DiGeorge anomaly in a patient with isochromosome 18p born to a diabetic mother

The DiGeorge anomaly (DGA) is an etiologically heterogeneous developmental field defect in which cardiovascular malformations, hypocalcemia, thymic hypoplasia, and characteristic dysmorphisms are major clinical features. The 22q11.2 deletion is the most common single etiology of DGA, although a number of other chromosomal abnormalities and teratogens, including maternal diabetes, have been implicated as well. We present a patient, born to a diabetic mother, with interrupted aortic arch type B (IAA-B), neonatal hypocalcemia, thymic hypoplasia, and dysmorphic features including microcephaly, thick, overfolded helices, and anteriorly-placed anus. Cytogenetic studies showed the presence of a marker chromosome, identified by fluorescence in-situ hybridization (FISH) as an isochromosome 18p [i(18p)]. We did not detect a 22q11.2 deletion by FISH using a cosmid probe corresponding to locus D22S75. The patient is the first example of either DGA or IAA-B in a patient with i(18p). We review the genetic abnormalities associated with DGA, and discuss the potential contributions of maternal diabetes and i(18p) in our patient.     

Mutational spectrum of DMD mutations in dystrophinopathy patients: application of modern diagnostic techniques to a large cohort

Mutations in the DMD gene, encoding the dystrophin protein, are responsible for the dystrophinopathies Duchenne Muscular Dystrophy (DMD), Becker Muscular Dystrophy (BMD), and X-linked Dilated Cardiomyopathy (XLDC). Mutation analysis has traditionally been challenging, due to the large gene size (79 exons over 2.2 Mb of genomic DNA). We report a very large aggregate data set comprised of DMD mutations detected in samples from patients enrolled in the United Dystrophinopathy Project, a multicenter research consortium, and in referral samples submitted for mutation analysis with a diagnosis of dystrophinopathy. We report 1,111 mutations in the DMD gene, including 891 mutations with associated phenotypes. These results encompass 506 point mutations (including 294 nonsense mutations) and significantly expand the number of mutations associated with the dystrophinopathies, highlighting the utility of modern diagnostic techniques. Our data supports the uniform hypermutability of CGA>TGA mutations, establishes the frequency of polymorphic muscle (Dp427m) protein isoforms and reveals unique genomic haplotypes associated with “private” mutations. We note that 60% of these patients would be predicted to benefit from skipping of a single DMD exon using antisense oligonucleotide therapy, and 62% would be predicted to benefit from an inclusive multiexonskipping approach directed toward exons 45 through 55. Hum Mutat 30:1657–1666, 2009. © 2009 Wiley-Liss, Inc.     

A palindrome-driven complex rearrangement of 22q11.2 and 8q24.1 elucidated using novel technologies

Constitutional translocations at the same 22q11.21 low copy repeat B (LCR-B) breakpoint involved in the recurrent t(11;22) are relatively abundant. A novel 46,XY,t(8;22)(q24.13;q11.21) rearrangement was investigated to determine whether the recurrent LCR-B breakpoint is involved. Investigations demonstrated an inversion of the 3Mb region typically deleted in patients with the 22q11.2 deletion syndrome. The 22q11.21 inversion appears to be mediated by low copy repeats, and is presumed to have taken place prior to translocation with 8q24.13. Despite predictions based on inversions observed in other chromosomes harboring low copy repeats, this 22q11.2 inversion has not been observed previously. The current studies utilize novel laser microdissection and MLPA (multiplex ligation-dependent probe amplification) approaches, as adjuncts to FISH, to map the breakpoints of the complex rearrangements of 22q11.21 and 8q24.21. The t(8;22) occurs between the recurrent site on 22q11.21 and an AT-rich site at 8q24.13, making it the fifth different chromosomal locus characterized at the nucleotide level engaged in a translocation with the unstable recurrent breakpoint at 22q11.21. Like the others, this breakpoint occurs at the center of a palindromic sequence. This sequence appears capable of forming a perfect 145 bp stem-loop. Remarkably, this site appears to have been involved in a previously reported t(3;8) occurring between 8q24.13 and FRA3B on 3p14.2. Further, the fragile site-like nature of all of the breakpoint sites involved in translocations with the recurrent site on 22q11.21, suggests a mechanism based on delay of DNA replication in the initiation of these chromosomal rearrangements.     

The long pentraxin PTX3 as a link among innate immunity, inflammation, and female fertility

The long pentraxin 3 (PTX3) is member of a complex superfamily of multifunctional proteins characterized by a cyclic multimeric structure. PTX3 is highly conserved in evolution and is produced by innate-immunity cells in response to proinflammatory signals and Toll-like receptor engagement. PTX3 plays complex, nonredundant functions in vivo, acting as a predecessor of antibodies, recognizing microbes, activating complement, facilitating pathogen recognition by phagocytes, and hence, playing a nonredundant role in resistance against selected pathogens. In addition, PTX3 is essential in female fertility by acting as a nodal point for the assembly of the cumulus oophorus hyaluronan-rich extracellular matrix. Thus, the prototypic long pentraxin PTX3 is a multifunctional, soluble pattern recognition receptor acting as a nonredundant component of the humoral arm of innate immunity and involved in matrix deposition and female fertility.     

Recurrent deletions and reciprocal duplications of 10q11.21q11.23 including CHAT and SLC18A3 are likely mediated by complex low-copy repeats

We report 24 unrelated individuals with deletions and 17 additional cases with duplications at 10q11.21q21.1 identified by chromosomal microarray analysis. The rearrangements range in size from 0.3 to 12 Mb. Nineteen of the deletions and eight duplications are flanked by large, directly oriented segmental duplications of >98% sequence identity, suggesting that nonallelic homologous recombination (NAHR) caused these genomic rearrangements. Nine individuals with deletions and five with duplications have additional copy number changes. Detailed clinical evaluation of 20 patients with deletions revealed variable clinical features, with developmental delay (DD) and/or intellectual disability (ID) as the only features common to a majority of individuals. We suggest that some of the other features present in more than one patient with deletion, including hypotonia, sleep apnea, chronic constipation, gastroesophageal and vesicoureteral refluxes, epilepsy, ataxia, dysphagia, nystagmus, and ptosis may result from deletion of the CHAT gene, encoding choline acetyltransferase, and the SLC18A3 gene, mapping in the first intron of CHAT and encoding vesicular acetylcholine transporter. The phenotypic diversity and presence of the deletion in apparently normal carrier parents suggest that subjects carrying 10q11.21q11.23 deletions may exhibit variable phenotypic expressivity and incomplete penetrance influenced by additional genetic and nongenetic modifiers.