Atsuyoshi Takao

Role of TBX1 in human del22q11.2 syndrome.

BACKGROUND Del22q11.2 syndrome is the most frequent known chromosomal microdeletion syndrome, with an incidence of 1 in 4000-5000 livebirths. It is characterised by a 3-Mb deletion on chromosome 22q11.2, cardiac abnormalities, T-cell deficits, cleft palate facial anomalies, and hypocalcaemia. At least 30 genes have been mapped to the deleted region. However, the association of these genes with the cause of this syndrome is not clearly understood. METHODS To test for the chromosomal deletion at 22q11.2, we did fluorescence in-situ hybridisation analysis with ten probes on 22q11.2 in 235 unrelated patients with clinically diagnosed del22q11.2 syndrome. To investigate mutations in the coding sequence of TBX1, we also did genetic analysis in 13 patients from ten families who have the 22q11.2 syndrome phenotype but no detectable deletion of 22q11.2. FINDINGS 96% (225 of 235) of patients had a defined 1.5-3-Mb deletion at 22q11.2. We identified three mutations of TBX1 in two unrelated patients without the 22q11.2 deletion-one with sporadic conotruncal anomaly face syndrome/velocardiofacial syndrome and one with sporadic DiGeorges syndrome-and in three patients from a family with conotruncal anomaly face syndrome/velocardiofacial syndrome. We did not record these three mutations in 555 healthy controls (1110 chromosomes; p<0.0001). INTERPRETATION Our results suggest that the TBX1 mutation is responsible for five major phenotypes in del22q11.2 syndrome. Therefore, we conclude that TBX1 is a major genetic determinant of the del22q11.2 syndrome.

Conotruncal anomaly face syndrome is associated with a deletion within chromosome 22q11.

The conotruncal anomaly face syndrome was described in a Japanese publication in 1976 and comprises dysmorphic facial appearance and outflow tract defects of the heart. The authors subsequently noted similarities to Shprintzen syndrome and DiGeorge syndrome. Chromosome analysis in five cases did not show a deletion at high resolution, but fluorescent in situ hybridisation using probe DO832 showed a deletion within chromosome 22q11 in all cases.

Phenotypes with GATA4 or NKX2.5 mutations in familial atrial septal defect.

Recently, GATA4 and NKX2.5 were reported as the disease genes of atrial septal defect (ASD) but the relationship between the locations of their mutations and phenotypes is not clear. We analyzed GATA4 and NKX2.5 mutations in 16 familial ASD cases, including four probands with atrioventricular conduction disturbance (AV block) and two with pulmonary stenosis (PS), by PCR and direct sequencing, and examined their phenotypes clinically. Five mutations, including two GATA4 and three NKX2.5 mutations, were identified in 31.3% of the probands with ASD, and three of them were novel. The two GATA4 mutations in the probands without AV block were S52F and E359Xfs (c.1075delG) that was reported previously, and three NKX2.5 mutations in the probands with AV block were A88Xfs (c.262delG), R190C, and T178M. Additionally, we observed some remarkable phenotypes, i.e., dextrocardia with E359Xfs (c.1075delG) and cribriform type ASD with R190C, both of which are expected to be clues for further investigations. Furthermore, progressive, most severe AV block was closely related with a missense mutation in a homeodomain or with a nonsense/frame‐shift mutation of NKX2.5 for which classification has not been clearly proposed. This pinpoints essential sites of NKX2.5 in the development of the conduction system.

AORTIC ARCH ANOMALIES ASSOCIATED WITH CHROMOSOME 22Q11 DELETION (CATCH 22)

Chromosome 22q11 deletion or CATCH 22 is associated with DiGeorge syndrome, conotruncal anomaly face syndrome, and velocardiofacial syndrome. Associated congenital heart diseases include tetralogy of Fallot, truncus arteriosus, and ventricular septal defect. Associated anomalies of the aortic arch, aortic branches, ductus arteriosus, and pulmonary arteries are more frequent in patients with the deletion than in those without the deletion. Associated anomalies include right aortic arch, cervical aorta, aberrant origin or isolation of the subclavian artery, the absence of the ductus arteriosus, major aortopulmonary collateral arteries, isolation of the left pulmonary artery, and vascular ring formed by the right aortic arch, retroesophageal aortic arch, and left descending aorta.

Molecular and clinical study of 183 patients with conotruncal anomaly face syndrome

To investigate molecular and clinical aspects of conotruncal anomaly face (CAF), we studied the correlation between deletion size and phenotype and the mode of inheritance in 183 conotruncal anomaly face syndrome (CAFS) patients. Hemizygosity for a region of 22q11.2 was found in 180 (98%) of the patients with CAFS by fluorescence in situ hybridization (FISH) using the N25(D22S75) DiGeorge critical region (DGCR) probe. No hemizygosity was found in three (2%) of the patients with CAFS by FISH using nine DiGeorge critical region probes and a SD10P1 probe (DGA II locus). None of these three patients had mental retardation and just one had nasal intonation, which was observed in almost all of the 180 CAFS patients who carried deletions (mental retardation, 92%; nasal voice, 88%). Nineteen of 143 families (13%) had familial CAFS and 16 affected parents (84%) were mothers. Although only two of the affected parents had cardiovascular anomalies, the deletion size in the 16 affected parents and their affected family members, who were studied by FISH analysis, was the same. It indicates that extragenic factors may play a role in the genesis of phenotypic variability, especially in patients with cardiovascular anomalies. No familial cases were found among CAFS patients with absent thymus/DiGeorge anomaly (DGA). Also, in all 18 CAFS patients with completely absent thymus/DGA and all 6 CAFS patients with schizophrenia, it was revealed that the deletion was longer distally. A study of the origin of the deletion using microsatellite analyses in 48 de novo patients showed that in 65% of CAFS patients it was maternal, while in 64% of DGA patients it was paternal. The findings of this study indicated that CAF was almost always associated with the deletion of 22q11.2. As well as the major features of the syndrome, other notable extracardiac anomalies were found to be susceptibility to infection, schizophrenia, atrophy or dysmorphism of the brain, thrombocytopenia, short stature, facial palsy, anal atresia, and mild limb abnormalities.

Tetralogy of Fallot associated with chromosome 22q11 deletion

Abstract In summary, all patients with tetralogy and 22qH deletion had 1 to 4 additional conotruncal anomalies, such as high aortic arch, right aortic arch, infundibular septal defect, aberrant origin of the subclavian artery, major aortopulmonary collateral arteries, and anomalous ductus arteriosus causing isolation of either the left pulmonary artery or the subclavian artery.

Distal type of aortopulmonary window. Report of 4 cases.

We have studied 14 patients with aortopulmonary window (10 male and 4 female, age range 1 month to 41 years). Four of these had a distal defect with characteristic haemodynamic and angiographic features. Aortopulmonary window may be classified into 3 types: type I (proximal) defects occur in the proximal part of aortopulmonary septum; type II (distal) defects occur in the distal part of the aortopulmonary septum adjacent to the right pulmonary artery; the type III defect is a combination of types I and II. In type I, injection of contrast media into the aortic root opacifies the main pulmonary trunk and then both pulmonary arteries. In type II, the right pulmonary artery is preferentially opacified simulating the finding of right pulmonary artery arising from the ascending aorta. In one case of type II, injection into the right ventricle showed preferential flow to the left pulmonary artery, because of the large shunt of unopacified blood into the right pulmonary artery, but in both types I and II the left and right pulmonary arteries are usually opacified simultaneously after injection into the main pulmonary trunk. In type I either transaortic or transpulmonary closure is the appropriate surgical procedure. In types II and III, the transaortic approach provides better exposure and facilitates the operative repair.

Natural history of subarterial infundibular ventricular septal defect

Development of aortic valvular deformities was studied retrospectively in 395 inpatients with subarterial infundibular ventricular septal defect (siVSD). Aortic valvular deformities included prolapse into siVSD without aortic regurgitation (77 patients), prolapse and aortic regurgitation (95 patients), and aneurysm of the sinus of Valsalva (36 patients). No aortic valvular deformity was found in 187 patients, and 111 of these 187 patients had associated pulmonary hypertension. Prolapse and regurgitation of the aortic valve developed most frequently at the age 5 to 8 years. Aneurysm of the sinus of Valsalva was not found before the age of 10 years but began to develop during the teens and was diagnosed most frequently in the twenties. Patients with pulmonary hypertension did not develop aortic valvular deformities except in one instance. All inpatients with siVSD and without pulmonary hypertension over the age of 30 years had developed some aortic valvular deformities.

Phenotypic discordance in monozygotic twins with 22q11.2 deletion

We report on male monozygotic twins with 22q11.2 deletion and discordant phenotypes. The twins had twin-to-twin transfusion syndrome. Twin 1, the smaller of the pair, had Tetralogy of Fallot, a characteristic facial appearance, swallowing dysfunction, anal atresia, short stature, and mental retardation, whereas twin 2 had a characteristic facial appearance but no other signs of the 22q11 deletion syndrome. Fluorescence in situ hybridization analysis showed a microdeletion on chromosome 22q11.2 in both twins. Zygosity analysis gave a probability of monozygosity greater than 99.999%. These observations indicate that environmental factors or postzygotic events play a role in the phenotypic variability in the twins.

Detection of coronary artery stenosis in children with Kawasaki disease. Usefulness of pharmacologic stress 201Tl myocardial tomography.

This study determined the feasibility and accuracy of quantitative 201Tl myocardial single-photon emission computed tomography (SPECT) after dipyridamole infusion to detect coronary obstructive lesions in children with Kawasaki disease. 201Tl distribution after dipyridamole infusion was measured in 23 normal children, and with these normal values, quantitative analysis of SPECT was performed in 49 patients. Thirty-four patients had coronary stenosis 90% or greater on angiograms. Side effects resulting from systemic vasodilation were observed in about 70%. Angina pectoris and ischemic ST changes were observed only in patients with coronary stenosis. These symptoms disappeared after aminophylline infusion. Results of visual and quantitative analysis of SPECT were compared. SPECT data were shown on two-dimensional polar maps, and the extent and severity scores were calculated. The sensitivity of SPECT for detection of overall coronary stenosis was 91% (visual analysis) and 88% (quantitative analysis). The specificity of SPECT was 60% visually and 93% quantitatively. The sensitivity of quantitative analysis to detect individual coronary stenosis was similar to that of visual analysis. However, the specificity of visual analysis to detect individual coronary artery stenosis was significantly less than that of quantitative analysis. From these data, we conclude that quantitative analysis of myocardial SPECT after dipyridamole infusion is a safe and accurate diagnostic method for identifying coronary stenosis in children with Kawasaki disease.