Segmental Paternal Uniparental Disomy (patUPD) of 14q32 With Abnormal Methylation Elicits the Characteristic Features of Complete patUPD14

Uniparental disomy (UPD) for chromosome 14 is associated with well-recognized phenotypes, depending on the parent of origin. Studies in mouse models and human patients have implicated the involvement of the distal region of the long arm of chromosome 14 in the distinctive phenotypes. This involvement is supported by the identification of an imprinting cluster at chromosome 14q32, encompassing the differentially methylated regions (DMRs), IG-DMR and MEG3-DMR, as well as the maternally expressed genes GTL2, DI03, and RTL1 and the paternally expressed genes DLK1, RTL1as, and MEG8. Here we report on a preterm female infant with distal segmental paternal UPD14 (upd(14)pat) of 14q32-14q32.33, which resulted in thoracic deformity secondary to rib abnormalities ("coat-hanger" rib sign), polyhydramnios, and other congenital abnormalities characteristically described in cases of complete upd(14)pat. Microsatellite investigation demonstrated UPD of markers D14S250 and D14S1010, encompassing a similar to 3.5 Mb region of distal 14q and involving the imprinting cluster. This case provided insight into the etiology of the phenotypic effects of upd(14)pat, prompting methylation analysis of the GTL2 promoter and the DMR between GTL2 and DLK1. We compare the physical findings seen in this case with those of patients with other causes of abnormal methylation of 14q32, which consistently result in certain distinct clinical features, regardless of the cytogenetic and molecular etiology. (C) 2010 Wiley-Liss, Inc.