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PubMed2003

High specificity PCR screening for 22q11.2 microdeletion in three different ethnic groups.

Congenital heart defects are the most common of all human birth defects. Numerous studies have shown that a deletion within chromosome 22q11 is associated with DiGeorge syndrome and certain forms of sporadic congenital cardiovascular disease. We have determined the value of a PCR assay using markers D22S941, D22S944 and D22S264 designed for the screening of 22q11.2 deletion through consecutive homozygosity in an ethnically admixed urban population. The study population comprised 149 unrelated men and women from three different ethnic groups (white, mulatto and black). Test specificity for the overall population was estimated at 98.3%. We found no significant difference when comparing heterozygosity indices and ethnicity (P value = 0.43 (D22S944), 0.22 (D22S264), and 0.58 (D22S941)). There was no significant difference regarding assay specificity between the three different ethnic groups studied. This assay could constitute a cost-effective way to screen a large number of patients at increased risk, since PCR techniques are easily available, are fast, can be automatized, and are significantly less expensive than fluorescence in situ hybridization.

Chromosome Deletion↗
PubMed2006

Three-color FISH analysis of TMPRSS2/ERG fusions in prostate cancer indicates that genomic microdeletion of chromosome 21 is associated with rearrangement.

The recent description of novel recurrent gene fusions in approximately 80% of prostate cancer (PCa) cases has generated increased interest in the search for new translocations in other epithelial cancers and emphasizes the importance of understanding the origins and biologic implications of these genomic rearrangements. Analysis of 15 PCa cases by reverse transcription-polymerase chain reaction was used to detect six ERG-related gene fusion transcripts with TMPRSS2. No TMPRSS2/ETV1 chimeric fusion was detected in this series. Three-color fluorescence in situ hybridization confirms that TMPRSS2/ERG fusion may be accompanied by a small hemizygous sequence deletion on chromosome 21 between ERG and TMPRSS2 genes. Analysis of genomic architecture in the region of genomic rearrangement suggests that tracts of microhomology could facilitate TMPRSS2/ERG fusion events.

Chromosome Aberrations↗
PubMed1998

Childhood-onset schizophrenia associated with parkinsonism in a patient with a microdeletion of chromosome 22.

The deletion of a gene or genes on chromosome 22q11 is responsible for the velocardiofacial syndrome (VCFS), which is associated with cardiac anomalies, short stature, palate abnormalities, learning disabilities, and developmental delay. Herein we describe a 30-year-old man with VCFS in whom a chronic psychotic disorder originated during childhood. A 10% rate of psychotic disorders has been reported in association with this genetic syndrome. In our patient, the clinical manifestation was complicated by extrapyramidal symptoms that predated the onset of psychotic symptoms. To our knowledge, extrapyramidal symptoms have not previously been reported in a patient with VCFS. The diagnosis of VCFS was confirmed with the fluorescence in situ hybridization probe for VCFS. The role of the atypical antipsychotic drug clozapine is discussed with respect to treating this patient who has severe psychotic symptoms coexisting with extrapyramidal symptoms and seizures. In light of the observation that patients with VCFS have an unexpectedly high rate of psychotic disorders, issues concerning the genetics of schizophrenia are intriguing.

Abnormalities, Multiple↗
PubMed1999

Systematic characterisation of disease associated balanced chromosome rearrangements by FISH: cytogenetically and genetically anchored YACs identify microdeletions and candidate regions for mental retardation genes.

Disease associated balanced chromosome rearrangements (DBCRs) have been instrumental in the isolation of many disease genes. To facilitate the molecular cytogenetic characterisation of DBCRs, we have generated a set of >1200 non-chimeric, cytogenetically and genetically anchored CEPH YACs, on average one per 3 cM, spaced over the entire human genome. By fluorescence in situ hybridisation (FISH), we have performed a systematic search for YACs spanning translocation breakpoints. Patients with DBCRs and either syndromic or non-syndromic mental retardation (MR) were ascertained through the Mendelian Cytogenetics Network (MCN), a collaborative effort of, at present, 270 cytogenetic laboratories throughout the world. In this pilot study, we have characterised 10 different MR associated chromosome regions delineating candidate regions for MR. Five of these regions are narrowed to breakpoint spanning YACs, three of which are located on chromosomes 13q21, 13q22, and 13q32, respectively, one on chromosome 4p14, and one on 6q25. In two out of six DBCRs, we found cytogenetically cryptic deletions of 3-5 Mb on one or both translocation chromosomes. Thus, cryptic deletions may be an important cause of disease in seemingly balanced chromosome rearrangements that are associated with a disease phenotype. Our region specific FISH probes, which are available to MCN members, can be a powerful tool in clinical cytogenetics and positional cloning.

Adolescent↗
PubMed1999

A microdeletion within DAX-1 in X-linked adrenal hypoplasia congenita and hypogonadotrophic hypogonadism.

BACKGROUND: X-linked adrenal hypoplasia congenita (AHC) is a developmental disorder characterized by primary adrenal gland failure, which produces extreme and potentially fatal endocrine deficiencies. Hypogonadotrophic hypogonadism (HHG) also may be associated with AHC. AHC has been shown to result from a variety of mutations in the DAX-1 gene, which encodes a member of the nuclear hormone receptor superfamily. METHODS: The proband, one of the world's oldest living patients with AHC and HHG, was diagnosed in 1955. He was on corticosteroid replacement therapy since that time and androgen replacement therapy since puberty. We sequenced his DAX-1 gene. RESULTS: We found a 4 bp ACTC deletion between nucleotides 1464 and 1467 in the second exon of the normal DAX-1 sequence. This mutation caused a shift in the reading frame and predicted a premature stop codon at amino acid position 416. The mutation abolished a recognition site for DdeI, allowing for confirmation by restriction analysis. CONCLUSIONS: The position of the mutation confirms the functional importance of the COOH-terminal 10% of the DAX-1 sequence. The clinical history also reinforces the importance of early diagnosis in AHC, which can be associated with longevity and no obvious morbidity after more than 40 years of hormone replacement therapy.

Adrenal Cortex Hormones↗
PubMedDate not supplied

Microdeletion of 22q11 (CATCH 22) in children with conotruncal heart defect and extracardiac malformations.

CATCH 22 is a medical acronym for cardiac defects, abnormal facies, thymic hypoplasia, cleft palate, and hypocalcemia, and a variable deletion on chromosome 22q11. The deletion within the chromosome region of 22q11 may occur in patients with dysmorphologic and cardiological syndromes: DiGeorge syndrome (DGS), velocardiofacial syndrome (VCFS), and conotruncal anomaly face syndrome (CAFS). In this study, using N25 (D22S75) DiGeorge chromosome region probe. fluorescence in situ hybridization (FISH) analyses were performed on 32 patients with congenital heart diseases. Twenty-nine of 32 patients had conotruncal heart disease. A 22q11 deletion was detected in two patients (6.9%) of the 29 patients with conotruncal heart disease. One of our 22qdel (+) patients had unilateral facial nerve palsy. Although it is not a frequent finding, unilateral facial nerve palsy will be included among the symptoms of CATCH 22 syndrome. After careful clinical evaluation of patients with conotruncal cardiac anomalies, only syndromic cases should be screened for this deletion.

Abnormalities, Multiple↗
PubMed1992

Microdeletions of chromosome 17p13 as a cause of isolated lissencephaly.

Lissencephaly (agyria-pachygyria) is a brain malformation manifested by a smooth cerebral surface, resulting from arrest of neuronal migration at 10-14 wk gestation. Type I, or classical, lissencephaly can occur either in association with the Miller-Dieker syndrome (MDS) or as an isolated finding, termed "isolated lissencephaly sequence" (ILS). About 90% of MDS patients have visible or submicroscopic deletions of 17p13.3. We therefore investigated the possibility that some ILS patients have smaller deletions in this chromosomal region. Forty-five ILS patients with gyral abnormalities ranging from complete agyria to mixed agyria/pachygyria and complete pachygyria were studied. RFLP analysis with five polymorphic loci in 17p13.3 was performed on all patients and their parents. Somatic cell hybrids were constructed on three patients, to confirm a deletion or to determine the boundaries of a deletion. In-situ hybridization using cosmid probes from within a newly defined lissencephaly critical region was performed on 31 patients as a further method of deletion detection. Six submicroscopic deletions were detected (13.3%). Three of the deletions among 45 ILS patients were detected by RFLP analysis, 4 deletions in 31 patients were detected by in situ hybridization, and one deletion was detected only by somatic cell hybrid studies (in situ hybridization was not performed). Overall, in situ hybridization proved to be the most rapid and sensitive method of deletion detection. The centromeric boundary of these deletions overlapped that of MDS patients, while the telomeric boundary for four ILS deletions was proximal to that of MDS and narrows the critical region for a lissencephaly locus.(ABSTRACT TRUNCATED AT 250 WORDS)

Base Sequence↗
PubMed1992

A genetic etiology for DiGeorge syndrome: consistent deletions and microdeletions of 22q11.

DiGeorge syndrome (DGS), a developmental field defect of the third and fourth pharyngeal pouches, is characterized by aplasia or hypoplasia of the thymus and parathyroid glands and by conotruncal cardiac malformations. Cytogenetic studies support the presence of a DGS critical region in band 22q11. In the present study, we report the results of clinical, cytogenetic, and molecular studies of 14 patients with DGS. Chromosome analysis, utilizing high-resolution banding techniques, detected interstitial deletions in five probands and was inconclusive for a deletion in three probands. The remaining six patients had normal karyotypes. In contrast, molecular analysis detected DNA deletions in all 14 probands. Two of 10 loci tested, D22S75 and D22S259, are deleted in all 14 patients. A third locus, D22S66, is deleted in the eight DGS probands tested. Physical mapping using somatic cell hybrids places D22S66 between D22S75 and D22S259, suggesting that it should be deleted in the remaining six cases. Parent-of-origin studies were performed in five families. Four probands failed to inherit a maternal allele, and one failed to inherit a paternal allele. On the basis of these families, and of six maternally and five paternally derived unbalanced-translocation DGS probands in the literature, parent of origin or imprinting does not appear to play an important role in the pathogenesis of DGS. Deletion of the same three loci in all 14 DGS probands begins to delineate the region of chromosome 22 critical for DGS and confirms the hypothesis that submicroscopic deletions of 22q11 are etiologic in the vast majority of cases.

Blotting, Southern↗