Partial trisomy of 11 and 22 due to familial translocation t(11;22)(q23;q11), inherited in three generations

Identification of a Novel Splice Site Mutation in RUNX2 Gene in a Family with Rare Autosomal Dominant Cleidocranial Dysplasia

Background:

Pathogenic variants of RUNX2, a gene that encodes an osteoblast-specific transcription factor, have been shown as the cause of CCD, which is a rare hereditary skeletal and dental disorder with dominant mode of inheritance and a broad range of clinical variability. Due to the relative lack of clinical complications resulting in CCD, the medical diagnosis of this disorder is challenging, which leaves it underdiagnosed.

Methods:

In this study, nine healthy and affected members of an Iranian family were investigated. PCR and sequencing of all exons and exon-intron boundaries of RUNX2 (NM_001024630) gene was performed on proband. Co-segregation analysis was conducted in the other family members for the identified variant. Additionally, a cohort of 100 Iranian ethnicity-matched healthy controls was screened by ARMS-PCR method.

Results:

The novel splice site variant (c.860-2A>G), which was identified in the intron 6 of RUNX2 gene, co-segregated with the disease in the family, and it was absent in healthy controls. Pathogenicity of this variant was determined by several software, including HSF, which predicts the formation or disruption of splice donor sites, splice acceptor sites, exonic splicing silencer sites, and exonic splicing enhancer sites. In silico analysis predicted this novel variant to be disease causing.

Conclusion:

The identified variant is predicted to have an effect on splicing, which leads to exon skipping and producing a truncated protein via introducing a premature stop codon.

Phenotypic delineation of Emanuel syndrome (supernumerary derivative 22 syndrome): Clinical features of 63 individuals

Emanuel syndrome is characterized by multiple congenital anomalies and developmental disability. It is caused by the presence of a supernumerary derivative chromosome that contains material from chromosomes 11 and 22. The origin of this imbalance is 3:1 malsegregation of a parental balanced translocation between chromosomes 11 and 22, which is the most common recurrent reciprocal translocation in humans. Little has been published on the clinical features of this syndrome since the 1980s and information on natural history is limited. We designed a questionnaire to collect information from families recruited through an international online support group, Chromosome 22 Central. Data gathered include information on congenital anomalies, medical and surgical history, developmental and behavioral issues, and current abilities. We received information on 63 individuals with Emanuel syndrome, ranging in age from newborn to adulthood. As previously recognized, congenital anomalies were common, the most frequent being ear pits (76%), micrognathia (60%), heart malformations (57%), and cleft palate (54%). Our data suggest that vision and hearing impairment, seizures, failure to thrive and recurrent infections, particularly otitis media, are common in this syndrome. Psychomotor development is uniformly delayed, however the majority of individuals (over 70%) eventually learn to walk with support. Language development and ability for self-care are also very impaired. This study provides new information on the clinical spectrum and natural history of Emanuel syndrome for families and physicians caring for these individuals.

Vertebral fusion in a patient with supernumerary-der(22)t(11;22) syndrome

A patient with a 47,XX,+der(22)t(11;22)(q23.3;q11.2) karyotype exhibited brisk tendon reflex and Babinski sign with suggested pyramidal sign. A three-dimensional computed tomographic reconstruction revealed a T1-T2 vertebral fusion without hemivertebrae. Sagittal magnetic resonance imaging revealed degenerative disk changes, mild disk herniation, and mild spinal cord compression. Congenital vertebral fusion may be one of the anomalies in supernumerary-der(22)t(11;22) syndrome. Once clinical diagnosis of this chromosome aberration is established, radiologic evaluation of vertebrae and spinal neuroimaging should be performed.

Prenatal diagnosis of a cleidocranial dysplasia-like phenotype associated with a de novo balanced t(2q;6q)(q36;q16) translocation

Cleidocranial dysplasia (CCD) is a congenital disorder of bone development characterized by persistently open or delayed closure of cranial sutures and wormian bones, hypoplastic and/or aplastic clavicles, wide pubic symphysis, dental anomalies and short stature. The condition is inherited as an autosomal-dominant trait and the human CBFA1 gene has been identified as the CCD gene. We describe a prenatal form of the skeletal disorder that included clavicular hypoplasia, absence of ossification of the cranial parietal bones and very poor ossification of the frontal and pubic bones. Growth restriction affecting only the long bones was also noted. The fetal karyotype revealed an apparently de novo balanced t(2q;6q)(q36;q16) translocation. This particular form of skeletal disorder associated with the absence of family history and an apparently de novo balanced translocation led the parents to opt for termination of the pregnancy.

At least nine cases of trisomy 11q23-->qter in one generation as a result of familial t(11;13) translocation

Carriers of balanced reciprocal translocations may have a (high) risk for producing liveborn children with an unbalanced karyotype. We report a large family in which a translocation between the long arm of chromosome 11 and the short arm of chromosome 13 is segregating in at least five generations. During the course of our study 15 carriers of the balanced translocation were identified and nine cases of partial trisomy of the long arm of chromosome 11 were detected during pre- and postnatal studies. Several of the patients were thoroughly clinically examined and compared with similar published cases.

11q trisomy detected by fluorescence in situ hybridization

A patient with psychomotor developmental delay, multiple minor anomalies, congenital heart disease and left inguinal hernia is reported. His karyotype was 45,X/46,X,+mar (3:37 cells), and the marker chromosome was identified as t(Y;11)(q12;q14?) using fluorescence in situ hybridization and fluorescent chromosome painting. He was diagnosed as mosaic for de novo 11q trisomy.

Pericentric inversion of chromosome 6 in a patient with cleidocranial dysplasia

We describe a male patient with a pericentric inversion of chromosome 6 and classic cleidocranial dysplasia (CCD), mild to moderate mental retardation, hearing deficiency, and unusual facial appearance. We conclude that there is a causal relationship between the chromosomal disorder and the CCD.

Apparent cleidocranial dysplasia associated with abnormalities of 8q22 in three individuals

Cleidocranial dysplasia is an autosomal dominant, generalised skeletal disorder characterised by variable clavicular hypoplasia, frontal bossing, multiple Wormian bones, and delayed eruption of the teeth. The gene locus for this syndrome has not yet been assigned. Three individuals with manifestations of cleidocranial dysplasia associated with rearrangements of chromosome 8q22 are described. The evidence presented suggests that the gene for cleidocranial dysplasia may be located on chromosome 8q in humans in a region showing homology to mouse chromosome 3.

Congenital cardiovascular malformations (CCVM) and structural chromosome abnormalities: a report of 9 cases and literature review

Nine cases of congenital cardiovascular malformations (CCVM) with associated unbalanced structural chromosomal abnormalities were ascertained in a population-based study of heart defects, constituting 0.4% of the 2,103 cases of CCVM in the Baltimore-Washington Infant Study (BWIS). This represents a four-fold increase over the general population rate. In an effort to determine possible phenotype/karyotype correlations, the literature was searched for cases with similar karyotypic abnormalities. This comparison of 223 literature cases of karyotypic abnormalities with nine similar cases ascertained by heart malformation has provided the opportunity to review cardiac defects reported in cases of structural abnormalities of chromosomes 1, 3, 7, 8, 9, 10, 11, 15, and 18. The most common cardiac malformation present in the chromosomal cases was ventricular septal defect (VSD) (39%); similarly VSD is the most common CCVM among children with heart defects, although it is the primary defect in only 20% of the BWIS cases. Among all heart defects in the BWIS, atrial septal defect (ASD) represents 5.5% of all cases, but in cases of 8p duplication, ASD is present in 41%. In addition, 40% of cases of 9p duplication had an ASD. Similarly, 35% of cases of 11q duplication had an ASD. While the suggestion of specific karyotype/phenotype association is premature, information on additional cases might clarify the possibility that genetic determinants related to septum formation may reside on chromosome 8, 9, and/or 11. The variety of chromosomal abnormalities in cases with ventricular septal defect indicates one type of genetic heterogeneity that may be involved in this very common heart defect.

Regional localization and molecular characterization of a DNA sequence on the long arm of chromosome 22

A human genomic DNA fragment, p22hom13 (D22S16), was isolated from a chromosome 22-specific library. After elimination of repetitive sequences, a single copy BamHI-EcoRI fragment was subcloned into pTZ18. By using mouse/human somatic cell hybrids and in situ hybridization, the new DNA probe was mapped to chromosome 22q13-qter. Its application in the analysis of the distal part of chromosome 22 and its diagnostic use in translocations are discussed.

Congenital heart disease in supernumerary der(22),t(11;22) syndrome

Congenital heart disease occurred in 62% of the reported cases of supernumerary der(22) syndrome. These were most commonly acyanotic lesions such as atrial septal defect, ventricular septal defect or patent ductus arteriosus. Heart disease did not, however, appear to be a major determinant of survival.

Balanced reciprocal translocations: risk factors for aneuploid segregant viability

Reciprocal translocations were studied in two groups of balanced carrier couples: 202 had 210 translocation aneuploid between (LB) infants, and 95 couples had repetitive abortions (AB) without liveborn aneuploids. The observed translocation aneuploidies in the LB group were compared to predicted potential aneuploidies in AB by frequency of chromosome involvement, meiotic segregation mode, and mean trisomic, monosomic and combined genomic imbalances. Qualitative and quantitative differences identified genomic regions and chromosomes possibly vital for in utero survivability. LB aneuploidies indicate non-random chromosome involvement, selection of least detrimental segregants and segments, and predominant transmission from maternal balanced carriers (especially in 3:1 tertiary segregation, 93.5%). For an individual with a balanced reciprocal translocation and untested reproductive capability, an approach is given for predicting whether a translocation aneuploid conceptus will be liveborn or aborted.

Partial 11q trisomy syndrome

The syndrome caused by partial trisomy for 11q is reviewed on the basis of a patient of our own and 20 cases (including a stillbirth) from the literature. The main symptoms are presented in Tables 1 and 2. The syndrome can be suspected when, in addition to mental retardation, the following characteristics are present: short nose, long philtrum, micrognathia, retracted lower lip, and micropenis in males. In 15 families, the mother was a balanced translocation carrier and in four the father. The translocation had arisen de novo in two patients. The chromosome number was 46 in 13 affected individuals (including the stillbirth) and 47 in eight. In seven of the latter patients the other translocation chromosome was 22, and in one, chromosome 9. The breakpoints on 11q ranged from 11q121 to 11q232 (Fig. 5). There is no apparent correlation between the length of the trisomic segment and the number or severity of the symptoms (Table 2). This could be explained by assuming that most, if not all, symptoms are caused by trisomy for the Q-dark region distal to 11q232, whereas trisomy for the rest of the 11q up to q121 has few phenotypic effects. These observations support the idea that Q-dark segments, and especially certain hot spots, have a high gene density in contrast with Q-brighter regions.

Incomplete trisomy 22. I. Familial 11/22 translocation with 3:1 meiotic disjunction. Delineation of a common clinical picture and report of nine new cases from six families

A syndrome due to 3:1 meiotic segregation of balanced 11/22 translocation is defined from nine personally observed patients and 22 cases from the literature with apparently the same aberration. Frequent findings include a characteristic face with deep-set eyes, flat nose, prominent upper lip, receding mandible and preauricular pits or tags, male genital hypoplasia, anal atresia or other anomalies of the anus, cleft palate, and congenital heart defect. Less frequent are severe reduction of the auricles, an additional pair of ribs, and hypoplasia of the diaphragm. Perinatal mortality is high. Growth is usually and psychomotor development is invariably and severely delayed. Balanced 11/22 translocations are apparently disproportionally frequent; as the balanced rearrangement is not easy to detect, it is important to be aware of it at the family investigation of cases with extra chromosomes similar to a No. 22 or 22q-. The unbalanced products are most probably trisomic for both a segment of 22 (22q-) and a distal segment of 11q; the exact determination of the breakpoints is not possible at present due to the similar banding characteristics of the two segments involved in the translocation.

Reciprocal translocations: a way to predict the mode of imbalanced segregation by pachytene-diagram drawing

The study of 151 reciprocal translocations associated with abnormal probands shows that the mode of imbalance at birth is determined by the nature of the involved chromosomes and by the position of the breakpoints. For each of the three modes (adjacent-1, adjacent-2, and 3:1) there is a corresponding pachytene diagram, so that for each translocation variety it is possible to predict the most probable mode of imbalance. The determining factor is the relative length of the different branches of the cross formed by the tetravalent. However, some heterochromatic regions (9qh, short arms of acrocentric chromosomes) and possibly R-negative regions have a minor role. The factors involved in these mechanisms seem to be the selection and the chiasma position; their respective roles are discussed.