First known microdeletion within the Wolf-Hirschhorn syndrome critical region refines genotype-phenotype correlation

Deletions within HSA band 4p16.3 cause Wolf-Hirschhorn syndrome (WHS), which comprises mental retardation and developmental defects. A WHS critical region (WHSCR) of approximately 165 kb has been defined on the basis of 2 atypical interstitial deletions; however, genotype-phenotype correlation remains controversial, due to the large size of deletion usually involving several megabases. We report on the first known patient with a small de novo interstitial deletion restricted to the WHSCR who presented with a partial WHS phenotype consisting only of low body weight for height, speech delay, and minor facial anomalies; shortness of stature, microcephaly, seizures and mental retardation were absent. The deletion was initially demonstrated by FISH analysis, and breakpoints were narrowed with a "mini-FISH" technique using 3-5 kb amplicons. A breakpoint-spanning PCR assay defined the distal breakpoint as disrupting the WHSC1 gene within intron 5, exactly after an AluJb repeat. The proximal breakpoint was not found to be associated with a repeated sequence or a known gene. The deletion encompasses 191.5 kb and includes WHSC2, but not LETM1. Thus, manifestations attributable to this deletion are reduced weight for height, minor facial anomalies, ADHD and some learning and fine motor deficiencies, while seizures may be associated with deletions of LETM1.     

First known microdeletion within the Wolf‐Hirschhorn syndrome critical region refines genotype–phenotype correlation

Deletions within HSA band 4p16.3 cause Wolf‐Hirschhorn syndrome (WHS), which comprises mental retardation and developmental defects. A WHS critical region (WHSCR) of approximately 165 kb has been defined on the basis of 2 atypical interstitial deletions; however, genotype–phenotype correlation remains controversial, due to the large size of deletion usually involving several megabases. We report on the first known patient with a small de novo interstitial deletion restricted to the WHSCR who presented with a partial WHS phenotype consisting only of low body weight for height, speech delay, and minor facial anomalies; shortness of stature, microcephaly, seizures and mental retardation were absent. The deletion was initially demonstrated by FISH analysis, and breakpoints were narrowed with a “mini‐FISH” technique using 3–5 kb amplicons. A breakpoint‐spanning PCR assay defined the distal breakpoint as disrupting the WHSC1 gene within intron 5, exactly after an AluJb repeat. The proximal breakpoint was not found to be associated with a repeated sequence or a known gene. The deletion encompasses 191.5 kb and includes WHSC2, but not LETM1. Thus, manifestations attributable to this deletion are reduced weight for height, minor facial anomalies, ADHD and some learning and fine motor deficiencies, while seizures may be associated with deletions of LETM1. © 2001 Wiley‐Liss, Inc.     

Deletion of a 760 kb region at 4p16 determines the prenatal and postnatal growth retardation characteristic of Wolf-Hirschhorn syndrome

Background

Recently the genotype/phenotype map of Wolf‐Hirschhorn syndrome (WHS) has been refined, using small 4p deletions covering or flanking the critical region in patients showing only some of the WHS malformations. Accordingly, prenatal‐onset growth retardation and failure to thrive have been found to result from haploinsufficiency for a 4p gene located between 0.4 and 1.3 Mb, whereas microcephaly results from haploinsufficiency of at least two different 4p regions, one of 2.2–2.38 Mb and a second one of 1.9–1.28 Mb.

Methods and Results

We defined the deletion size of a ring chromosome (r(4)) in a girl with prenatal onset growth retardation, severe failure to thrive and true microcephaly but without the WHS facial gestalt and mental retardation. A high‐resolution comparative genome hybridisation array revealed a 760 kb 4p terminal deletion.

Conclusions

This case, together with a familial 4p deletion involving the distal 400 kb reported in normal women, may narrow the critical region for short stature on 4p to 360–760 kb. This region is also likely to contain a gene for microcephaly. “In silico” analysis of all genes within the critical region failed to reveal any strikingly suggestive expression pattern; all genes remain candidates for short stature and microcephaly.Attempts are ongoing to better correlate specific symptoms or malformations in patients with 4p deletions to specific genes or, at least, molecularly defined regions. The most recent genotype–phenotype map¹ confirmed that WHSC1 hemizygosity is essential to the development of the Wolf‐Hirschhorn syndrome (WHS) facial gestalt with the typical “Greek helmet” profile whereas the other key features (growth retardation, microcephaly, cleft palate, mental retardation and epilepsy) result from haploinsufficiency of more than one gene in that region. Particularly, the presence of a dose‐sensitive gene at 4p15–p16, involved in linear growth, was suggested several years ago because of the finding of prenatal and postnatal harmonic short stature in most patients with WHS.² Patients with the typical WHS facial gestalt but normal stature and interstitial rather than terminal 4p deletions confirmed the presence on 4p of at least two genes with complete penetrance, one for linear growth and the other, more proximal, for distinctive facial features.We have detected a 760 Kb terminal deletion of the short arm of chromosome 4 due to a ring chromosome in a 34‐month‐old girl examined for growth retardation with microcephaly and normal psychomotor development. Comparison of this case to other critical 4p cases seems to define a 360 kb region containing a gene(s) for which haploinsufficiency correlates with short stature and microcephaly.     

The new Wolf-Hirschhorn syndrome critical region (WHSCR-2): a description of a second case

The Wolf-Hirschhorn syndrome (WHS), is a well known contiguous gene syndrome characterized by microcephaly, hypertelorism, prominent glabella, epicanthal folds, cleft lip or palate, cardiac defects, growth and mental retardation and seizures. The currently accepted WHS critical region (WHSCR) is localized between the loci D4S166 and D4S3327, where a deletion seems to generate all the clinical manifestations of the syndrome. Here we present a patient with a subtelomeric deletion of 4p16.3 showing growth and psychomotor delay with a typical WHS facial appearance and two episodes of seizures in conjunction with fever. The high-resolution G-banded karyotype was normal. Fluorescence in situ hybridization (FISH) with a set of cosmids from 4p16.3, showed that the deletion in this patient was from the D4S3327 to the telomere, enabling the size of the deletion to be estimated as 1.9 Mb, excluding the accepted WHSCR deletion. This patient supports the recent proposal by Zollino et al. [2003] that the critical region for WHS is located distally to the WHSCR between the loci D4S3327 and D4S98-D4S16, and it is called "WHSCR-2" [Zollino et al., 2003].     

Molecular and cytogenetic characterization of a recurrent unbalanced translocation (4;21) (p16.3;q22.1): Relevance to the Wolf-Hirschhorn and Down syndrome critical regions

We report on an aneuploidy syndrome due to the unbalanced segregation of a familial translocation (4;21)(p16.3;q22.1) causing a partial 4p monosomy and a partial 21q trisomy. The three affected children presented with severe failure to thrive, short stature, microcephaly, profound hypotonia, and mental retardation. The face, very similar in the three children, is characterized by frontal bossing, upslanting of the palpebral fissures, short nose, and deep set ears, giving the overall appearance of the Down syndrome. The molecular study has defined the aneuploid segment on both 4p and 21q. Most of the Down syndrome critical region was found to be trisomic, while only part of the candidate Wolf-Hirschhorn syndrome critical region was deleted, suggesting that this region is not critical for the major malformations characteristic for WHS. © 1996 Wiley-Liss, Inc.     

Diagnosis of a terminal deletion of 4p with duplication of Xp22.31 in a patient with findings of Opitz G/BBB syndrome and Wolf-Hirschhorn syndrome

Opitz G/BBB syndrome (OS) is a congenital midline malformation syndrome characterized by hypertelorism, hypospadias, cleft lip/palate, laryngotracheoesophageal abnormalities, imperforate anus, developmental delay and cardiac defects. The X-linked form is caused by mutations in the MID1 gene, while no gene has yet been identified for the autosomal dominant form. Here, we report on a 15-year-old boy who was referred for MID1 mutation analysis with findings typical of OS, including apparent hypertelorism, hypospadias, a history of feeding difficulties, dysphagia secondary to esophageal arteria lusoria, growth retardation and developmental delay. No MID1 mutation was found, but subsequent sub-megabase resolution array CGH unexpectedly documented a 2.34 Mb terminal 4p deletion, suggesting a diagnosis of WHS, and a duplication in Xp22.31. Wolf-Hirschhorn syndrome (WHS) is a contiguous gene deletion syndrome involving terminal chromosome 4p deletions, in particular 4p16.3. WHS is characterized by typical facial appearance ("Greek helmet facies"), mental retardation, congenital hypotonia, and growth retardation. While the severity of developmental delay in this patient supports the diagnosis of WHS rather than OS, this case illustrates the striking similarities of clinical findings in seemingly unrelated syndromes, suggesting common or interacting pathways at the molecular and pathogenetic level. This is the first report of arteria lusoria (esophageal vascular ring) in a patient with WHS.     

High resolution characterization of an interstitial deletion of less than 1.9 Mb at 4p16.3 associated with Wolf-Hirschhorn syndrome

Wolf-Hirschhorn syndrome (WHS) caused by 4p16.3 deletions comprises growth and mental retardation, distinct facial appearance and seizures. This study characterized a subtle interstitial deletion of 4p16.3 in a girl with mild retardation and possessing facial traits characteristic of WHS. The patient had generalized seizures in conjunction with fever at 3 and 5 years of age. Fluorescence in situ hybridization (FISH) with a series of markers in the 4p16.3 region showed that the interstitial deletion in this patient was between the probes D4S96 and D4S182, enabling the size of the deletion to be estimated as less than 1.9 Mb. This is the smallest interstitial deletion of 4p16.3 which has been reported. The patient contributes to a refinement of the phenotypic map of the WHS region in 4p16.3. The critical region for the characteristic facial changes of WHS, failure to thrive and developmental delay is now localized to a region of less than 700 kb. The mental retardation of this patient was mild suggesting that small interstitial deletion may have less severe phenotypic consequences. Am. J. Med. Genet. 71:453–457, 1997. © 1997 Wiley-Liss, Inc.     

Characterizing the functional consequences of haploinsufficiency of NELF-A (WHSC2) and SLBP identifies novel cellular phenotypes in Wolf-Hirschhorn syndrome

Wolf-Hirschhorn syndrome (WHS) is a contiguous gene deletion disorder associated with the distal part of the short arm of chromosome 4 (4p16.3). Employing a unique panel of patient-derived cell lines with differing-sized 4p deletions, we provide evidence that haploinsufficiency of SLBP and/or WHSC2 (NELF-A) contributes to several novel cellular phenotypes of WHS, including delayed progression from S-phase into M-phase, reduced DNA replication in asynchronous culture and altered higher order chromatin assembly. The latter is evidenced by reduced histone-chromatin association, elevated levels of soluble chaperone-bound histone H3 and increased sensitivity to micrococcal nuclease digestion in WHS patient-derived cells. We also observed increased camptothecin-induced inhibition of DNA replication and hypersensitivity to killing. Our work provides a novel pathogenomic insight into the aetiology of WHS by describing it, for the first time, as a disorder of impaired chromatin reorganization. Delayed cell-cycle progression and impaired DNA replication likely underlie or contribute to microcephaly, pre- and postnatal growth retardation, which constitute the core clinical features of WHS.     

Yq- in a child with livedo reticularis, snub nose, microcephaly, and profound mental retardation.

A child with terminal deletion of the long arm of the Y chromosome (Yq--) presented with marked livedo reticularis, snub nose, microcephaly, short stature, and other dysmorphic features. He was profoundly mentally retarded. Most of the patients with Yq- have been reported as having varying dysmorphic features, mental retardation, and short stature. This child, in addition to the above, has livedo reticularis and microcephaly. He was of normal birthweight and, therefore, does not come into the syndrome of microcephaly, snub nose, livedo reticularis, and low birthweight dwarfism. Further information on Yq- should be obtained to ascertain if consistent patterns of abnormalities exist.     

Deletion of the distal long arm of chromosome 1: A definable syndrome

Based on analysis of 15 cases, there appears to be a characteristic facial appearance and pattern of associated malformations that would allow clinical delineation of deletion of the distal bands of 1q. Characteristic manifestations include round face with prominent “cupid's bow” and downturned corners of the mouth, thin vermilion borders of lips, long upper lip with smooth philtrum, short and broad nose, epicanthal folds, apparently low-set ears, micrognathia, microcephaly, abnormal hands and feet, variable cardiac, genital, and other anomalies, moderate to severe mental retardation, and growth retardation. The deletion includes 1q42 or 1q43→qter and was a de novo defect in nine of 15 cases.     

Deletion of chromosome 2 (p11-p13): case report and review.

The case of a young man with del(2) (p11.2p13) is reported. Accounts of previous cases of deletion of the short arm of chromosome 2 are reviewed. Common features include mental retardation, proportional short stature and weight, dysmorphic facial features (a prominent nose, abnormal ears), and abnormal hands. Growth and developmental delay are present during the postnatal period.     

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.     

Interstitial deletion in 3q in a patient with blepharophimosis-ptosis-epicanthus inversus syndrome (BPES) and microcephaly, mild mental retardation and growth delay: clinical report and review of the literature

We present a boy with blepharophimosis, ptosis, epicanthus inversus, microcephaly, mild mental retardation, and growth delay. Chromosomal analysis revealed a male karyotype with an interstitial deletion in the long arm of chromosome 3. DNA-analysis showed that the deletion is of maternal origin and encompasses the region between markers D3S1535 and D3S1593. The deletion contains not only the FOXL2 gene, but also the gene encoding ataxia-telangiectasia and Rad3-related protein (ATR). Mutations in FOXL2 have been shown to cause blepharophimosis-ptosis-epicanthus inversus syndrome (BPES). ATR has been identified as a candidate gene for Seckel syndrome, an autosomal recessive syndrome that comprises growth retardation, microcephaly, and mental retardation. We hypothesize that our patient has a contiguous gene syndrome and that the non-BPES-associated abnormalities (microcephaly, mild mental retardation, and growth delay) are the result of the deletion of the maternal ATR gene. However, it has not yet been excluded that haploinsufficiency of some other gene in this region plays a role.     

Mosaic variegated aneuploidy with growth hormone deficiency and congenital heart defects

We describe a 12-year-old boy with mosaic variegated aneuploidy (MVA), subnormal response to growth hormone (GH) stimulation testing, and short stature. In addition to features more commonly described in MVA such as microcephaly, cognitive deficits, and certain facial features, he also has features not commonly reported in MVA, including short limb segments, epidermoid cysts, ventricular septal defect, and subaortic stenosis. Chromosomal analysis revealed hyperdiploid chromosome numbers ranging from 47 to 70; modal number 50, in 24% of the metaphases. This case demonstrates that although the phenotype of MVA almost always includes growth failure, microcephaly, and mental retardation, additional features may vary greatly across individuals. His clinical features and course suggest that in addition to GH deficiency, he may have an intrinsic inability of the growth plate to respond to growth hormone.     

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.     

Malignant hematological disorders in children with Wolf-Hirschhorn syndrome

Wolf-Hirschhorn syndrome (WHS) is a rare chromosomal disorder attributable to a deletion at the short arm of chromosome 4. This syndrome is associated with characteristic facial appearance, multiple congenital abnormalities, mental retardation, feeding difficulties and failure to thrive. We report two girls with WHS who developed myelodysplastic syndrome (MDS). According to the "Category, Cytology, Cytogenetic (CCC)"classification of childhood MDS, patient 1 had refractory cytopenia with ring sideroblasts at the age of 6 years, while patient 2 had refractory cytopenia with dysplasia at the age of 5-1/2 years. Patient 1 progressed to refractory cytopenia with excess blasts within a year, while patient 2 progressed to acute lymphoblastic leukemia within 1 month of presentation. It is possible that allelic loss of a tumor suppressor gene such as WHSC1 and/or FGFR3 from the deleted segment 4p16.3 plays a critical role in the process of malignant transformation. To our knowledge, this is the first report of severe hematological complications like MDS and leukemia in children with WHS and may be an important genetic model for understanding malignant hematological transformation. This report also underscores the importance of evaluating children with WHS for hematopoietic dysfunction.     

An apparently new mental retardation syndrome in three elderly sisters

Three elderly sisters with profound mental retardation in association with the clinical features of microcephaly, short stature, brachydactyly type D, flattened occiput, down-slanting palpebral fissures, low-set large ears, broad prominent nose and kyphoscoliosis have been investigated. Each was more than 60 years of age and their clinical features were strikingly similar. The disorder has several manifestations in common with Rubenstein-Taybi syndrome and appears to be inherited as an autosomal recessive in this family.     

Caudal deficiency sequence in 7q terminal deletion

We describe a male infant with signs of caudal deficiency sequence. In addition, he showed growth retardation, microcephaly, prominent forehead, bulbous nose tip, large dysplastic ears, hypospadia, partial sacral agenesis, and neurologic bladder dysfunction. Chromosome examination showed a terminal 7q deletion 46,XY,del(7)(pter----q32:). Four previous reported cases of 7q terminal deletion and signs of caudal deficiency are reviewed. Chromosome aberrations may, at least in some cases, be responsible for developmental defects.     

A novel 4p16.3 microduplication distal to WHSC1 and WHSC2 characterized by oligonucleotide array with new phenotypic features

Larger imbalances on chromosome 4p in the form of deletions associated with Wolf-Hirschhorn syndrome (WHS) and duplications of chromosome 4p have a defined clinical phenotype. The critical region for both these clinical disorders has been narrowed based on the genotype-phenotype correlations. However, cryptic rearrangements in this region have been reported infrequently. We report on a male patient with a microduplication of chromosome 4p, who presents with findings of macrocephaly, irregular iris pigmentation-heterochromia, and preserved linear growth in addition to overlapping features of trisomy 4p such as seizures, delayed psychomotor development, and dysmorphic features including prominent glabella, low-set ears, and short neck. Using a high-density oligonucleotide microarray, we have identified a novel submicroscopic duplication involving dosage sensitive genes TACC3, FGFR3, and LETM1. The microduplication did not involve WHSC1 and WHSC2 which are considered in the critical region for WHS and trisomy 4p. This patient's presentation and genomic findings help further delineate clinical significance of re-arrangements in the 4p16 region without the involvement of WHS critical region.