Bisulphite sequencing of the transient neonatal diabetes mellitus DMR facilitates a novel diagnostic test but reveals no methylation anomalies in patients of unknown aetiology

Height and body mass index in molecularly confirmed Silver-Russell syndrome and the long-term effects of growth hormone treatment

OBJECTIVE

Silver-Russell syndrome (SRS) causes short stature. Growth hormone (GH) treatment aims to increase adult height. However, data are limited on the long-term outcomes of GH in patients with molecularly confirmed SRS. This study evaluated height, body mass index (BMI) and GH treatment in molecularly confirmed SRS.

DESIGN

An observational study with retrospective data collection.

PATIENTS

Individuals with molecularly confirmed SRS aged ≥13 years.

MEASUREMENTS

Data were collected on height, height gain (change in height standard deviation score [SDS] from childhood to final or near-final height), BMI and gain in BMI (from childhood to adulthood) and previous GH treatment.

RESULTS

Seventy-one individuals (40 female) were included. The median age was 22.0 years (range 13.2-69.7). The molecular diagnoses: H19/IGF2:IG-DMR LOM in 80.3% (57/71); upd(7)mat in 16.9% (12/71) and IGF2 mutation in 2.8% (2/71). GH treatment occurred in 77.5% (55/71). Total height gain was greater in GH-treated individuals (median 1.53 SDS vs. 0.53 SDS, p = .007), who were shorter at treatment initiation (-3.46 SDS vs. -2.91 SDS, p = .04) but reached comparable heights to GH-untreated individuals (-2.22 SDS vs. -2.74 SDS, p = .7). In GH-treated individuals, BMI SDS was lower at the most recent assessment (median -1.10 vs. 1.66, p = .002) with lower BMI gain (2.01 vs. 3.58, p = .006) despite similar early BMI SDS to GH-untreated individuals (median -2.65 vs. -2.78, p = .3).

CONCLUSIONS

These results support the use of GH in SRS for increasing height SDS. GH treatment was associated with lower adult BMI which may reflect improved metabolic health even following discontinuation of therapy.

Longitudinal Glycaemic Profiles during Remission in 6q24-Related Transient Neonatal Diabetes Mellitus

INTRODUCTION

Transient neonatal diabetes mellitus (TNDM) is a rare condition that is characterized by the presence of diabetes mellitus during the first 6 months of life and remission by 18 months of age. It usually relapses at a median age of 14 years. Hyperinsulinaemic hypoglycaemia is a relatively common complication during remission. Although β-cell function is reported to be impaired at relapse, the clinical course of glycaemic profiles during remission in patients with TNDM remains largely unknown.

CASE PRESENTATION

Longitudinal glycaemic profiles were investigated annually from remission (185 days) to relapse (14.5 years) in a patient with TNDM due to paternal 6q24 duplication using the oral glucose tolerance test (glucose intake: 1.75 g/kg to a maximum of 75 g). The patient's β-cell function and insulin sensitivity were assessed by calculating the insulinogenic index, homeostasis model assessment of β-cell function (HOMA-β), homeostasis model assessment of insulin resistance (HOMA-IR), quantitative insulin sensitivity check index, and Matsuda index. Early insulin response to glucose intake was impaired throughout remission, whereas fasting insulin and β-cell function by HOMA-β gradually increased in the first few years since remission, followed by a gradual decline in function. In contrast, HOMA-IR fluctuated and peaked at 6.5 years of age.

CONCLUSION

This is the first report of annual longitudinal glycaemic profiles in a patient with 6q24-related TNDM during remission. We identified fluctuations in β-cell function and insulin resistance during remission.

Prenatal diagnosis of 7 cases with uniparental disomy by utilization of single nucleotide polymorphism array

Background

The phenotypes of uniparental disomy (UPD) are variable, which may either have no clinical impact, lead to clinical signs and symptoms. Molecular analysis is essential for making a correct diagnosis. This study involved a retrospective analysis of 4512 prenatal diagnosis samples and explored the molecular characteristics and prenatal phenotypes of UPD using a single nucleotide polymorphism (SNP) array.

Results

Out of the 4512 samples, a total of seven cases of UPD were detected with an overall frequency of 0.16%. Among the seven cases of UPD, two cases are associated with chromosomal aberrations (2/7), four cases (4/7) had abnormal ultrasonographic findings. One case presented with iso-UPD (14), and two case presented with mixed hetero/iso-UPD (15), which were confirmed by Methylation-specific multiplex ligation-dependent probe amplification (MS-MLPA) as maternal UPD (15) associated with Prader-Willi syndrome (PWS). Four cases had iso-UPD for chromosome 1, 3, 14, and 16, respectively; this is consistent with the monosomy rescue mechanism. Another three cases presented with mixed hetero/isodisomy were consistent with a trisomy rescue mechanism.

Conclusion

The prenatal phenotypes of UPD are variable and molecular analysis is essential for making a correct diagnosis and genetic counselling of UPD. The SNP array is a useful genetic test in prenatal diagnosis cases with UPD.

Chromosome 6q24-related diabetes mellitus

Chromosome 6q24-related diabetes mellitus is the most common cause of transient neonatal diabetes (TNDM), accounting for approximately two-thirds of all TNDM cases. Patients with 6q24-TNDM develop insulin-requiring diabetes soon after birth, followed by the gradual improvement and eventual remission of the disorder by 18 mo of age. The most important clinical feature of affected patients is a small-for-gestational age (SGA) birth weight, which reflects the lack of insulin in utero. It is believed that 6q24-TNDM is caused by the overexpression of the paternal allele of the imprinted locus in chromosome 6q24, which contains only two expressed genes, PLAGL1 and HYMAI. Identified mechanisms include: (1) duplication of the paternal allele, (2) paternal uniparental disomy, and (3) hypomethylation of the maternal allele. Many patients with TNDM relapse after puberty. Relapsed 6q24-related diabetes is no longer transient and typically occurs in non-obese patients who are autoantibody negative. Thus, these patients possess features indistinguishable from those of maturity-onset diabetes of the young (MODY). Conversely, it has been shown that not all patients with 6q24-related diabetes have a history of TNDM. 6q24-related diabetes should therefore be considered as one of the differential diagnoses for patients with MODY-like diabetes, especially when they are SGA at birth.

Gene Variants Associated with Transient Neonatal Diabetes Mellitus in the Very Low Birth Weight Infant

BACKGROUND

Transient and permanent neonatal diabetes mellitus (NDM), usually defined as diabetes diagnosed within the first 6 months of life, are rare conditions occurring in 1:90,000-260,000 live births. The origin of NDM is rarely related to type 1 diabetes, but rather to single gene defects.

METHODS

Genetic analysis was performed using targeted parallel sequencing including 323 diabetes genes. Data were filtered by a locally developed program.

RESULTS

A very low birth weight neonate born at 28 weeks postmenstrual age developed diabetes 13 days after birth. The patient was treated with continuous subcutaneous insulin infusion. After 1 month, insulin treatment could be stopped. At 18 months of age, the child was normoglycemic and developing normally. Genetic analysis revealed a novel variant (p.Pro190Leu) in HNF4A, which is located in the ligand binding domain of the transcription factor, and the p.Glu23Lys variant in KCNJ11, which is associated with type 2 diabetes.

CONCLUSION

Here, we describe a novel HNF4A variant associated with transient NDM in a premature infant. We hypothesize that the neonatal phenotype previously described in carriers of HNF4A mutations was modified by the additional variant in KCNJ11 and prematurity.

DNA methylation analysis in constitutional disorders: Clinical implications of the epigenome

Genomic, chromosomal, and gene-specific changes in the DNA sequence underpin both phenotypic variations in populations as well as disease associations, and the application of genomic technologies for the identification of constitutional (inherited) or somatic (acquired) alterations in DNA sequence forms a cornerstone of clinical and molecular genetics. In addition to the disruption of primary DNA sequence, the modulation of DNA function by epigenetic phenomena, in particular by DNA methylation, has long been known to play a role in the regulation of gene expression and consequent pathogenesis. However, these epigenetic factors have been identified only in a handful of pediatric conditions, including imprinting disorders. Technological advances in the past decade that have revolutionized clinical genomics are now rapidly being applied to the emerging discipline of clinical epigenomics. Here, we present an overview of epigenetic mechanisms with a focus on DNA modifications, including the molecular mechanisms of DNA methylation and subtypes of DNA modifications, and we describe the classic and emerging genomic technologies that are being applied to this study. This review focuses primarily on constitutional epigenomic conditions associated with a spectrum of developmental and intellectual disabilities. Epigenomic disorders are discussed in the context of global genomic disorders, imprinting disorders, and single gene disorders. We include a section focused on integration of genetic and epigenetic mechanisms together with their effect on clinical phenotypes. Finally, we summarize emerging epigenomic technologies and their impact on diagnostic aspects of constitutional genetic and epigenetic disorders.

Neonatal diabetes in Ukraine: incidence, genetics, clinical phenotype and treatment

BACKGROUND

Neonatal diabetes has not been previously studied in Ukraine. We investigated the genetic etiology in patients with onset of diabetes during the first 9 months of life.

METHODS

We established a Pediatric Diabetes Register to identify patients diagnosed with diabetes before 9 months of age. Genetic testing was undertaken for 42 patients with permanent or transient diabetes diagnosed within the first 6 months of life (n=22) or permanent diabetes diagnosed between 6 and 9 months (n=20).

RESULTS

We determined the genetic etiology in 23 of 42 (55%) patients; 86% of the patients diagnosed before 6 months and 20% diagnosed between 6 and 9 months. The incidence of neonatal diabetes in Ukraine was calculated to be 1 in 126,397 live births.

CONCLUSIONS

Genetic testing for patients identified through the Ukrainian Pediatric Diabetes Register identified KCNJ11 and ABCC8 mutations as the most common cause (52%) of neonatal diabetes. Transfer to sulfonylureas improved glycemic control in all 11 patients.

The effect of early, comprehensive genomic testing on clinical care in neonatal diabetes: an international cohort study

BACKGROUND

Traditional genetic testing focusses on analysis of one or a few genes according to clinical features; this approach is changing as improved sequencing methods enable simultaneous analysis of several genes. Neonatal diabetes is the presenting feature of many discrete clinical phenotypes defined by different genetic causes. Genetic subtype defines treatment, with improved glycaemic control on sulfonylurea treatment for most patients with potassium channel mutations. We investigated the effect of early, comprehensive testing of all known genetic causes of neonatal diabetes.

METHODS

In this large, international, cohort study, we studied patients with neonatal diabetes diagnosed with diabetes before 6 months of age who were referred from 79 countries. We identified mutations by comprehensive genetic testing including Sanger sequencing, 6q24 methylation analysis, and targeted next-generation sequencing of all known neonatal diabetes genes.

FINDINGS

Between January, 2000, and August, 2013, genetic testing was done in 1020 patients (571 boys, 449 girls). Mutations in the potassium channel genes were the most common cause (n=390) of neonatal diabetes, but were identified less frequently in consanguineous families (12% in consanguineous families vs 46% in non-consanguineous families; p<0·0001). Median duration of diabetes at the time of genetic testing decreased from more than 4 years before 2005 to less than 3 months after 2012. Earlier referral for genetic testing affected the clinical phenotype. In patients with genetically diagnosed Wolcott-Rallison syndrome, 23 (88%) of 26 patients tested within 3 months from diagnosis had isolated diabetes, compared with three (17%) of 18 patients referred later (>4 years; p<0·0001), in whom skeletal and liver involvement was common. Similarly, for patients with genetically diagnosed transient neonatal diabetes, the diabetes had remitted in only ten (10%) of 101 patients tested early (<3 months) compared with 60 (100%) of the 60 later referrals (p<0·0001).

INTERPRETATION

Patients are now referred for genetic testing closer to their presentation with neonatal diabetes. Comprehensive testing of all causes identified causal mutations in more than 80% of cases. The genetic result predicts the best diabetes treatment and development of related features. This model represents a new framework for clinical care with genetic diagnosis preceding development of clinical features and guiding clinical management.

FUNDING

Wellcome Trust and Diabetes UK.

Abnormalities in chromosome 6q24 as a cause of early-onset, non-obese, non-autoimmune diabetes mellitus without history of neonatal diabetes

AIMS

Abnormalities in the imprinted locus on chromosome 6q24 are the most common causes of transient neonatal diabetes mellitus (6q24-related transient neonatal diabetes). 6q24-Related transient neonatal diabetes is characterized by the patient being small-for-gestational age, diabetes mellitus at birth, spontaneous remission within the first few months and frequent recurrence of diabetes after childhood. However, it is not clear whether individuals with 6q24 abnormalities invariably develop transient neonatal diabetes. This study explored the possibility that 6q24 abnormalities might cause early-onset, non-autoimmune diabetes without transient neonatal diabetes.

METHODS

The 6q24 imprinted locus was screened for abnormalities in 113 Japanese patients with early-onset, non-obese, non-autoimmune diabetes mellitus who tested negative for mutations in the common maturation-onset diabetes of the young (MODY) genes and without a history of transient neonatal diabetes. Positive patients were further analysed by combined loss of heterozygosity / comparative genomic hybridization analysis and by microsatellite analysis. Detailed clinical data were collected through the medical records of the treating hospitals.

RESULTS

Three patients with paternal uniparental isodisomy of chromosome 6q24 were identified. None presented with hyperglycaemia in the neonatal period. Characteristically, these patients were born small-for-gestational age, representing 27.2% of the 11 patients whose birth weight standard deviation score (SDS) for gestational age was below -2.0.

CONCLUSIONS

Abnormalities in the imprinted locus on chromosome 6q24 do not necessarily cause transient neonatal diabetes. Non-penetrant 6q24-related diabetes could be an underestimated cause of early-onset, non-autoimmune diabetes in patients who are not obese and born small-for-gestational age.

Clinical characteristics and molecular genetic analysis of 22 patients with neonatal diabetes from the South-Eastern region of Turkey: predominance of non-KATP channel mutations

BACKGROUND

Neonatal diabetes mellitus (NDM) is a rare form of monogenic diabetes and usually presents in the first 6 months of life. We aimed to describe the clinical characteristics and molecular genetics of a large Turkish cohort of NDM patients from a single centre and estimate an annual incidence rate of NDM in South-Eastern Anatolian region of Turkey.

DESIGN AND METHODS

NDM patients presenting to Diyarbakir Children State Hospital between 2010 and 2013, and patients under follow-up with presumed type 1 diabetes mellitus, with onset before 6 months of age were recruited. Molecular genetic analysis was performed.

RESULTS

Twenty-two patients (59% males) were diagnosed with NDM (TNDM-5; PNDM-17). Molecular genetic analysis identified a mutation in 20 (95%) patients who had undergone a mutation analysis. In transient neonatal diabetes (TNDM) patients, the genetic cause included chromosome 6q24 abnormalities (n=3), ABCC8 (n=1) and homozygous INS (n=1). In permanent neonatal diabetes (PNDM) patients, homozygous GCK (n=6), EIF2AK3 (n=3), PTF1A (n=3), and INS (n=1) and heterozygous KCNJ11 (n=2) mutations were identified. Pancreatic exocrine dysfunction was observed in patients with mutations in the distal PTF1A enhancer. Both patients with a KCNJ11 mutation responded to oral sulphonylurea. A variable phenotype was associated with the homozygous c.-331C>A INS mutation, which was identified in both a PNDM and TNDM patient. The annual incidence of PNDM in South-East Anatolian region of Turkey was one in 48 000 live births.

CONCLUSIONS

Homozygous mutations in GCK, EIF2AK3 and the distal enhancer region of PTF1A were the commonest causes of NDM in our cohort. The high rate of detection of a mutation likely reflects the contribution of new genetic techniques (targeted next-generation sequencing) and increased consanguinity within our cohort.

Relapsing 6q24-related transient neonatal diabetes mellitus successfully treated with a dipeptidyl peptidase-4 inhibitor: a case report

The most common form of transient neonatal diabetes mellitus (TNDM) is 6q24-related TNDM. Patients are treated with insulin during the neonatal period until spontaneous remission. However, diabetes often recurs in adolescence, and there is no standard therapy for patients with a relapse. A paternal duplication at the 6q24 critical region spanning the pleiomorphic adenoma gene-like 1 PLAGL1 gene was found in a Japanese patient with TNDM relapse. The patient was treated with a dipeptidyl peptidase-4 (DPP4) inhibitor, alogliptin, at a dose of 25 mg per day. Immediately after treatment initiation, his hemoglobin A1c (HbA1c) levels dropped from 7.0-7.5% (52-58 mmol/mol) to 6.0-6.5% (41-47 mmol/mol) and remained stable for over a year. We reported the successful treatment of relapsed 6q24-related TNDM with a DPP4 inhibitor. Although insulin has been the conventional treatment for such patients, treatments targeting the GLP1 pathway can be a useful alternative because these patients retain the β cell mass and responsiveness through G protein-coupled pathways.

Sulfonylurea treatment before genetic testing in neonatal diabetes: pros and cons

CONTEXT

Diabetes in neonates nearly always has a monogenic etiology. Earlier sulfonylurea therapy can improve glycemic control and potential neurodevelopmental outcomes in children with KCNJ11 or ABCC8 mutations, the most common gene causes.

OBJECTIVE

Assess the risks and benefits of initiating sulfonylurea therapy before genetic testing results become available.

DESIGN, SETTING, AND PATIENTS

Observational retrospective study of subjects with neonatal diabetes within the University of Chicago Monogenic Diabetes Registry.

MAIN OUTCOME MEASURES

Response to sulfonylurea (determined by whether insulin could be discontinued) and treatment side effects in those treated empirically.

RESULTS

A total of 154 subjects were diagnosed with diabetes before 6 months of age. A genetic diagnosis had been determined in 118 (77%), with 73 (47%) having a mutation in KCNJ11 or ABCC8. The median time from clinical diagnosis to genetic diagnosis was 10.4 weeks (range, 1.6 to 58.2 wk). In nine probands, an empiric sulfonylurea trial was initiated within 28 days of diabetes diagnosis. A genetic cause was subsequently found in eight cases, and insulin was discontinued within 14 days of sulfonylurea initiation in all of these cases.

CONCLUSIONS

Sulfonylurea therapy appears to be safe and often successful in neonatal diabetes patients before genetic testing results are available; however, larger numbers of cases must be studied. Given the potential beneficial effect on neurodevelopmental outcome, glycemic control, and the current barriers to expeditious acquisition of genetic testing, an empiric inpatient trial of sulfonylurea can be considered. However, obtaining a genetic diagnosis remains imperative to inform long-term management and prognosis.

Segmental uniparental isodisomy of chromosome 6 causing transient diabetes mellitus and merosin-deficient congenital muscular dystrophy

Segmental uniparental isodisomy (iUPD) is a rare genetic event that may cause aberrant expression of imprinted genes, and reduction to homozygosity of a recessive mutation. Transient neonatal diabetes mellitus (TNDM) is typically caused by imprinting aberrations in chromosome 6q24 TNDM differentially-methylated region (DMR). Approximately, 15.12 Mb upstream in 6q22-q23 is located LAMA2, the gene responsible of merosin-deficient congenital muscular dystrophy type 1A (MDC1A). We investigated a patient diagnosed both with TNDM and MDC1A, born from a twin dichorionic discordant pregnancy. Parents are first-degree cousins. Methylation sensitive-PCR of the imprinted 6q24 TNDM CpG island showed only the non-methylated (paternal) allele. Microsatellite markers and SNP array profiling disclosed normal biparental inheritance at 6p and a segmental paternal iUPD, between 6q22.33 and 6q27. Sequencing of LAMA2 exons showed a homozygous frameshift mutation, c.7490_7493dupAAGA, which predicts p.Asp2498GlufsX4, in exon 54. Her father, but not her mother, was a carrier of the mutation. While segmental paternal iUPD6 causing TNDM was reported twice, there are no previous reports of MDC1A caused by this event. This is a child with two genetic disorders, yet neither is caused by the parental consanguinity, which reinforces the importance of considering different etiological mechanisms in the genetic clinic.

Clinical presentation of 6q24 transient neonatal diabetes mellitus (6q24 TNDM) and genotype-phenotype correlation in an international cohort of patients

AIMS/HYPOTHESIS

6q24 transient neonatal diabetes mellitus (TNDM) is a rare form of diabetes presenting in the neonatal period that remits during infancy but, in a proportion of cases, recurs in later life. We aim to describe the clinical presentation of 6q24 TNDM in the largest worldwide cohort of patients with defined molecular aetiology, in particular seeking differences in presentation or clinical history between aetiological groups.

METHODS

One-hundred and sixty-three patients with positively diagnosed 6q24 TNDM were ascertained from Europe, the Americas, Asia and Australia. Clinical data from referrals were recorded and stratified by the molecular aetiology of patients.

RESULTS

6q24 TNDM patients presented at a modal age of one day, with growth retardation and hyperglycaemia, irrespective of molecular aetiology. There was a positive correlation between age of presentation and gestational age, and a negative correlation between adjusted birthweight SD and age of remission. Congenital anomalies were significantly more frequent in patients with paternal uniparental disomy of chromosome 6 or hypomethylation of multiple imprinted loci defects than in those with 6q24 duplication or isolated hypomethylation defects. Patients with hypomethylation had an excess representation of assisted conception at 15%.

CONCLUSIONS/INTERPRETATION

This, the largest case series of 6q24 TNDM published, refines and extends the clinical phenotype of the disorder and confirms its clinical divergence from other monogenic TNDM in addition to identifying previously unreported clinical differences between 6q24 subgroups.

Transient neonatal diabetes, ZFP57, and hypomethylation of multiple imprinted loci: a detailed follow-up

OBJECTIVE

Transient neonatal diabetes mellitus 1 (TNDM1) is the most common cause of diabetes presenting at birth. Approximately 5% of the cases are due to recessive ZFP57 mutations, causing hypomethylation at the TNDM locus and other imprinted loci (HIL). This has consequences for patient care because it has impact on the phenotype and recurrence risk for families. We have determined the genotype, phenotype, and epigenotype of the first 10 families to alert health professionals to this newly described genetic subgroup of diabetes.

RESEARCH DESIGN AND METHODS

The 10 families (14 homozygous/compound heterozygous individuals) with ZFP57 mutations were ascertained through TNDM1 diagnostic testing. ZFP57 was sequenced in probands and their relatives, and the methylation levels at multiple maternally and paternally imprinted loci were determined. Medical and family histories were obtained, and clinical examination was performed.

RESULTS

The key clinical features in probands were transient neonatal diabetes, intrauterine growth retardation, macroglossia, heart defects, and developmental delay. However, the finding of two homozygous relatives without diabetes and normal intelligence showed that the phenotype could be very variable. The epigenotype always included total loss of methylation at the TNDM1 locus and reproducible combinations of differential hypomethylation at other maternally imprinted loci, including tissue mosaicism.

CONCLUSIONS

There is yet no clear genotype-epigenotype-phenotype correlation to explain the variable clinical presentation, and this results in difficulties predicting the prognosis of affected individuals. However, many cases have a more severe phenotype than seen in other causes of TNDM1. Further cases and global epigenetic testing are needed to clarify this.

Genomic imprinting is a parental effect established in mammalian germ cells

Genomic imprinting is an epigenetic phenomenon in which either the paternal or the maternal allele of imprinted genes is expressed in somatic cells. It is unique to eutherian mammals, marsupials, and flowering plants. It is absolutely required for normal mammalian development. Dysregulation of genomic imprinting can cause a variety of human diseases. About 150 imprinted genes have been identified so far in mammals and many of them are clustered such that they are coregulated by a cis-acting imprinting control region, called the ICR. One hallmark of the ICR is that it contains a germ line-derived differentially methylated region that is methylated on the paternal chromosome or on the maternal chromosome. The DNA methylation imprint is reset in the germ line and differential methylation at an ICR is restored upon fertilization. The DNA methylation imprint is resistant to a genome-wide demethylation process in early embryos and is stably maintained in postimplantation embryos. Maintenance of the DNA methylation imprint is dependent on two distinct maternal effect genes (Zfp57 and PGC7/Stella). In germ cells, around midgestation, the DNA methylation imprint is erased and undergoes another round of the DNA methylation imprint cycle that includes erasure, resetting, restoration, and maintenance of differential DNA methylation.

Prenatal diagnosis of trisomy 6 rescue resulting in paternal UPD6 with novel placental findings

Uniparental disomy (UPD) is defined by the inheritance of both copies of a chromosome pair from one single parent. Although 23 cases of paternal UPD6 have been reported earlier, the occurrence of trisomy 6 rescue with paternal UPD6 has not been previously reported. The phenotype of paternal UPD6 results from biallelic expression of the maternally imprinted, paternally expressed ZAC and HYMAI genes, and includes transient neonatal diabetes mellitus (TNDM), intra-uterine growth restriction (IUGR), macroglossia, and minor anomalies. Trisomy rescue has been proposed as a pathogenic mechanism leading to UPD of other chromosomes. We report on the first case of a prenatally diagnosed infant with UPD6 and describe the clinical, cytogenetic, molecular, and novel placental findings in a female infant with paternal UPD6. Low-level trisomy 6 and paternal UPD6 were prenatally diagnosed through amniocentesis. After birth trisomy 6 was documented in the placenta but was not found in three different cell lines from the infant. The placenta was small with a peculiar pattern of vascular proliferation. Our results of trisomy 6 cells predominantly present in the placenta and only in low levels in the amniotic fluid suggest that the distribution and proportion of trisomic and diploid UPD cells contribute to the variability of fetal and placental phenotypes.

Study of DNA methylation patterns of imprinted genes in children born after assisted reproductive technologies reveals no imprinting errors: A pilot study

Assisted reproductive technology (ART) including in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) have been shown to be associated with abnormal genomic imprinting, thus increasing the incidence of imprinting disorders such as Beckwith-Wiedemann syndrome (BWS) and Angelman syndrome (AS) in ART-conceived children. Furthermore, a recent study described abnormal DNA methylation in clinically normal children conceived by ART. However, data from different studies are conflicting or inconclusive. This study examined DNA methylation patterns of multiple imprinted genes in children born after ART to primarily evaluate the impact of ART on genomic imprinting. A total of 101 newborns conceived by ART (40 ICSI and 61 IVF) and 60 naturally conceived newborns were involved in our study. After obtaining the approval of the Institutional Ethics Committee, umbilical cord blood was collected from each infant. Genomic DNA was isolated from each blood sample and treated using sodium bisulfite. Subsequently, using methylation-specific PCR (MS-PCR), we analyzed six differentially methylated regions (DMRs) including KvDMR1, SNRPN, MEST, MEG3, TNDM and XIST. Meanwhile, information regarding twin pregnancies, gestational age, and birth weight of the neonates was documented. None of the cases presented with phenotypic abnormalities. Children conceived by ART were more likely to have low birth weight and to be born before term, compared with children conceived spontaneously. However, 7 months to 3 years of clinical follow-up showed that none of the children had clinical symptoms of any imprinting diseases. Furthermore, the MS-PCR results showed that all 161 children had normal DNA methylation patterns at six DMRs despite the different mode of conception. Our data did not indicate a higher risk of DNA-methylation defects in children born after ART. However, further studies using quantitative methods are needed to confirm these results.

Further refinement of the critical minimal genetic region for the imprinting disorder 6q24 transient neonatal diabetes

AIMS/HYPOTHESIS

Transient neonatal diabetes (TND) is associated with overexpression of genes within a critical region on 6q24. This study aims to refine the boundaries of this region to reduce the number of potential candidate genes for 6q24 TND.

METHODS

Fifteen patients with transient neonatal diabetes and submicroscopic chromosome 6 duplications were investigated. The duplications were confirmed by microsatellite analysis and subsequently mapped using tiled chromosome 6 array Comparative Genomic Hybridisation (aCGH) and MLPA. Duplication boundaries were compared to identify the minimal shared region of duplication. These data were then used with available clinical data to identify associations between size of 6q24 duplication and severity of TND phenotype.

RESULTS

Alignment of the minimal region of duplication to the human genome reduced the minimal TND critical region, formerly estimated at 440 kb, to 160-173 kb, revealing PLAGL1 (pleiomorphic adenoma gene-like 1) and HYMAI (imprinted in hydatidiform mole) to be the only genes wholly included therein. Additionally, the complete paternal duplication of a region containing the theoretical protein FAM164B was associated with the severe growth restriction observed in 6q24 duplication patients.

CONCLUSIONS/INTERPRETATION

This study has significantly reduced the critical region associated with 6q24 TND. It has eliminated several previous TND candidate genes, leaving the overlapping imprinted genes PLAGL1 and HYMAI as the only remaining complete candidate genes for 6q24 TND. Moreover, these data provide the first evidence that an additional region, encompassing the theoretical protein FAM164B, may have a critical role in the growth restriction phenotype observed in many 6q24 TND patients.

6q24 transient neonatal diabetes

Transient Neonatal Diabetes (type 1) is the commonest cause of diabetes presenting in the first week of life. The majority of infants recover by 3 months of age but are predisposed to developing type 2 diabetes in later life. It is associated with low birth weight but rapid catch up by 1 year of life. The condition is usually due to genetic or epigenetic aberrations at an imprinted locus on chromosome 6q24 and can be sporadic or inherited. Early diagnosis alters medical treatment strategies and differentiates it from other types of early onset diabetes. In some individuals, diabetes may be the initial presentation of a more complex imprinting disorder due to recessive mutations in the gene ZFP57 and may be associated with other developmental problems.

Neonatal diabetes mellitus: a model for personalized medicine

Neonatal diabetes mellitus occurs in approximately 1 out of every 100,000 live births. It can be either permanent or transient, and recent studies indicate that is likely to have an underlying genetic cause, particularly when diagnosed before 6 months of age. Permanent neonatal diabetes is most commonly due to activating mutations in either of the genes encoding the two subunits of the ATP-sensitive potassium channel. In most of these patients, switching from insulin to oral sulfonylurea therapy leads to improved metabolic control, as well as possible amelioration of occasional associated neurodevelopmental disabilities. It remains to be determined what is the most appropriate treatment of other causes. The diagnosis and treatment of neonatal diabetes, therefore, represents a model for personalized medicine.

Silver-Russell patients showing a broad range of ICR1 and ICR2 hypomethylation in different tissues

In all known congenital imprinting disorders an association with aberrant methylation or mutations at specific loci was well established. However, several patients with transient neonatal diabetes mellitus (TNDM), Silver-Russell syndrome (SRS) and Beckwith-Wiedemann syndrome (BWS) exhibiting multilocus hypomethylation (MLH) have meanwhile been described. Whereas TNDM patients with MLH show clinical symptoms different from carriers with isolated 6q24 aberrations, MLH carriers diagnosed as BWS or SRS present only the syndrome-specific features. Interestingly, SRS and BWS patients with nearly identical MLH patterns in leukocytes have been identified. We now report on the molecular findings in DNA in three SRS patients with hypomethylation of both 11p15 imprinted control regions (ICRs) in leukocytes. One patient was a monozygotic (MZ) twin, another was a triplet. While the hypomethylation affected both oppositely imprinted 11p15 ICRs in leukocytes, in buccal swab DNA only the ICR1 hypomethylation was visible in two of our patients. In the non-affected MZ twin of one of these patients, aberrant methylation was also present in leukocytes but neither in buccal swab DNA nor in skin fibroblasts. Despite mutation screening of several factors involved in establishment and maintenance of methylation marks including ZFP57, MBD3, DNMT1 and DNMT3L the molecular clue for the ICR1/ICR2 hypomethylation in our patients remained unclear. Furthermore, the reason for the development of the specific SRS phenotype is not obvious. In conclusion, our data reflect the broad range of epimutations in SRS and illustrate that an extensive molecular and clinical characterization of patients is necessary.

Incidence of neonatal diabetes in Austria-calculation based on the Austrian Diabetes Register

BACKGROUND

Neonatal diabetes mellitus (NDM) is a rare monogenic form of diabetes which is diagnosed in the first 6 months of life. Several studies in the last few years provide information on genetic causes for NDM.

OBJECTIVE

The aim of this study was to identify all patients with diabetes in the first 6 months of life through the Austrian Diabetes Register, which is available since 1989. A retrospective data analyses was performed to calculate the current incidence of NDM.

SUBJECTS AND METHODS

Ten patients were registered with diabetes onset within the first 6 months of life in the Austrian Diabetes Register. Evaluation of detailed clinical data was performed by sending a questionnaire to all diabetes centers.

RESULTS

Ten patients from nine different families with NDM were diagnosed in Austria from 1989 until September 2007. Seven patients (one male, six females) had transient NDM (TNDM), three (two males, one female) showed a permanent course [permanent neonatal diabetes mellitus (PNDM)]. One had immunodeficiency, polyendocrinopathy and enteropathy X-linked (IPEX) syndrome and another showed aplasia of the pancreas; no genetic etiology was found in the third case. In three out of seven patients with a transient course of NDM a genetic diagnosis was possible. Two female siblings had activating point mutations in the ABCC8 gene, although one patient had paternal uniparental isodisomy of chromosome 6q24. One patient's family did not consent to genetic testing.

CONCLUSIONS

The incidence of NDM in Austria is 1/160 949, with an incidence of 1/ 536 499 for PNDM and 1/229 928 for TNDM.

PCR-based methods for detecting single-locus DNA methylation biomarkers in cancer diagnostics, prognostics, and response to treatment

BACKGROUND

DNA methylation is a highly characterized epigenetic modification of the human genome that is implicated in cancer. The altered DNA methylation patterns found in cancer cells include not only global hypomethylation but also discrete hypermethylation of specific genes. In particular, numerous tumor suppressor genes undergo epigenetic silencing because of hypermethylated promoter regions. Some of these genes are considered promising DNA methylation biomarkers for early cancer diagnostics, and some have been shown to be valuable for predicting prognosis or the response to therapy.

CONTENT

PCR-based methods that use sodium bisulfite-treated DNA as a template are generally accepted as the most analytically sensitive and specific techniques for analyzing DNA methylation at single loci. A number of new methods, such as methylation-specific fluorescent amplicon generation (MS-FLAG), methylation-sensitive high-resolution melting (MS-HRM), and sensitive melting analysis after real-time methylation-specific PCR (SMART-MSP), now complement the traditional PCR-based methods and promise to be valuable diagnostic tools. In particular, the HRM technique shows great potential as a diagnostic tool because of its closed-tube format and cost-effectiveness.

SUMMARY

Numerous traditional and new PCR-based methods have been developed for detecting DNA methylation at single loci. All have characteristic advantages and disadvantages, particularly with regard to use in clinical settings.

Investigating parent of origin effects in studies of type 2 diabetes and obesity

The role of parent-of-origin effects (POE) in the etiology of complex diseases such as type 2 diabetes (T2DM) and obesity is currently of intense interest, but still largely unclear. POE are transmittable genetic effects whereby the expression of the phenotype in the offspring depends upon whether the transmission originated from the mother or father. In mammals, POE can be caused by genetic imprinting, intrauterine effects, or maternally inherited mitochondrial genes. In this paper, we describe the different mechanisms underlying POE, characterize known examples of POE in rare forms of diabetes, and review the evidence from linkage and association studies for POE in T2DM and obesity. Finally, we summarize some of the new and established statistical and experimental approaches commonly used to detect POE. Through this paper, we hope emphasizes the potentially significant importance of POE in the etiology of T2DM and obesity.

Diagnosis and treatment of neonatal diabetes: a United States experience

BACKGROUND/OBJECTIVE

Mutations in KCNJ11, ABCC8, or INS are the cause of permanent neonatal diabetes mellitus in about 50% of patients diagnosed with diabetes before 6 months of age and in a small fraction of those diagnosed between 6 and 12 months. The aim of this study was to identify the genetic cause of diabetes in 77 consecutive patients referred to the University of Chicago with diabetes diagnosed before 1 yr of age.

METHODS

We used Oragene DNA Self-Collection kit to obtain a saliva sample for DNA. We sequenced the protein-coding regions of KCNJ11, ABCC8, and INS using standard methods.

RESULTS

We enrolled 32 patients diagnosed with diabetes before 6 months of age and 45 patients diagnosed between 6 and 12 months. We identified a mutation in KCNJ11 in 14 patients from 12 families and in INS in 7 patients from 4 families. Three of the patients with an INS mutation were diagnosed with diabetes between 6 and 12 months of age. Finally, we found that two patients had an abnormality of chromosome 6q24 associated with transient neonatal diabetes mellitus.

CONCLUSIONS

We were able to establish a genetic cause of diabetes in 63% of patients diagnosed with diabetes before 6 months of age and in 7% of patients diagnosed between 6 and 12 months. Genetic testing, which is critical for guiding appropriate management, should be considered in patients diagnosed with diabetes before 1 yr of age, especially if they are autoantibody negative, although the presence of autoantibodies does not rule out a monogenic cause.

Coincidence of a novel KCNJ11 missense variant R365H with a paternally inherited 6q24 duplication in a patient with transient neonatal diabetes

OBJECTIVE

Neonatal diabetes is a heterogeneous group of disorders with diabetes manifestation in the first 6 months of life. The most common etiology in permanent neonatal diabetes is mutations of the ATP-sensitive K(+) channel subunits; in transient neonatal diabetes, chromosome 6q24 abnormalities are the most common cause.

RESEARCH DESIGN AND METHODS

We report a sporadic case of diabetes without ketoacidosis diagnosed on the fourth day of life.

RESULTS

Analysis of the KCNJ11 gene found a novel R365H mutation in the proband and her unaffected father. The functional analysis did not support pathogenicity of this variant. When the patient's diabetes remitted in the seventh month of life, the 6q24 region was analyzed and a paternally inherited duplication was identified.

CONCLUSIONS

Our case reports a coincidental novel KCNJ11 variant in a patient with transient neonatal diabetes due to a 6q24 duplication, illustrating the difficulty in testing neonates before the clinical course of neonatal diabetes is known.

Hypomethylation of multiple imprinted loci in individuals with transient neonatal diabetes is associated with mutations in ZFP57

We have previously described individuals presenting with transient neonatal diabetes and showing a variable pattern of DNA hypomethylation at imprinted loci throughout the genome. We now report mutations in ZFP57, which encodes a zinc-finger transcription factor expressed in early development, in seven pedigrees with a shared pattern of mosaic hypomethylation and a conserved range of clinical features. This is the first description of a heritable global imprinting disorder that is compatible with life.

Clinical characterisation of the multiple maternal hypomethylation syndrome in siblings

We present the first clinical report of sibs with the multiple maternal hypomethylation syndrome. Both sisters presented with transient neonatal diabetes mellitus (TNDM). By methylation-specific PCR of bisulphite-treated DNA, we found a mosaic spectrum of hypomethylation at the following maternally methylated loci in both sibs: ZAC (6q24), KCNQ1OT1 (11p15.5), GRB10 (7p11.2-12), PEG3 (19q13), PEG1/MEST (7q32), and NESPAS (20q13). While the older sister has a milder phenotype, the younger one was severely ill and died at 11 months of age. Despite phenotypic differences, the sisters had several manifestations of both TNDM and BWS in common. The family is highly consanguineous, and the parents are first cousins. We suggest that the genetic defect in this family is a novel, most likely autosomal recessive defect of methylation mechanisms, either in the sisters or in their mother, affecting her oocyte imprinting. The recurrence with affected sibs as reported in this family has implications for genetic counselling.

Mutations in the ABCC8 gene encoding the SUR1 subunit of the KATP channel cause transient neonatal diabetes, permanent neonatal diabetes or permanent diabetes diagnosed outside the neonatal period

AIM

Mutations in the ABCC8 gene encoding the SUR1 subunit of the pancreatic ATP-sensitive potassium channel cause permanent neonatal diabetes mellitus (PNDM) and transient neonatal diabetes mellitus (TNDM). We reviewed the existing literature, extended the number of cases and explored genotype-phenotype correlations.

METHODS

Mutations were identified by sequencing in patients diagnosed with diabetes before 6 months without a KCNJ11 mutation.

RESULTS

We identified ABCC8 mutations in an additional nine probands (including five novel mutations L135P, R306H, R1314H, L438F and M1290V), bringing the total of reported families to 48. Both dominant and recessive mutations were observed with recessive inheritance more common in PNDM than TNDM (9 vs. 1; p < 0.01). The remainder of the PNDM probands (n = 12) had de novo mutations. Seventeen of twenty-five children with TNDM inherited their heterozygous mutation from a parent. Nine of these parents had permanent diabetes (median age at diagnosis: 27.5 years, range: 13-35 years). Recurrent mutations of residues R1183 and R1380 were found only in TNDM probands and dominant mutations causing PNDM clustered within exons 2-5.

CONCLUSIONS

ABCC8 mutations cause PNDM, TNDM or permanent diabetes diagnosed outside the neonatal period. There is some evidence that the location of the mutation is correlated with the clinical phenotype.

Mutations in ATP-sensitive K+ channel genes cause transient neonatal diabetes and permanent diabetes in childhood or adulthood

Transient neonatal diabetes mellitus (TNDM) is diagnosed in the first 6 months of life, with remission in infancy or early childhood. For approximately 50% of patients, their diabetes will relapse in later life. The majority of cases result from anomalies of the imprinted region on chromosome 6q24, and 14 patients with ATP-sensitive K+ channel (K(ATP) channel) gene mutations have been reported. We determined the 6q24 status in 97 patients with TNDM. In patients in whom no abnormality was identified, the KCNJ11 gene and/or ABCC8 gene, which encode the Kir6.2 and SUR1 subunits of the pancreatic beta-cell K(ATP) channel, were sequenced. K(ATP) channel mutations were found in 25 of 97 (26%) TNDM probands (12 KCNJ11 and 13 ABCC8), while 69 of 97 (71%) had chromosome 6q24 abnormalities. The phenotype associated with KCNJ11 and ABCC8 mutations was similar but markedly different from 6q24 patients who had a lower birth weight and who were diagnosed and remitted earlier (all P < 0.001). K(ATP) channel mutations were identified in 26 additional family members, 17 of whom had diabetes. Of 42 diabetic patients, 91% diagnosed before 6 months remitted, but those diagnosed after 6 months had permanent diabetes (P < 0.0001). K(ATP) channel mutations account for 89% of patients with non-6q24 TNDM and result in a discrete clinical subtype that includes biphasic diabetes that can be treated with sulfonylureas. Remitting neonatal diabetes was observed in two of three mutation carriers, and permanent diabetes occurred after 6 months of age in subjects without an initial diagnosis of neonatal diabetes.

Tissue-specific imprinting of the ZAC/PLAGL1 tumour suppressor gene results from variable utilization of monoallelic and biallelic promoters

The tumour suppressor gene ZAC/PLAGL1 is widely expressed in many human tissues during fetal development and throughout life. It encodes a DNA-binding protein which shares with p53 the ability to regulate apoptosis and cell cycle arrest concurrently. Owing to its anti-proliferative properties, down-regulation or loss of ZAC is believed to deregulate cell growth, and loss of expression has been observed in a number of different cancers. In addition, overexpression of ZAC during fetal development is believed to underlie the rare disorder transient neonatal diabetes mellitus (TNDM). Imprinted expression of ZAC has been demonstrated in many human and mouse tissues, although biallelic transcription has been noted in human peripheral blood leucocytes (PBL). We report here the identification of a second ZAC promoter, which is responsible for the observed biallelic expression. The promoter lies within a previously uncharacterized CpG island ~55 kb upstream of the imprinted CpG island. In PBL, the imprinted CpG island (P1) is differentially methylated and produces monoallelic transcripts, as in other tissues. However, biallelic transcripts predominate and are derived from the alternative CpG island (P2), which is unmethylated. Biallelic P2 expression was also found in adult pancreas, and ZAC expression from this promoter was identified at a low level in all adult human tissues tested. These findings show that regulation of ZAC expression is more complex than previously realized. The existence of the apparently independently-regulated P2 promoter has important implications for the study of ZAC dysregulation in cancer and TNDM.

Genetic and epigenetic defects at the 6q24 imprinted locus in a cohort of 13 patients with transient neonatal diabetes: new hypothesis raised by the finding of a unique case with hemizygotic deletion in the critical region

BACKGROUND

Transient neonatal diabetes (TND) is a rare form of diabetes usually present in the first few days after birth that resolves within 1 year but that has a tendency to recur later in life. It can be associated with chromosome 6 paternal uniparental disomy (UPD), paternal duplications or loss of maternal methylation at the 6q24 imprinted locus.

OBJECTIVE

To report on a cohort of 13 sporadic TND cases, including five with birth defects (congenital abnormalities of heart, brain and bone) and eight without.

RESULTS

The hallmarks of diabetes were similar in patients with or without 6q24 defects. The chromosome 6 abnormalities in our patients (n = 13) included 2 of 13 (approximately 15.4%) cases of paternal UPD6, 2 of 11 (approximately 18%) cases of complete and 3 of 11 (approximately 27%) cases of partial loss of the maternal methylation signature upstream of ZAC1-HYMAI imprinted genes in non-UPD cases, and 1 of 13 (approximately 7.7%) cases of hemizygotic deletion.

CONCLUSION

The deletion was found in a patient with severe congenital abnormalities. This genetic lesion was not reported previously. The hypothesis of an effect on regulatory elements critical for imprinting and tissue-specific gene expression in early development by the deletion is raised. The data presented here may contribute to the diagnosis and the understanding of imprinting in the region.

Interstitial deletion of 6q without phenotypic effect

Cytogenetically detectable euchromatic deletions without phenotypic consequences are rarely encountered. We report on a 34-year-old woman with normal intelligence referred for karyotyping because of recurrent abortions. With the exception of a bicuspid aortic valve without hemodynamic consequences, which is a common minor anomaly in the general population, no dysmorphic features were found on physical examination. Conventional chromosome analysis (GTG-banding) revealed an interstitial deletion in the long arm of chromosome 6. With array comparative genomic hybridization (array-CGH) the size of the deletion was estimated to be between 9.9 and 11.6 Mb and the refined karyotype was 46,XX,del(6)(q22.31q23.1).

A maternal hypomethylation syndrome presenting as transient neonatal diabetes mellitus

The expression of imprinted genes is mediated by allele-specific epigenetic modification of genomic DNA and chromatin, including parent of origin-specific DNA methylation. Dysregulation of these genes causes a range of disorders affecting pre- and post-natal growth and neurological function. We investigated a cohort of 12 patients with transient neonatal diabetes whose disease was caused by loss of maternal methylation at the TNDM locus. We found that six of these patients showed a spectrum of methylation loss, mosaic with respect to the extent of the methylation loss, the tissues affected and the genetic loci involved. Five maternally methylated loci were affected, while one maternally methylated and two paternally methylated loci were spared. These patients had higher birth weight and were more phenotypically diverse than other TNDM patients with different aetiologies, presumably reflecting the influence of dysregulation of multiple imprinted genes. We propose the existence of a maternal hypomethylation syndrome, and therefore suggest that any patient with methylation loss at one maternally-methylated locus may also manifest methylation loss at other loci, potentially complicating or even confounding the clinical presentation.

Epimutation of the TNDM locus and the Beckwith–Wiedemann syndrome centromeric locus in individuals with transient neonatal diabetes mellitus

Transient neonatal diabetes mellitus (TNDM) is characterised by intra-uterine growth retardation, while Beckwith-Wiedemann syndrome (BWS) is a clinically heterogeneous overgrowth syndrome. Both TNDM and BWS may be caused by aberrant loss of methylation (LOM) at imprinted loci on chromosomes 6q24 and 11p15.5 respectively. Here we describe two patients with a clinical diagnosis of TNDM caused by LOM at the maternally methylated imprinted domain on 6q24; in addition, these patients had LOM at the centromeric differentially methylated region of 11p15.5. This shows that imprinting anomalies can affect more than one imprinted locus and may alter the clinical presentation of imprinted disease.

Monozygous triplets discordant for transient neonatal diabetes mellitus and for imprinting of the TNDM differentially methylated region

Transient neonatal diabetes mellitus (TNDM) is associated with paternal over-expression of an imprinted locus on chromosome 6q24, which contains one differentially methylated region (DMR); maternal demethylation at the DMR accounts for approximately 20% of cases. Here we report female monozygous triplets, two of whom have TNDM arising from loss of maternal methylation within the TNDM DMR.