4p16.3 microdeletions and microduplications detected by chromosomal microarray analysis: New insights into mechanisms and critical regions

Burden of Rare Copy Number Variants in Microcephaly: A Brazilian Cohort of 185 Microcephalic Patients and Review of the Literature

Microcephaly presents heterogeneous genetic etiology linked to several neurodevelopmental disorders (NDD). Copy number variants (CNVs) are a causal mechanism of microcephaly whose investigation is a crucial step for unraveling its molecular basis. Our purpose was to investigate the burden of rare CNVs in microcephalic individuals and to review genes and CNV syndromes associated with microcephaly. We performed chromosomal microarray analysis (CMA) in 185 Brazilian patients with microcephaly and evaluated microcephalic patients carrying < 200 kb CNVs documented in the DECIPHER database. Additionally, we reviewed known genes and CNV syndromes causally linked to microcephaly through the PubMed, OMIM, DECIPHER, and ClinGen databases. Rare clinically relevant CNVs were detected in 39 out of the 185 Brazilian patients investigated by CMA (21%). In 31 among the 60 DECIPHER patients carrying < 200 kb CNVs, at least one known microcephaly gene was observed. Overall, four gene sets implicated in microcephaly were disclosed: known microcephaly genes; genes with supporting evidence of association with microcephaly; known macrocephaly genes; and novel candidates, including OTUD7A, BBC3, CNTN6, and NAA15. In the review, we compiled 957 known microcephaly genes and 58 genomic CNV loci, comprising 13 duplications and 50 deletions, which have already been associated with clinical findings including microcephaly. We reviewed genes and CNV syndromes previously associated with microcephaly, reinforced the high CMA diagnostic yield for this condition, pinpointed novel candidate loci linked to microcephaly deserving further evaluation, and provided a useful resource for future research on the field of neurodevelopment.

Clinical and epilepsy characteristics in Wolf-Hirschhorn syndrome (4p-): A review

Wolf-Hirschhorn syndrome (WHS) is araredisorderwithan estimated prevalence being around 1 in 50,000 births. The syndrome is caused by the deletion of a critical region (Wolf-Hirschhorn Syndrome Critical region- WHSCR) on chromosome 4p16.3. WHS is clinically characterized by pre-and postnatal growth restriction, hypotonia, intellectual disability, craniofacial dysmorphismand congenital fusion anomalies. The clinical aspects are variable due to the deletion size.Consistently, epilepsy is one of the major concerns for parents and professionals caring for children with WHS. Seizures tend to occur in over 90% of patients, with onset within the first 3 years of life, and a peak incidence at around 6-12 months of age. Approximately 20% of patients had the first seizure onset within the first 6 months of age, almost 50% at 6 to 12 months of age and about 25% later than 12 months of age. The main types of epileptic seizures occurring in patients with WHS were generalized tonic-clonic seizures (around 70%). These were followed by tonic spasms (20%); focal seizures with impaired awareness (12%) and clonicseizures in 7% of patients.Seizures are often triggered by fever, followed by infections of various systems. Particularly, half of WHS patients experience status epilepticus in the first years of life, which can be fatal. Due to limited number of reports on the topic of EEG abnormalities in epilepsy among WHS patients, it is difficult to determine whether there are any characteristic deviations for WHS. Although more than 300 persons with WHS have been reported in the literature, there is sparse knowledge about epilepsy and methods of its anti-seizure medication (ASM) management with an assessment of their effectiveness. The purpose of this systematic review is to briefly summarize achievements and advances in the field of epilepsy in Wolf-Hirschhorn syndrome.

Determining the Linguistic Profile of Children With Rare Genetic Disorders

PURPOSE

Language studies on populations with rare genetic disorders are limited. Hence, there is little data on commonly found or expected developmental linguistic traits and cognitive mechanisms that may be impaired. Based on the hypothesis that there is a close connection between language and cognition and the relevance of specific genetic changes in the development of each, our goal was to provide linguistic data on relationships with other executive functioning mechanisms.

METHOD

This study assessed language skills, communicative behaviors, and executive functions in four children, aged 7-9 years, with rare genetic disorders, using standardized protocols and tests.

RESULTS

The findings revealed different levels of language impairment and executive functioning problems in each case. The overall executive function index performance for each of the four cases studied was clinically significantly high, indicating executive dysfunction.

CONCLUSIONS

The cases analyzed illustrate different types of atypical development that affect both language and other cognitive mechanisms and underscore the importance of executive skills and the various ways in which they are involved in diverse levels of language that might be affected to a greater or lesser degree in rare genetic disorders. In conclusion, we found that language dysfunction is a salient feature of the rare genetic disorders included in our study, although this is not necessarily true for all genetic disorders. Along with these conclusive results, we performed a qualitative analysis of the linguistic and cognitive components that enable functional communication in order to allow optimal interpretation of the data we have collected, laying the foundations for a more effective therapeutic approach.

Wolf-Hirschhorn Syndrome with Hyperparathyroidism: A Case Report and a Narrative Review of the Literature

Wolf-Hirschhorn syndrome (WHS) is a contiguous gene deletion condition. The WHS core phenotype includes developmental delays, intellectual disabilities, seizures, and distinctive facial features. Various other comorbidities have also been reported, such as hearing loss, heart defects, as well as eye problems and kidney problems. In this report, we present a case of WHS accompanied by hyperparathyroidism and hypercalcemia, which has not been previously reported. A girl was born at 37 weeks of gestation by vaginal delivery. She was small for the gestational age (2,045 g) and admitted to neonatal intensive care unit. She had typical WHS facial features and was found to have bilateral small kidneys associated with transient metabolic acidosis and renal insufficiency. She had right-sided sensorineural hearing loss, a small atrial septal defect, and colpocephaly and hypoplasia of corpus callosum. She had a single seizure which was well controlled with an oral antiepileptic medication. Cytogenetic studies demonstrated a large terminal chromosome 4p deletion (21.4 Mb) and 4p duplication (2.1 Mb) adjacent to the deletion. A unique finding in this patient is her consistently elevated levels of parathyroid hormone and serum calcium, suggesting hyperparathyroidism. We present this rare case along with a review of the literature and hope to draw an attention to a potential relationship between WHS and hyperparathyroidism.

Identification of an 85-kb Heterozygous 4p Microdeletion With Full Genome Analysis in Autosomal Dominant Charcot-Marie-Tooth Disease

Background and Objectives

Charcot-Marie-Tooth disease (CMT) is a syndrome of a hereditary neurodegenerative condition affecting the peripheral nervous system and is a single gene disorder. Deep phenotyping coupled with advanced genetic techniques is critical in discovering new genetic defects of rare genetic disorders such as CMT.

Methods

We applied multidisciplinary investigations to examine the neurophysiology and nerve pathology in a family that fulfilled the diagnosis of CMT2. When phenotype-guided first-tier genetic tests and whole-exome sequencing did not yield a molecular diagnosis, we conducted full genome analysis by examining phased whole-genome sequencing and whole-genome optical mapping data to search for the causal variation. We then performed a systematic review to compare the reported patients with interstitial microdeletion in the short arm of chromosome 4.

Results

In this family with CMT2, we reported the discovery of a heterozygous 85-kb microdeletion in the short arm of chromosome 4 (4p16.3)[NC_000004.12:g.1733926_1819031del] spanning 3 genes [TACC3 (intron 6-exon 16), FGFR3 (total deletion), and LETM1 (intron 10-exon14)] that cosegregated with disease phenotypes in family members. The clinical features of peripheral nerve degeneration in our family are distinct from the well-known 4p microdeletion syndrome of Wolf-Hirschhorn syndrome, in which brain involvement is the major phenotype.

Discussion

In summary, we used the full genome analysis approach to discover a new microdeletion in a family with CMT2. The deleted segment contains 3 genes (TACC3, FGFR3, and LETM1) that likely play a role in the pathogenesis of nerve degeneration.

Pathogenic copy number variations are associated with foetal short femur length in a tertiary referral centre study

Shortened foetal femur length (FL) is a common abnormal phenotype that often causes anxiety in pregnant women, and standard clinical treatments remain unavailable. We investigated the clinical characteristics, genetic aetiology and obstetric pregnancy outcomes of foetuses with short FL and provided a reference for perinatal management of such cases. Chromosomal microarray analysis was used to analyse the copy number variations (CNV) in short FL foetuses. Of the 218 foetuses with short FL, 33 foetuses exhibited abnormal CNVs, including 19 with pathogenic CNVs and 14 with variations of uncertain clinical significance. Of the 19 foetuses with pathogenic CNVs, four had aneuploidy, 14 had deletions/duplications, and one had pathogenic uniparental diploidy. The 7q11.23 microdeletion was detected in three foetuses. The severity of short FL was not associated with the rate of pathogenic CNVs. The duration of short FL for the intrauterine ultrasound phenotype in foetuses carrying a pathogenic CNV was independent of the gestational age. Further, maternal age was not associated with the incidence of foetal pathogenic CNVs. Adverse pregnancy outcomes occurred in 77 cases, including termination of pregnancy in 63 cases, postnatal dwarfed foetuses with intellectual disability in 11 cases, and three deaths within 3 months of birth. Pathogenic CNVs closely related to foetal short FL were identified, among which the 7q11.23 microdeletion was highly associated with short FL development. This study provides a reference for the perinatal management of foetuses with short FL.

22q11 Copy Number Variations in a Brazilian Cohort of Children with Congenital Heart Disorders

Introduction

Congenital heart disease (CHD) is the most common type of congenital defect reported to be one of the leading causes of mortality in the first year of life. Microdeletion and microduplication syndromes (MMS) are associated with cardiac malformations. Understanding which genetic factors are involved in these conditions directly impacts treatment decisions. We aimed to identify the occurrence of genetic alterations and their association with MMS in CHD pediatric patients evaluated in a reference service of Southern Brazil.

Methods

Participants were recruited during 2010 in the intensive care unit of a pediatric hospital. MMs and regions of chromosome 22 were screened by SALSA MLPA Probemix P245 Microdeletion Syndromes-1A kit for detection of copy number variations (CNVs).

Results

MMS were detected in 11 from 207 patients (5.3%). Heterozygous deletion in the 22q11.2 chromosome region was the most prevalent CNV (5 from 11 patients). Also, atypical RTDR1 deletion and 22q11.2 duplication were detected. MLPA was able to reveal microdeletions in SNRPN and NF1 genes in patients with a normal karyotype and FISH.

Conclusion

Our study reports the prevalence and variability of genomic alterations associated with MMS in CHD pediatric patients. The results by MLPA are of great help in planning and specialized care.

Rare CNVs and Known Genes Linked to Macrocephaly: Review of Genomic Loci and Promising Candidate Genes

Macrocephaly frequently occurs in single-gene disorders affecting the PI3K-AKT-MTOR pathway; however, epigenetic mutations, mosaicism, and copy number variations (CNVs) are emerging relevant causative factors, revealing a higher genetic heterogeneity than previously expected. The aim of this study was to investigate the role of rare CNVs in patients with macrocephaly and review genomic loci and known genes. We retrieved from the DECIPHER database de novo <500 kb CNVs reported on patients with macrocephaly; in four cases, a candidate gene for macrocephaly could be pinpointed: a known microcephaly gene-TRAPPC9, and three genes based on their functional roles-RALGAPB, RBMS3, and ZDHHC14. From the literature review, 28 pathogenic CNV genomic loci and over 300 known genes linked to macrocephaly were gathered. Among the genomic regions, 17 CNV loci (~61%) exhibited mirror phenotypes, that is, deletions and duplications having opposite effects on head size. Identifying structural variants affecting head size can be a preeminent source of information about pathways underlying brain development. In this study, we reviewed these genes and recurrent CNV loci associated with macrocephaly, as well as suggested novel potential candidate genes deserving further studies to endorse their involvement with this phenotype.

Prenatal sonographic findings in confirmed cases of Wolf-Hirschhorn syndrome

Background

Wolf-Hirschhorn syndrome (WHS) is a common genetic condition and prenatal diagnosis is difficult due to heterogeneous expression of this syndrome and rather non-specific ultrasound findings. Objective of this study was to examine the prenatal ultrasound findings in fetuses with Wolf-Hirschhorn syndrome (WHS).

Methods

Retrospective assessment of 18 pregnancies that were seen at three tertiary referral centers (Universities of Bonn, Tuebingen and Nuernberg / Germany). Findings of prenatal ultrasound examinations, genetic results and outcome were compared. Additionally, findings of our study were compared to previous small case series from the literature and then compared to data on postnatal frequencies and abnormalities in affected patients.

Results

Median gestational age at the time of examination was 23 + 1 weeks’ (range: 13 + 4 to 29 + 1 weeks’) with female-to-male ratio of > 2.5:1. Most frequent ultrasound findings were facial abnormalities, symmetric IUGR and microcephaly that presented in 94.4, 83.3 and 72.2% of cases, respectively. The combination of microcephaly and hypoplastic nasal bone was a particularly characteristic finding. Growth retardation presented in all fetuses > 20 weeks, but not below. Other frequent abnormalities included cardiac anomalies in 50 and single umbilical artery (SUA) in 44.4% of fetuses.

Conclusion

WHS should be considered in the presence of symmetric IUGR together with microcephaly, hypoplastic nasal bone and facial abnormalities on prenatal ultrasound. Genetic testing by chromosomal microarray analysis (CMA) is strongly recommended in this context.

Familial Translocation t(2;4) (q37.3;p16.3), Resulting in a Partial Trisomy of 2q (or 4p) and a Partial Monosomy of 4p (or 2q), Causes Dysplasia

Background: Wolf-Hirschhorn syndrome, a well-known contiguous microdeletion syndrome, is caused by deletions on chromosome 4p. While the clinical symptoms and the critical region for this disorder have been identified based on genotype-phenotype correlations, duplications in this region have been infrequently reported.

Conclusion: Our case report shows that both deletions and duplications of the Wolf-Hirshhorn critical region cause intellectual disability/developmental delay and multiple congenital anomalies.

Wolf-Hirschhorn Syndrome: Clinical and Genetic Study of 7 New Cases, and Mini Review

Wolf–Hirschhorn syndrome (WHS), a rare disorder determined by distal 4p deletion, is characterized by a pre and postnatal growth retardation, hypotonia, intellectual disability, epilepsy, craniofacial dysmorphism, and congenital fusion anomalies. The clinical aspects are dependent on the deletion’ size. Our aim was to identify rare specific characteristics in a cohort of seven cases with 4p deletion and to assess the utility of Multiplex ligation-dependent probe amplification (MLPA) (cheap and sensitive test)—combined kits—as a diagnostic test and selection tool for cases that require other investigations (chromosomal microarray analysis—CMA, karyotype). For all cases we conducted a clinical examination with the main features identified: facial dysmorphism, intellectual disability, postnatal development delay, cardiac defects and hypotonia. In some cases, we observed seizures, structural brain abnormalities, immunodeficiencies, and renal anomalies. Prenatal growth retardation was detected in a relatively small number of cases, but postnatal growth failure was a constant feature. In all cases, the clinical diagnosis was confirmed by genetic analyses: karyotype and/or MLPA. In conclusion, renal and brain defects, as well as immunodeficiency are rare manifestations and should be looked for. Although CMA is the standard test, in our experience, MLPA is also a reliable screening method as the identified cases were either confirmed by MLPA or selected for further investigations.

Clinical and genetic characterization of ten Egyptian patients with Wolf-Hirschhorn syndrome and review of literature

Background

Wolf–Hirschhorn syndrome (WHS) (OMIM 194190) is a multiple congenital anomalies/intellectual disability syndrome. It is caused by partial loss of genetic material from the distal portion of the short arm of chromosome.

Methods

We studied the phenotype–genotype correlation.

Results

We present the clinical manifestations and cytogenetic results of 10 unrelated Egyptian patients with 4p deletions. Karyotyping, FISH and MLPA was performed for screening for microdeletion syndromes. Array CGH was done for two patients. All patients exhibited the cardinal clinical manifestation of WHS. FISH proved deletion of the specific WHS locus in all patients. MLPA detected microdeletion of the specific locus in two patients with normal karyotypes, while array CGH, performed for two patients, has delineated the extent of the deleted segments and the involved genes. LETM1, the main candidate gene for the seizure phenotype, was found deleted in the two patients tested by array CGH; nevertheless, one of them did not manifest seizures. The study emphasized the previous.

Conclusion

WHS is a contiguous gene syndrome resulting from hemizygosity of the terminal 2 Mb of 4p16.3 region. The Branchial fistula, detected in one of our patients is a new finding that, to our knowledge, was not reported.

Implementation of chromosomal microarrays in a cohort of patients with intellectual disability at the Argentinean public health system

Intellectual disability is a neurodevelopmental disorder in which genetic, epigenetic and environmental factors are involved. In consequence, the determination of its etiology is usually complex. Though many countries have migrated from conventional cytogenetic analysis to chromosomal microarrays as the first-tier genetic test for patients with this condition, this last technique was implemented in our country a few years ago. We report on the results of the implementation of chromosomal microarrays in a cohort of 133 patients with intellectual disability and dysmorphic features, normal karyotype and normal subtelomeric MLPA results in an Argentinean public health institution. Clinically relevant copy number variants were found in 12% of the patients and one or more copy number variants classified as variants of uncertain significance were found in 5.3% of them. Although the diagnostic yield of chromosomal microarrays is greater than conventional cytogenetics for these patients, there are financial limitations to adopt this technique as a first-tier test in our country, especially in the public health system.

Increased TBX6 gene dosages induce congenital cervical vertebral malformations in humans and mice

BACKGROUND

Congenital vertebral malformations (CVMs) manifest with abnormal vertebral morphology. Genetic factors have been implicated in CVM pathogenesis, but the underlying pathogenic mechanisms remain unclear in most subjects. We previously reported that the human 16p11.2 BP4-BP5 deletion and its associated TBX6 dosage reduction caused CVMs. We aim to investigate the reciprocal 16p11.2 BP4-BP5 duplication and its potential genetic contributions to CVMs.

METHODS AND RESULTS

Patients who were found to carry the 16p11.2 BP4-BP5 duplication by chromosomal microarray analysis were retrospectively analysed for their vertebral phenotypes. The spinal assessments in seven duplication carriers showed that four (57%) presented characteristics of CVMs, supporting the contention that increased TBX6 dosage could induce CVMs. For further in vivo functional investigation in a model organism, we conducted genome editing of the upstream regulatory region of mouse Tbx6 using CRISPR-Cas9 and obtained three mouse mutant alleles (Tbx6up1 to Tbx6up3 ) with elevated expression levels of Tbx6. Luciferase reporter assays showed that the Tbx6up3 allele presented with the 160% expression level of that observed in the reference (+) allele. Therefore, the homozygous Tbx6up3/up3 mice could functionally mimic the TBX6 dosage of heterozygous carriers of 16p11.2 BP4-BP5 duplication (approximately 150%, ie, 3/2 gene dosage of the normal level). Remarkably, 60% of the Tbx6up3/up3 mice manifested with CVMs. Consistent with our observations in humans, the CVMs induced by increased Tbx6 dosage in mice mainly affected the cervical vertebrae.

CONCLUSION

Our findings in humans and mice consistently support that an increased TBX6 dosage contributes to the risk of developing cervical CVMs.

The Many Faces of Xenopus: Xenopus laevis as a Model System to Study Wolf-Hirschhorn Syndrome

Wolf–Hirschhorn syndrome (WHS) is a rare developmental disorder characterized by intellectual disability and various physical malformations including craniofacial, skeletal, and cardiac defects. These phenotypes, as they involve structures that are derived from the cranial neural crest, suggest that WHS may be associated with abnormalities in neural crest cell (NCC) migration. This syndrome is linked with assorted mutations on the short arm of chromosome 4, most notably the microdeletion of a critical genomic region containing several candidate genes. However, the function of these genes during embryonic development, as well as the cellular and molecular mechanisms underlying the disorder, are still unknown. The model organism Xenopus laevis offers a number of advantages for studying WHS. With the Xenopus genome sequenced, genetic manipulation strategies can be readily designed in order to alter the dosage of the WHS candidate genes. Moreover, a variety of assays are available for use in Xenopus to examine how manipulation of WHS genes leads to changes in the development of tissue and organ systems affected in WHS. In this review article, we highlight the benefits of using X. laevis as a model system for studying human genetic disorders of development, with a focus on WHS.

18q22.1-qter deletion and 4p16.3 microduplication in a boy with speech delay and mental retardation: case report and review of the literature

Background

Deletions involving the long arm of chromosome 18 have been associated with a highly variable phenotypic spectrum that is related to the extent of the deleted region. Duplications in chromosomal region 4p16.3 have also been shown to cause 4p16.3 microduplication syndrome. Most reported patients of trisomy 4p16.3 have more duplications, including the Wolf-Hirschhorn critical region (WHSCR). Here, we present a patient with speech delay and mental retardation caused by a deletion of 18q (18q22.1-qter) and terminal microduplication of 4p (4p16.3-pter) distal to WHSCR.

Case presentation

The patient was a 23-month-old boy with moderate growth retardation, severe speech delay, mental retardation, and dysmorphic features. Single nucleotide polymorphism (SNP) array analysis confirmed an 11.2-Mb terminal deletion at 18q22.1 and revealed a 1.8-Mb terminal duplication of 4p16.3. Our patient showed clinical overlap with these two syndromes, although his overall features were milder than what had been previously described. Some dosage-sensitive genes on the 18q terminal deleted region and 4p16.3 duplicated region of the present case may have contributed to his phenotype.

Conclusions

This is the first report of a patient with combined terminal deletion of 18q22.1 and duplication of 4p16.3. In this report, we provide clinical and molecular evidence supporting that the microduplication in 4p16.3, distal to WHSCR, is pathogenic. The coexistence of two chromosome aberrations complicates the clinical picture and creates a chimeric phenotype. This report provides further information on the genotype-phenotype correlation of 18q terminal deletion and 4p microduplication.

Small 4p16.3 deletions: Three additional patients and review of the literature

Wolf-Hirschhorn syndrome is a well-defined disorder due to 4p16.3 deletion, characterized by distinct facial features, intellectual disability, prenatal and postnatal growth retardation, and seizures. Genotype-phenotype correlations based on differently sized deletions have been attempted, and some candidate genes have been suggested. We report on clinical characteristics of three patients with pure interstitial submicroscopic 4p16.3 deletions, ranging in size from 68 to 166 kb, involving WHSCR1 and/or part of WHSCR2, and review published cases with overlapping 4p16.3 losses. The present study highlights a major role of NSD2 gene in the pathogenesis of the WHS main features and predicts that loss-of-function mutations affecting NSD2 gene could result in microcephaly, prenatal and postnatal growth retardation, psychomotor and language delay, and craniofacial features. Absent seizures in all subjects corroborate the suggestion that this specific feature is causally linked with at least one additional causative gene. Finally, we suggest that mir-943 could play a role in the pathogenesis of CHD in some of these patients.

Prenatal diagnosis of a 1.6-Mb 4p16.3 interstitial microdeletion encompassing FGFRL1 and TACC3 associated with bilateral cleft lip and palate of Wolf-Hirschhorn syndrome facial dysmorphism and short long bones

OBJECTIVE

We present prenatal diagnosis of a 4p16.3 interstitial microdeletion associated with bilateral cleft lip and palate and short long bones on prenatal ultrasound, and we discuss the genotype-phenotype correlation.

MATERIALS AND METHODS

A 32-year-old woman underwent amniocentesis at 22 weeks of gestation because of bilateral cleft lip and palate and short limbs on prenatal ultrasound. Conventional cytogenetic analysis was performed on cultured amniocytes and parental bloods. Oligonucleotide array comparative genomic hybridization (aCGH) was performed on the DNAs extracted from uncultured amniocytes, parental bloods and umbilical cord. Metaphase fluorescence in situ hybridization (FISH) was performed on cultured amniocytes.

RESULTS

Amniocentesis revealed a karyotype of 46,XY. The parental karyotypes were normal. aCGH analysis on uncultured amniocytes revealed a 1.66-Mb interstitial microdeletion at 4p16.3 encompassing 23 Online Mendelian Inheritance of in Man (OMIM) genes including FGFRL1 and TACC3. The parents did not have such a deletion. The pregnancy was subsequently terminated, and a malformed fetus was delivered with typical Wolf-Hirschhorn syndrome (WHS) facial appearance and bilateral cleft lip and palate. aCGH analysis of the umbilical cord confirmed the prenatal diagnosis with a result of arr 4p16.3 (72,447-1,742,649) × 1.0 [GRCh37 (hg19)]. Metaphase FISH analysis of cultured amniocytes confirmed a 4p16.3 microdeletion.

CONCLUSION

Haploinsufficiency of FGFRL1 and TACC3 at 4p16.3 can be associated with bilateral cleft lip and palate of WHS facial dysmorphism and short long bones. Prenatal diagnosis of facial cleft with short long bones should raise a suspicion of chromosome microdeletion syndromes.

Prenatal diagnosis of Wolf-Hirschhorn syndrome: from ultrasound findings, diagnostic technology to genetic counseling

PURPOSE

Wolf-Hirschhorn syndrome (WHS) is a contiguous gene syndrome due to terminal chromosome 4p deletions. We explored prenatal diagnosis of WHS by ultrasound as well as karyotype and single nucleotide polymorphism array (SNP array) to characterize the structural variants of WHS prenatally.

METHODS

Ten prenatal cases of WHS were evaluated for the indication of the invasive testing, the ultrasound features, and cytogenetic and microarray results.

RESULTS

Eight cases were diagnosed by karyotyping and SNP array, while two cases were detected only by SNP array. Combining our cases with 37 prenatal cases from the literature, the most common sonographic features were IUGR (97.7%) and typical facial appearance (82.9%). Other less common phenotypes included renal hypoplasia (36.2%), cardiac malformation (29.8%), cleft lip and palate (25.5%), cerebral abnormalities (25.5%), skeletal anomalies (21.3%), and increased nuchal translucency/nuchal fold thickness (NT/NF) (19%).

CONCLUSIONS

The most common intrauterine phenotypes of WHS were severe IUGR and typical facial appearance with other less consistent ultrasound findings. Noninvasive prenatal testing (NIPT) is one very promising screening tool for WHS. SNP array can improve diagnostic precision for detecting WHS, especially for the cryptic aberrations that cannot be identified by the traditional karyotyping. Ectopic kidney may be a previously unrecognized phenotype of WHS.

A direct regulatory link between microRNA-137 and SHANK2: implications for neuropsychiatric disorders

BACKGROUND

Mutations in the SHANK genes, which encode postsynaptic scaffolding proteins, have been linked to a spectrum of neurodevelopmental disorders. The SHANK genes and the schizophrenia-associated microRNA-137 show convergence on several levels, as they are both expressed at the synapse, influence neuronal development, and have a strong link to neurodevelopmental and neuropsychiatric disorders like intellectual disability, autism, and schizophrenia. This compiled evidence raised the question if the SHANKs might be targets of miR-137.

METHODS

In silico analysis revealed a putative binding site for microRNA-137 (miR-137) in the SHANK2 3'UTR, while this was not the case for SHANK1 and SHANK3. Luciferase reporter assays were performed by overexpressing wild type and mutated SHANK2-3'UTR and miR-137 in human neuroblastoma cells and mouse primary hippocampal neurons. miR-137 was also overexpressed or inhibited in hippocampal neurons, and Shank2 expression was analyzed by quantitative real-time PCR and Western blot. Additionally, expression levels of experimentally validated miR-137 target genes were analyzed in the dorsolateral prefrontal cortex (DLPFC) of schizophrenia and control individuals using the RNA-Seq data from the CommonMind Consortium.

RESULTS

miR-137 directly targets the 3'UTR of SHANK2 in a site-specific manner. Overexpression of miR-137 in mouse primary hippocampal neurons significantly lowered endogenous Shank2 protein levels without detectable influence on mRNA levels. Conversely, miR-137 inhibition increased Shank2 protein expression, indicating that miR-137 regulates SHANK2 expression by repressing protein translation rather than inducing mRNA degradation. To find out if the miR-137 signaling network is altered in schizophrenia, we compared miR-137 precursor and miR-137 target gene expression in the DLPFC of schizophrenia and control individuals using the CommonMind Consortium RNA sequencing data. Differential expression of 23% (16/69) of known miR-137 target genes was detected in the DLPFC of schizophrenia individuals compared with controls. We propose that in further targets (e.g., SHANK2, as described in this paper) which are not regulated on RNA level, effects may only be detectable on protein level.

CONCLUSION

Our study provides evidence that a direct regulatory link exists between miR-137 and SHANK2 and supports the finding that miR-137 signaling might be altered in schizophrenia.

Cytogenomic Integrative Network Analysis of the Critical Region Associated with Wolf-Hirschhorn Syndrome

Deletions in the 4p16.3 region are associated with Wolf-Hirschhorn syndrome (WHS), a contiguous gene deletion syndrome involving variable size deletions. In this study, we perform a cytogenomic integrative analysis combining classical cytogenetic methods, fluorescence in situ hybridization (FISH), chromosomal microarray analysis (CMA), and systems biology strategies, to establish the cytogenomic profile involving the 4p16.3 critical region and suggest WHS-related intracellular cell signaling cascades. The cytogenetic and clinical patient profiles were evaluated. We characterized 12 terminal deletions, one interstitial deletion, two ring chromosomes, and one classical translocation 4;8. CMA allowed delineation of the deletions, which ranged from 3.7 to 25.6 Mb with breakpoints from 4p16.3 to 4p15.33. Furthermore, the smallest region of overlapping (SRO) encompassed seven genes in a terminal region of 330 kb in the 4p16.3 region, suggesting a region of susceptibility to convulsions and microcephaly. Therefore, molecular interaction networks and topological analysis were performed to understand these WHS-related symptoms. Our results suggest that specific cell signaling pathways including dopamine receptor, NAD+ nucleosidase activity, and fibroblast growth factor-activated receptor activity are associated with the diverse pathological WHS phenotypes and their symptoms. Additionally, we identified 29 hub-bottlenecks (H-B) nodes with a major role in WHS.

Wolf-Hirschhorn Syndrome: Clinical and Genetic Data from a First Case Diagnosed in Central Africa

Wolf-Hirschhorn syndrome (WHS) is a multiple congenital anomaly-intellectual disability syndrome caused by a deletion involving chromosome 4p16.3. We report clinical and genetic findings of the first WHS patient diagnosed in central Africa. This boy who presented with cleft palate, microcephaly, severe growth delay, and intellectual disability was 12 years old. Typical craniofacial features were present, though the characteristic "Greek helmet" appearance of the nose was less evident, probably reflecting a variable expression related to the genetic background. The clinical diagnosis of WHS was confirmed by array CGH, which revealed a terminal 4p16.3 deletion of 3.47 Mb, typically associated with a milder phenotype, contributing to the long survival of this child in a developing country.