A complex rearrangement on chromosome 22 affecting both homologues; haplo-insufficiency of the Cat eye syndrome region may have no clinical relevance

De novo Unbalanced 1;22 Translocation with 22q11 Deletion Syndrome

This report describes a newborn girl presenting with some of the common features of DiGeorge syndrome/velocardiofacial syndrome (DGS/VCFS), including hypocalcemia, atrial septal defect, and aortic stenosis. Several genetic tests were carried out to determine the origin of the clinical phenotype. MLPA was initially performed followed by aCGH, cytogenetic analysis, and FISH. Cytogenetic analysis of the proband's parents was also done. MLPA revealed a deletion in 22q11.1q11.2 spanning from the cat eye syndrome region to the most commonly deleted region in DGS/VCFS patients. The size of the deletion as defined by aCGH was 3.2 Mb. The karyotype of the proband was 45,XX,der(1)t(1;22)(p36.3;q11.2)dn,-22, the karyotypes of the parents were normal. FISH analysis showed that the 22q11 deletion occurred in the der(1). No loss or gain of chromosomal material was evident for chromosome 1, as confirmed by MLPA, aCGH, and FISH. Unbalanced translocations resulting in DGS are relatively rare, with limited reports in the literature. To our knowledge, this is the second case involving chromosome 1 and the first one with breakpoints in 1p36 and 22q11.2. This case also emphasizes the importance of combining diagnostic methods to better understand a given genetic abnormality.

Analysis of chromosome 22q11 copy number variations by multiplex ligation-dependent probe amplification for prenatal diagnosis of congenital heart defect

BACKGROUND

Congenital heart defects (CHD) represent one of the most common birth defects. This study aimed to evaluate the value of multiplex ligation-dependent probe amplification (MLPA) as a tool to detect the copy number variations (CNVs) of 22q11 in fetuses with CHD.

RESULTS

A large cohort of 225 fetuses with CHD was screened by fetal echocardiography. Once common chromosome abnormalities in 30 fetuses were screened out by conventional G-banding analysis, the CNVs of chromosome 22q11 in the remaining 195 fetuses were determined by MLPA for prenatal genetic counseling. In 195 CHD fetuses with normal karyotype, 11 cases had pathological CNVs, including 22q11.2 deletion (seven cases), the deletion of 22q11 cat eye syndrome (CES) region (one case), 22q11.2 duplication (one case), 22q13.3 deletion (one case) and 17p13.3 deletion (one case). In total, our findings from MLPA screening represented 4.9 % in our cohort. Among these, three cases were inherited CNVs, and eight cases were de novo. These CNVs were further verified by single nucleotide polymorphism (SNP)-array analysis, and their chromosomal location was refined.

CONCLUSION

This study indicated that MLPA could serve as an effective test for routine prenatal diagnosis of 22q11 in fetuses with CHD.

22q11.2 Deletion Syndrome due to a Translocation t(6;22) in a Patient Conceived via in vitro Fertilization

We report on a patient conceived via in vitro fertilization (IVF) with a 22q11.2 deletion due to an unusual unbalanced translocation involving chromosomes 6 and 22 in a karyotype with 45 chromosomes. Cytogenomic studies showed that the patient has a 3.3-Mb deletion of chromosome 22q and a 0.4-Mb deletion of chromosome 6p, which resulted in haploinsufficiency of the genes responsible for the 22q11.2 deletion syndrome and also of the IRF4 gene, a member of the interferon regulatory factor family of transcription factors, which is expressed in the immune system cells. The rearrangement could be due to the manipulation of the embryo or as a sporadic event unrelated to IVF. Translocation involving chromosome 22 in a karyotype with 45 chromosomes is a rare event, with no previous reports involving chromosomes 6p and 22q.

Schmid-Fraccaro syndrome: severe neurologic features

Schmid-Fraccaro syndrome is a rare genetic disease, characterized by modifications of chromosome 22 (partial trisomy or tetrasomy), accompanied by eye abnormality (coloboma) and anal atresia. Clinical and phenotypic features are variable, and neurologic disturbance with delays of mental, psychologic, and motor development may be present. Its definitive diagnosis is based on karyotype. We report on a 17-year-old girl with Schmid-Fraccaro syndrome and severe cognitive deficits and motor deficits, who presented at our healthcare unit for a medical consultation. Her physical examination was remarkable for bilateral coloboma of the iris, hypertelorism, bilateral preauricular tags, scoliosis, and cardiac systolic murmur. After her birth, she was evaluated for anal atresia and congenital cardiac disease, which led to a genetic investigation and a diagnosis of Schmid-Fraccaro syndrome. Life expectancy in Schmid-Fraccaro syndrome depends on the number and variety of malformations, but in most cases the prognosis is favorable.

Unambiguous molecular detections with multiple genetic approach for the complicated chromosome 22q11 deletion syndrome

Background

Chromosome 22q11 deletion syndrome (22q11DS) causes a developmental disorder during the embryonic stage, usually because of hemizygous deletions. The clinical pictures of patients with 22q11DS vary because of polymorphisms: on average, approximately 93% of affected individuals have a de novo deletion of 22q11, and the rest have inherited the same deletion from a parent. Methods using multiple genetic markers are thus important for the accurate detection of these microdeletions.

Methods

We studied 12 babies suspected to carry 22q11DS and 18 age-matched healthy controls from unrelated Taiwanese families. We determined genomic variance using microarray-based comparative genomic hybridization (array-CGH), quantitative real-time polymerase chain reaction (qPCR) and multiplex ligation-dependent probe amplification (MLPA).

Results

Changes in genomic copy number were significantly associated with clinical manifestations for the classical criteria of 22q11DS using MPLA and qPCR (p < 0.01). An identical deletion was shown in three affected infants by MLPA. These reduced DNA dosages were also obtained partially using array-CGH and confirmed by qPCR but with some differences in deletion size.

Conclusion

Both MLPA and qPCR could produce a clearly defined range of deleted genomic DNA, whereas there must be a deleted genome that is not distinguishable using MLPA. These data demonstrate that such multiple genetic approaches are necessary for the unambiguous molecular detection of these types of complicated genomic syndromes.