Pseudoachondroplasia with de novo deletion [del(11)(q21q22.2)]

Mutant COMP shapes growth and development of skull and facial structures in mice and humans

BACKGROUND

Cartilage oligomeric matrix protein (COMP) is an important extracellular matrix protein primarily functioning in the musculoskeletal tissues and especially endochondral bone growth. Mutations in COMP cause the skeletal dysplasia pseudoachondroplasia (PSACH) that is characterized by short limbs and fingers, joint laxity, and abnormalities but a striking lack of skull and facial abnormalities.

METHODS

This study examined both mice and humans to determine how mutant-COMP affects face and skull growth.

RESULTS

Mutant COMP (MT-COMP) mice were phenotypically distinct. Snout length and skull height were diminished in MT-COMP mouse and the face more closely resembled younger controls. Three-dimensional facial measurements of PSACH faces showed widely spaced eyes, reduced lower facial height, and decreased nasal protrusion, which correlated with a more juvenile appearing face. Neither MT-COMP mice nor PSACH individuals show midface hypoplasia usually associated with abnormal endochondral bone growth. MT-COMP mice do show delayed endochondral and membranous skull ossification that normalizes with age.

CONCLUSION

Therefore, mutant-COMP affects both endochondral and intramembranous bones of the skull resulting in a reduction of the nose and lower facial height in mice and humans, in addition to its well-defined role in the growth plate chondrocytes.

Directly Transmitted 12.3-Mb Deletion with a Consistent Phenotype in the Variable 11q21q22.3 Region

A phenotype is emerging for the proximal pair of G-dark bands in 11q (11q14.1 and q14.3) but not yet for the distal pair (11q22.1 and q22.3). A mother and daughter with the same directly transmitted 12.3-Mb interstitial deletion of 11q21q22.3 (GRCh37: 93,551,765-105,817,723) both had initial feeding difficulties and failure to thrive, speech delay, learning difficulties, and mild dysmorphism. Among 17 patients with overlapping deletions, developmental or speech delay, dysmorphism, hypotonia, intellectual disability or learning difficulties, short stature, and coloboma were each found in 2 or more. These results may provide the basis for a consistent phenotype for this region. Among the 53 deleted and additional breakpoint genes, CNTN5, YAP1, and GRI4 were the most likely candidates. Non-penetrance of haploinsufficient genes and dosage compensation among related genes may account for the normal cognition in the mother and variable phenotypes that can extend into the normal range.

Interstitial deletion at 11q14.2-11q22.1 may cause severe learning difficulties, mental retardation and mild heart defects in 13-year old male

Interstitial deletions of the long arm of chromosome 11 are rare, and they could be assumed as non-recurrent chromosomal rearrangements due to high variability of the size and the breakpoints of the deleted region. The exact region of the deletion was difficult to be determined before the use of molecular cytogenetic techniques such as array comparative genomic hybridization (aCGH). Here, a 13-year old boy with severe learning difficulties, mental retardation and mild heart defects is described. Conventional G-band karyotyping was performed and it is found that the patient is a carrier of a de novo interstitial deletion on the long arm of chromosome 11, involving 11q14 and 11q22 breakpoints. Further investigation, using aCGH, specified the deleted region to 11q14.2-11q22.1. There was a difficulty in correlating the genotype with the phenotype of the patient due to lack of similar cases in literature. More studies should be done in order to understand the genetic background that underlies the phenotypic differences observed in similar cases.

Interstitial 11q deletion: genomic characterization and neuropsychiatric follow up from early infancy to adolescence and literature review

BACKGROUND

Interstitial deletions of chromosome 11 long arm are rarely observed and the associated phenotype ranges from normal to severe, depending on the position and size of the deletion and on the presence of unmasked recessive genes on the normal homologous. To our knowledge 32 cases are reported in literature with three family cases. Phenotype-genotype correlation is not very clear and the most common features are characteristic facial dysmorphisms, palate anomalies and developmental delay. Growth retardation is not typical and other major malformations are reported in some cases.

CASE PRESENTATION

We described a child with 11q interstitial deletion diagnosed at birth with hypotonia and minor dysmorphisms using standard cytogenetic techniques; array CGH was subsequently performed to define the deletion at a molecular level.

CONCLUSIONS

This case gave us the opportunity to attempt a genotype-phenotype correlation reviewing the literature and to describe a rehabilitative program that improved the development perspectives of this child.

The 22q11.2 deletion syndrome as a window into complex neuropsychiatric disorders over the lifespan

Evidence is rapidly accumulating that rare, recurrent copy number variants represent large effect risk factors for neuropsychiatric disorders. 22q11.2 deletion syndrome (22q11DS) (velocardiofacial syndrome or DiGeorge syndrome) is the most common known contiguous gene deletion syndrome and is associated with diverse neuropsychiatric disorders across the life span. One of the most intriguing aspects of the syndrome is the variability in clinical and cognitive presentation: children with 22q11DS have high prevalence of autism spectrum, attention deficit, and anxiety disorders, as well as psychotic-like features, and up to 30% of adolescents and adults develop schizophrenia-like psychosis. Recently, cases of early-onset Parkinson's disease in adults have been reported, collectively suggesting a role for disrupted dopaminergic neurotransmission in the observed neuropsychiatric phenotypes. There is also some evidence that 22q11DS-associated autism spectrum disorder and schizophrenia represent two unrelated phenotypic manifestations, consistent with a neuropsychiatric pleiotropy model. This genetic lesion thus provides a unique model for the discovery of specific genomic risk and (potentially) protective factors for neuropsychiatric disease. Here, we provide an overview of neuropsychiatric findings to date, which highlight the value of this syndrome in mapping the developmental trajectory of dimensional phenotypes that traverse multiple diagnostic categories. Potential sources of genetic variability that may contribute to the disorder's heterogeneous presentation are reviewed. Because of its known genetic etiology, animal models can readily be developed that recapitulate specific aspects of the syndrome. Future research directions involve translational models and potential for drug screenable targets in the context of this human model system.

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.

Karyotype-phenotype insights from 11q14.1-q23.2 interstitial deletions: FZD4 haploinsufficiency and exudative vitreoretinopathy in a patient with a complex chromosome rearrangement

We detected a unique de novo complex chromosome rearrangement (CCR) in a patient with multiple abnormalities including growth retardation, facial anomalies, exudative vitreoretinopathy (EVR), cleft palate, and minor digital anomalies. Cytogenetic analysis, fluorescent in situ hybridization, and microsatellite genotyping showed a reciprocal translocation between chromosomes 5 and 8, and a complex translocation-deletion-inversion process in the formation of derivative chromosomes 11 and 16. High-density whole-genome oligonucleotide array comparative genomic hybridization (oaCGH) defined a 35-megabase interstitial deletion of 11q14.1-q23.2 and a 1 megabase deletion of 16q22.3-q23.1. The Frizzled-4 (FZD4) gene is located within this 11q deletion. Parental studies and sequencing analysis confirmed that the patient was hemizygous for FZD4 due to the loss of a paternal allele on the derivative chromosome 11. Mutations in FZD4 are known to cause autosomal dominant exudative vitreoretinopathy (EVR1). Our patient's findings suggest that haploinsufficiency of the FZD4 gene product can also be a disease-causing mechanism for EVR1. We reviewed the clinical manifestations of 23 cases with 11q14-q23 interstitial deletions, with particular scrutiny of the present case and four reported cases characterized by molecular cytogenetics. These findings were used to construct a regional deletion map consisting of a haplosufficient segment at 11q14.3, a flanking centromeric segment at 11q14.1-q14.2, and a flanking telomeric segment at 11q21-q23.3. We propose that deletions of the FZD4 gene located within the centromeric segment cause retinal dysgenesis, while deletions within the telomeric segment account for dysmorphic craniofacial features, growth and mental retardation, and mild digital anomalies. These results provide insight into karyotype-phenotype correlations and prompt a rational analytic approach to cases with interstitial deletions of the 11q14-q23 region.