Combined 22q11.1-q11.21 deletion with 15q11.2-q13.3 duplication identified by array-CGH in a 6 years old boy

Sperm meiotic segregation of a balanced interchromosomal reciprocal insertion resulting in recurrent spontaneous miscarriage

RESEARCH QUESTION

Is sperm fluorescence in-situ hybridization (FISH) useful to evaluate the risk of chromosomally unbalanced gametes in interchromosomal reciprocal insertion (IRI) carriers? How do these imbalances lead to recurrent miscarriages?

DESIGN

This study reports a clinical and molecular study of a rare familial balanced IRI resulting in recurrent spontaneous miscarriage. Sperm FISH was performed to estimate the number of unbalanced gametes.

RESULTS

A 31-year-old healthy male (proband) and his 28-year-old female partner were referred to the Genetics Department for three spontaneous miscarriages occurring during the first trimester of pregnancy. FISH analysis of the proband with the LSI TRA/D (14q11.2) and DiGeorge N25 (22q11.2) break-apart probes showed the presence of a balanced IRI between 14q11.2 and 22q11.2 chromosomal regions. This IRI was also identified in the proband's father. Sperm FISH with the same probes showed that more than 40% of gametes of the proband were unbalanced for either 14q11.2 or 22q11.2, despite normal sperm parameters. FISH analysis of a product of conception indicated that unbalanced gametes result in a non-viable fetus.

CONCLUSIONS

This study shows the value of sperm FISH analysis in improving genetic reproductive advice for IRI carriers. Disruption of critical genes through this rearrangement and their consequent functional impairment could result in recurrent miscarriages. In this case, several genes located in the 14q11.2 region, particularly RNase 3, would be good candidates to explain the lethality of the imbalances.

Case history and genome-wide scans for copy number variants in a family with patient having 15q11.1-q11.2 duplication and 22q11.2 deletion, and schizophrenia

Many studies have indicated that chromosomes 15q11 and 22q11 may be associated with the genetic etiologies of schizophrenia. We have followed an adult schizophrenia case with 15q11.1-q11.2 duplication and 22q11.2 deletion. Here we report his clinical history, and copy number variants (CNVs) identified by microarray and real-time PCR in the patient and his parents. This is the first report describing a detailed phenotype of an adult schizophrenic case with both 15q11 and 22q11 CNVs as revealed by novel and trustworthy technologies. Subjects were a 33-year-old male patient with 15q11 and 22q11 CNVs, and his normal parents. He fulfilled the DSM-IV criteria for schizophrenia at age 18 years. He was also diagnosed with 22q11.2 deletion syndrome by fluorescence in situ hybridization (FISH) at age 18 years. To search for CNVs in more detail, whole-genome array-CGH analyses including ∼ 420,000 probes were carried out in the patient and his parents. For validations of the CNVs detected by array-CGH, real-time PCR analyses of these CNVs were performed. The patient had two disease-specific CNVs, 15q11.1-q11.2 duplication (∼ 2.7 Mb) and 22q11.21 deletion (∼ 2.9 Mb). These two regions are important for the development of schizophrenia, and this patient had shown symptoms of schizophrenia. Thus, the two areas may contain causal genes for schizophrenia.

Constitutional chromosomal events at 22q11 and 15q26 in a child with a pilocytic astrocytoma of the spinal cord

We report on a 9-years-old patient with mild intellectual disability, facial dimorphisms, bilateral semicircular canal dysplasia, periventricular nodular heterotopias, bilateral hippocampal malrotation and abnormal cerebellar foliation, who developed mild motor impairment and gait disorder due to a pilocytic astrocytoma of the spinal cord. Array-CGH analysis revealed two paternal inherited chromosomal events: a 484.3 Kb duplication on chromosome 15q26.3 and a 247 Kb deletion on 22q11.23. Further, a second de novo 1.5 Mb deletion on 22q11.21 occurred. Chromosome 22 at q11.2 and chromosome 15 at q24q26 are considered unstable regions subjected to copy number variations, i.e. structural alterations of genome, mediated by low copy repeat sequences or segmental duplications. The link between some structural CNVs, which compromise fundamental processes controlling DNA stability, and genomic disorders suggest a plausible scenario for cancer predisposition.

Evaluation of the genes at the breakpoints cannot account simultaneously for the phenotype and tumour development in this patient. The two paternal inherited CNVs arguably are not pathogenic and do not contribute to the clinical manifestations. Similarly, although the de novo large deletion at 22q11.21 overlaps with the Di George (DGS) critical region and results in haploinsufficiency of genes compromising critical processes for DNA stability, this case lacks several hallmarks of DGS.

Osteogenesis imperfecta, tricho-dento-osseous syndrome and intellectual disability: a familial case with 17q21.33-q22 (COL1A1 and DLX3) deletion and 7q32.3-q33 duplication resulting from a reciprocal interchromosomal insertion

We report on a 22-year-old woman with features of osteogenesis imperfecta (OI), tricho-dento-osseous (TDO) syndrome and intellectual disability. Whole genome oligonucleotide microarray analysis revealed a copy number gain of 3 Mb in 7q32.3-q33 and a loss of 3.4 Mb in 17q21.33-q22. FISH analysis showed that the third copy of 7q32 was inserted into the long arm of one chromosome 17, exactly in the region 17q21.33-q22 that was deleted. The maternal uncle presented with clinical features similar to the proposita and had the same chromosomal anomalies. The mother of the proposita and two other family members were balanced carriers of this rearrangement, interpreted as an interchromosomal reciprocal insertion. Reciprocal insertion/four-break rearrangement is a very rare chromosomal event. The deleted region on chromosome 17 contains 39 genes, including COL1A1 and DLX3 involved in OI and TDO syndrome respectively. The CACNA1G gene on the deleted segment of chromosome 17 may be a good candidate gene to explain the intellectual impairment. © 2013 Wiley Periodicals, Inc.