More Clinical Overlap between 22q11.2 Deletion Syndrome and CHARGE Syndrome than Often Anticipated.

CHARGE (coloboma, heart defects, atresia of choanae, retardation of growth and development, genital hypoplasia, and ear abnormalities) and 22q11.2 deletion syndromes are variable, congenital malformation syndromes that show considerable phenotypic overlap. We further explored this clinical overlap and proposed recommendations for the genetic diagnosis of both syndromes. We described 2 patients clinically diagnosed with CHARGE syndrome, who were found to carry a 22q11.2 deletion, and searched the literature for more cases. In addition, we screened our cohort of CHD7 mutation carriers (n = 802) for typical 22q11.2 deletion features and studied CHD7 in 20 patients with phenotypically 22q11.2 deletion syndrome but without haploinsufficiency of TBX1. In total, we identified 5 patients with a clinical diagnosis of CHARGE syndrome and a proven 22q11.2 deletion. Typical 22q11.2 deletion features were found in 30 patients (30/802, 3.7%) of our CHD7 mutation-positive cohort. We found truncating CHD7 mutations in 5/20 patients with phenotypically 22q11.2 deletion syndrome. Differentiating between CHARGE and 22q11.2 deletion syndromes can be challenging. CHD7 and TBX1 probably share a molecular pathway or have common target genes in affected organs. We strongly recommend performing CHD7 analysis in patients with a 22q11.2 deletion phenotype without TBX1 haploinsufficiency and conversely, performing a genome-wide array in CHARGE syndrome patients without a CHD7 mutation.

Dispersal and phylogeography of the agamid lizard Amphibolurus nobbi in fragmented and continuous habitat.

Approximately 90% of native vegetation has been cleared for agriculture in central New South Wales, Australia. Habitat loss has reduced and fragmented populations of the agamid lizard Amphibolurus nobbi. We compared genetic structure of populations of this species in an unmodified landscape with those from small nature reserves and linear remnants in farming areas. We ask: Is there evidence for reduced dispersal and population fragmentation among farm populations? Using 2008 bp mtDNA sequences and allozyme electrophoresis, we found that small populations in farming areas had as much genetic variation as populations in nature reserves. Application of nested clade analysis (NCA) indicated isolation-by-distance effects among populations from uncleared areas, but not among populations within farming locations. The genetic evidence therefore implied a high level of migration in the cleared landscapes. High dispersal after fragmentation may have resulted from either a burst of movement at the time of land clearing with dragons from many sources finding refuge in a few remnants, or from ongoing rapid dispersal through unsuitable habitat. A phylogeny based on mtDNA revealed that A. nobbi populations in the study area are deeply divided into two reciprocally monophyletic groups. Although we did not sample the entire species range, one of these evolutionarily significant units was only detected in remnant vegetation in the agricultural landscape. Therefore, a substantial subclade of this species may be vulnerable to extinction. Our findings emphasize that local populations of widespread species can harbour important intraspecific genetic diversity, supporting the case for maintaining widespread species throughout production landscapes.

Chromosome 22q11 deletion in patients with truncus arteriosus.

The association between truncus arteriosus and chromosome 22q11 deletion is well recognized, but the frequency of a chromosome 22q11 deletion has not been characterized in a large series of patients with truncus arteriosus, and little is known about cardiovascular morphologic features associated with a chromosome 22q11 deletion in this group of patients. We prospectively enrolled 50 consecutive patients with truncus arteriosus who were admitted to The Children's Hospital of Philadelphia between November 1991 and December 2001. Patients were studied for chromosome 22q11 deletion using fluorescence in situ hybridization. Correlations between anatomic features and chromosome 22q11 deletion were assessed. A chromosome 22q11 deletion was detected in 20 of the 50 patients (40%). Anatomic features that were significantly associated with a chromosome 22q11 deletion included a right-sided aortic arch, an abnormal aortic arch branching pattern, both abnormal sidedness and branching of the aortic arch, and the combined category of either abnormal sidedness or branching of the aortic arch. There was a trend toward the association of discontinuous pulmonary arteries with a chromosome 22q11 deletion. Interruption of the aortic arch and truncal valve morphology and function did not correlate significantly with the presence of a chromosome 22q11 deletion. In conclusion, a chromosome 22q11 deletion is common in patients with truncus arteriosus, and those with abnormal sidedness and/or branching of the aortic arch are significantly more likely to have a deletion. Clinically important anatomic variables, such as abnormalities of the truncal valve and interrupted aortic arch, were not associated with a chromosome 22q11 deletion in this series.

Early ultrasound diagnosis of Neu-Laxova syndrome.

We report the mid-trimester prenatal diagnosis of Neu-Laxova syndrome (NLS) in two at risk families utilizing serial sonographic examinations. Ultrasound and pathologic findings from seven affected pregnancies, the largest case series of NLS to date, are presented. One fetus had anencephaly and incomplete rachischisis, an anomaly that has not been previously reported in association with NLS. Ultrasonographic detection of severe intrauterine growth restriction (IUGR), abnormally postured limbs, microcephaly, and edema allowed prenatal diagnosis of NLS in five of these at risk pregnancies during the mid-trimester. Growth curves derived from serial sonograms reveal abnormalities of all standard biometric measurements. The growth discrepancy was most pronounced in the measurements of the biparietal diameter, which were consistently less than two standard deviations below the mean across all gestational ages. This case series confirms that aberrant growth and anomalies may be detected sufficiently early in gestation to permit prenatal diagnosis of NLS.

Association of chromosome 22q11 deletion with isolated anomalies of aortic arch laterality and branching.

OBJECTIVES: The purpose of this study was to determine the frequency of chromosome 22q11 deletions in patients with isolated anomalies of the aortic arch and its branches. BACKGROUND: Chromosome 22q11 deletions are often present in patients with certain forms of congenital cardiovascular disease, including tetralogy of Fallot, truncus arteriosus and interruption of the aortic arch. Among patients with these anomalies, chromosome 22q11 deletion is more common in those with abnormal aortic arch laterality or branching. METHODS: We studied 66 patients with isolated anomalies of the aortic arch and no associated intracardiac defects for deletions within chromosome 22q11, using fluorescence in situ hybridization with the cosmid probe N25 (D22S75). Arch anomalies included: double aortic arch (n = 22); right aortic arch with aberrant left subclavian artery (n = 28); right aortic arch with mirror-image branching and a vascular ring formed by a left-sided ductus from the descending aorta (n = 5); right aortic arch with mirror-image branching and no vascular ring (n = 4); and left aortic arch with aberrant right subclavian artery (n = 7). In addition, four patients had a cervical aortic arch, four had aortic coarctation and six had hypoplasia/atresia of the proximal pulmonary arteries. RESULTS: Chromosome 22q11 deletions were found in 16 patients (24%) across the full spectrum of anomalies studied. Among the morphologic variables analyzed, only hypoplasia/atresia of the proximal pulmonary arteries correlated with the deletion (p = 0.03). Among patients with a double arch, the frequency of chromosome 22q11 deletion was higher in those with an atretic minor arch than it was in those with a patent minor arch (p = 0.02). CONCLUSIONS: Chromosome 22q11 deletion is associated with isolated anomalies of laterality or branching of the aortic arch in 24% of cases in our series. These findings should alert the clinician to consider deletion screening in patients with isolated anomalies of the aortic arch.

Phenotype of the 22q11.2 deletion in individuals identified through an affected relative: cast a wide FISHing net!

PURPOSE: The chromosome 22q11.2 deletion has been identified in the majority of patients with DiGeorge syndrome, velocardiofacial syndrome, and conotruncal anomaly face syndrome and in some patients with the autosomal dominant Opitz G/BBB syndrome and Cayler cardiofacial syndrome. In addition, 22q11.2 deletion studies are becoming part of a standardized diagnostic workup for some isolated defects such as conotruncal cardiac anomalies and velopharyngeal incompetence. However, there is little information available on the clinical findings of unselected patients. For example, those individuals identified during prenatal diagnosis, as part of a generalized screening protocol, or following the diagnosis in a relative. This information will be invaluable in defining the variability of the disorder and in observing long-term outcome in the absence of targeted remediations. This study allows one to examine the first unselected cohort of patients and serves to highlight the importance of deletion testing in parents of affected probands. METHODS: Thirty individuals with a 22q11.2 deletion were identified following the diagnosis in a relative. Nineteen were adults ascertained only following the diagnosis in their child, 10 were children identified following the diagnosis in their sibling, and one was a child diagnosed prenatally following the diagnosis in her parent. RESULTS: Sixty percent of patients had no visceral anomalies. In fact, only 6 of the 19 adults (32%) and 6 of the 11 children (55%) had major findings which would have brought them to medical attention. Deletion sizing demonstrated the same large 3-4 MB deletion in most families despite wide inter and intrafamilial variability and there was no difference in clinical findings based on the parent of origin. Thus, no genotype-phenotype correlations could be made. CONCLUSION: We report the first unselected cohort of patients with the 22q11.2 deletion identified through an affected relative. Analysis of this series of 30 patients, many with very mild manifestations of the deletion, allows one to examine the outcome in individuals who lacked specific remediations for this disorder. It emphasizes the importance of broadening the index of suspicion in order to provide appropriate recurrence risk counseling, cognitive remediation, and medical management. Further, it underscores the lack of familial concordance and the current lack of genotype-phenotype correlations in this disorder, and it raises the possibility that the deletion is more common than previously reported.

Prenatal diagnosis of the 22q11.2 deletion syndrome.

The development of fluorescence in situ hybridization (FISH)- and polymerase chain reaction (PCR)-based assays for the detection of deletions of chromosome 22q11.2 has enabled the medical community to offer couples at risk prenatal diagnostic testing. Current indications for testing include a previous child with a 22q11.2 deletion or DiGeorge/velocardiofacial syndrome, an affected parent with a 22q11.2 deletion, and in utero detection of a conotruncal cardiac defect. Antenatal knowledge of the deletion status provides couples and clinicians with an accurate diagnosis, prognostic information, and recurrence risk, which may assist couples with their reproductive decisions. However, there are limitations to prenatal testing, which should be reviewed prior to testing.

Dysphagia in children with a 22q11.2 deletion: unusual pattern found on modified barium swallow.

OBJECTIVES: To delineate feeding dysfunction in a population of children with a 22q11.2 deletion and report the associated findings noted during the modified barium swallow (MBS). STUDY DESIGN: Seventy-five children with a chromosome 22q11.2 deletion and history of persistent feeding difficulty received a feeding evaluation, including an MBS for those children for whom there was concern about airway penetration. RESULTS: A consistent pattern of feeding difficulty, independent of palatal or cardiac involvement, emerged from the evaluations. This group typically has trouble coordinating the suck/swallow/breath pattern, resulting in slow nipple feedings interrupted by gagging or regurgitation. Recurrent vomiting and constipation are common. With advancement to chewable table foods, gagging or refusal develops, related to an immature oral transport pattern. The MBS studies demonstrate pharyngeal hypercontractility, cricopharyngeal prominence, and/or diverticula. CONCLUSIONS: Because of the consistency of dysphagic symptoms and MBS findings, we propose that dysmotility, especially through the pharyngoesophageal segment, is central to the dysphagia affecting this group. Dysphagia related to dysmotility may be underdiagnosed in this population or erroneously attributed to cardiac disease. Therefore attention to feeding status and investigation with MBS and gastrointestinal studies as warranted are recommended for all patients with a 22q11.2 deletion and feeding problems.

Tightly clustered 11q23 and 22q11 breakpoints permit PCR-based detection of the recurrent constitutional t(11;22).

Palindromic AT-rich repeats (PATRRs) on chromosomes 11q23 and 22q11 at the constitutional t(11;22) breakpoint are predicted to induce genomic instability, which mediates the translocation. A PCR-based translocation-detection system for the t(11;22) has been developed with PCR primers flanking the PATRRs of both chromosomes, to examine the involvement of the PATRRs in the recurrent rearrangement. Forty unrelated carriers of the t(11;22) balanced translocation, plus two additional, independent cases with the supernumerary-der(22) syndrome, were analyzed to compare their translocation breakpoints. Similar translocation-specific junction fragments were obtained from both derivative chromosomes in all 40 carriers of the t(11;22) balanced translocation and from the der(22) in both of the offspring with unbalanced supernumerary-der(22) syndrome, suggesting that the breakpoints in all cases localize within these PATRRs and that the translocation is generated by a similar mechanism. This PCR strategy provides a convenient technique for rapid diagnosis of the translocation, indicating its utility for prenatal and preimplantation diagnosis in families including carriers of the balanced translocation.

Communication disorders in the 22Q11.2 microdeletion syndrome.

The 22q11.2 microdeletion syndrome is a genetic disorder that is being recognized with increasing frequency. Confirmation of the diagnosis can be made using fluorescence in situ hybridization. Many medical and developmental problems are present in children with this syndrome. Communication disorders are among the most common features of this syndrome and include articulation, language, resonance, and voice problems. The purpose of this paper is to provide a description of the communicative and developmental features in a sample of children with the 22q11.2 microdeletion syndrome seen for evaluation. Because communication and feeding disorders may be presenting features of this syndrome, speech and language pathologists must be familiar with this syndrome and its various characteristics. Awareness of these features and a multidisciplinary approach are necessary for the identification and treatment of the complex communicative and medical problems present in this population.

Chromosome 22-specific low copy repeats and the 22q11.2 deletion syndrome: genomic organization and deletion endpoint analysis.

The 22q11.2 deletion syndrome, which includes DiGeorge and velocardiofacial syndromes (DGS/VCFS), is the most common microdeletion syndrome. The majority of deleted patients share a common 3 Mb hemizygous deletion of 22q11.2. The remaining patients include those who have smaller deletions that are nested within the 3 Mb typically deleted region (TDR) and a few with rare deletions that have no overlap with the TDR. The identification of chromosome 22-specific duplicated sequences or low copy repeats (LCRs) near the end-points of the 3 Mb TDR has led to the hypothesis that they mediate deletions of 22q11.2. The entire 3 Mb TDR has been sequenced, permitting detailed investigation of the LCRs and their involvement in the 22q11.2 deletions. Sequence analysis has identified four LCRs within the 3 Mb TDR. Although the LCRs differ in content and organization of shared modules, those modules that are common between them share 97-98% sequence identity with one another. By fluorescence in situ hybridization (FISH) analysis, the end-points of four variant 22q11.2 deletions appear to localize to the LCRs. Pulsed-field gel electrophoresis and Southern hybridization have been used to identify rearranged junction fragments from three variant deletions. Analysis of junction fragments by PCR and sequencing of the PCR products implicate the LCRs directly in the formation of 22q11.2 deletions. The evolutionary origin of the duplications on chromosome 22 has been assessed by FISH analysis of non-human primates. Multiple signals in Old World monkeys suggest that the duplication events may have occurred at least 20-25 million years ago.

Allelic variants of the follistatin gene in polycystic ovary syndrome.

In an earlier study of 37 candidate genes for polycystic ovary syndrome (PCOS), the strongest evidence for genetic linkage was found with the region of the follistatin gene. We have now carried out studies to detect variation in the follistatin gene and assess its relevance to PCOS. By sequencing the gene in 85 members of 19 families of PCOS patients, we found sequence variants at 17 sites. Of these, 16 sites have variants that are too rare to make a major contribution to susceptibility; the only common variant is a single base pair change in the last exon at a site that is not translated. In our sample of 249 families, the evidence for linkage between PCOS and this variant is weak. We also examined the expression of the follistatin gene; messenger RNA levels in cultured fibroblasts from PCOS and control women did not differ appreciably. We conclude that contributions to the etiology of PCOS from the follistatin gene, if any, are likely to be small.

Longitudinal analysis of lymphocyte function and numbers in the first year of life in chromosome 22q11.2 deletion syndrome (DiGeorge syndrome/velocardiofacial syndrome).

Chromosome 22q11.2 deletion syndrome is a common syndrome typically consisting of variable cardiac defects, hypoparathyroidism, developmental delay, and immunodeficiency. The hemizygous deletion has variable effects on the immune system even within the same kindred, and the extent of the immunodeficiency is difficult to predict. Some patients have shown improvement over time; however, this is the first prospective longitudinal study of the dynamic nature of the immunodeficiency. Nineteen patients were studied prospectively between 1994 and 1997. The results of the newborn immunologic studies in the chromosome 22q11.2 deletion group were significantly different from those of a group of newborns with cardiac disease due to other causes. Peripheral blood T-cell numbers were decreased in the chromosome 22q11.2 deletion group, although T-cell function was largely preserved. The group as a whole demonstrated few changes in the first year of life, but a subset of patients with markedly diminished T-cell numbers did demonstrate improvement. Therefore, improvement in peripheral blood T-cell counts is variable in chromosome 22q11.2 deletion syndrome. The patients with the lowest T-cell counts improved the most in the first year of life.

cDNA cloning and characterization of a human sperm antigen (SPAG6) with homology to the product of the Chlamydomonas PF16 locus.

Serum from an infertile male with high-titer anti-sperm antibodies was used to identify a novel human sperm antigen by screening of a testis expression library. The clone, initially designated Repro-SA-1 (HUGO-approved symbol SPAG6), was found to encode a sequence highly enriched in testis. The deduced amino acid sequence of the full-length cDNA revealed striking homology to the product of the Chlamydomonas reinhardtii PF16 locus, which encodes a protein localized to the central pair of the flagellar axoneme. The human gene encodes 1.8- and 2.8-kb mRNAs highly expressed in testis but not in prostate, ovary, spleen, thymus, small intestine, colon, peripheral blood leukocytes, heart, brain, placenta, liver, muscle, kidney, and pancreas. The gene was mapped to chromosome 10p11.2-p12. Antibodies raised against SPAG6 sequences localized the protein to the tails of permeabilized human sperm. Both the Chlamydomonas protein and SPAG6 contain eight contiguous armadillo repeats, which place them in a family of proteins known to mediate protein-protein interactions. The cloning of the human homologue of the Chlamydomonas PF16 locus provides a new avenue to explore the role of the axoneme central pair in human sperm function.

Thirty-seven candidate genes for polycystic ovary syndrome: strongest evidence for linkage is with follistatin.

Polycystic ovary syndrome (PCOS) is a common endocrine disorder of women, characterized by hyperandrogenism and chronic anovulation. It is a leading cause of female infertility and is associated with polycystic ovaries, hirsutism, obesity, and insulin resistance. We tested a carefully chosen collection of 37 candidate genes for linkage and association with PCOS or hyperandrogenemia in data from 150 families. The strongest evidence for linkage was with the follistatin gene, for which affected sisters showed increased identity by descent (72%; chi(2) = 12.97; nominal P = 3.2 x 10(-4)). After correction for multiple testing (33 tests), the follistatin findings were still highly significant (P(c) = 0.01). Although the linkage results for CYP11A were also nominally significant (P = 0.02), they were no longer significant after correction. In 11 candidate gene regions, at least one allele showed nominally significant evidence for population association with PCOS in the transmission/disequilibrium test (chi(2) >/= 3.84; nominal P < 0.05). The strongest effect in the transmission/disequilibrium test was observed in the INSR region (D19S884; allele 5; chi(2) = 8.53) but was not significant after correction. Our study shows how a systematic screen of candidate genes can provide strong evidence for genetic linkage in complex diseases and can identify those genes that should have high (or low) priority for further study.

Cognitive and behavior profile of preschool children with chromosome 22q11.2 deletion.

A microscopic deletion of chromosome 22q11.2 has been identified in most patients with the DiGeorge, velocardiofacial syndrome, conotruncal anomaly face syndrome, and in some patients with isolated conotruncal cardiac anomalies. This study presents the neurodevelopmental outcome, including cognitive development, language development, speech, neuromuscular development, and behavioral characteristics of 40 preschool children (ages 13 to 63 months) who have been diagnosed with the 22q11.2 deletion. The impact of cardiac disease, cardiac surgery, and the palatal anomalies on this population was also studied. In the preschool years, children with a 22q11.2 deletion are most commonly found to be developmentally delayed, have mild hypotonia, and language and speech delays. The more significantly delayed children are at high risk to be subsequently diagnosed with mild or moderate mental retardation. The global delays and the variations in intelligence found are directly associated with the 22q11.2 deletion and are not explained by physical anomalies such as palatal defects or cardiac defects, or therapeutic interventions such as cardiac surgery. Our findings demonstrate that there is a pattern of significant speech disorders within this population. All of the children had late onset of verbal speech. Behavioral outcomes included both inhibition and attention disorders. Early intervention services are strongly recommended beginning in infancy to address the delays in gross motor skills, speech and language, and global developmental delays.

Psychoeducational profile of the 22q11.2 microdeletion: A complex pattern.

OBJECTIVES: To examine the psychoeducational profile associated with the chromosome 22q11.2 microdeletion (DiGeorge/velocardiofacial syndrome). STUDY DESIGN: Thirty-three patients (aged 6 to 27 years) with a 22q11.2 microdeletion underwent psychoeducational testing as part of a comprehensive evaluation. Nonparametric statistics were used to compare verbal and performance IQ, academic achievement scores, and receptive versus expressive language scores. Post hoc comparisons were made of IQ subtest scores and of language versus verbal IQ. RESULTS: Full-scale IQ ranged from the normal to the moderately retarded range. Mean verbal IQ was significantly higher than mean performance IQ. In a similar manner, mean reading and spelling scores were superior to the mean mathematics score, although achievement scores typically were in the range of verbal IQ. In addition, many children showed clinically significant language impairments, with mean language scores lower than mean verbal IQ. CONCLUSIONS: The IQ and academic profiles are reminiscent of a "nonverbal learning disability," although achievement was not discrepant from IQ. The coincidence of language impairment with a relative strength in reading belies a unique neuropsychologic profile. Educational programming for these children must address both verbal and nonverbal deficits.