Maternal UPD of chromosome 7 in a patient with Silver-Russell syndrome and Pendred syndrome.

BACKGROUND: Silver-Russell syndrome (SRS) is a heterogeneous imprinting disorder featuring severe intrauterine and postnatal growth retardation and dysmorphic features. Pendred syndrome (PDS) is an autosomal recessive disorder caused by mutations in the SLC26A4 gene characterized by sensorineural hearing loss. METHODS: Karyotyping analysis was performed to investigate any chromosomal abnormalities. Whole-genome copy number variation and loss of heterozygosity were analyzed using an Affymetrix CytoScan 750 K Microarray. Variant screening was performed by targeted next-generation sequencing on all known deafness-causing genes. RESULTS: The proband was a patient with SRS caused by maternal uniparental disomy 7. The PDS of the proband was caused by homozygous variant c.919-2A > G of SLC26A4; both mutated alleles were inherited from his mother. CONCLUSION: This is the first report of uniparental disomy 7 leading to SRS and Pendred syndrome. Patients with intrauterine growth retardation or those born small for gestational age and exhibiting postnatal growth failure should undergo molecular testing to reach a clinical diagnosis.

Contribution of gene mutations to Silver-Russell syndrome phenotype: multigene sequencing analysis in 92 etiology-unknown patients.

BACKGROUND: Silver-Russell syndrome (SRS) is characterized by growth failure and dysmorphic features. Major (epi)genetic causes of SRS are loss of methylation on chromosome 11p15 (11p15 LOM) and maternal uniparental disomy of chromosome 7 (upd(7)mat). However, IGF2, CDKN1C, HMGA2, and PLAG1 mutations infrequently cause SRS. In addition, other imprinting disturbances, pathogenic copy number variations (PCNVs), and monogenic disorders sometimes lead to SRS phenotype. This study aimed to clarify the frequency and clinical features of the patients with gene mutations among etiology-unknown patients with SRS phenotype. RESULTS: Multigene sequencing was performed in 92 out of 336 patients referred to us for genetic testing for SRS. The clinical features of the patients were evaluated based on the Netchine-Harbison clinical scoring system. None of the patients showed 11p15 LOM, upd(7)mat, abnormal methylation levels for six differentially methylated regions (DMRs), namely, PLAGL1:alt-TSS-DMR on chromosome 6, KCNQ1OT1:TSS-DMR on chromosome 11, MEG3/DLK1:IG-DMR on chromosome 14, MEG3:TSS-DMR on chromosome 14, SNURF:TSS-DMR on chromosome 15, and GNAS A/B:TSS-DMR on chromosome 20, PCNVs, or maternal uniparental disomy of chromosome 16. Using next-generation sequencing and Sanger sequencing, we screened four SRS-causative genes and 406 genes related to growth failure and/or skeletal dysplasia. We identified four pathogenic or likely pathogenic variants in responsible genes for SRS (4.3%: IGF2 in two patients, CDKN1C, and PLAG1), and five pathogenic variants in causative genes for known genetic syndromes presenting with growth failure (5.4%: IGF1R abnormality (IGF1R), SHORT syndrome (PIK3R1), Floating-Harbor syndrome (SRCAP), Pitt-Hopkins syndrome (TCF4), and Noonan syndrome (PTPN11)). Functional analysis indicated the pathogenicity of the CDKN1C variant. The variants we detected in CDKN1C and PLAG1 were the second and third variants leading to SRS, respectively. Our patients with CDKN1C and PLAG1 variants showed similar phenotypes to previously reported patients. Furthermore, our data confirmed IGF1R abnormality, SHORT syndrome, and Floating-Harbor syndrome are differential diagnoses of SRS because of the shared phenotypes among these syndromes and SRS. On the other hand, the patients with pathogenic variants in causative genes for Pitt-Hopkins syndrome and Noonan syndrome were atypical of these syndromes and showed partial clinical features of SRS. CONCLUSIONS: We identified nine patients (9.8%) with pathogenic or likely pathogenic variants out of 92 etiology-unknown patients with SRS phenotype. This study expands the molecular spectrum of SRS phenotype.

Molecular and clinical analyses of two patients with UPD(16)mat detected by screening 94 patients with Silver-Russell syndrome phenotype of unknown aetiology.

BACKGROUND: Recently, a patient with maternal uniparental disomy of chromosome 16 (UPD(16)mat) presenting with Silver-Russell syndrome (SRS) phenotype was reported. SRS is characterised by growth failure and dysmorphic features. OBJECTIVE: To clarify the prevalence of UPD(16)mat in aetiology-unknown patients with SRS phenotype and phenotypic differences between UPD(16)mat and SRS. METHODS: We studied 94 patients with SRS phenotype of unknown aetiology. Sixty-three satisfied the Netchine-Harbison clinical scoring system (NH-CSS) criteria, and 25 out of 63 patients showed both protruding forehead and relative macrocephaly (clinical SRS). The remaining 31 patients met only three NH-CSS criteria, but were clinically suspected as having SRS. To detect UPD(16)mat, we performed methylation analysis for the ZNF597:TSS-differentially methylated region (DMR) on chromosome 16 and subsequently performed microsatellite, SNP array and exome analyses in the patients with hypomethylated ZNF597:TSS-DMR. RESULTS: We identified two patients (2.1%) with a mixture of maternal isodisomy and heterodisomy of chromosome 16 in 94 aetiology-unknown patients with SRS phenotype. Both patients exhibited preterm birth and prenatal and postnatal growth failure. The male patient had ventricular septal defect and hypospadias. Whole-exome sequencing detected no gene mutations related to their phenotypes. CONCLUSION: We suggest considering genetic testing for UPD(16)mat in SRS phenotypic patients without known aetiology.

Genome-wide analysis of differential DNA methylation in Silver-Russell syndrome.

Silver-Russell Syndrome (SRS) is clinically heterogeneous disorder characterized by low birth weight, postnatal growth restriction, and variable dysmorphic features. Current evidence strongly implicates imprinted genes as an important etiology of SRS. Although almost half of the patients showed DNA hypomethylation at the H19/IGF2 imprinted domain, and approximately 7%-10% of SRS patients have maternal uniparental disomy of chromosome 7 (UPD (7) mat); the rest of the SRS patients shows unknown etiology. In this study, we investigate whether there are further DNA methylation defects in SRS patients. We measured DNA methylation in seven SRS patients and five controls at more than 485,000 CpG sites using DNA methylation microarrays. We analyzed methylation changes genome-wide and identified the differentially methylated regions (DMRs) using bisulfite sequencing and digital PCR. Our analysis identifies epimutations at the previously characterized domains of H19/IGF2, providing proof of principle that our methodology can detect the changes in DNA methylation at imprinted loci. In addition, our results showed a novel SRS associated imprinted gene OSBPL5 located on chromosome 11p14 with the probe cg25963939, which is hypomethylated in 4/7 patients (P=0.023, ß=-0.243). We also report DMRs in other genes including TGFß3, HSF1, GAP43, NOTCH4 and MYH14. These DMRs were found to be associated with SRS using GO pathway analysis. In this study, we identified the probe cg25963939, located at the 5'UTR of imprinted gene OSBPL5, as a novel DMR that is associated with SRS. This finding provides new insights into the mechanism of SRS etiology and aid the further stratification of SRS patients by molecular phenotypes.

Epigenetic Alterations in Density Selected Human Spermatozoa for Assisted Reproduction.

Epidemiological evidence indicates that assisted reproductive technologies (ART) may be associated with several epigenetic diseases such as Beckwith-Wiedemann syndrome (BWS) or Silver-Russell syndrome (SRS). Selection of sperm by density-gradients in ART has improved DNA integrity and sperm quality; however, epigenetic alterations associated with this approach are largely unknown. In the present study, we investigated DNA methylation and histone retention profiles in raw sperm and selected sperm derived from the same individual and separated by using density-gradients. Results from a study group consisting of 93 males demonstrated that both global DNA methylation and histone retention levels decreased in density selected sperm. Compared to unselected raw sperm, histone transition rates decreased by an average of 27.2% in selected sperm, and the global methylation rate was 3.8% in unselected sperm and 3.3% in the selected sperm. DNA methylation and histone retention location profiling analyses suggested that these alterations displayed specific location patterns in the human genome. Changes in the pattern of hypomethylation largely occurred in transcriptional factor gene families such as HOX, FOX, and GATA. Histone retention increased in 67 genes, whereas it was significantly clustered in neural development-related gene families, particularly the olfactory sensor gene family. Although a causative relationship could not be established, the results of the present study suggest the possibility that sperm with good density also possess unique epigenetic profiles, particularly for genes involved in neural and olfactory development. As increasing evidence demonstrates that epigenetics plays a key role in embryonic development and offspring growth characteristics, the specific epigenetic alterations we observed in selected sperm may influence the transcriptional process and neural development in embryos.