Familial partial 7q monosomy resulting from segregation of an insertional chromosome rearrangement

The contribution of 7q33 copy number variations for intellectual disability

Copy number variations (CNVs) at the 7q33 cytoband are very rarely described in the literature, and almost all of the cases comprise large deletions affecting more than just the q33 segment. We report seven patients (two families with two siblings and their affected mother and one unrelated patient) with neurodevelopmental delay associated with CNVs in 7q33 alone. All the patients presented mild to moderate intellectual disability (ID), dysmorphic features, and a behavioral phenotype characterized by aggressiveness and disinhibition. One family presents a small duplication in cis affecting CALD1 and AGBL3 genes, while the other four patients carry two larger deletions encompassing EXOC4, CALD1, AGBL3, and CNOT4. This work helps to refine the phenotype and narrow the minimal critical region involved in 7q33 CNVs. Comparison with similar cases and functional studies should help us clarify the relevance of the deleted genes for ID and behavioral alterations.

Deletion of 7q33-q35 in a Patient with Intellectual Disability and Dysmorphic Features: Further Characterization of 7q Interstitial Deletion Syndrome

This case report concerns a 16-year-old girl with a 9.92 Mb, heterozygous interstitial chromosome deletion at 7q33-q35, identified using array comparative genomic hybridization. The patient has dysmorphic facial features, intellectual disability, recurrent infections, self-injurious behavior, obesity, and recent onset of hemihypertrophy. This patient has overlapping features with previously reported individuals who have similar deletions spanning the 7q32-q36 region. It has been difficult to describe an interstitial 7q deletion syndrome due to variations in the sizes and regions in the few patients reported in the literature. This case contributes to the further characterization of an interstitial distal 7q deletion syndrome.

7q36 deletion and 9p22 duplication: effects of a double imbalance

The etiology of mental retardation/developmental delay (MRDD) remains a challenge to geneticists and clinicians and can be correlated to environmental and genetic factors. Chromosomal aberrations are common causes of moderate to severe mental retardation and may represent 10% of these occurrences. Here we report the case of a boy with development delay, hypoplasia of corpus callosum, microcephaly, muscular hypotonia, and facial dysmorphisms. A deletion of 7q36.1 → 36.3 and duplication of 9p22.3 → 23 was detected as a result of an unbalanced translocation of paternal origin. Breakpoint delimitation was achieved with array comparative genomic hybridization assay. Additional multiplex ligation dependent probe amplification (MLPA) analyzes confirmed one copy loss of 7q36.3 region and one copy gain of 9p24.3 region. Patient resultant phenotype is consistent with the already described findings for both 7q deletion and 9p duplication syndromes.

Deletion of 7q34-q36.2 in two siblings with mental retardation, language delay, primary amenorrhea, and dysmorphic features

We describe a chromosome rearrangement, ins(7;13)(q32q34;q32), which segregates in a three generation family, giving rise to three individuals with an unbalanced rearrangement. Two of the individuals, a sister and a brother, were investigated further in this study. They had minor facial dysmorphism and neuropsychiatric disorders including mental retardation, language delay and epilepsy. The sister had primary amenorrhea. Array CGH revealed a 12.2 Mb deletion at 7q34-q36.2 including more than 60 genes where CNTNAP2 and NOBOX are of special interest. Comparison of the clinical and cytogenetic findings of our patients with previously reported patients, supports that haploinsuffiency of CNTNAP2 can result in language delay and/or autism spectrum disorder. Furthermore, we report on the second women with a deletion involving NOBOX who is affected by primary amenorrhea.

Interstitial deletion of 7q31.32 → q33 secondary to a paracentric inversion of a maternal chromosome 7

Carriers of paracentric inversions (PAIs) are usually asymptomatic. However, such inversions may lead to the formation of recombinant gametes and then to an abnormal gestation. Here we report a girl with a 7q31.32 → q33 deletion secondary to a maternal PAI of chromosome 7. This finding was confirmed through FISH and whole-genome array-CGH analyses. The deficiency of the chromosome 7 observed in our patient was never described before and we did not find any known gene localized within the deficient segment that could be related to her findings of hypoplastic iliac bones, hypoplastic labia minora and postaxial polydactyly. This case highlights the fact that rare viable recombinants can be developed from PAIs, an issue that must be discussed in the genetic counseling.

Molecular cytogenetic characterization of an insertional translocation, ins(6;7)(p25;q33q34): Deletion/duplication of 7q33-34 and clinical correlations

A balanced insertional translocation between chromosomes 6 and 7, ins(6;7)(p25;q33q34) has been extensively investigated. The insertional translocation was found in several members of a three-generation family, where some were healthy balanced carriers while others had clinical symptoms due to deletion or duplication of 7q33-34. The deleted/duplicated segment could only be detected using high resolution banding and fluorescent in situ hybridization. A number of BAC/PAC clones located on chromosome 6 and 7 were used to characterize the breakpoint regions in detail and to determine the size of the deletion, which was 7.6 Mb, containing up to 68 genes. However, the insert on chromosome 6 was only 7.4 Mb, due to a deletion of 227 kb at the distal breakpoint on 7q. This small deletion was also found in the "balanced" carriers, and although the chromosome segment contains at least eight genes, none of the carriers seem to be affected by haploinsufficiency, since the phenotype is apparently normal. This is the first detailed characterization and phenotype correlation of such a deletion/duplication of distal 7q.

Chromosomal abnormalities and epilepsy: a review for clinicians and gene hunters

PURPOSE

We analyzed databases on chromosomal anomalies and epilepsy to identify chromosomal regions where abnormalities are associated with clinically recognizable epilepsy syndromes. The expectation was that these regions could then be offered as targets in the search for epilepsy genes.

METHODS

The cytogenetic program of the Oxford Medical Database, and the PubMed database were used to identify chromosomal aberrations associated with seizures and/or EEG abnormalities. The literature on selected small anomalies thus identified was reviewed from a clinical and electroencephalographic viewpoint, to classify the seizures and syndromes according to the current International League Against Epilepsy (ILAE) classification.

RESULTS

There were 400 different chromosomal imbalances described with seizures or EEG abnormalities. Eight chromosomal disorders had a high association with epilepsy. These comprised: the Wolf-Hirschhorn (4p-) syndrome, Miller-Dieker syndrome (del 17p13.3), Angelman syndrome (del 15q11-q13), the inversion duplication 15 syndrome, terminal deletions of chromosome 1q and 1p, and ring chromosomes 14 and 20. Many other segments had a weaker association with seizures. The poor quality of description of the epileptology in many reports thwarted an attempt to make precise karyotype-phenotype correlations.

CONCLUSIONS

We identified certain chromosomal regions where aberrations had an evident association with seizures, and these regions may be useful targets for gene hunters. New correlations with specific epilepsy syndromes were not revealed. Clinicians should continue to search for small chromosomal abnormalities associated with specific epilepsy syndromes that could provide important clues for finding epilepsy genes, and the epileptology should be rigorously characterized.

Ectrodactyly and proximal/intermediate interstitial deletion 7q

We report on an individual with severe mental retardation, seizures, microcephaly, unusual face, scoliosis, and cleft feet and cleft right hand. The chromosomal study showed a proximal interstitial deletion 7q (q11.23q22). From our review of the literature, 11 patients have been reported with ectrodactyly (split hand/split foot malformation) and proximal/intermediate interstitial deletions or rearrangements of 7q. The critical segment for ectrodactyly seems to be located between 7q21.2 and 7q22.1. This malformation is present in 41% of the patients whose deletion involves the critical segment.

An interstitial deletion of chromosome 7(q35)

We describe a patient with developmental delay, mild dysmorphic features, and monosomy of 7q35. Only one other patient with an interstitial deletion of this band has been previously reported. A review of clinical features of these two children did not show similarities in dysmorphic features. Reports of patients with other 7q interstitial deletions are listed.

Partial monosomy of 7q32 in a case of de novo rcp(7;15)(q32;q15)

A de novo apparently balanced translocation between chromosomes 7 and 15 with breakpoints in q32 and q15 respectively is reported in a female child. Clinical features included general growth and psychomotor retardation, feeding problems, microcephaly, low set ears, a short neck, and brachydactyly. These findings suggested possible physical or functional partial monosomy of the 7q32 or 15q15 segments. The phenotype of this case is similar to other cases of 7q deletion.

The interstitial deletion of bands q33-35 of long arm of chromosome 7: a review with a new case report

Interstitial or terminal deletion resulting in partial monosomy of various segments of the long arm of chromosome 7 was first recorded over two decades ago. Since then, a number of reports have correlated the severity of clinical manifestations with the length of the deletion involved. However, difficulty remains in defining a so-called "distinct syndrome". We present a new case with the shortest interstitial deletion of the long arm of chromosome 7 bands q33-35, i.e. 46,XX,del(7)(pter----q33::q35----qter). A 4-year-old black female was referred for cytogenetic evaluation due to neurodevelopmental delay. Pertinent physical examination at birth was cleft lip and cleft palate which required corrective surgery. At 2 years of age, a myringotomy tube was inserted for repeated ear infection and a hearing aid was required for conductive deafness. Neurological examination revealed poor eye contact, and severe mental and motor retardation. We reviewed 21 cases of a partial interstitial deletion of varied segments of the long arm of chromosome 7, but we were unable to establish a definite relationship with the deletion of various 7q segments with any specific clinical manifestations.

Partial trisomy 4p resulting from a balanced intrachromosomal insertion, 4(q313p14p16)

Partial trisomy 4p was found in a child with dysmorphic features. Cytogenetic investigations in the parents revealed an intrachromosomal insertion in the mother, 46,XX,ins (4) (q313p14p16). The proband was trisomic for 4p(p14p16) as a result of a recombination event in the mother's chromosome 4 at meiosis. The clinical features of the proband are compared with those found in the literature.

A summary of 7q interstitial deletions and exclusion mapping of the gene for beta-glucuronidase

Three patients are described with different phenotypes and differing de novo interstitial deletions of the long arm of a chromosome 7. The first patient has a deletion with loss of the proximal 7q11.23 band. Only three other cases have been reported with this particular deletion. Our second case shows mild dysmorphism similar to the other four patients reported with deletion of bands 7q21.12----21.3. Our third patient has a deletion of the 7q22.1----32.2 segment and has many of the phenotypic features of the other reported cases of del 7q22----32. GUSB, the gene for beta-glucuronidase, has been localised to the 7cen----q22 region. Analysis of beta-glucuronidase levels in blood leucocytes of our patients has helped more precisely to assign this gene locus to 7q21.11 or 7q22.1.

Familial partial trisomy 5p resulting from segregation of an insertional translocation

A case of duplication of segment p13-p15 of the short arm of chromosome 5 as the result of an insertional translocation in a mentally retarded girl with congenital anomalies is reported. Some of the apparently balanced carriers of the inverted insertion showed minor congenital anomalies.

Genetic markers on chromosome 7

Chromosome 7 is frequently associated with chromosome aberrations, rearrangements, and deletions. It also contains many important genes, gene families, and disease loci. This brief review attempts to summarise these and other interesting aspects of chromosome 7. With the rapid accumulation of cloned genes and polymorphic DNA fragments, this chromosome has become an excellent substrate for molecular genetic studies.

Absence of a lateral rectus muscle associated with duplication of the chromosome segment 7q32----q34

Absence of the right lateral rectus muscle and hypoplasia of the left was found in a child with congenital esotropia. He had mental and physical retardation, bilateral optic nerve hypoplasia, and many minor dysmorphic features, including brachycephaly, high forehead, poorly folded, low set ears, epicanthic folds, exaggerated Cupid's bow, long philtrum, and single palmar creases. Unusual features were a markedly ridged palate and a plantar crease which passed from the first and second interspace across the lateral border of the foot. He was found to have an unbalanced karyotype with duplication of chromosome segment 7q32----q34 (46,XY,der(2),inv?ins(2;7) (q21;q32q34)mat). The mother, maternal aunt, and sister of the proband all had a balanced rearrangement and were phenotypically normal.

Pure monosomy and trisomy 2q24.2----q3105 due to an inv ins(7;2)(q21.2;q3105q24.2) segregating in four generations

An inv ins(7;2)(q21.2;q3105q24.2) was found to segregate through four generations of a family. Adjacent-1 segregation aneusomies were ascertained in five patients: three monosomics and two trisomics; and the corresponding syndromes were delineated. The comparative analysis between these and other previously described 2q aneusomic individuals led to the conclusion that a large cleft between first and second toes is a constant feature in monosomy 2q24----q31. No other trait could plausibly be mapped. Risks of 7.9 to 31.6% for aneusomic children and of 26.3% for abortion were estimated in the present family.

Terminal and interstitial deletions of the long arm of chromosome 7: a review with five new cases

Sixteen cases of terminal deletions and 17 cases of interstitial deletions of the long arm of chromosome 7 have been reported to date. We present two new cases of the former and three of the latter. The somatic changes in these patients are tabulated and an update on the anomalies associated with the various cytogenetic entities is presented. Changes found in over one-third of patients with 7q terminal deletion syndrome include: developmental delay, pre- and postnatal growth retardation, generalized hypotonia, abnormal electroencephalograms with or without seizures, feeding problems in infancy, microcephaly, prominent forehead, ocular hypertelorism, eye defects, broad nasal bridge, bulbous nasal tip, auricular malformations, micrognathia, chest abnormalities, genital malformations in males, and abnormal palmar and plantar creases. Evidence for the localization of the Kidd blood group gene on chromosome 7 distal to band q32, as suggested by previous reports, is reviewed; we conclude that the evidence does not warrant placement of the gene in this region of the genome.

Interstitial deletion of chromosome 7: a case report and review of the literature

A de novo deletion 7q11 leads to q21.2 was identified in a newborn with genital and other minor clinical abnormalities and some degree of psychomotor retardation. A review of the literature revealed a number of cases of deletion 7q, which can be categorized into three groups according to their breakpoints. Attempts to correlate phenotype with genotype in these cases have been only moderately successful, and as yet only deletion 7q32 leads to qter can be associated with a definite clinical syndrome, although a tentative syndrome may be postulated in association with deletion of region 7q22 leads to 7q31.

A fourth case of ring chromosome 7

An 8-year-old child with a ring chromosome 7 is presented, the first female and the fourth such individual to be described. The associated anomalies were rather benign: she presented with short stature, minor skeletal alterations, and normal intelligence. The only truly striking feature was the presence of multiple large, pigmented naevi, suggestive of a hamartomatous origin, but unlike those typical of any particular syndrome. Though other ring 7 patients have had naevus flammeus, and one had café-au-lait spots, our proband is the first with an anomaly of chromosome 7 to have such extensive lesions. These four cases of ring 7, which show great phenotypic variation, are reviewed, and the clinical presentation of the proband is also compared with that of patients suffering from terminal, interstitial and translocation-derived 7p and 7q deletions. The formation and behavior of ring chromosomes are discussed, as are the cytogenetic factors which may influence their phenotypic expression.

Partial monosomy 7q syndrome due to distal interstitial deletion

A female infant was ascertained at 10 weeks because of failure to thrive and a peculiar cry and was found to have few morphologic variants. Her karyotype was 46,XX,del(7)(q3105::q3405). The parental karyotypes were normal. At one year she manifested physical retardation and development delay and required surgery for gastroesophageal incompetence. The phenotypic characteristics of this patient and those of six previously reported cases of 7q medial or distal interstitial deletion include many anomalies. Morphologic abnormalities of the head, ears, eyes, mouth, chest, hands, feet, and nerves combined with characteristics of birth weight, growth, and development define a detectable syndrome. An unusual cry may help in the recognition of this new syndrome.