A double cryptic chromosome imbalance is an important factor to explain phenotypic variability in Wolf–Hirschhorn syndrome

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.

Oligonephronia and Wolf-Hirschhorn syndrome: A further observation

Wolf-Hirschhorn syndrome (WHS) is a rare chromosomal disorder caused by a partial deletion of chromosome 4 (4p16.3p16.2). We describe a case of a male 9 years old children with WHS proteinuria and hypertension. Laboratory data showed creatinine 1.05 mg/dl, GFR 65.9 ml/min/1.73 m² , cholesterol 280 mg/dl, triglyceride 125 mg/dl with electrolytes in the normal range. Urine collection showed protein 2.72 g/L with a urine protein/creatinine ratio (U_P /U_Cr ratio) of 4.2 and diuresis of 1,100 ml. Renal ultrasound showed reduced kidney dimensions with diffusely hyperechogenic cortex and poorly visualized pyramids. Renal biopsy showed oligonephronia with focal segmental glomerulosclerosis associated with initial tubulointerstitial sclerotic atrophy. The child began therapy with Angiotensin-converting enzyme inhibitors (ACE-inhibitors) to reduce proteinuria and progression of chronic kidney disease. In the literature the anomalies of number of glomeruli oligonephronia and oligomeganephronia (OMN) are described in two forms, one without any associated anomalies, sporadic, and solitary and the other with one or more anomalies. Our review of the literature shows that the pathogenesis of this anomaly is unknown but the role of chromosome 4 is very relevant. Many cases of OMN are associated with anomalies on this chromosome, in the literature cases series we observed this association in 14/48 cases (29.2%) and in 7 of these 14 cases with WHS. Our case and the review of literature demonstrate how periodic urinalysis and renal ultrasound monitoring is recommended in patients affected by WHS and the renal biopsy must be performed when there is the onset of proteinuria.

Mosaicism for structural non-centromeric autosomal rearrangements in disease-defined carriers: sex differences in the rearrangements profile and maternal age distributions

Background

Mosaicism for an autosomal structural rearrangement (Rea) associated with clinical manifestation of chromosomal imbalance is rare. Consequently, there is a lack of basic epidemiological characterization of this kind of mosaicism, such as population rate, cytogenetic profile of Reas involved, maternal age distribution, and sex (male to female) ratio among Rea carriers. The objectives of the present study were: (i) determination of the Rea profile in clinically affected individuals, (ii) comparative analysis of the cytogenetic profile and involvement of single chromosomes to rearrangements in affected and previously reported asymptomatic carriers, (iii) analysis of the male/female ratio in carriers of various types of Rea, and, (iv) examination of parental ages distributions according to carriers’ sex.

Results

Two hundred and forty six disease-defined cases of mosaicism for autosomal non-centromeric Rea with a normal cell line of known sex were identified from the literature. There was a significant difference in single chromosome involvements compared to structural rearrangements between affected and asymptomatic carriers of unbalanced Rea, p =0.0030. In affected carriers, chromosome 18 was most frequently involved in structural rearrangements (12.6% of 246 instances). The least frequently rearranged were chromosomes 16 and 21 (0.8% and 1.2%, respectively). In asymptomatic carriers, the most frequently rearranged were chromosomes 5 and 21 (13% of 51 instances each). Among carriers of “loss” or “gain/loss” of genomic material, a female predominance was observed (50 M/89 F, different from population ratio of 1.06 at p = 0.0002). Carriers of either “gain” or balanced Rea demonstrated typical male predominance (41 M/30 F and 18 M/16 F), not different from 1.06. Maternal and paternal ages were reported in 129 and in 109 cases, respectively. There was a significant difference in maternal age distribution between male and female carriers, with mean maternal age of 25.2 years vs 28.3 years (p = 0.032). However, there was no difference in paternal age, with mean paternal age of 29.4 in both groups.

Conclusion

The data suggested that structural rearrangements of certain chromosomes involved in mosaicism may not be tolerated by the embryo, while others have higher survival prospects. Maternal age appears to be a risk factor for somatic mosaicism of structural Rea in female offspring or might cause an adverse effect on male embryo viability.

Electronic supplementary material

The online version of this article (doi:10.1186/s13039-017-0321-9) contains supplementary material, which is available to authorized users.

Familial Constitutional Rearrangement of Chromosomes 4 & 8: Phenotypically Normal Mother and Abnormal Progeny

Balanced chromosome translocations carriers mostly do not have recognizable phenotypic expression but may have more risk of recurrent spontaneous abortions &/or children with serious birth defects due to unbalanced chromosome complements. Unbalanced chromosomal rearrangements have variable clinical expression and are rare. We present here a case report of three siblings affected with intellectual disability and minor dysmorphic features of face and limbs, born to a non-consanguineous couple in which mother had 5 abortions. The constitutional chromosome analysis revealed balanced translocation t (4;8) in mother and all the three siblings were karyotypically normal. Chromosomal microarray in one of the probands revealed partial monosomy 8pter-p23 and a partial trisomy 4pter-p16. Phenotypic features were recorded in 3 probands using Human Phenotype Ontology terms to query web-based tool Phenomizer. The harmonized description using globally accepted ontology is very important especially in case of rare genetic conditions and the heterogeneous phenotypes which make it even more challenging. The prevalence of sub-microscopic unbalanced translocations may be under-reported due to lesser use of molecular genetic analysis. The familial expression of abnormal phenotypes including intellectual disability make the individuals candidate for molecular genetic analysis and phenotyping to help defer the status of idiopathic mental retardation and identify sub-entity of genetic condition.

Phenotypic variations in wolf-hirschhorn syndrome

Wolf-Hirschhorn syndrome (WHS) is a rare chromosomal disorder caused by terminal deletion of the short arm of chromosome 4. The clinical picture includes growth retardation, severe mental retardation, characteristic "Greek helmet" like face, seizures and midline defects in the brain, heart, palate and genitalia. Recently-used molecular techniques increase the number of diagnosed cases due to the detection of smaller deletions. The severity of the clinical presentation is variable depending on the haploinsufficiency of genes in a deleted region. We present six children with WHS with variable clinical appearance. The assessment of several elements (facial dysmorphism, mental retardation, additional congenital anomalies) provided classification into minor, mild or severe forms. Three of the children had a visible cytogenetic deletion on chromosome 4p, two had microdeletions detected with fluorescent in situ hybridization (FISH), and one child with a less characteristic clinical picture had a mosaic type of the deletion. Correlation between the clinical presentation and the length of the deleted region was confirmed.

Diagnosis of familial Wolf-Hirschhorn syndrome due to a paternal cryptic chromosomal rearrangement by conventional and molecular cytogenetic techniques

The use of conventional cytogenetic techniques in combination with fluorescent in situ hybridization (FISH) and single-nucleotide polymorphism (SNP) microarrays is necessary for the identification of cryptic rearrangements in the diagnosis of chromosomal syndromes. We report two siblings, a boy of 9 years and 9 months of age and his 7-years- and 5-month-old sister, with the classic Wolf-Hirschhorn syndrome (WHS) phenotype. Using high-resolution GTG- and NOR-banding karyotypes, as well as FISH analysis, we characterized a pure 4p deletion in both sibs and a balanced rearrangement in their father, consisting in an insertion of 4p material within a nucleolar organizing region of chromosome 15. Copy number variant (CNV) analysis using SNP arrays showed that both siblings have a similar size of 4p deletion (~6.5 Mb). Our results strongly support the need for conventional cytogenetic and FISH analysis, as well as high-density microarray mapping for the optimal characterization of the genetic imbalance in patients with WHS; parents must always be studied for recognizing cryptic balanced chromosomal rearrangements for an adequate genetic counseling.

Surgical treatment of lone atrial fibrillation by mid-sternotomy Maze procedure under standard cardiopulmonary bypass

The aim of article is to give a brief description to the surgical strategies for patients with lone atrial fibrillation without associated cardiac operations, and present the possible indications of on-pump Maze procedures through a mid-sternotomy approach.

Fine-grained facial phenotype-genotype analysis in Wolf-Hirschhorn syndrome

Wolf-Hirschhorn syndrome is caused by anomalies of the short arm of chromosome 4. About 55% of cases are due to de novo terminal deletions, 40% from unbalanced translocations and 5% from other abnormalities. The facial phenotype is characterized by hypertelorism, protruding eyes, prominent glabella, broad nasal bridge and short philtrum. We used dense surface modelling and pattern recognition techniques to delineate the milder facial phenotype of individuals with a small terminal deletion (breakpoint within 4p16.3) compared to those with a large deletion (breakpoint more proximal than 4p16.3). Further, fine-grained facial analysis of several individuals with an atypical genotype and/or phenotype suggests that multiple genes contiguously contribute to the characteristic Wolf-Hirschhorn syndrome facial phenotype.

Impact of chromosome 4p- syndrome on communication and expressive language skills: a preliminary investigation

PURPOSE

The purpose of this investigation was to examine the impact of Chromosome 4p- syndrome on the communication and expressive language phenotype of a large cross-cultural population of children, adolescents, and adults.

METHOD

A large-scale survey study was conducted and a descriptive research design was used to analyze quantitative and qualitative data regarding the communication and expressive language manifestations of 200 children, youth, and adults from 16 countries and Puerto Rico who had been diagnosed with 4p conditions, including Wolf-Hirschhorn syndrome (WHS), Pitt-Rogers-Danks syndrome (PRDS), Proximal 4p Deletion syndrome, and complex chromosomal rearrangements associated with 4p-.

RESULTS

Individuals with Chromosome 4p- syndrome represent a heterogeneous population with complex phenotypic profiles. The majority of the participants exhibited communication and expressive language skills below the 36-month developmental functioning level. A relatively small cohort of the study population exhibited advanced expressive language skills, a finding not reported in the professional literature.

CONCLUSION

Results broaden the spectrum of expressive language skills associated with Chromosome 4p- syndrome and highlight the communication potential of a subset of individuals with 4p abnormalities for development of advanced language structures. It is hypothesized that the largest 4p deletion, which includes the 4p16.3 band and contiguous gene regions, results in the most severely affected expressive language phenotype.

On the nosology and pathogenesis of Wolf-Hirschhorn syndrome: genotype-phenotype correlation analysis of 80 patients and literature review

Based on genotype-phenotype correlation analysis of 80 Wolf-Hirschhorn syndrome (WHS) patients, as well as on review of relevant literature, we add further insights to the following aspects of WHS: (1) clinical delineation and phenotypic categories; (2) characterization of the basic genomic defect, mechanisms of origin and familiarity; (3) identification of prognostic factors for mental retardation; (4) chromosome mapping of the distinctive clinical signs, in an effort to identify pathogenic genes. Clinically, we consider that minimal diagnostic criteria for WHS, defining a "core" phenotype, are typical facial appearance, mental retardation, growth delay and seizures (or EEG anomalies). Three different categories of the WHS phenotype were defined, generally correlating with the extent of the 4p deletion. The first one comprises a small deletion not exceeding 3.5 Mb, that is usually associated with a mild phenotype, lacking major malformations. This category is likely under-diagnosed. The second and by far the more frequent category is identified by large deletions, averaging between 5 and 18 Mb, and causes the widely recognizable WHS phenotype. The third clinical category results from a very large deletion exceeding 22-25 Mb causing a severe phenotype, that can hardly be defined as typical WHS. Genetically, de novo chromosome abnormalities in WHS include pure deletions but also complex rearrangements, mainly unbalanced translocations. With the exception of t(4p;8p), WHS-associated chromosome abnormalities are neither mediated by segmental duplications, nor associated with a parental inversion polymorphism on 4p16.3. Factors involved in prediction of prognosis include the extent of the deletion, the occurrence of complex chromosome anomalies, and the severity of seizures. We found that the core phenotype maps within the terminal 1.9 Mb region of chromosome 4p. Therefore, WHSCR-2 should be considered the critical region for this condition. We also confirmed that the pathogenesis of WHS is multigenic. Specific and independent chromosome regions were characterized for growth delay and seizures, as well as for the additional clinical signs that characterize this condition. With the exception of parental balanced translocations, familial recurrence is uncommon.

Comprehensive analysis of Wolf–Hirschhorn syndrome using array CGH indicates a high prevalence of translocations

Wolf-Hirschhorn syndrome (WHS) is caused by deletions involving chromosome region 4p16.3. The minimal diagnostic criteria include mild-to-severe mental retardation, hypotonia, growth delay and a distinctive facial appearance. Variable manifestations include feeding difficulties, seizures and major congenital anomalies. Clinical variation may be explained by variation in the size of the deletion. However, in addition to having a deletion involving 4p16.3, previous studies indicate that approximately 15% of WHS patients are also duplicated for another chromosome region due to an unbalanced translocation. It is likely that the prevalence of unbalanced translocations resulting in WHS is underestimated since they can be missed using conventional chromosome analyses such as karyotyping and WHS-specific fluorescence in situ hybridization (FISH). Therefore, we hypothesized that some of the clinical variation may be due to an unrecognized and unbalanced translocation. Array comparative genomic hybridization (aCGH) is a new technology that can analyze the entire genome at a significantly higher resolution over conventional cytogenetics to characterize unbalanced rearrangements. We used aCGH to analyze 33 patients with WHS and found a much higher than expected frequency of unbalanced translocations (15/33, 45%). Seven of these 15 cases were cryptic translocations not detected by a previous karyotype combined with WHS-specific FISH. Three of these 15 cases had an unbalanced translocation involving the short arm of an acrocentric chromosome and were not detected by either aCGH or subtelomere FISH. Analysis of clinical manifestations of each patient also revealed that patients with an unbalanced translocation often presented with exceptions to some expected phenotypes.

Wolf-Hirschhorn syndrome-associated chromosome changes are not mediated by olfactory receptor gene clusters nor by inversion polymorphism on 4p16

The basic genomic defect in Wolf-Hirschhorn syndrome (WHS), including isolated 4p deletions and various unbalanced de novo 4p;autosomal translocations and above all t(4p;8p), is heterogeneous. Olfactory receptor gene clusters (ORs) on 4p were demonstrated to mediate a group of WHS-associated t(4p;8p)dn translocations. The breakpoint of a 4-Mb isolated deletion was also recently reported to fall within the most distal OR. However, it is still unknown whether ORs mediate all 4p-autosomal translocations, or whether they are involved in the origin of isolated 4p deletions. Another unanswered question is whether a parental inversion polymorphism on 4p16 can act as predisposing factor in the origin of WHS-associated rearrangements. We investigated the involvement of the ORs in the origin of 73 WHS-associated rearrangements. No hotspots for rearrangements were detected. Breakpoints on 4p occurred within the proximal or the distal olfactory receptor gene cluster in 8 of 73 rearrangements (11%). These were five t(4p;8p) translocations, one t(4p;7p) translocation and two isolated terminal deletions. ORs were not involved in one additional t(4p;8p) translocation, in a total of nine different 4p;autosomal translocations and in the majority of isolated deletions. The presence of a parental inversion polymorphism on 4p was investigated in 30 families in which the 4p rearrangements, all de novo, were tested for parental origin (7 were maternal and 23 paternal). It was detected only in the mothers of 3 t(4p;8p) cases. We conclude that WHS-associated chromosome changes are not usually mediated by low copy repeats. The 4p16.3 inversion polymorphism is not a risk factor for their origin.

Unmasking of a hemizygous WFS1 gene mutation by a chromosome 4p deletion of 8.3 Mb in a patient with Wolf–Hirschhorn syndrome

The Wolf-Hirschhorn syndrome (WHS (MIM 194190)), which is characterized by growth delay, mental retardation, epilepsy, facial dysmorphisms, and midline fusion defects, shows extensive phenotypic variability. Several of the proposed mutational and epigenetic mechanisms in this and other chromosomal deletion syndromes fail to explain the observed phenotypic variability. To explain the complex phenotype of a patient with WHS and features reminiscent of Wolfram syndrome (WFS (MIM 222300)), we performed extensive clinical evaluation and classical and molecular cytogenetic (GTG banding, FISH and array-CGH) and WFS1 gene mutation analyses. We detected an 8.3 Mb terminal deletion and an adjacent 2.6 Mb inverted duplication in the short arm of chromosome 4, which encompasses a gene associated with WFS (WFS1). In addition, a nonsense mutation in exon 8 of the WFS1 gene was found on the structurally normal chromosome 4. The combination of the 4p deletion with the WFS1 point mutation explains the complex phenotype presented by our patient. This case further illustrates that unmasking of hemizygous recessive mutations by chromosomal deletions represents an additional explanation for the phenotypic variability observed in chromosomal deletion disorders.

Phenotype definition in epilepsy

Phenotype definition consists of the use of epidemiologic, biological, molecular, or computational methods to systematically select features of a disorder that might result from distinct genetic influences. By carefully defining the target phenotype, or dividing the sample by phenotypic characteristics, we can hope to narrow the range of genes that influence risk for the trait in the study population, thereby increasing the likelihood of finding them. In this article, fundamental issues that arise in phenotyping in epilepsy and other disorders are reviewed, and factors complicating genotype-phenotype correlation are discussed. Methods of data collection, analysis, and interpretation are addressed, focusing on epidemiologic studies. With this foundation in place, the epilepsy subtypes and clinical features that appear to have a genetic basis are described, and the epidemiologic studies that have provided evidence for the heritability of these phenotypic characteristics, supporting their use in future genetic investigations, are reviewed. Finally, several molecular approaches to phenotype definition are discussed, in which the molecular defect, rather than the clinical phenotype, is used as a starting point.

Microarray-based comparative genomic hybridization analysis of Wolf-Hirschhorn syndrome in a fetus with deletion of 4p15.3 to 4pter

BACKGROUND

Wolf-Hirschhorn syndrome (WHS), caused by the deletion of a segment in chromosome 4, is characterized by mental and developmental defects. Clinical manifestations of WHS include intrauterine growth restriction, failure to thrive in the neonatal period that is present simultaneously with hypotonia, typical "Greek helmet" facial appearance, cleft lip and palate, mental deficiency, and seizures.

CASE

We present a case of WHS with prenatal conventional cytogenetics of 46,XY,der(4)t(4;13)(p15.3;p11.2)pat. High-resolution mapping using microarray-based comparative genomic hybridization (array-CGH), including Affymetrix 10K arrays and cDNA microarrays, confirmed the loss of genes in the deleted region.

CONCLUSIONS

The correlation between these candidate genes and the phenotypes of WHS may expand our understanding of the defective development caused by 4p deletion.

Cri du chat syndrome determined by the 5p15.3-->pter deletion--diagnostic problems

A cytogenetic analysis was performed on an 8-day-old girl, who was suspected of Cri du chat syndrome (CdCS) on the basis of a cat-like cry, despite her dysmorphic features not being characteristic of this syndrome. The cytogenetic analysis revealed a partial deletion of the short arm of chromosome 5, but did not allow precise specification of the break points. Fluorescence in situ hybridization (FISH) analysis, using the specific probe for CdCS, revealed two signals in all the cells analyzed. However, one of two signals was less intense than the other. Thus, telomere probes were applied for all chromosomes. Two signals from 5q and one signal from 5p were observed. The results allowed us to establish the location of the deleted fragment as 5p15.3-->5pter [46,XX,del(5)(p15.3)]. The analysis of a genotype-phenotype correlation confirmed that the cat-like cry, but not the characteristic dysmorphic features of CdCS are correlated with the deletion of 5p15.3.

The Hunter-McAlpine syndrome results from duplication 5q35-qter

In 1977 Hunter et al. J Med Genet 1977: 14 (6): 430-437, reported a family with six affected members, connected over three generations through unaffected individuals. Subsequently, several other patients purported to have the condition were reported. The condition became known as the Hunter-McAlpine syndrome, and there was debate as to whether or not it was identical to the Ruvalcaba syndrome or a type of tricho-rhino-phalangeal syndrome. In this article we confirm that the original family and a patient reported by Ades et al. Clin Dysmorphol 1993: 2 (2): 123-130 have cryptic translocations resulting in duplication of 5q35-qter. Similarities are noted between our patients and others in the literature with duplication of this chromosome segment.