BWS was detected. OGM, with its power to detect all classes of structural variants, including copy number variants, at a higher resolution than traditional cytogenetic methods can play a significant role in prenatal care and management as a next-generation cytogenomic tool. This study further supports the hypotheses that the amplification/duplication-triplication of the H19/IGF2 region could be related to BWS if it is of paternal origin.

Components of IGF-axis in growth disorders: a systematic review and patent landscape report

PURPOSE

In this review, epi/genetic mutations of IGF-axis components associated with growth disorders have been summarized alongwith assessment of relevant diagnostic and therapeutic technology through patent literature.

METHODOLOGY

PROSPERO protocol registration CRD42021279468. For scientific literature search Literature databases (PubMed, EMBASE, ScienceDirect, and Google Scholar) were queried using the appropriate syntax. Various filters were applied based on inclusion and exclusion criteria. Search results were further refined by two authors for finalizing studies to be included in this synthesis. For patent documents search Patent databases (Patentscope and Espacenet) were queried using keywords: IGF or IGFBP. Filters were applied according to International Patent Classification (IPC) and Cooperative Patent Classification (CPC). Search results were reviewed by two authors for inclusion in the patent landscape report.

RESULTS

For scientific literature analysis, out of 545 search results, 196 were selected for review based on the inclusion criteria. For Patent literature search, out of 485 results, 37 were selected for this synthesis.

CONCLUSION

Dysregulation of IGF-axis components leads to various abnormalities and their key role in growth and development suggests epi/mutations or structural defects among IGF-axis genes can be associated with growth disorders and may explain some of the idiopathic short stature cases. Trend of patent filings indicate advent of recombinant technology for therapeutics.

Interaction of PM2.5 and pre-pregnancy body mass index on birth weight: A nationwide prospective cohort study

BACKGROUND

Fine particulate matter (PM_2.5), one of the most common air pollutants worldwide, has been associated with many adverse birth outcomes in some studies. Pre-pregnancy body mass index (BMI) is an important indicator of maternal obesity that may also contribute to a wide range of birthweight outcomes. Both PM_2.5 and maternal obesity have been found associated with issues on neonatal birthweight respectively, and more attentions and interests are focusing on their combined effect on pregnancy outcomes.

PURPOSE

To explore the modifying effect of pre-pregnancy BMI on the association between gestational PM_2.5 and birthweight; to investigate the interactive effect between gestational PM_2.5 and pre-pregnancy BMI on birthweight among pregnant women during three trimesters and the whole pregnancy.

METHODS

This nationwide cohort study used the National Free Preconception Health Examination Project (NFPHEP) data collected from January 1, 2010, to December 31, 2012. A total population of 248,501 Chinese women from 220 counties registered this project. Pre-pregnancy BMI as a common anthropometric examination was collected during preconception investigation, and gestational PM_2.5 was derived from a hindcast model for historical PM_2.5 estimation from satellite-retrieved aerosol optic depth. Subgroup analysis was conducted to explore a potential modifying effect on the association between PM_2.5 and birthweight during pregnancy by four pre-pregnancy BMI subgroups. Interaction analysis by introducing product terms to multivariable linear regression was also used to examine whether there was an interactive relationship between PM_2.5 and pre-pregnancy BMI.

RESULTS

Totally, 193,461 participants were included in our study. The average concentration of PM_2.5 was 75.33 μg/m³. Higher exposure of PM_2.5 during the entire pregnancy was associated with higher birthweight (17.15 g per 10 μg/m3; 95% CI:16.15, 18.17). Each 10 μg/m³ increase in PM_2.5 during the first, second, and third trimesters was associated with increases in birthweight by 14.93 g (95%CI: 13.96, 15.89), 13.75 g (95% CI: 12.81, 14.69), and 8.79 g (95% CI: 8.09, 9.49), respectively. Higher pre-pregnancy BMI per kg/m² was associated with an increase of birthweight by 7.012 g (95% CI: 6.121, 7.902). Product terms between PM_2.5 and pre-pregnancy BMI were significant for the first, second trimesters, and the entire duration of pregnancy.

CONCLUSIONS

Our results found both gestational PM_2.5 exposure and pre-pregnancy BMI respectively correlated with the increase of birthweight. A negative interaction between pre-pregnancy BMI and gestational PM_2.5 was discovered in term of birthweight gain. Avoidance of high-dose exposure to PM_2.5 during the early and middle stages of pregnancy and pre-pregnancy overweight/obesity may help prevent high birthweight.

Prenatal Detection of Uniparental Disomies (UPD): Intended and Incidental Finding in the Era of Next Generation Genomics

Prenatal detection of uniparental disomy (UPD) is a methodological challenge, and a positive testing result requires comprehensive considerations on the clinical consequences as well as ethical issues. Whereas prenatal testing for UPD in families which are prone to UPD formation (e.g., in case of chromosomal variants, imprinting disorders) is often embedded in genetic counselling, the incidental identification of UPD is often more difficult to manage. With the increasing application of high-resolution test systems enabling the identification of UPD, an increase in pregnancies with incidental detection of UPD can be expected. This paper will cover the current knowledge on uniparental disomies, their clinical consequences with focus on prenatal testing, genetic aspects and predispositions, genetic counselling, as well as methods (conventional tests and high-throughput assays).

Clinical spectrum and management of imprinting disorders

Imprinting disorders are exceptional within the group of monogenic syndromes. They are associated with molecular changes affecting imprinted regions and usually do not follow the rules of Mendelian inheritance. They account for a relevant proportion of congenital disorders, especially within the syndromal growth entities with endocrine, neurological, and skeletal characteristics. In patients with imprinting disorders and accelerated growth, significant tumor risks have to be considered. The number of known imprinting disorders increases with the identification of new regions in which parentally imprinted genes are located. Imprinting disorders are caused by genomic pathogenic variants affecting imprinted genes, as well as by aberrant imprinting marks (epimutations) in the patients themselves. Additionally, maternal effect mutations have recently been identified that trigger secondary epimutations in the offspring. These maternal effect mutations explain not only imprinting disorders in their children, but also recurrent reproductive failure in the families. This review aims to provide an overview of the recent findings in 13 well-known imprinting disorders relating to clinical diagnosis, management and counseling.

Need for a precise molecular diagnosis in Beckwith-Wiedemann and Silver-Russell syndrome: what has to be considered and why it is important

Abstract

Molecular diagnostic testing of the 11p15.5-associated imprinting disorders Silver-Russell and Beckwith-Wiedemann syndrome (SRS, BWS) is challenging due to the broad spectrum of molecular defects and their mosaic occurrence. Additionally, the decision on the molecular testing algorithm is hindered by their clinical heterogeneity. However, the precise identification of the type of defect is often a prerequisite for the clinical management and genetic counselling. Four major molecular alterations (epimutations, uniparental disomies, copy number variants, single nucleotide variants) have been identified, but their frequencies vary between SRS and BWS. Due to their molecular aetiology, epimutations in both disorders as well as upd(11)pat in BWS are particular prone to mosaicism which might additionally complicate the interpretation of testing results. We report on our experience of molecular analysis in a total cohort of 1448 patients referred for diagnostic testing of BWS and SRS, comprising a dataset from 737 new patients and from 711 cases from a recent study. Though the majority of positively tested patients showed the expected molecular results, we identified a considerable number of clinically unexpected molecular alterations as well as not yet reported changes and discrepant mosaic distributions. Additionally, the rate of multilocus imprinting disturbances among the patients with epimutations and uniparental diploidies could be further specified. Altogether, these cases show that comprehensive testing strategies have to be applied in diagnostic testing of SRS and BWS. The precise molecular diagnosis is required as the basis for a targeted management (e.g. ECG (electrocardiogram) and tumour surveillance in BWS, growth treatment in SRS). The molecular diagnosis furthermore provides the basis for genetic counselling. However, it has to be considered that recurrence risk calculation is determined by the phenotypic consequences of each molecular alteration and mechanism by which the alteration arose.

Key messages

The detection rates for the typical molecular defects of Beckwith-Wiedemann syndrome or Silver-Russell syndrome (BWS, SRS) are lower in routine cohorts than in clinically well-characterised ones.

A broad spectrum of (unexpected) molecular alterations in both disorders can be identified.

Multilocus imprinting disturbances (MLID) are less frequent in SRS than expected.

The frequency of MLID and uniparental diploidy in BWS is confirmed.

Mosaicism is a diagnostic challenge in BWS and SRS.

The precise determination of the molecular defects affecting is the basis for a targeted clinical management and genetic counselling.

Disturbed genomic imprinting and its relevance for human reproduction: causes and clinical consequences

BACKGROUND

Human reproductive issues affecting fetal and maternal health are caused by numerous exogenous and endogenous factors, of which the latter undoubtedly include genetic changes. Pathogenic variants in either maternal or offspring DNA are associated with effects on the offspring including clinical disorders and nonviable outcomes. Conversely, both fetal and maternal factors can affect maternal health during pregnancy. Recently, it has become evident that mammalian reproduction is influenced by genomic imprinting, an epigenetic phenomenon that regulates the expression of genes according to their parent from whom they are inherited. About 1% of human genes are normally expressed from only the maternally or paternally inherited gene copy. Since numerous imprinted genes are involved in (embryonic) growth and development, disturbance of their balanced expression can adversely affect these processes.

OBJECTIVE AND RATIONALE

This review summarises current our understanding of genomic imprinting in relation to human ontogenesis and pregnancy and its relevance for reproductive medicine.

SEARCH METHODS

Literature databases (Pubmed, Medline) were thoroughly searched for the role of imprinting in human reproductive failure. In particular, the terms ‘multilocus imprinting disturbances, SCMC, NLRP/NALP, imprinting and reproduction’ were used in various combinations.

OUTCOMES

A range of molecular changes to specific groups of imprinted genes are associated with imprinting disorders, i.e. syndromes with recognisable clinical features including distinctive prenatal features. Whereas the majority of affected individuals exhibit alterations at single imprinted loci, some have multi-locus imprinting disturbances (MLID) with less predictable clinical features. Imprinting disturbances are also seen in some nonviable pregnancy outcomes, such as (recurrent) hydatidiform moles, which can therefore be regarded as a severe form of imprinting disorders. There is growing evidence that MLID can be caused by variants in the maternal genome altering the imprinting status of the oocyte and the embryo, i.e. maternal effect mutations. Pregnancies of women carrying maternal affect mutations can have different courses, ranging from miscarriages to birth of children with clinical features of various imprinting disorders.

WIDER IMPLICATIONS

Increasing understanding of imprinting disturbances and their clinical consequences have significant impacts on diagnostics, counselling and management in the context of human reproduction. Defining criteria for identifying pregnancies complicated by imprinting disorders facilitates early diagnosis and personalised management of both the mother and offspring. Identifying the molecular lesions underlying imprinting disturbances (e.g. maternal effect mutations) allows targeted counselling of the family and focused medical care in further pregnancies.

Loss of methylation of H19-imprinted gene derived from assisted reproductive technologies can be mitigated by cleavage-stage embryo transfer in mice

PURPOSE

Studies on rodents have shown that assisted reproductive technologies (ARTs) are associated with perturbation of genomic imprinting in blastocyst-stage embryos. However, the vulnerable developmental window for ART influence on the genomic imprinting of embryos is still undetermined. The purpose of this study was to establish the specific embryonic development stage at which the loss of methylation of H19 imprinting control regions (ICRs) was caused by ART occurrence. Additionally, we explored protocols to safeguard against possible negative impacts of ART on embryo H19 imprinting.

METHODS

Mouse embryos were generated under four different experimental conditions, divided into four groups: control, in vitro culture (IVC), in vitro fertilization (IVF), and intracytoplasmic sperm injection (ICSI). The methylation levels of H19 ICR of the grouped or individual embryos were analyzed by bisulfite-sequencing PCR.

RESULTS

Our data showed that the loss of methylation of H19 ICR in mouse blastocysts was inflicted to a similar extent by IVC, IVF, and ICSI. Specifically, we observed a significant loss of methylation of H19 ICR between the mouse 8-cell and morula stages. In addition, we revealed that the transfer of mouse embryos generated by ARTs in the uterus at the 8-cell stage induced the occurrence of methylation patterns in the blastocysts closer to the in vivo ones.

CONCLUSIONS

Our findings indicate that the loss of methylation of H19 ICR caused by ARTs occurs between the 8-cell and the morula stages, and the transfer of cleavage embryos to the uterus mitigates the loss methylation of H19 derived by mice ARTs.

Novel familial distal imprinting centre 1 (11p15.5) deletion provides further insights in imprinting regulation

BACKGROUND

Deletions of the imprinting centre 1 (IC1) in 11p15.5 are rare and their clinical significance is not only influenced by their parental origin but also by their exact genomic localization. In case the maternal IC1 allele is affected, the deletion is associated with the overgrowth disorder Beckwith-Wiedemann syndrome (BWS) and a gain of methylation (GOM) of the IC1. The consequences of deletions of the paternal IC1 allele depend on the localization and probably the binding sites of methylation-specific DNA-binding factors affected by the change. It has been suggested that distal deletions of the paternal allele are associated with a normal IC1 methylation and phenotype, whereas proximal alterations cause a loss of methylation (LOM) and Silver-Russell syndrome (SRS) features.

RESULTS

In a patient referred for molecular BWS testing and his family, a deletion within the IC1 was identified by MLPA. It was associated with a GOM, corresponding to the transmission of the alteration via the maternal germline. Accordingly, the deletion was also detectable in the maternal grandmother, but here the paternal chromosome 11p15.5 was affected and a IC1 LOM was observed. By nanopore sequencing, the localization of the deletion could be precisely determined.

CONCLUSIONS

We report for the first time both GOM and LOM of the IC1 in the same family, caused by transmission of a 2.2-kb deletion in 11p15.5. Nanopore sequencing allowed the precise characterization of the change by long-read sequencing and thereby provides further insights in the regulation of imprinting in the IC1.