Three cases of isolated terminal deletion of chromosome 8p without heart defects presenting with a mild phenotype.

Individuals with isolated terminal deletions of 8p have been well described in the literature, however, molecular characterization, particularly by microarray, of the deletion in most instances is lacking. The phenotype of such individuals falls primarily into two categories: those with cardiac defects, and those without. The architecture of 8p has been demonstrated to contain two inversely oriented segmental duplications at 8p23.1, flanking the gene, GATA4. Haploinsufficiency of this gene has been implicated in cardiac defects seen in numerous individuals with terminal 8p deletion. Current microarray technologies allow for the precise elucidation of the size and gene content of the deleted region. We present three individuals with isolated terminal deletion of 8p distal to the segmental duplication telomeric to GATA4. These individuals present with a relatively mild and nonspecific phenotype including mildly dysmorphic features, developmental delay, speech delay, and early behavior issues.

Prenatal diagnosis of two fetuses with deletions of 8p23.1, critical region for congenital diaphragmatic hernia and heart defects.

Microdeletions of 8p23.1 are mediated by low copy repeats and can cause congenital diaphragmatic hernia (CDH) and cardiac defects. Within this region, point mutations of the GATA4 gene have been shown to cause cardiac defects. However, the cause of CDH in these deletions has been difficult to determine due to the paucity of mutations that result in CDH, the lack of smaller deletions to refine the region and the reduced penetrance of CDH in these large deletions. Mice deficient for one copy of the Gata4 gene have been described with CDH and heart defects suggesting mutations in Gata4 can cause the phenotype in mice. We report on the SNP microarray analysis on two fetuses with deletions of 8p23.1. The first had CDH and a ventricular septal defect (VSD) on ultrasonography and a family history of a maternal VSD. Microarray analysis detected a 127-kb deletion which included the GATA4 and NEIL2 genes which was inherited from the mother. The second fetus had an incomplete atrioventricular canal defect on ultrasonography. Microarray analysis showed a 315-kb deletion that included seven genes, GATA4, NEIL2, FDFT1, CTSB, DEFB136, DEFB135, and DEFB134. These results suggest that haploinsufficiency of the two genes in common within 8p23.1; GATA4 and NEIL2 can cause CDH and cardiac defects in humans.

Clinical comparison of overlapping deletions of 19p13.3.

We present three patients with overlapping interstitial deletions of 19p13.3 identified by high resolution SNP microarray analysis. All three had a similar phenotype characterized by intellectual disability or developmental delay, structural heart abnormalities, large head relative to height and weight or macrocephaly, and minor facial anomalies. Deletion sizes ranged from 792 Kb to 1.0 Mb and included a common region arr [hg19] 19p13.3 (3,814,392-4,136,989), containing eight genes: ZFR2, ATCAY, NMRK2, DAPK3, EEF2, PIAS4, ZBTB7A, MAP2K2, and two non-coding RNA's MIR637 and SNORDU37. The patient phenotypes were compared with three previous single patient reports with similar interstitial 19p13.3 deletions and six additional patients from the DECIPHER and ISCA databases to determine if a common haploinsufficient phenotype for the region can be established.

UPD detection using homozygosity profiling with a SNP genotyping microarray.

Single nucleotide polymorphism (SNP) based chromosome microarrays provide both a high-density whole genome analysis of copy number and genotype. In the past 21 months we have analyzed over 13,000 samples primarily referred for developmental delay using the Affymetrix SNP/CN 6.0 version array platform. In addition to copy number, we have focused on the relative distribution of allele homozygosity (HZ) throughout the genome to confirm a strong association of uniparental disomy (UPD) with regions of isoallelism found in most confirmed cases of UPD. We sought to determine whether a long contiguous stretch of HZ (LCSH) greater than a threshold value found only in a single chromosome would correlate with UPD of that chromosome. Nine confirmed UPD cases were retrospectively analyzed with the array in the study, each showing the anticipated LCSH with the smallest 13.5 Mb in length. This length is well above the average longest run of HZ in a set of control patients and was then set as the prospective threshold for reporting possible UPD correlation. Ninety-two cases qualified at that threshold, 46 of those had molecular UPD testing and 29 were positive. Including retrospective cases, 16 showed complete HZ across the chromosome, consistent with total isoUPD. The average size LCSH in the 19 cases that were not completely HZ was 46.3 Mb with a range of 13.5-127.8 Mb. Three patients showed only segmental UPD. Both the size and location of the LCSH are relevant to correlation with UPD. Further studies will continue to delineate an optimal threshold for LCSH/UPD correlation.