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

<p>Abstract</p> <p>Background</p> <p>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.</p> <p>Methods</p> <p>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).</p> <p>Results</p> <p>Changes in genomic copy number were significantly associated with clinical manifestations for the classical criteria of 22q11DS using MPLA and qPCR (<it>p </it>< 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.</p> <p>Conclusion</p> <p>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.</p

Pan-ethnic carrier screening and prenatal diagnosis for spinal muscular atrophy: clinical laboratory analysis of >72 400 specimens

Spinal muscular atrophy (SMA) is a leading inherited cause of infant death with a reported incidence of ∼1 in 10 000 live births and is second to cystic fibrosis as a common, life-shortening autosomal recessive disorder. The American College of Medical Genetics has recommended population carrier screening for SMA, regardless of race or ethnicity, to facilitate informed reproductive options, although other organizations have cited the need for additional large-scale studies before widespread implementation. We report our data from carrier testing (n=72 453) and prenatal diagnosis (n=121) for this condition. Our analysis of large-scale population carrier screening data (n=68 471) demonstrates the technical feasibility of high throughput testing and provides mutation carrier and allele frequencies at a level of accuracy afforded by large data sets. In our United States pan-ethnic population, the calculated a priori carrier frequency of SMA is 1/54 with a detection rate of 91.2%, and the pan-ethnic disease incidence is calculated to be 1/11 000. Carrier frequency and detection rates provided for six major ethnic groups in the United States range from 1/47 and 94.8% in the Caucasian population to 1/72 and 70.5% in the African American population, respectively. This collective experience can be utilized to facilitate accurate pre- and post-test counseling in the settings of carrier screening and prenatal diagnosis for SMA

Breakpoint mapping of 13 large parkin deletions/duplications reveals an exon 4 deletion and an exon 7 duplication as founder mutations

Early-onset Parkinson’s disease (EOPD) has been associated with recessive mutations in parkin (PARK2). About half of the mutations found in parkin are genomic rearrangements, i.e., large deletions or duplications. Although many different rearrangements have been found in parkin before, the exact breakpoints involving these rearrangements are rarely mapped. In the present study, the exact breakpoints of 13 different parkin deletions/duplications, detected in 13 patients out of a total screened sample of 116 EOPD patients using Multiple Ligation Probe Amplification (MLPA) analysis, were mapped using real time quantitative polymerase chain reaction (PCR), long-range PCR and sequence analysis. Deletion/duplication-specific PCR tests were developed as a rapid and low cost tool to confirm MLPA results and to test family members or patients with similar parkin deletions/duplications. Besides several different deletions, an exon 3 deletion, an exon 4 deletion and an exon 7 duplication were found in multiple families. Haplotype analysis in four families showed that a common haplotype of 1.2 Mb could be distinguished for the exon 7 duplication and a common haplotype of 6.3 Mb for the deletion of exon 4. These findings suggest common founder effects for distinct large rearrangements in parkin

Validation of a high resolution NGS method for detecting spinal muscular atrophy carriers among phase 3 participants in the 1000 Genomes Project

BACKGROUND: Spinal muscular atrophy (SMA) is the most common pan-ethnic cause of early childhood death due to mutations in a single gene, SMN1. Most chromosome 5 homologs have a functional gene and dysfunctional copy, SMN2, with a single synonymous base substitution that results in faulty RNA splicing. However, the copy number of SMN1 and SMN2 is highly variable, and one in 60 adults worldwide are SMA carriers. Although population-wide screening is recommended, current SMA carrier tests have not been incorporated into targeted gene panels. METHODS: Here we describe a novel computational protocol for determining SMA carrier status based solely on individual exome data. Our method utilizes a Bayesian hierarchical model to quantify an individual’s carrier probability given only his or her SMN1 and SMN2 reads at six loci of interest. RESULTS: We find complete concordance with results obtained with the current qPCR-based testing standard in known SMA carriers and affecteds. We applied our protocol to the phase 3 cohort of the 1,000 Genomes Project and found carrier frequencies in multiple populations consistent with the present literature. CONCLUSION: Our process is a convenient, robust alternative to qPCR, which can easily be integrated into the analysis of large multi-gene NGS carrier screens. ELECTRONIC SUPPLEMENTARY MATERIAL: The online version of this article (doi:10.1186/s12881-015-0246-2) contains supplementary material, which is available to authorized users

Methylenetethrahydrofolate reductase (MTHFR) 677t allele and male infertility in Italy

The 677T allele of the MTHFR gene has been suggested to represent a factor of risk for male infertility. In order to confirm this association, we investigated the presence of the 677T allele in 93 Italian infertile patients, selected after the exclusion of other possible genetic causes of infertility, and in 105 Italian fertile controls. The homozygous 677TT genotype was present in 20.4% of patients and 27.6% of controls. These results do not support an association between the MTHFR 677T allele and male infertility in Ital

Whole gene deletion and splicing mutations expand the PINK1 genotypic spectrum

Autosomal recessive parkinsonism is a genetic condition closely resembling Parkinson disease, the only distinguishing features being an earlier age at onset and a slower disease progression. Three causative genes have been identified so far. While exon rearrangements are frequently encountered in the Parkin gene, most PINK1 mutations are represented by single nucleotide changes. We report a sporadic parkinsonian patient carrying a deletion of the entire PINK1 gene and a splice site mutation (g.15445_15467del23) which produces several aberrant mRNAs. This report expands the genotypic spectrum of PINK1 mutations, with relevant implications for molecular analysis of this gene